Patent Publication Number: US-7897054-B2

Title: Centrifuge container and methods of use

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/001,257, filed Dec. 10, 2007, now abandoned which is a continuation of U.S. patent application Ser. No. 11/003,681filed Dec. 3, 2004, now U.S. Pat. No. 7,306,741, which is a continuation of U.S. patent application Ser. No. 10/462,426, filed Jun. 16, 2003, now U.S. Pat. No. 6,827,863, which is a divisional of U.S. patent application Ser. No. 09/832,711 filed Apr. 9, 2001, now U.S. Pat. NO. 6,579,219, the entire content of which is specifically incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to novel methods, devices and apparatuses for the centrifugal separation of a liquid into its components of varying specific gravities, and is more particularly directed toward a blood separation device useful, for example, in the separation of blood components for use in various therapeutic regimens. 
     2. Description of the State of Art 
     Centrifugation utilizes the principle that particles suspended in solution will assume a particular radial position within the centrifuge rotor based upon their respective densities and will therefore separate when the centrifuge is rotated at an appropriate angular velocity for an appropriate period of time. Centrifugal liquid processing systems have found applications in a wide variety of fields. For example, centrifugation is widely used in blood separation techniques to separate blood into its component parts, that is, red blood cells, platelets, white blood cells, and plasma. 
     The liquid portion of the blood, referred to as plasma, is a protein-salt solution in which red and white blood cells and platelets are suspended. Plasma, which is 90 percent water, constitutes about 55 percent of the total blood volume. Plasma contains albumin (the chief protein constituent), fibrinogen (responsible, in part, for the clotting of blood), globulins (including antibodies) and other clotting proteins. Plasma serves a variety of functions, from maintaining a satisfactory blood pressure and providing volume to supplying critical proteins for blood clotting and immunity. Plasma is obtained by separating the liquid portion of blood from the cells suspended therein. 
     Red blood cells (erythrocytes) are perhaps the most recognizable component of whole blood. Red blood cells contain hemoglobin, a complex iron-containing protein that carries oxygen throughout the body while giving blood its red color. The percentage of blood volume composed of red blood cells is called the “hematocrit.” 
     White blood cells (leukocytes) are responsible for protecting the body from invasion by foreign substances such as bacteria, fungi and viruses. Several types of white blood cells exist for this purpose, such as granulocytes and macrophages, which protect against infection by surrounding and destroying invading bacteria and viruses, and lymphocytes, which aid in the immune defense. 
     Platelets (thrombocytes) are very small cellular components of blood that help the clotting process by sticking to the lining of blood vessels. Platelets are vital to life, because they help prevent both massive blood loss resulting from trauma and blood vessel leakage that would otherwise occur in the course of normal, day-to-day activity. 
     If whole blood is collected and prevented from clotting by the addition of an appropriate anticoagulant, it can be centrifuged into its component parts. Centrifugation will result in the red blood cells, which weigh the most, packing to the most outer portion of the rotating container, while plasma, being the least dense will settle in the central portion of the rotating container. Separating the plasma and red blood cells is a thin white or grayish layer called the buffy coat. The buffy coat layer consists of the white blood cells and platelets, which together make up about 1 percent of the total blood volume. 
     These blood components, discussed above, may be isolated and utilized in a wide range of diagnostic and therapeutic regimens. For example, red blood cells are routinely transfused into patients with chronic anemia resulting from disorders such as kidney failure, malignancies, or gastrointestinal bleeding and those with acute blood loss resulting from trauma or surgery. The plasma component is typically frozen by cryoprecipitation and then slowly thawed to produce cryoprecipitated antihemophiliac factor (AHF), which is rich in certain clotting factors, including Factor VIII, fibrinogen, von Willebrand factor and Factor XIII. Cryoprecipitated AHF is used to prevent or control bleeding in individuals with hemophilia and von Willebrand&#39;s disease. Platelets and white blood cells, which are found in the buffy layer component, can be used to treat patients with abnormal platelet function (thrombocytopenia) and patients that are unresponsive to antibiotic therapy, respectively. 
     Various techniques and apparatus have been developed to facilitate the collection of whole blood and the subsequent separation of therapeutic components therefrom. Centrifugal systems, also referred to as blood-processing systems, generally fall into two categories, discontinuous-flow and continuous-flow devices. 
     In discontinuous-flow systems, whole blood from the donor or patient flows through a conduit into the rotor or bowl where component separation takes place. These systems employ a bowl-type rotor with a relatively large (typically 200 ml or more) volume that must be filled with blood before any of the desired components can be harvested. When the bowl is full, the drawing of fresh blood is stopped, the whole blood is separated into its components by centrifugation, and the unwanted components are returned to the donor or patient through the same conduit intermittently, in batches, rather than on a continuous basis. When the return has been completed, whole blood is again drawn from the donor or patient, and a second cycle begins. This process continues until the required amount of the desired component has been collected. 
     Discontinuous-flow systems have the advantage that the rotors are relatively small in diameter but have the disadvantage that the extracorporeal volume (i.e., the amount of blood that is out of the donor at any given time during the process) is large. This, in turn, makes it difficult or impossible to use discontinuous systems on people whose size and weight will not permit the drawing of the amount of blood required to fill the rotor. Discontinuous-flow devices are used for the collection of platelets and/or plasma, and for the concentration and washing of red blood cells. They are used to reconstitute previously frozen red blood cells and to salvage red blood cells lost intraoperatively. Because the bowls in these systems are rigid and have a fixed volume, however, it is difficult to control the hematocrit of the final product, particularly if the amount of blood salvaged is insufficient to fill the bowl with red blood cells. 
     One example of a discontinuous-flow system is disclosed by McMannis, et al., in his U.S. Pat. No. 5,316,540, and is a variable volume centrifuge for separating components of a fluid medium, comprising a centrifuge that is divided into upper and lower chambers by a flexible membrane, and a flexible processing container bag positioned in the upper chamber of the centrifuge. The McMannis, et al., system varies the volume of the upper chamber by pumping a hydraulic fluid into the lower chamber, which in turn raises the membrane and squeezes the desired component out of the centrifuge. The McMannis, et al., system takes up a fairly large amount of space, and its flexible pancake-shaped rotor is awkward to handle. The McMannis, et al., system does not permit the fluid medium to flow into and out of the processing bag at the same time, nor does it permit fluid medium to be pulled out of the processing bag by suction. 
     In continuous-flow systems, whole blood from the donor or patient also flows through one conduit into the spinning rotor where the components are separated. The component of interest is collected and the unwanted components are returned to the donor through a second conduit on a continuous basis as more whole blood is being drawn. Because the rate of drawing and the rate of return are substantially the same, the extracorporeal volume, or the amount of blood that is out of the donor or patient at any given time in the procedure, is relatively small. These systems typically employ a belt-type rotor, which has a relatively large diameter but a relatively small (typically 100 mL or less) processing volume. Although continuous-flow systems have the advantage that the amount of blood that must be outside the donor or patient can be relatively small, they have the disadvantage that the diameter of the rotor is large. These systems are, as a consequence, large. Furthermore, they are complicated to set up and use. These devices are used almost exclusively for the collection of platelets. 
     Continuous-flow systems are comprised of rotatable and stationary parts that are in fluid communication. Consequently, continuous-flow systems utilize either rotary seals or a J-loop. A variety of types of rotary centrifuge-seals have been developed. Some examples of rotary centrifuge seals which have proven to be successful are described in U.S. Pat. Nos. 3,409,203 and 3,565,330, issued to Latham. In these patents, rotary seals are disclosed which are formed from a stationary rigid low friction member in contact with a moving rigid member to create a dynamic seal, and an elastomeric member which provides a resilient static seal as well as a modest closing force between the surfaces of the dynamic seal. 
     Another rotary seal suitable for use in blood-processing centrifuges is described in U.S. Pat. No. 3,801,142 issued to Jones, et al. In this rotary seal, a pair of seal elements having confronting annular fluid-tight sealing surfaces of non-corrodible material are provided. These are maintained in a rotatable but fluid-tight relationship by axial compression of a length of elastic tubing forming one of the fluid connections to these seal elements. 
     Related types of systems, which incorporate rotatable, disposable annular separation chambers, coupled via rotary seals to stationary tubing members are disclosed in U.S. Pat. Nos. 4,387,848; 4,094,461; 4,007,871; and 4,010,894. 
     One drawback present in the above-described continuous-flow systems has been their use of a rotating seal or coupling element between that portion of the system carried by the centrifuge rotor and that portion of the system which remains stationary. While such rotating seals have provided generally satisfactory performance, they have been expensive to manufacture and have unnecessarily added to the cost of the flow systems. Furthermore, such rotating seals introduce an additional component into the system which if defective can cause contamination of the blood being processed. 
     One flow system heretofore contemplated to overcome the problem of the rotating seal utilizes a rotating carriage on which a single housing is rotatably mounted. An umbilical cable extending to the housing from a stationary point imparts planetary motion to the housing and thus prevents the cable from twisting. To promote the desired ends of sterile processing and avoid the disadvantages of a discontinuous-flow system within a single sealed system, a family of dual member centrifuges can be used to effect cell separation. One example of this type of centrifuge is disclosed in U.S. Pat. No. RE 29,738 to Adams entitled “Apparatus for Providing Energy Communication Between a Moving and a Stationary Terminal.” As is now well known, due to the characteristics of such dual member centrifuges, it is possible to rotate a container containing a fluid, such as a unit of donated blood and to withdraw a separated fluid component, such as plasma, into a stationary container, outside of the centrifuge without using rotating seals. Such container systems utilize a J-loop and can be formed as closed, sterile transfer sets. 
     The Adams patent discloses a centrifuge having an outer rotatable member and an inner rotatable member. The inner member is positioned within and rotatably supported by the outer member. The outer member rotates at one rotational velocity, usually called “one omega,” and the inner rotatable member rotates at twice the rotational velocity of the outer housing or “two omega.” There is thus a one-omega difference in rotational speed of the two members. For purposes of this document, the term “dual member centrifuge” shall refer to centrifuges of the Adams type. 
     The dual member centrifuge of the Adams patent is particularly advantageous in that, as noted above, no seals are needed between the container of fluid being rotated and the non-moving component collection containers. The system of the Adams patent provides a way to process blood into components in a single, sealed, sterile system wherein whole blood from a donor can be infused into the centrifuge while the two members of the centrifuge are being rotated. 
     An alternate to the apparatus of the Adams patent is illustrated in U.S. Pat. No. 4,056,224 to Lolachi entitled “Flow System for Centrifugal Liquid Processing Apparatus.” The system of the Lolachi patent includes a dual member centrifuge of the Adams type. The outer member of the Lolachi centrifuge is rotated by a single electric motor which is coupled to the internal rotatable housing by belts and shafts. 
     U.S. Pat. No. 4,108,353 to Brown entitled “Centrifugal Apparatus With Oppositely Positioned Rotational Support Means” discloses a centrifuge structure of the Adams type which includes two separate electrical motors. One electric motor is coupled by a belt to the outer member and rotates the outer member at a desired nominal rotational velocity. The second motor is carried within the rotating exterior member and rotates the inner member at the desired higher velocity, twice that of the exterior member. 
     U.S. Pat. No. 4,109,855 to Brown, et al., entitled “Drive System For Centrifugal Processing Apparatus” discloses yet another drive system. The system of the Brown, et al., patent has an outer shaft, affixed to the outer member for rotating the outer member at a selected velocity. An inner shaft, coaxial with the outer shaft, is coupled to the inner member. The inner shaft rotates the inner member at twice the rotational velocity as the outer member. A similar system is disclosed in U.S. Pat. No. 4,109,854 to Brown entitled “Centrifugal Apparatus With Outer Enclosure.” 
     The continuous-flow systems described above are large and expensive units that are not intended to be portable. Further, they are also an order of magnitude more expensive than a standard, multi-container blood collection set. There exists the need, therefore, for a centrifugal system for processing blood and other biological fluids that is compact and easy to use and that does not have the disadvantages of prior-art continuous-flow systems. 
     Whole blood that is to be separated into its components is commonly collected into a flexible plastic donor bag, and the blood is centrifuged to separate it into its components through a batch process. This is done by spinning the blood bag for a period of about 10 minutes in a large refrigerated centrifuge. The main blood constituents, i.e., red blood cells, platelets and white cells, and plasma, having sedimented and formed distinct layers, are then expressed sequentially by a manual extractor in multiple satellite bags attached to the primary bag. 
     More recently, automated extractors have been introduced in order to facilitate the manipulation. Nevertheless, the whole process remains laborious and requires the separation to occur within a certain time frame to guarantee the quality of the blood components. This complicates the logistics, especially considering that most blood donations are performed in decentralized locations where no batch processing capabilities exist. 
     This method has been practiced since the widespread use of the disposable plastic bags for collecting, blood in the 1970&#39;s and has not evolved significantly since then. Some attempts have been made to apply haemapheresis technology in whole blood donation. This technique consists of drawing and extracting on-line one or more blood components while a donation is performed, and returning the remaining constituents to the donor. However, the complexity and costs of haemapheresis systems preclude their use by transfusion centers for routine whole blood collection. 
     There have been various proposals for portable, disposable, centrifugal apparatus, usually with collapsible bags, for example as in U.S. Pat. Nos. 3,737,096, or 4,303,193 to Latham, Jr., or with a rigid walled bowl as in U.S. Pat. No. 4,889,524 to Fell, et al. These devices all have a minimum fixed holding volume which requires a minimum volume usually of about 250 ml to be processed before any components can be collected. 
     U.S. Pat. No. 5,316,540 to McMannis, et al. discloses a centrifugal processing apparatus, wherein the processing chamber is a flexible processing bag which can be deformed to fill it with biological fluid or empty it by means of a membrane which forms part of the drive unit. The bag comprises a single inlet/outlet tubing for the introduction and removal of fluids to the bag, and consequently cannot be used in a continual, on-line process. Moreover, the processing bag has a the disadvantage of having 650 milliliter capacity, which makes the McMannis, et al., device difficult to use as a blood processing device. 
     As discussed above, centrifuges are often used to separate blood into its components for use in a variety of therapeutic regimens. One such application is the preparation of a bioadhesive sealant. Bioadhesive sealants, also referred to as fibrin glues, are a relatively new technological advance which attempt to duplicate the biological process of the final stage of blood coagulation. Clinical reports document the utility of fibrin glue in a variety of surgical fields, such as, cardiovascular, thoracic, transplantation, head and neck, oral, gastrointestinal, orthopedic, neurosurgical, and plastic surgery. At the time of surgery, the two primary components comprising the fibrin glue, fibrinogen and thrombin, are mixed together to form a clot. The clot is applied to the appropriate site, where it adheres to the necessary tissues, bone, or nerve within seconds, but is then slowly reabsorbed by the body in approximately 10 days by fibrinolysis. Important features of fibrin glue is its ability to: (1) achieve haemostasis at vascular anastomoses particularly in areas which are difficult to approach with sutures or where suture placement presents excessive risk; (2) control bleeding from needle holes or arterial tears which cannot be controlled by suturing alone; and (3) obtain haemostasis in heparinized patients or those with coagulopathy. See, Borst, H. G., et al.  J. Thorac. Cardiovasc. Surg.,  84:548-553 (1982); Walterbusch, G. J., et al.,  Thorac. Cardiovasc. Surg.,  30:234-23 5 (1982); and Wolner, F. J., et al.,  Thorac. Cardiovasc. Surg.,  30:236-237 (1982). 
     Despite the effectiveness and successful use of fibrin glue by medical practitioners in Europe, neither fibrin glue nor its essential components fibrinogen and thrombin are widely used in the United States. In large part, this stems from the 1978 U.S. Food and Drug Administration ban on the sale of commercially prepared fibrinogen concentrate made from pooled donors because of the risk of transmission of viral infection, in particular the hepatitis-causing viruses such as HBV and HCV (also known as non-A and non-B hepatitis virus). In addition, the more recent appearance of other lipid-enveloped viruses such as HIV, associated with AIDS, cytomegalovirus (CMV), as well as Epstein-Barr virus and the herpes simplex viruses in fibrinogen preparations makes it unlikely that there will be a change in this policy in the foreseeable future. For similar reasons, human thrombin is also not currently authorized for human use in the United States; Bovine thrombin, which is licensed for human use in the United States, is obtained from bovine sources which do not appear to carry significant risks for HIV and hepatitis, although other bovine pathogens, such as bovine spongiform and encephalitis, may be present. 
     There have been a variety of methods developed for preparing fibrin glue. For example, Rose, et al. in U.S. Pat. No. 4,627,879 discloses a method of preparing a cryoprecipitated suspension containing fibrinogen and Factor XIII useful as a precursor in the preparation of a fibrin glue which involves (a) freezing fresh frozen plasma from a single donor such as a human or other animal, e.g. a cow, sheep or pig, which has been screened for blood transmitted diseases, e.g. one or more of syphilis, hepatitis or acquired immune deficiency syndrome, at about 80° C. for at least about 6 hours, preferably for at least about 12 hours; (b) raising the temperature of the frozen plasma, e.g. to between about 0° C. and room temperature, so as to form a supernatant and a cryoprecipitated suspension containing fibrinogen and Factor XIII; and (c) recovering the cryoprecipitated suspension. The fibrin glue is then prepared by applying a defined volume of the cryoprecipitate suspension described above and applying a composition containing a sufficient amount of thrombin, e.g. human, bovine, ovine or porcine thrombin, to the site so as to cause the fibrinogen in the suspension to be converted to the fibrin glue which then solidifies in the form of a gel. 
     A second technique for preparing fibrin glue is disclosed by Marx in his U.S. Pat. No. 5,607,694. Essentially, a cryoprecipitate as discussed previously serves as the source of the fibrinogen component and then Marx adds thrombin and liposomes. A third method discussed by Berruyer, M., et al., ( J. Thorac. Cardiovasc. Surg.,  105(5):892-897 (1992)) discloses a fibrin glue prepared by mixing bovine thrombin not only with human coagulant proteins, such as fibrinogen, fibronectin, Factor XIII, and plasminogen, but also with bovine aprotinin and calcium chloride. 
     The above patents by Rose, et al. and Marx, and the technical paper by Berruyer, et al. each disclose methods for preparing fibrin sealants; however, each of these methods suffer disadvantages associated with the use of bovine thrombin as the activating agent. A serious and life threatening consequence associated with the use of fibrin glues comprising bovine thrombin is that patients have been reported to have a bleeding diathesis after receiving topical bovine thrombin. This complication occurs when patients develop antibodies to the bovine factor V in the relatively impure bovine thrombin preparations. These antibodies cross-react with human factor V, thereby causing a factor V deficiency that can be sufficiently severe to induce bleeding and even death. See, Rapaport, S.I., et al.  Am. J. Clin. Pathol.,  97:84-91 (1992); Berruyer, M., et al.  J. Thorac. Cardiovasc. Surg.,  105:892-897 (1993); Zehnder, J., et al.,  Blood,  76(10):2011-2016 (1990); Muntean, W., et al.,  Acta Paediatr.,  83:84-7 (1994); Christine, R.J., et al.,  Surgery,  127:708-710 (1997). 
     A further disadvantage associated with the methods disclosed by Marx and Rose, et al. is that the cryoprecipitate preparations require a large amount of time and monetary commitment to prepare. Furthermore, great care must be taken to assure the absence of any viral contaminants. 
     A further disadvantage associated with the methods previously disclosed is that while human thrombin is contemplated for use as an activator, human thrombin is not available for clinical use and there is no evidence that patients will not have an antigenic response to human thrombin. By analogy, recombinant human factor VIII has been shown to produce antigenic responses in hemophiliacs. See, Biasi, R. de.,  Thrombosis and Haemostasis,  71(5):544-547 (1994). Consequently, until more clinical studies are performed on the effect of human recombinant thrombin one cannot merely assume that the use of recombinant human thrombin would obviate the antigenic problems associated with bovine thrombin. A second difficulty with thrombin is that it is autocatalytic, that is, it tends to self-destruct, making handling and prolonged storage a problem. 
     Finally, as discussed above, fibrin glue is comprised primarily of fibrinogen and thrombin thus lacking an appreciable quantity of platelets. Platelets contain growth factors and healing factors which are assumed to be more prevalent in a platelet concentrate. Moreover, platelets aid in acceleration of the clotting process. 
     There is still a need, therefore, for a centrifugal system for processing blood and other biological fluids, that is compact and easy to use and that does not have the disadvantages of prior-art continuous-flow systems and furthermore there exists a need for a convenient and practical method for preparing a platelet gel composition wherein the resulting platelet gel poses a zero risk of disease transmission and a zero risk of causing an adverse physiological reaction. 
     There is also a widespread need for a system that, during blood collection, will automatically separate the different components of whole blood that are differentiable in density and size, with a simple, low cost, disposable unit. 
     There is further a need for a centrifugal cell processing system wherein multiple batches of cells can be simultaneously and efficiently processed without the use of rotational coupling elements. 
     There is yet a further need for a platelet concentrate that aids in increasing the rate of fibrin clot formation, thereby facilitating haemostasis. 
     Preferably the apparatus will be essentially self-contained. Preferably, the equipment needed to practice the method will be relatively inexpensive and the blood contacting set will be disposable each time the whole blood has been separated. 
     SUMMARY OF THE INVENTION 
     Accordingly, one aspect of this invention provides a method and apparatus for the separation of components suspended or dissolved in a fluid medium by centrifugation. More specifically, one object of this invention is to provide a method for the separation and isolation of one or more whole blood components, such as platelet rich plasma, white blood cells and platelet poor plasma, from anticoagulated whole blood by centrifugation, wherein the components are isolated while the centrifuge is rotating. 
     Another aspect of this invention is to utilize the isolated cell components in a therapeutic regimen. 
     Another aspect of this invention provides an apparatus for the separation of whole blood components, wherein the apparatus contains a centrifuge bag that provides for simultaneous addition of whole blood from a source container and the withdrawal of a specific blood component during centrifugation. 
     Another aspect of this invention provides disposable, single-use centrifuge bags for holding whole blood during the separation of components of the whole blood by centrifugation, wherein the bag is adapted for use in a portable, point-of-use centrifuge. 
     Another aspect of this invention provides a portable centrifuge containing a disposable centrifuge bag that maximizes the amount of a predetermined blood fraction that can be harvested from an aliquot of blood that is of greater volume than the capacity of the disposable centrifuge bag. 
     More specifically, one embodiment of this invention comprises a flexible, disposable centrifuge bag adapted to be rotated about an axis, comprising: 
     a) one or more tubes, and 
     b) upper and lower flexible sheets, each sheet having a doughnut shaped configuration, an inner perimeter defining a central core and an outer perimeter, wherein the upper and lower sheets are superimposed and completely sealed together at their outer perimeters, and wherein the tubes are sandwiched between the upper and lower sheets and extend from the central core toward the outer perimeter, such that when the upper and lower sheets are sealed at the inner perimeter the tubes are sealed between the upper and lower sheets at the inner perimeter and are in fluid communication with the environment inside and outside the centrifuge bag. The one or more tubes are fluidly connected to a umbilical cable comprising one or more lumen equal to the number of tubes of the centrifuge bag. 
     Yet another embodiment of the present invention comprises a rigid molded container adapted to be rotated about an axis, comprising a rigid, annular body having an axial core that is closed at the top end and opened at the bottom end. The rigid molded container further comprises an interior collection chamber for receiving and holding a fluid medium to be centrifuged, the chamber having an outer perimeter, an inner perimeter, and a generally off-centered “figure eight” shaped cross-sectional area. The rigid molded container further comprises a first channel which extends radially from the core and is in fluid communication with a point near the outer perimeter of the chamber, and a second channel which extends radially from the core and is in fluid communication with an area near the narrow portion or “neck” of the figure eight-shaped chamber. The first and second channels thus provide fluid communication with the environment inside and outside the interior collection chamber. The first and second channels are fluidly connected to a dual lumen tubing having an inlet lumen and an outlet lumen. 
     Yet another embodiment of the present invention is an apparatus and method for separating components contained in a fluid medium. More particularly, the present invention utilizes the principles of centrifugation to allow for the separation of whole blood into fractions such as platelet rich plasma and platelet poor plasma. In one aspect of the present invention, the above-described separation of the components is provided by utilizing a rotatable centrifuge motor comprising a base having a central column and a disposable centrifuge bag having a central core and which is positionable within the centrifuge motor and rotatable therewith. The disposable centrifuge bag, which holds the whole blood during centrifugation, further comprises an inlet tube for introducing the whole blood to the centrifuge bag, and an outlet tube for removing the desired blood fraction from the centrifuge bag. The inlet and outlet tubes are in fluid communication with a dual lumen tubing. The centrifuge bag is removably fixed within the centrifuge rotor by inserting the raised column through the bag center core and securing with the cover. During the rotation of the centrifuge, components of the whole blood will assume a radial, horizontal position within the centrifuge bag based upon a density of such components, and thus the fluid medium components will be separated from other components having different densities. 
     Once a desired degree of separation of whole blood has been achieved, the present invention provides for the specific removal of the desired fraction within one or more of the regions from the centrifuge bag through the outlet tube during continued rotation of the centrifuge, thereby allowing for on-line removal of the desired fraction. Additional aliquots may be added to the centrifuge bag via the inlet tube simultaneously or after the desired component has been harvested. In one embodiment, the centrifuge bag is a flexible, transparent, generally flat doughnut-shaped bag. In another embodiment, the centrifuge bag is a rigid, transparent container having an interior chamber for receiving and holding the fluid medium during centrifugation, the interior chamber having a generally off-centered figure eight cross-sectional configuration. 
     Another aspect of the present invention comprises a disposable centrifuge bag having an inlet tube and an outlet tube, wherein the outlet tube is fluidly connected with a bent fitting. 
     Another aspect of the present invention comprises a centrifuge rotor for holding a centrifuge bag, the rotor comprising a base and a cover, the base further having a first grooved, raised center column and the cover having a second grooved, raised center column. The centrifuge bag is a flexible, doughnut-shaped bag comprising inlet and outlet tubes in fluid communication with the environment inside and outside the centrifuge bag, wherein the tubes are seated in the base and cover column grooves to hold the centrifuge bag in a fixed position relative to the base and cover, such that the bag does not spin independently of the base and cover but rather spins concurrently and at the same rate of rotation as the base and cover. 
     Another aspect of the present invention comprises a centrifuge rotor for holding a centrifuge bag, the rotor comprising a base and a cover for securing a centrifuge bag therebetween, the centrifuge cover fiber comprising one or more concentric indicator circles that are spaced from the center of the cover or the base to aid the operator in visualizing the distal ends of these tubes. 
     Another aspect of the present invention for the separation of components of a fluid medium (e.g., whole blood) utilizes a centrifuge rotor comprising an interior chamber having a complex configuration, wherein the chamber holds a flexible, doughnut-shaped centrifuge bag for retaining the fluid medium during centrifugation. The centrifuge rotor is defined by a base having a lower chamber, and a cover having an upper chamber. When the cover is superimposed on the base, the upper and lower chambers define the annular interior chamber of the rotor. The interior rotor chamber has a generally off-centered figure eight-shaped cross-sectional configuration specifically designed to maximize the collection of the desired component (e.g., platelet rich plasma) by centrifugation of a fluid medium (e.g., anticoagulated whole blood). The centrifuge bag is formed from a substantially flexible material, such that the profile of the centrifuge bag during centrifugation is thus determined at least in part by the volume of the fluid medium contained therein. When the centrifuge bag is filled to maximum capacity, it assumes the configuration of the interior of the rotor chamber. 
     Another aspect of this invention comprises a method for on-line harvesting of a predetermined component of a fluid medium. One embodiment of the present invention utilizes a centrifuge and a disposable centrifuge bag for containing the fluid medium during separation and which is positionable within the centrifuge, the centrifuge bag further comprising at least one inlet tube and at least one outlet tube. The centrifuge includes a centrifuge rotor having a base portion, a cover, and an outer rim. The base portion and the cover define the interior of the centrifuge rotor, which is separated into upper and lower chambers. The disposable centrifuge bag is positionable horizontally within the lower chamber and may be appropriately secured to the centrifuge base by the cover. The centrifuge bag is fluidly connected via a dual lumen tubing to a source (e.g., to a container comprising anticoagulated autologous whole blood) and collection container (e.g., for receiving platelet rich plasma or some other component that will then be further processed). The dual lumen tubing comprises an inlet lumen fluidly connected to the inlet tube of the centrifuge bag and an outlet lumen fluidly connected to the outlet tube of the centrifuge bag. The centrifuge bag is substantially annular relative to the rotational axis of the centrifuge. When the centrifuge bag is positioned within the centrifuge rotor and appropriately secured thereto to allow for simultaneous rotation, the fluid medium may be provided to the centrifuge bag via the inlet lumen of the tubing during rotation of the centrifuge. The components of the bag assume radial, horizontal positions base based on their densities. When a desired degree of separation has been achieved, the desired fraction may be removed from the centrifuge bag via the outlet lumen during continued rotation of the centrifuge. The position of the fraction to be harvested may be shifted into the area of the outlet tube as needed, either by withdrawing components that are positioned near the outer perimeter through the inlet tube, or by adding additional aliquots of the fluid medium to the bag. In one embodiment of this method, the bag is a flexible, transparent doughnut-shaped bag. In another embodiment of this method, the bag is a rigid, transparent bag comprising an interior chamber having an off-centered, figure eight cross-sectional configuration. 
     This invention further provides a centrifugal liquid processing system that may be automated. 
     This invention further provides a centrifuge having an internal lead drive mechanism allowing for a compact size. 
     This invention further provides a method and device for the production and isolation of thrombin for all medical uses. 
     This invention further provides a method for preparing a completely autologous platelet gel. 
     This invention further provides an autologous platelet gel wherein the risks associated with the use of bovine and recombinant human thrombin are eliminated. 
     This invention further provides an autologous platelet gel for any application. 
     This invention further provides cellular components to be used in medical applications. 
     Additional advantages and novel features of this invention shall be set forth in part in the description and examples that follow, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention. The aspects and the advantages of the invention may be further realized and attained by means of the instrumentalities and in combinations particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specifications, illustrate embodiments of the present invention, and together with the description serve to explain the principles of the invention. 
       In the Drawings: 
         FIG. 1  is a perspective view illustrating one embodiment of the continuous-flow centrifugal processing system of the present invention illustrating a centrifuge and side-mounted motor positioned within a protective housing or enclosure of the invention. 
         FIG. 2  is an exploded side view of the centrifuge and the side-mounted motor of the centrifugal processing system of  FIG. 1  illustrating the individual components of the centrifuge. 
         FIG. 3  is a partial perspective view of the lower case assembly of the drive shaft assembly of  FIG. 2 . 
         FIG. 4  is an exploded side view of the lower case assembly of  FIG. 3 . 
         FIG. 5  is an exploded perspective view of the components of the lower case assembly of  FIG. 3 . 
         FIG. 6  is a top view of the lower bearing assembly which is positioned within the lower case assembly of  FIG. 3 . 
         FIG. 7  is a perspective view of the lower bearing assembly of  FIG. 6 . 
         FIG. 8  is an exploded side view of the lower bearing assembly of  FIGS. 6 and 7 . 
         FIG. 9  is a perspective view of the receiving tube guide of the centrifuge of  FIG. 2 . 
         FIG. 10  is an exploded, perspective view of a gear of the mid-shaft gear assembly of  FIG. 2 . 
         FIG. 11  is a perspective view of the gear of  FIG. 10  as it appears assembled. 
         FIG. 12  is an exploded, perspective view of the top bearing assembly of the centrifuge of  FIG. 2 . 
         FIG. 13  is a perspective view of the top case shell of the top bearing assembly of  FIG. 12 . 
         FIG. 14  is a perspective view of the centrifuge of the present invention shown in  FIG. 1 , having a quarter section cut away along lines  14 - 14  of  FIG. 1 . 
         FIG. 15  is a perspective view of one embodiment of a centrifuge rotor base. 
         FIG. 16  is a perspective view of one embodiment of a centrifuge rotor cover. 
         FIG. 17  is a side cross-sectional view of one embodiment of a rotor of this invention taken along view lines  17  of  FIG. 14  for holding a disposable centrifuge bag, showing a dual lumen tubing connected to the bag. 
         FIG. 18  is a side cross-sectional view of one embodiment of a rotor of this invention taken along view lines  18  of  FIG. 1  for holding a disposable centrifuge bag, showing the grooved columns of the base and cover. 
         FIG. 19  is an enlarged perspective view similar to  FIG. 1  illustrating an alternate embodiment of a centrifuge driven by a side-mounted motor (with only the external drive belt shown). 
         FIG. 20  is a cutaway side view of the centrifuge of  FIG. 19  illustrating the internal pulley drive system utilized to achieve a desired drive ratio and illustrating the rotor base configured for receiving a centrifuge bag. 
         FIG. 21  is a cutaway side view similar to  FIG. 20  with the rotor base removed to better illustrate the top pulley and the location of both idler pulleys relative to the installed internal drive belt. 
         FIG. 22  is a sectional view of the centrifuge of  FIG. 20  further illustrating the internal pulley drive system an showing the routing of the centrifuge tube (or umbilical cable). 
         FIG. 23  is a top view of a further alternate centrifuge similar to the centrifuge of  FIG. 19  but including internal, separate bearing members (illustrated as four cam followers) that allows the inclusion of guide shaft to be cut through portions of the centrifuge for positioning of the centrifuge tube (or umbilical cable). 
         FIG. 24  is a perspective view similar to  FIG. 19  illustrating the centrifuge embodiment of  FIG. 23  further illustrating the guide slot and showing that the centrifuge can be driven by an external drive belt. 
         FIG. 25  is a top view of a flexible, disposable centrifuge bag of this invention. 
         FIG. 26  is a perspective view of a flexible, disposable centrifuge bag of this invention. 
         FIGS. 27 ,  28 ,  29 , and  30  are illustrations of bent fittings of this invention having “T” shaped, “curved T” shaped, “L” shaped, and “J” shaped configurations, respectively. 
         FIG. 31  is an illustration of an inlet and/or outlet tube of this invention. 
         FIG. 32  is a top view of a disposable centrifuge bag of this invention after the centrifugation of whole blood, showing the separated blood components. 
         FIGS. 33-39  are schematic illustrations of one method of this invention for separating whole blood components using a disposable centrifuge bag of this invention. 
         FIG. 40  is a top view of an alternate embodiment of a disposable centrifuge bag of the present invention having inner and outer chambers. 
         FIG. 41  is a top view of the disposable centrifuge bag shown in  FIG. 34  illustrating movement of the red blood cell layer from the outer perimeter toward the inner perimeter. 
         FIG. 42  is a bottom view of an alternate embodiment of a disposable centrifuge bag of the present invention having inner and outer chambers in fluid communication with outlet and inlet ports. 
         FIG. 43  is a side cross-sectional view of a rigid disposable centrifuge bag of this invention. 
         FIG. 44  is a schematic illustration of separated blood components contained in a centrifuge bag having an elliptical cross-sectional view of the centrifuge bag shown in  FIG. 43 . 
         FIG. 45  is a side cross-sectional view of a rigid disposable centrifuge bag of this invention. 
         FIG. 46  is a schematic illustration of the surface areas and various dimensions of the figure eight configuration as shown in  FIG. 45 . 
         FIG. 47  is a schematic illustration of separated blood components contained in a centrifuge bag having a figure eight side cross-sectional configuration. 
         FIG. 48  is a side cross-sectional view of an alternative embodiment of an assembled centrifuge rotor of this invention comprising the rotor cover of  FIG. 49  and the rotor base of  FIG. 50 . 
         FIG. 49  is a side cross-sectional view of an alternative embodiment of a rotor cover of this invention. 
         FIG. 50  is a side cross-sectional view of an alternative embodiment of a rotor base of this invention. 
         FIG. 51  is a perspective view of the rotor base of  FIG. 50 . 
         FIG. 52  is a perspective view of the rotor cover of  FIG. 49 . 
         FIG. 53  is a block diagram illustrating the components of a centrifugal processing system of the present invention. 
         FIG. 54  is a graph illustrating the timing and relationship of transmission of control signals and receipt of feedback signals during operation of one embodiment of the automated centrifugal processing system of  FIG. 53 . 
         FIG. 55  is a side view of an alternative embodiment of the automated centrifugal processing system of  FIG. 53  showing a centrifuge having a rotor wherein the reservoir extends over the outer diameter of the centrifuge portion that facilitates use of an externally positioned sensor assembly. 
         FIG. 56  is a side view of a further alternative embodiment of the external sensor assembly feature of the centrifugal processing system of the invention without an extended rotor and illustrating the positioning of a reflector within the centrifuge. 
         FIG. 57  is a side view of yet another embodiment of the external sensor assembly feature of the centrifugal processing system of the invention illustrating a single radiant energy source and detector device. 
         FIG. 58  is a block diagram of a an automated centrifugal processing system, similar to the embodiment of  FIG. 47 , including components forming a temperature control system for controlling temperatures of separated and processed products. 
         FIG. 59  is a perspective view of components of the temperature control system of  FIG. 58 . 
         FIG. 60  is, schematic and sectional view of the dispenser of the present invention. 
         FIG. 61  is a flow diagram representing the method for isolating platelet rich plasma and platelet poor plasma for use in preparing a platelet gel of the present invention. 
         FIG. 62  is a flow diagram representing the final portion of the method for preparing a platelet gel of the present invention using platelet rich plasma as a starting material. 
         FIG. 63  is a flow diagram representing the final portion of the method for preparing a platelet gel of the present invention using platelet poor plasma as a starting material. 
         FIG. 64  is a graphic representation of the effect that the serum-to-plasma ratio has on clotting times. 
         FIG. 65  graphically represents the effect of calcium addition on the clotting times of platelet rich plasma and platelet poor plasma. 
         FIG. 66  is a graphic representation of the relationship between clotting time and actual gel time using blood drawn from a donor. 
         FIG. 67  is a graphic representation of the relationship between clotting time and actual gel time using blood drawn from a donor. 
         FIG. 68  graphically represents the effect of calcium addition on clotting times and gel times using blood drawn from a donor. 
         FIG. 69  graphically represents the effect of calcium addition on clotting times and gel times using blood drawn from a donor. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The centrifugal processing system  10  of the present invention is best shown in  FIG. 1  having a stationary base  12 , a centrifuge  20  rotatably mounted to the stationary base  12  for rotation about a predetermined axis A, a rotor  202  for receiving a disposable bag (not shown) designed for continuous-flow. As illustrated, the centrifugal processing system  10  includes a protective enclosure  11  comprising the main table plate or stationary base  12 , side walls  13 , and a removable lid  15  made of clear or opaque plastic or other suitable materials to provide structural support for components of the centrifugal processing system  10 , to provide safety by enclosing moving parts, and to provide a portable centrifugal processing system  10 . The centrifugal processing system  10  further includes a clamp  22  mounted over an opening (not shown) in the lid  15 . Clamp  22  secures at a point at or proximately to axis A without pinching off the flow of fluid that travels through umbilical cable  228 . A side mounted motor  24  is provided and connected to the centrifuge  20  by way of a drive belt  26  for rotating the drive shaft assembly  28  (see  FIG. 2 ) and the interconnected and driven rotor assembly  200  in the same rotational direction with a speed ratio selected to control binding of umbilical cable  228  during operation of the system, such as a speed ratio of 2:1 (i.e., the rotor assembly  200  rotates twice for each rotation of the drive shaft assembly  28 ). The present invention is further directed toward a dispensing device  902 , best shown in  FIG. 60  for the withdrawal and manipulation of specific blood components for various therapeutic regimens such as but not limited to the production of platelet rich plasma, platelet poor plasma, and white blood cells which may be used for the production of autologous thrombin and autologous platelet gels. 
     Referring now to  FIG. 2 , the continuous-flow centrifugal processing system  10  comprises a centrifuge  20  to which a rotor  202  is removably or non-removably attached. The design of centrifuge  20  and its self-contained mid-shaft gear assembly  108  (comprised of gears  110 ,  110 ′,  131 , and  74 ) is a key component of the invention thereby allowing for the compact size of the entire centrifugal processing system  10  and providing for a desired speed ratio between the drive shaft assembly  28  and the rotor assembly  200 . 
     The centrifuge  20  is assembled, as best seen in  FIG. 2 , by inserting the lower bearing assembly  66  into lower case shell  32  thus resulting in lower case assembly  30 . Cable guide  102  and gears  110  and  110 ′ are then positioned within lower case assembly  30 , as will be discussed in more detail below, so that gears  110  and  110 ′ are moveably of engaged with lower bearing assembly  66 . Upper bearing assembly  130  is then inserted within top case shell  126  thus resulting in bearing assembly  124  which is then mated to lower case assembly  30 , such that gears  110  and  110 ′ are also moveably engaged with upper bearing assembly  130 , and held in place by fasteners  29 . Lower bearing assembly  66  is journaled to stationary base or main table plate  12  by screws  14 , thus allowing centrifuge  20  to rotate along an axis A, perpendicular to main table plate  12  (as shown in  FIG. 1 ). 
     Referring now to  FIGS. 3 ,  4 , and  5 , the lower case assembly  30  is preferably, but not necessarily, machined or molded from a metal material and includes a lower case shell  32 , timing belt ring  46 , timing belt flange  50 , and bearing  62  (e.g., ball bearings and the like). Lower case shell  32  includes an elongated main body  40  with a smaller diameter neck portion  36  extending from one end of the main body  40  for receiving timing belt ring  46  and timing belt flange  50 . The larger diameter main body  40  terminates into the neck portion  36  thereby forming an external shoulder  38  having a bearing surface  42  for timing belt ring  46 . Timing belt ring  46  and timing belt flange  50 , as best seen in  FIG. 5 , have inner diameters that are slightly larger than the outer diameter of neck portion  36  allowing both to fit over neck portion  36 . Shoulder  38  further contains at least one and preferably four internally thread holes  44  that align with hole guides  48  and  52  in timing belt ring  46  and timing belt flange  50 , respectively (shown in  FIG. 5 ). Consequently, when assembled, screws  54  are received by hole guides  52  and  48  and are threaded into thread holes  44  thus securing timing belt  46  and timing belt flange  50  onto neck portion  36 . Lower case shell  32  also has an axial or sleeve bore  56  extending there through, and an internal shoulder  58 , the upper surface  60  of which is in approximately the same horizontal plane as external shoulder  38 . Bearing  62  (shown in  FIG. 4 ) is press fit concentrically into sleeve bore  56  so that it sits flush with upper surface  60 . Internal shoulder  58  also has a lower weight bearing surface  64  which seats on the upper surface  68  of lower bearing assembly  66 , shown in  FIGS. 6-8 . 
     Lower bearing assembly  66  comprises a lower gear insert  70 , ball bearings  84 , gear  74  and spring pins  76  and  76 ′. As will become clear, the gear  74  may be of any suitable gear design for transferring an input rotation rate to a mating or contacting gear, such as the gears  110 ,  110 ′ of the mid-shaft gear assembly  108 , with a size and tooth number selected to provide a desired gear train or speed ratio when combined with contacting gears. For example, the gear  74  may be configured as a straight or spiral bevel gear, a helical gear, a worm gear, a hypoid gear, and the like out of any suitable material. In a preferred embodiment, the gear  74  is a spiral gear to provide a smooth tooth action at the operational speeds of the centrifugal processing system  10 . The upper surface  68  of lower gear insert  70  comprises an axially positioned sleeve  72 , which receives and holds gear  74 . gear  74  is preferably retained within sleeve  72  by the use of at least one and preferably two spring pins  76  and  76 ′ which are positioned within spring pinholes  73  and  73 ′ extending horizontally through lower gear insert  70  into sleeve  72 . Thus, when gear  74  having spring pin receptacles  77  and  77 ′ is inserted into sleeve  72  the spring pins  76  and  76 ′ enter the corresponding receptacles  77  and  77 ′ thus holding the gear  74  in place. Of course, other assembly techniques may be used to position and retain gear  74  within the lower gear assembly  66  and such techniques are considered within the breadth of this disclosure. For example, gear  74  may be held in sleeve  72  by a number of other methods, such as, but not limited to being press fit or frictionally fit, or alternatively gear  74  and lower gear insert  70  may be molded from a unitary body. 
     The base  78  of lower gear insert  70  has a slightly larger diameter than upper body  80  of lower gear insert  70  as a result of a slight flare. This slight flare produces shoulder  82  upon which ball bearing  84  is seated. Once assembled lower bearing assembly  66  is received by sleeve bore  56  extending through neck portion  36  of lower case shell  32 . A retaining ring  86  is then inserted into the annular space produced by the difference of the outer diameter of the lower bearing assembly  66  and the inner diameter of sleeve bore  56  above ball bearings  84 . A second retaining ring  87  (shown in  FIG. 2 ) is also inserted into the annular space produced by the difference between the outer diameter of the lower bearing assembly  66  and the inner diameter of sleeve bore  56  below ball bearing  84 , thereby securing lower gear insert  70  within lower case shell  32 . Consequently, ball bearings  62  and  84  are secured by retaining rings  86  and  87 , respectively, resulting in lower case shell  32  being journaled for rotation about lower bearing assembly  66  but fixed against longitudinal and transverse movement thereon. Therefore, when assembled lower bearing assembly  66  is mounted to stationary base  12 , by securing screws  14  into threaded holes  79  located in the base  78 . Lower case shell  32  is thus able to freely rotate about stationary lower bearing assembly  66  when the drive belt  26  is engaged. 
     Referring now to  FIG. 5 , extending from the opposite end of neck portion  36  on lower case shell  32  are a number of protrusions or fingers  88 ,  90 ,  92 , and  94 . Positioned between protrusions  88  and  90 , and between protrusions  92  and  94  are recessed slots  96  and  98 , respectively, for receiving tube guide  102  ( FIG. 9 ). The function of tube guide  102  will be discussed in further detail below, but in short it guides umbilical cable  228  connected to centrifuge bag  226  through the mid-shaft gear assembly  108  and out of the centrifuge  20 . 
     Positioned between protrusions  90  and  92 , and between protrusions  88  and  94  are recessed slots  104  and  106 , respectively, for receiving gears  110  and  110 ′ of mid-shaft gear assembly  108  ( FIG. 2 ). The gears  110  and  110 ′ are preferably configured to provide mating contact with the gear  74  and to produce a desired, overall gear train ratio within the centrifuge  20 . In this regard, the gears  110  and  110 ′ are preferably selected to have a similar configuration (e.g., size, tooth number, and the like) as the gear  74 , such as a spiral gear design. As illustrated in  FIGS. 2 and 14  mid-shaft gear assembly  108  comprises a pair of gears  110  and  110 ′ engaged with gears  74  and  131 . While the construction of gears and gear combinations is well known to one skilled in the mechanical arts, a brief description is disclosed briefly herein. 
       FIG. 10  illustrates an exploded view depicting the assembly of gear  110 , and  FIG. 11  is a perspective view of the gear  110  of  FIG. 10  as it appears assembled. Gear  110 ′ is constructed in the same manner. Gear  111  is locked onto mid-gear shaft  112  using key stock  114  and external retaining ring  116 . Ball bearing  118  is then attached to mid gear shaft  112  using a flat washer  120  and cap screw  122 . Recessed slots  104  and  106  of lower case shell  32  then receive ball bearing  118  and  118 ′ (not shown). In an alternate embodiment ball bearing  118  can be replaced by bushings (not shown). When assembled, gears  110  and  110 ′ make contact with the lower gear  74  (see  FIGS. 2 and 14 ) to provide contact surfaces for transferring a force from the stationary gear  74  to the gears  110  and  110 ′ to cause the gears  110  and  110 ′ to rotate at a predetermined rate that creates a desired output rotation rate for the driven rotor assembly  200 . The rotor assembly  200  is driven by the drive shaft assembly  28  which is rotated by the drive motor  24  at an input rotation rate or speed, and in a preferred embodiment, the drive shaft assembly  28  through the use of the gears  110  and  110 ′ is configured to rotate the rotor assembly  200  at an output rotation rate that is twice the input rotation rate (i.e., the ratio of the output rotation rate to the input rotation rate is 2:1). This ratio is achieved in the illustrated embodiment by locking the gears  110  and  110 ′ located within the drive shaft assembly  28  to rotate about the centrifuge center axis, A, with the lower case shell  32  which is rotated by the drive motor  24 . The gears  110  and  110 ′ also contact the stationary gear  74  which forces the gears  110 ,  110 ′ to rotate about their rotation axes which are traverse to the centrifuge center axis, A, and as illustrated, the rotation axes of the gears  110 ,  110 ′ coincide. By rotating with the lower case shell  32  and rotating about the gear rotation axes, the gears  110 ,  110 ′ are able to provide the desired input to output rotation rate of 2:1 to the rotor assembly  200 . 
     In this regard, gears  110  and  110 ′ and tube guide  102  are locked into position by attaching top bearing assembly  124  to lower case assembly  30 . Top-bearing assembly  124  (as shown in  FIG. 12 ) comprises top case shell  126 , ball bearing  128 , and an upper bearing  130 . Top case shell  126 , as best seen in  FIGS. 12 and 13 , comprises an upper surface  132 , a lower lip  134  and a central or axial bore  136  there through. Upper surface  132  slightly overhangs axial bore  136  resulting in a shoulder  138  having a lower surface  140  (shown in  FIG. 13 ). Lower lip  134  is a reverse image of upper lip  100  on lower case shell  32  (shown in  FIG. 5 ). 
     Upper bearing assembly  130  ( FIG. 12 ) comprises an upper surface  133  and a lower surface  135  wherein the upper surface  133  has a means for receiving a rotor  202 . On the lower surface  135  a concentrically positioned column  137  protrudes radially outward perpendicular to lower surface  135 . Upper bearing assembly  130  further comprises an axially positioned bore  139  that traverses column  137  and upper surface  133  and receives upper gear insert  131 . Upper gear insert  131  also contains an axial bore  142  and thus when positioned concentrically within column  137  axial bores  139  and  142  allow for umbilical cable  228  to travel through upper bearing assembly  130  of top case shell  126  down to cable guide  102  (shown in  FIG. 14 ). As discussed previously with respect to lower bearing assembly  66 , upper gear insert  131  may be any suitable gear design for receiving an input rotation rate from a mating or contacting gear, such as the gears  110 ,  110 ′ of the mid-shaft gear assembly  108 , with a size and tooth number selected to provide a desired gear train or speed ratio when combined with contacting gears. For example, gear insert  131  may be configured as a straight or spiral bevel gear, a helical gear, a worm gear, a hypoid gear, and the like. In a preferred embodiment, gear  131  is a spiral gear to provide a smooth tooth action at the operational speeds of the centrifugal processing system  10 . Gear insert  131  is preferably retained within column  137  by use of at least one and preferably two spring pins (not shown); however, other assembly techniques may be used to position and retain the gear insert  131  within the column  137  and such techniques are considered within the breadth of this disclosure. For example, gear insert  131  may be held in column  137  by a number of other methods, such as, but not limited to being press fit or frictionally fit or alternatively gear insert  131  and the upper bearing assembly may be molded from a unitary body. 
     Upper bearing assembly  130  is then inserted into axial bore  136  of top case shell  126  so that the lower surface  135  sits flush with upper surface  132  of top case shell  126 . Ball bearing  128  is then inserted into the annular space created between the outer diameter of column  137  and the inner side wall  141  of top case shell  126  thereby securing upper bearing assembly  130  into place. 
     Referring now to  FIG. 13 , lower lip  134  is contoured to mate with protrusions  88 ,  90 ,  92  and  94  extending from lower case shell  32 . Specifically, the outer diameter of lower lip  134  matches the outer diameter of the upper end of main body  40  of lower case shell  32  and recesses  144  and  148  receive and retain protrusions  88  and  92  respectively, while recesses  146  and  150  receive and retain protrusions  94  and  88 , respectively. Holes are placed through each recess and each protrusion so that when assembled, fasteners  152  (shown in  FIG. 12 ) can be inserted through the holes thereby fastening the top bearing assembly  124  to the lower case assembly  30 . 
     Positioned between recesses  144  and  146  and between recesses  148  and  150  are recessed slots  104 ′ and  106 ′, respectively, for receiving gears  110  and  110 ′ of mid-shaft gear assembly  108  ( FIGS. 2 and 14 ). The gears  110  and  110 ′ are preferably configured to provide mating contact with the gear insert  131  and to produce a desired, overall gear train ratio within the centrifuge  20 . In this regard, the gears  110  and  110 ′ are preferably selected to have a similar configuration (e.g., size, tooth number, and the like) as the gear  131 , such as a spiral gear design. Furthermore recessed slots  96 ′ and  98 ′ exist between recesses  144  and  150  and between recesses  146  and  148 , respectively. When gears  110  and  110 ′ are assembled as shown in  FIG. 14 , recessed slots  96  and  96 ′ from the lower case shell- 32  and top case shell  126 , respectively, form port  154 , and recessed slots  98  and  98 ′ form port  156  thereby allowing the umbilical cable  228  to exit centrifuge  20  through either port  154  or  156 . Described above is one method of assembling the centrifugal processing system  10  of the present invention; however, those skilled in the art will appreciate that the lower case assembly  30  and upper bearing assembly can be joined in number of ways that allow the four gears to be properly aligned with respect to one another. 
     In the above manner, the centrifugal processing system  10  provides a compact, portable device useful for separating blood and other fluids in an effective manner without binding or kinking fluid feed lines, cables, and the like entering and exiting the centrifuge  20 . The compactness of the centrifugal processing system  10  is furthered by the use of the entirely contained and interior gear train described above that comprises, at least in part, gear  74 , gears  110  and  110 ′, and gear insert  131  of the upper bearing  130 . The gear insert  131  of the upper bearing  130  is preferably selected to provide a contact surface(s) with the gears  110  and  110 ′ that transfers the rotation-rate of the gears  110  and  110 ′ and consequently from gear  74  and to the gear insert  131  of the upper bearing  130 . In one preferred embodiment, the gear insert  131  of the upper bearing  130  is a spiral gear rigidly mounted within the upper bearing  130  to rotate the rotor assembly  200  and having a design similar to that of the spiral gear  74 , i.e., same or similar face advance, circular pitch, spiral angle, and the like. During operation, the gear  74  remains stationary as the lower case shell  32  is rotated about the centrifuge axis, A, at an input rotation rate, such as a rotation rate chosen from the range of 0 rpm to 5000 rpm. The gears  110 ,  110 ′ are rotated both about the centrifuge axis, A, with the shell  32  and by contact with the stationary gear  74 . The spiral gears  110 ,  110 ′ contact the gear insert  131  of the upper bearing  130  causing the gear insert  131  and connected upper bearing  130  to rotate at an output rotation rate that differs, i.e., is higher, than the input rotation rate. 
     Although a number of gear ratios or train ratios (i.e., input rotation rate/output rotation rate) may be utilized to practice the invention, one embodiment of the invention provides for a gear train ratio of 1:2, where the combination and configuration of the gear  74 , gears  110 ,  110 ′, and gear  131  of the upper bearing  130  are selected to achieve this gear train ratio. Uniquely, the rotation of the gears  110 ,  110 ′ positively affects the achieved gear train ratio to allow, in one embodiment, the use of four similarly designed gears which lowers manufacturing costs while achieving the increase from input to output rotation speeds. Similarly, as will be understood by those skilled in the mechanical arts, numerous combinations of gears in differing number, size, and configuration that provides this ratio (or other selected ratios) may be utilized to practice the invention and such combinations are considered part of this disclosure. For example, although two gears  110 ,  110 ′ are shown in the mid-shaft gear assembly  108  to distribute transmission forces and provide balance within the operating centrifuge, more (or less) gears may be used to transmit the rotation of gear  74  to the gear of the upper bearing  130 . Also, just as the number, size, and configuration of the internal gears may be varied from the exemplary illustration of  FIGS. 1-14 , the material used to fabricate the gear  74 , the gears  110 ,  110 ′, and the gear insert  131  may be any suitable gear material known in the art. 
     Another feature of the illustrated centrifugal processing system  10  that advantageously contributes to compactness is the side-mounted drive motor  24 . As illustrated in  FIGS. 1 and 2 , the drive motor  24  is mounted on the stationary base  12  of the enclosure  11  adjacent the centrifuge  20 . The drive motor  24  may be selected from a number of motors, such as a standard electric motor, useful for developing a desired rotation rate in the centrifuge  20  of the centrifugal processing system  10 . The drive motor  24  may be manually operated or, as in a preferred embodiment, a motor controller may be provided that can be automatically operated by a controller of the centrifugal processing system  10  to govern operation of the drive motor  24  (as will be discussed in detail with reference to the automated embodiment of the invention). As illustrated in  FIG. 1 , a drive belt  26  may be used to rotate the drive shaft assembly  28  (and, therefore, the rotor assembly  200 ). In this embodiment, the drive belt  26  preferably has internal teeth (although teeth are not required to utilize a drive belt) selected to mate with the external teeth of the timing belt ring  46  of the lower case assembly  30  portion of the drive shaft assembly  28 . The invention is not limited to the use of a drive belt  26 , which may be replaced with a drive chain, an external gear driven by the motor  24 , and any other suitable drive mechanisms. When operated at a particular rotation rate, the drive motor  24  rotates the drive shaft assembly  28  at nearly the same rotation rate (i.e., the input rotation rate). A single speed drive motor  24  may be utilized or in some embodiments, a multi and/or variable speed motor  24  may be provided to provide a range of input rotation rates that may be selected by the operator or by a controller to obtain a desired output rotation rate (i.e., a rotation rate for the rotor assembly  200  and included centrifuge bag  226 . 
     The present invention generally includes an apparatus and methods for the separation of a predetermined fraction(s) from a fluid medium utilizing the principles of centrifugation. Although the principles of the present invention may be utilized in a plurality of applications, one embodiment of this invention comprises isolating predetermined fraction(s) (e.g., platelet rich plasma or platelet poor plasma) from anticoagulated whole blood. The platelet rich plasma may be used, for example, in the preparation of platelet concentrate or gel, and more particularly may be used to prepare autologous platelet gel during surgery using blood drawn from the patient before or during surgery. 
     The centrifuge  20  has been discussed above and demonstrates the compact and portable aspects of the present invention. To complete the device of the present invention a fluid collection device, also referred to as a bowl or rotor  202  is attached to the upper surface  133  of the upper bearing assembly  130  as shown in  FIGS. 1 and 2 . Rotor  202  is preferably mounted permanently to upper bearing assembly  130 , however, rotor  202  may also be capable of being removed. Rotor  202  comprises a rotor base  204  (shown in  FIG. 15 ) having a lower annular groove  212 , and a rotor cover  206  having an upper annular groove  214 . As shown in  FIGS. 17 and 18  the annular interior chamber  216  of rotor  202  is defined by upper and lower annular grooves  212  and  214 . The lower annular  212  receives a centrifuge bag  226  for containing the fluid medium to be centrifuged. Centrifuge bag  226  is connected to supply and receiving containers  398 ,  400 , respectively, via umbilical cable  228  which is preferably, but not limited to a dual lumen. There may be instances where a certain technique requires multiple outlet or inlet ports and consequently umbilical cable  228  of the present invention may comprise multiple lumens. Umbilical cable  228  according to the preferred embodiment comprises inlet lumen  230  and outlet lumen  232  such that a fluid medium may be provided to and removed from the centrifuge bag  226  during rotation of the centrifuge rotor  202 . 
     One embodiment of centrifuge rotor  202  is more particularly illustrated in  FIGS. 15 ,  16 ,  17  and  18 .  FIG. 15  is a perspective view of rotor base  204 , and  FIG. 16  is a perspective view of rotor cover  206 .  FIG. 17  is a cross-sectional side view of rotor  202  taken along view lines  17  in  FIG. 1 , and  FIG. 18  is a cross-sectional side view of rotor  202  taken along view lines  18  in  FIG. 1 . As illustrated in  FIG. 15 , rotor base  204  comprises raised annular rim  208  and raised column  218  that is axially disposed in base  204 . Raised column  218  further has a groove  222  extending across the diameter of column  218 . Annular groove  212  is defined by raised annular rim  208  and raised column  218 . The height of rim  208  is equal to the height of column  218 . Rotor cover  206  shown in  FIG. 16  comprises raised annular rim  210  and raised column  220  which is axially disposed in rotor cover  206 . Raised column  220  further has a groove  224  extending across the diameter of column  220 . Annular groove  214  is defined by rim  210  and column  220 . The height of rim  210  is equal to the height of column  220 . 
     Generally, when centrifuge rotor  202  is to be assembled for use, a flexible centrifuge bag such as a doughnut-shaped centrifuge bag  226  ( FIGS. 19 and 20 ) having a center core  242  is placed in rotor base  204  such that center column  218  extends through the core  242  of centrifuge bag  226  and the centrifuge bag  226  lies in annular groove  212 . Rotor cover  206  is superimposed on rotor base  204  such that grooves  222  and  224  are aligned, as illustrated in  FIGS. 17 and 18 . When rotor cover  204  is secured to rotor base  206  by appropriate screws, fasteners, or the like (not shown), rims  208  and  210  are in complete contact with each other such that annular groove  212  and annular groove  214  define rotor interior chamber  216 . In one embodiment, columns  218  and  220  are in complete contact with each other. Alternatively, the inner perimeter  240  of centrifuge bag  226  is secured between columns  218  and  220  such that columns  218  and  220  do not completely physically contact each other. 
     With the above description of one embodiment of the centrifuge in mind, another preferred embodiment of a centrifuge for use in the centrifugal-processing system  10  will be described. Referring to  FIGS. 19-22 , a preferred embodiment of a centrifuge  640  is illustrated that utilizes a uniquely arranged internal pulley system to obtain a desired input to output drive ratio (such as 2:1, as discussed above) rather than an internal gear assembly. The centrifuge  640  utilizes the side-mounted motor  24  (shown in  FIG. 1 ) through drive belt  26  to obtain the desired rotation rate at the rotor portion of the centrifuge. 
     Referring first to  FIG. 19 , the centrifuge  640  includes a rotor base  644  (or top plate) with a recessed surface  648  for receiving and supporting a centrifuge bag during the operation of the centrifuge  640 . The rotor base  644  is rigidly mounted with fasteners (e.g., pins, screws, and the like) to a separately rotable portion (i.e., a top pulley  698  discussed with reference to  FIGS. 20 and 21 ) of a lower case shell  660 . A cable port  656  is provided centrally in the rotor base  644  to provide a path for a centrifuge tube or umbilical cable that is to be fluidically connected to a centrifuge bag positioned on the recessed surface  648  of the rotor base  644 . It is important during operation of the centrifuge  640  to minimize and control contact and binding of the umbilical cable and moving parts (such as drive belts and pulleys). In this regard, the lower case shell  660  includes a side cable port  662  for the umbilical cable to enter the centrifuge  640 , which, significantly, the side cable port  662  is located between idler pulleys  666 ,  668  to provide a spacing between any inserted tube or cable and the moving drive components of the centrifuge  640 . 
     Idler shaft or pins  664  are mounted and supported within the lower case shell  660  to allow the pins  664  to physically support the pulleys  666 ,  668 . The idler pulleys  666 ,  668  are mounted on the pins  664  by bearings to freely rotate about the central axis of the pins  664  during operation of the centrifuge  640 . The idler pulleys  666 ,  668  are included to facilitate translation of the drive or motive force provided or imparted by the drive belt  26  to the lower case shell  660  to the rotor base  644 , as will be discussed in more detail with reference to  FIGS. 20 and 21 , and to physically support the internal drive belt  670  within the centrifuge  640 . The drive belt  26  is driven by the side-mounted motor  24  (shown in  FIG. 1 ) and contacts the lower case shell  660  to force the lower case shell  660  to rotate about its central axis. The lower case shell  660  is in turn mounted on the base  674  in a manner that allows the lower case shell  660  to freely rotate on the base  674  as the drive belt  26  is driven by the side-mounted motor  26 . The base  674  is mounted to a stationary base  12  (shown in  FIG. 1 ) such that the base  674  is substantially rigid and does not rotate with the lower case shell  660 . 
     Referring now to  FIGS. 20-22 , the centrifuge  640  is shown with a cutaway view to more readily facilitate the discussion of the use of the internal pulley assembly to obtain a desired output to input ratio, such as two to one. As shown, the base  674  includes vibration isolators  676  fabricated of a vibration absorbing material such as rubber, plastic, and the like through which the base  674  is mounted relatively rigidly to the stationary base  12  (of  FIG. 1 ). The drive belt  26  from the side-mounted motor  24  (of  FIG. 1 ) contacts (frictionally or with the use of teeth and the like as previously discussed) a drive pulley  680 , which is rigidly mounted to the lower case shell  660 . As the drive belt  26  is driven by the motor  24 , the lower case shell  660  through drive pulley  680  rotates about its center axis (which corresponds to the center axis of the centrifuge  640 ). This rotation rate of the lower case shell  660  can be thought of as the input rotation rate or speed. 
     To obtain a desired, higher rotation rate at the rotor base  644 , the lower case shell  660  is mounted on the base to freely rotate about the centrifuge center axis with bearings  690  that mate with the base  674 . The bearings  690  are held in place between the bottom pulley  692  and the base  674 , and the bottom pulley  692  is rigidly attached (with bolts or the like) to the base  674  to remain stationary while the lower case shell  660  rotates. The illustrated bearings  690  are two-piece bearings which allow the lower case shell  660  to rotate on the base  674 . An internal drive belt  670  is provided and inserted through the lower case shell  660  to contact the outer surfaces of the bottom pulley  692 . The belt  670  preferably is installed with an adequate tension to tightly mate with the bottom pulley  692  such that frictional forces cause the belt  670  to rotate around the stationary bottom pulley  692 . This frictional mating can be enhanced using standard rubber belts or belts with teeth (and of course, other drive devices such as chains and the like may be substituted for the belt  670 ). 
     The internal drive belt  670  passes temporarily outside the centrifuge  640  to contact the outer surfaces of the idler pulleys  666  and  668 . These pulleys  666 ,  668  do not impart further motion to the belt  670  but rotate freely on pins  664 . The idler pulleys  666 ,  668  are included to allow the rotation about the centrifuge center axis by lower case shell  660  to be translated to another pulley (i.e.; top pulley  698 ) that rotates about the same axis. To this end, the idler pulleys  666 ,  668  provide non-rigid (or rotable) support that assists in allowing the belt  670  to be twisted without binding and then fed back into an upper portion of the lower case assembly  660  (as shown clearly in  FIGS. 20 and 21 ). As the internal drive belt  670  is fed into the lower case assembly  660 , the belt  670  contacts the outer surfaces of a top pulley  698 . 
     During operation of the centrifuge- 640 , the movement of the internal drive belt  670  causes the top pulley  698  to rotate about the centrifuge center axis. The idler pulleys  666  and  668  by the nature of their placement and orientation within the centrifuge  640  relative to the pulleys  692  and  698  cause the rotor base  644  to rotate in the same direction as the lower case shell  660 . Significantly, the top pulley  698  rotated about the centrifuge center axis at twice the input rotation rate because it is mounted to the lower case shell  660  via bearings  694  (preferably, a two piece bearing similar to bearings  690  but other bearing configurations can be used) which are mounted to the center shaft  686  of the lower case shell  660  to frictionally contact an inner surface of the top pulley  698 . Since the internal drive belt  670  is rotating about the bottom pulley  692  and the idler pulleys  666 ,  668  are rotating about the centrifuge central axis by drive belt  26 , the top pulley  698  is turned about the centrifuge central axis in the same direction as the lower case shell  660  but at twice the rate. 
     In other words, the drive force of the drive belt  26  and the internal drive belt  670  are combined by the components of the centrifuge  640  to create the output rotation rate. While a number of output to input drive ratios may be utilized, as discussed previously, a 2:1 ratio is generally preferable, and the centrifuge  640  is preferably configured such that the second, faster rotation rate of the top pulley  698  is substantially twice that of the lower case shell  660 . The use of an internal drive belt  670  in combination with two pulleys rotating about the same axis and the structural support for the pulleys within a rotating housing results in a centrifuge that is very compact and that operates effectively at a 2:1 drive ratio with relatively low noise levels (which is desirable in many medical settings). 
     The 2:1 drive ratio obtained in the top pulley  698  is in turn passed on to the rotor base  644  by rigidly attaching the rotor base  644  to the top pulley  698  with fasteners  652 . Hence, a centrifuge bag placed on the recessed surface  648  of the rotor base  644  is rotated at a rate twice that of the umbilical cable  228  that is fed into lower case shell  660 , which effectively controls binding as discussed above. The bearing  694  (one or more pieces) wrap around the entire center shaft  686  of the lower case shell  660 . To provide a path for the umbilical cord  228  to pass through the centrifuge  640  to the rotor base  644  (which during operation will be enclosed with a rotor top or cover as shown in  FIG. 1 ), the rotor base  644  includes the cable port  656  and the center shaft  686  is configured to be hollow to form a center cable guide. This allows an umbilical cable  228  to be fed basically parallel to the centrifuge center axis to the centrifuge bag (not shown). The lower case shell  660  includes the side cable port  662  to provide for initial access to the centrifuge  640  and also includes the side cable guide (or tunnel)  684  to guide the cable  228  through the lower case shell  660  to the hollow portion of the center shaft  686 . The side port  662  and the side cable guide  684  are positioned substantially centrally between the two idler pulleys  666 ,  668  to position the cable  228  a distance away from the internal drive belt  670  to minimize potential binding and wear. 
     The centrifuge  640  illustrated in  FIGS. 19-22  utilizes two-piece bearings for both the bottom and top pulleys  692  and  698 , respectively, and to provide a path for the umbilical cable  228  a central “blind” pathway (via side cable guide  684 , the hollow center of the center shaft  686 , and cable ports  656 ,  662 ) was provided in the centrifuge  640 . While effective, this “blind” pathway can in practice present binding problems as the relatively stiff cable  228  is fed or pushed through the pathway. To address this issue, an alternate centrifuge embodiment  700  is provided and illustrated in  FIGS. 23 and 24 . In this embodiment, the upper portions of the centrifuge  700  include a guide slot between the idler pulleys  666 ,  668  that enables an umbilical cable  228  to be fed into the centrifuge  700  from the top with the no components to block the view of the operator inserting the cable  228 . 
     To allow a guide slot to be provided, the contiguous upper bearing  694  in the centrifuge  640  are replaced with bearing members that have at least one gap or separation that is at least slightly larger than the outer diameter of the cable  228 . A number of bearing members may be utilized to provide this cable entry gap and are included in the breadth of this disclosure. As illustrated, the centrifuge  700  includes a rotor base  702  that is rigidly fastened with fasteners  704  to the top pulley  698  (not shown) to rotate with this pulley at the output rate (e.g., twice the input rate) and to receive and support a centrifuge bag on recessed surface  716 . The rotor base  702  further includes the cable port  718  which is useful for aligning the center of the bag and cable  228  with the center of the centrifuge  700 . 
     To allow ready insertion of the cable  228  in the centrifuge  700 , the rotor base  702  further includes a cable guide slot  712  which as illustrated is a groove or opening in the rotor base  702  that allows the cable  228  to be inserted downward through the centrifuge  700  toward the side cable guide  724  of the lower case shell  720 . The lower case shell  720  also includes a cable guide slot  722  cut through to the top of the side cable guide  724 . Again, the guide slots  712  and  724  are both located in a portion of the centrifuge  700  that is between the idler pulleys  666 ,  668  to position an inserted cable  228  from contacting and binding with the internal drive belt  670 , which basically wraps around 180 degrees of the top pulley or lower case shell  720 . 
     As shown in  FIG. 23 , the bearing members  706  are spaced apart and preferably, at least one of these spaces or gaps is large enough to pass through the cable  228  to the center shaft of the lower case shell  720 . As illustrated, four cam followers are utilized for the bearing members  706 , although a different number may be employed. The cam followers  706  are connected to the top pulley to enable the top pulley to rotate and are connected, also, to the center shaft of the lower case shell  720  to rotate with the lower case shell  720 . The cam followers  706  ride in a bearing groove  710  cut in the lower case shell  720 . To provide an unobstructed path for the cable  228 , the cable guide slots  712  and  722  are positioned between the two cam followers  706  adjacent the idler pulleys  666 ,  668 , and preferably the guide slots  712 ,  722  are positioned substantially centrally between the pulleys  666 ,  668 . The guide slots  712 ,  722  are positioned between these cam followers  706  to position the cable  228  on the opposite side of the centrifuge  700  as the contact-surfaces between the internal drive belt  670  and the top pulley  698  (shown in  FIG. 20-22 ). In this manner, the use of separated bearing members  706  in combination with a pair of cable guide slots  712 ,  722  allows an operator to readily install the umbilical cable  228  without having to blindly go through the inside of the drive system and minimizes binding or other insertion difficulties. 
     A. Flexible, Disposable Centrifuge Bag 
     One embodiment of disposable flexible centrifuge bag  226  is more particularly illustrated in  FIGS. 25 and 26  The bag is an integral two stage self-balancing disposable design. The disposable centrifuge bag  226  has a substantially flat, toroidal- or doughnut-shaped configuration having outer and inner perimeters  238  and  240 , respectively, and comprises radially extending upper and lower sheets  234 ,  236  formed from a substantially flexible material. The upper and lower sheets  234 ,  236  are superimposed and completely sealed together at outer perimeter  238  by a heat weld, rf (radio frequency) weld or other comparable method of adhering two surfaces. Inner perimeter  240  defines core  242  of bag  226 . In one embodiment of the invention, centrifuge bag  226  further comprises an inlet tube  248  sandwiched between upper and lower sheets  234 ,  236  and extending from the center of core  242  defined by inner perimeter  240  to the outer perimeter  238  and an outlet tube  250  sandwiched between upper and lower sheets  234 ,  236  and extending from the center of the core  242  to the outer perimeter  238 . When upper and lower sheets  234 ,  236  are sealed together at inner perimeter  240 , inlet and outlet tubes  248 ,  250  are thereby sealed therebetween. Inlet and outlet tubes  248 ,  250  are each in fluid communication with the interior of centrifuge bag  226  and the environment outside centrifuge bag  226 . The length of outlet tube  250  is shorter than the length of inlet tube  248 . 
     In one embodiment of this invention, outlet tube  250  is a straight tube as shown in  FIG. 31 . Alternatively, outlet tube  250  includes a bent fitting  252  fluidly connected to the distal end of outlet tube  250  ( FIGS. 25 and 26 ). The bent fitting  252  may be of any number of configurations, although preferably bent fitting  252  is shaped in the form of a “T”, “curved T”, a “J”, or an “L”, as illustrated in  FIGS. 27 ,  28 ,  29  and  30 , respectively. Alternatively, outlet tube  250  and bent fitting  252  may be one contiguous molded unit rather than two connected pieces. Preferably, bent fitting  252  is in the shape of a “T” or a “curved T” as illustrated in  FIGS. 27 and 28 , respectively. The “T” or “curved T” design of bent fitting  252  ensures that the desired blood component (fraction) will be removed from the sides of the bent fitting  252 , rather than from a fraction located above or below the bent fitting, as discussed below in detail. 
     When the centrifuge bag  226  is positioned in the annular groove  212  of the centrifuge rotor  202  as described above, it is critical that inlet and outlet tubes  248 ,  250  are seated in groove  222 . Further, when rotor cover  206  is positioned over and removably secured to the centrifuge base  204 , it is important that inlet and outlet tubes  248 ,  250  are also seated in groove  224 . Seating inlet and outlet tubes  248 ,  250  in grooves  222 ,  224  ensures that centrifuge rotor  202  is held in a fixed position between rotor base  204  and rotor cover  206  such that the centrifuge bag  226  and centrifuge rotor  202  rotate together. That is, the fixed position of centrifuge bag  226  ensures that centrifuge bag  226  will not rotate independently of centrifuge bag  226  during centrifugation. 
     Inlet and outlet tubes  248 ,  250  are fluidly connected at their proximal ends to umbilical cable  228 , which in this particular embodiment is a dual lumen tubing connecting centrifuge bag  226  to source and receiving containers  398 ,  400 , respectively, for the introduction and removal of components from the centrifuge bag  226  during centrifugation (see  FIG. 17 ). Dual lumen tubing  228  comprises inlet lumen  230 , which connects inlet tube  248  of centrifuge bag  226  with source container  398 , and outlet lumen  232 , which connects outlet tube  250  centrifuge bag  226  with receiving container  400 . In one embodiment, the inlet and outlet tubes  248 ,  250  are adapted at their proximal ends for inserting into the inlet and outlet lumens  230  and  232 , respectively. Alternatively, connecting means  254  are inserted into the proximal ends of inlet and outlet tubes  248 ,  250  for connecting the tubes to the inlet and outlet lumens  230 ,  232  as illustrated in  FIG. 26 . 
     In operation, one end of umbilical cable  228  must be secured to rotor assembly  200  to prevent itself from becoming twisted during rotation of rotor assembly  200  by the coaxial half-speed rotation of drive shaft assembly  28 , which imparts a like rotation with respect to the rotor  202  axis and consequently to the umbilical cable  228  that is directed through cable guide  102 . That is, if rotor assembly  200  is considered as having completed a first rotation of 360° and drive shaft assembly  28  as having completed a 180° half-rotation in the same direction, the umbilical cable  228  will be subjected to a 180° twist in one direction about its axis. Continued rotation of rotor assembly  200  in the same direction for an additional 360° and drive shaft assembly  28  for an additional 180° in the same direction will result in umbilical cable  228  being twisted 180° in the opposite direction, returning umbilical cable  228  to its original untwisted condition. Thus, umbilical cable  228  is subjected to a continuous flexture or bending during operation of the centrifugal processing system  10  of the present invention but is never completely rotated or twisted about its own axis. 
     An alternative embodiment of a disposable centrifuge bag of this invention, shown in  FIG. 35  comprises two or more inlet tubes and/or two or more outlet tubes, wherein the tubes are fluidly connected to a multiple lumen tubing. 
     The disposable centrifuge bag  226  is formed from a transparent, substantially flexible material, including but not limited to, polyvinyl chloride, polyethylene, polyurethane, ethylene vinyl acetate and combinations of the above or other flexible materials. Based upon the flexibility of the centrifuge bag  226 , the profile of the flexible centrifuge bag  226 , shown in  FIGS. 25 and 26 , is determined at least in part by the amount of fluid contained therein. The profile of centrifuge bag  226  is further defined by the interior configuration of the centrifuge rotor, as discussed below in detail. The ability to manipulate the profile of centrifuge bag  226  based on the interior configuration of the centrifuge rotor is utilized at least in part to maximize the volume of fluid medium that can be contained in centrifuge bag  226  during centrifugation, as will be discussed below. 
     The fluid or medium to be centrifuged may be contained within source container  300 . For example, when the centrifuge  20  of this invention is used to prepare an autologous platelet gel, the fluid (i.e., whole blood), may be withdrawn from the patient during or prior to surgery into source container  398  containing an anticoagulant. The anticoagulated whole blood is introduced to centrifuge bag  226  through inlet tube  248  via inlet lumen  230  after the centrifuge bag  226  has been positioned in the centrifuge rotor  202  and rotation thereof is initiated. As discussed above, securing centrifuge bag  226  in centrifuge base  204  in grooves  222 ,  224  holds the centrifuge bag  226  in a fixed position therebetween, such that the centrifuge bag  226  cannot move independently of the centrifuge rotor  202 , and therefore the centrifuge bag  226  and rotor assembly  200  rotate concurrently at the same rate of rotation. Rotation of the centrifuge rotor  202  directs the heavier density constituents of the anticoagulated whole blood within the centrifuge bag  226  toward the outer perimeter  238  of the bag  226 , while the lighter density constituents remain closer to an inner region, as illustrated in  FIG. 32 . More specifically, as illustrated in  FIG. 32 , when the fluid medium being separated is whole blood, the whole blood is separated within centrifuge bag  226  into a red blood cell fraction ( 256 ), a white blood cell fraction ( 258 ), a platelet rich plasma fraction ( 260 ), and a platelet poor plasma fraction ( 262 ). As will be appreciated by those of skill in the art, whole blood fractions, red blood cells and plasma are differently colored, and consequently the separation of the fractions can be easily detected by the operator. At an appropriate time during centrifuging, suction or other drawing means may be applied to the interior of centrifuge bag  226  via outlet lumen  232  to remove the desired fraction from the centrifuge bag  226 . In a further embodiment, centrifuge cover  206  may further contain concentric index lines to assist the operator in viewing the positions of outlet tube  250  to the RBC plasma interface. Based on the speeds and times the location of the WBC and platelets can be varied with respect to the interface between the red blood cells and plasma. For example, if the rpm is held low (approximately 1,000-1,700, preferably 1,500) the plasma and platelets will separate from the RBC layer, as the rpm&#39;s are increased (1,400-1,700) the platelets will separate out of the plasma and reside at the plasma to RBC interface in greater concentrations. With increased speeds, the WBC&#39;s reside deeper into the RBC pack. 
     With further regard to bent fittings  252 , in, one embodiment a bent fitting is fluidly connected to the distal end of outlet tube  250 . While bent fitting  252  is shown in  FIG. 32  as having a “T” shape ( FIG. 27 ), this is for illustrative purposes only. Thus, it will be appreciated that bent fitting  252  as shown in  FIG. 32  could have a number of other configurations, such as those shown in  FIGS. 25-31 . The design of bent fitting  252  ensures that the desired component is withdrawn (e.g., the platelet rich plasma fraction  260 ) with less risk of contamination from withdrawing a portion of the adjacent fraction  258 . Thus, in one embodiment, the desired fraction is withdrawn when its position overlaps with the position of bent fitting  252 . Alternatively, the inlet tube  248  may be first used to draw off the red blood cell fraction  256 , and when it is desirable to remove the predetermined fraction from the centrifuge bag  226 , the predetermined fraction is drawn through bent fitting  252  and outlet tube  250  and directed to receiving container  400  via outlet lumen  232 . 
     With continued reference to  FIG. 32 , as the separation of the fluid medium is initiated by centrifugation, substantially annular regions having constituents of a particular density or range of densities begin to form. For purposes of illustration, the separation of whole blood will be discussed, and as shown in  FIG. 32  four regions are represented, each of which contains a particular type of constituent of a given density or range of densities. Moreover, it should be appreciated that there may be a given distribution of densities across each of the regions such that the regions may not be sharply defined. Consequently, in practice the regions may be wider (e.g., a larger radial extent) and encompass a range of densities of constituents. 
     In the example of  FIG. 32 , the first region  256  is the outermost of the four regions and contains red blood cells. The second region  258  contains white blood cells, which have a lower density than that of the red blood cells. The third region  260  contains the platelet rich plasma fraction, and the innermost region  262  contains the least dense platelet poor plasma fraction. In one embodiment, it may be desired to harvest the platelet rich plasma fraction in region  260 . In order to remove the platelet rich plasma fraction from the centrifuge bag  226 , vacuum or suction is provided via outlet lumen  232  to the centrifuge bag  226  to remove a desired portion of region  260 . A portion of the fraction  260  that is in the area of the bent fitting  252  is drawn through bent fitting  252  and into an appropriate one of the collection containers  400  ( FIG. 17 ). 
     More specifically,  FIGS. 33-39  illustrate one method of this invention for the separation of whole blood components, which is a dynamic process.  FIG. 33  shows one portion of the centrifuge bag  226 , illustrating the separation of the whole blood components after infusion of an aliquot of whole blood into centrifuge bag  226  and centrifugation for approximately 60 seconds to 10 minutes at a rate of rotation between 0 and 5,000 rpms. It will be understood by those of skill in the art that faster speeds of rotation will separate the blood in a shorter prior of time. 
       FIG. 33  shows the four separated hole blood fractions, with the denser fractions closer to outer perimeter  238 , and the less dense fractions closer to inner perimeter  240 . While it is well-known that hematocrits (i.e., the volume of blood, expressed as a percentage, that consists of red blood cells) will vary among individuals, ranging from approximately 29%-68%, such variations are easily adjusted for as a result of the novel design of centrifuge bag  226  and consequently will not affect the isolation of any of the desired fractions as discussed below in detail. Thus, for illustrative purposes, it will be assumed that centrifugation of an initial infusion of an aliquot of anticoagulated whole blood will give the profile shown in  FIG. 33 . In one embodiment, it is desired to harvest the platelet rich plasma fraction  260 . This may be achieved by performing a batch separation process or a continuous separation process as described below. 
     In one embodiment of a batch separation process of this invention for harvesting the platelet rich plasma fraction  260 , centrifuge bag  226  has a design as shown in  FIG. 32  wherein bent fitting  252  positioned approximately in the area where a platelet rich plasma fraction  260  is typically found after centrifugation of an aliquot of whole blood. This approximation is simplified by the placement of concentric indicator lines  205 ,  207 , and  209 , (not shown) in the upper surface of rotor cover  206 , wherein the concentric lines  205 ,  207  and  209  correspond approximately with the edges of regions  260 ,  258 , and  256 , respectively. Alternative, concentric lines similar to  205 ,  207  and  209  may be directly imprinted onto the surface of centrifuge bag  226 . 
     After centrifugation of an aliquot of blood contained in centrifuge bag  226 , a substantial portion of the platelet rich plasma fraction  260  is withdrawn from centrifuge bag  226  through bent fitting  252  while centrifuge rotor  202  is still spinning. As the volume of the platelet rich plasma fraction  260  is reduced upon withdrawal, the innermost fraction  262  naturally moves in the direction of the outer perimeter  238  due to centrifugal force, as shown in  FIG. 34 . The withdrawal of platelet rich plasma fraction  260  is terminated at a point where the platelet poor plasma fraction  262  is close to bent fitting  252  and before any significant portion of platelet poor plasma fraction  262  could be withdrawn through bent fitting  252 , as shown in  FIG. 34 . This point can be determined either visually by the operator by volume, or by a sensor, as described below in detail. After withdrawal of the desired platelet rich plasma fraction  260 , inlet lumen  230  is disconnected from the whole blood source container  398  and connected to a disposal container, after which the remaining fluid in centrifuge bag  226  is evacuated through inlet tube  248  and directed to the disposal container. The inlet lumen is then reconnected to the whole blood source container, and the above-described batch process is repeated as many times as required until the necessary quantity of the desired fraction is isolated. 
     Alternatively, the above-described process can be performed as a continuous process wherein the step of disconnecting the inlet lumen  230  from the whole blood source  398  can be avoided. The continuous process separation of whole blood may be achieve by using a disposable centrifuge bag  226 ′ as illustrated in  FIGS. 35-39  comprising an inlet tube  248  and three outlet tubes  245 ,  247  and  250 , wherein the tubes are connected to an umbilical cable comprising four lumens. More specifically, a disposable centrifuge bag for use in a continuous separation of whole blood comprises inlet tube  248  connected via an inlet lumen to a whole blood source container, a first outlet tube  250  connected to a first outlet lumen that is in turn connected to a platelet rich plasma receiving container, a second outlet tube  245  connected via a second outlet lumen to either a red blood cell receiving container or a waste container and a third outlet tube  247  connected via a third outlet lumen to a platelet poor plasma receiving container. In the continuous separation process, after withdrawal of the portion of platelet rich plasma or other cellular components as described above with reference to  FIGS. 33 and 34 . Centrifuge bag has the capacity to receive an additional volume (aliquot) of whole blood. Consequently, as shown in  FIG. 35  infusion of an aliquot of whole blood is reinitiated through first inlet tube  248  with continued centrifugation until the capacity of the centrifuge bag  226 ′ is reached. As a result of the additional volume of blood, the profile of the blood fractions in centrifuge bag  226 ′ will approximately assume the profile shown in  FIG. 35 . As can be seen in  FIG. 35 , the additional volume of blood results in a shift of the location of the blood fractions, such that the platelet rich plasma fraction  260  has shifted back into the area of the bent fitting  252 , and the platelet poor plasma fraction  262  has shifted back towards the inner perimeter  240  and away from the vicinity of the bent fitting  252 . Additional platelet rich plasma  260  can now be removed from centrifuge bag  226 ′ through outlet tube  250  as shown in  FIG. 35 . 
     As described above, removal of an additional volume of the platelet rich plasma fraction  260  results in a shift in the location of the platelet poor plasma fraction  262  closer to the outer perimeter  238  and consequently closer to the vicinity of bent fitting  252 , as shown in  FIG. 36 , at which point removal of platelet rich plasma is again temporarily terminated. 
     Additional infusions of whole blood aliquots to centrifuge bag  262 ′ and removal of platelet rich plasma (by shifting the position of the platelet rich plasma fraction  260  relative to the position of the bent fitting  252 ) as described above may be repeated a number of times. Eventually, however, the continued infusion of whole blood followed by removal of only the platelet rich plasma fraction will necessarily result in a gradual increase in the volumes (and consequently the widths) of the remaining blood fractions  256 ,  258  and  260  in centrifuge bag  226 ′. In particular, the volume, and therefore the width, of the red blood cell fraction  256  will increase to the extent that the other fractions are pushed closer to the inner perimeter  240  ( FIG. 37 ). As shown in  FIG. 37 , the increased volume of red blood cells now present in centrifuge bag  226 ′ shifts the location of the fractions towards the inner perimeter  240  such that the white blood cell fraction  260  is now in the vicinity of the bent fitting  252  as opposed to the desired platelet rich plasma fraction  262 . 
     The novel design of centrifuge bag  226 ′ advantageously provides means for shifting the fractions back to the desired locations when the situation shown in  FIG. 37  arises. That is, second outlet tube  245  serves as an inlet conduit for introduction of whole blood aliquots into centrifuge bag  226 ′, also serves the function of withdrawing fractions that are located close to the outer perimeter  238 . This is achieved in part by attaching the second outlet lumen to either a red blood cell receiving container or a waste container having a suction means (e.g., syringe, pump, etc.) As shown in  FIG. 38 , second outlet tube  245 , having its distal end close to outer perimeter  238 , can be operated to withdraw a substantial volume of the red blood cell fraction  256 , which in turn shifts the location of the remaining fractions  258 ,  260 ,  262 . The withdrawal of the red blood cell fraction  256  may be monitored visually by the operator, or by other means such as a sensor. Alternatively, the positions of the fractions may be shifted by withdrawing the platelet poor plasma fraction  262  through third outlet tube  247 , which is connected via a third outlet lumen to a platelet poor plasma receiving container. 
       FIG. 37  shows that, after withdrawal of a portion of the red blood cell fraction  256 , the centrifuge bag  226 ′ again has the capacity to receive an additional volume of whole blood for centrifugation. An additional infusion of an aliquot of whole blood through inlet tube  248  into the centrifuge bag  226 ′ of  FIG. 37  and centrifugation will produce the profile illustrated in  FIG. 39 . The above-described steps may be repeated as needed until the desired amount of platelet rich plasma has been harvested. All of the above-described steps occur while the centrifuge rotor  202  is spinning. 
     The above-described continuous separation method was illustrated in terms of performing the whole blood infusion step and the platelet rich plasma harvesting step sequentially. An alternative embodiment involves performing the infusion and harvesting steps substantially simultaneously, that is, the platelet rich plasma fraction is withdrawn at approximately the same time as an additional aliquot of whole blood is being added to the bag. This alternate embodiment requires that the centrifuge rotor spin at a rate that results in almost immediate separation of the blood components upon infusion of an aliquot of whole blood. 
     As stated previously, all of the above-described steps may be monitored either visually by the operator by volume, or by a sensor. If the steps are to be visually monitored, centrifuge cover  206  may further include one or more concentric indicator circles  205 ,  207 ,  209  (shown in  FIGS. 17 and 18 ) which may be spaced from the center of cover  206  at distances approximately equal to the outer edges of regions  260 ,  258   256 , respectively, to aid the operator in visualizing the positions of these regions with respect to  252 . 
       FIGS. 33-39  illustrate one embodiment of how the design of centrifuge bags  226  and  226 ′ permit the general locations of the various blood fractions to be shifted to allow for continuous harvesting of a desired blood fraction without the risk of contaminating the harvested blood fraction, and further allow for continual on-line harvesting of a large volume (10 to 5 L&#39;s) of blood using a small, portable centrifuge device comprising a 10 cc to 200 cc capacity disposable centrifuge bags  226  and  226 ′. 
     For example, the design of centrifuge bag  226  having inlet tube  248  and outlet tube  250  means that the desired component or fraction will be withdrawn from centrifuge bag  226  only through outlet tube  250 , while the addition of whole blood aliquots or the removal of other components (e.g., red blood cell fraction  256 ) will proceed only through dual functional inlet tube  248 . In this respect, the harvested fraction (e.g., platelet rich plasma fraction  260 ) is never withdrawn through inlet tube  248  which was previously exposed to other fluid media (e.g., whole blood or red blood cells). Thus, the design of centrifuge bag  226  offers a significant advantage over conventional centrifuge containers comprising only one tube which serves to both introduce the fluid medium to the container and to withdraw the harvested fraction from the container. 
     Furthermore, because of its unique design, the use of centrifuge bags  226  and  226 ′ are independent of composition of the whole blood to be centrifuged. For example, as stated above, hematocrits (i.e., the percent volume of blood occupied by red blood cells) vary from individual to individual, and consequently the profile illustrated in  FIG. 32  will vary from individual to individual. That is, the width of red blood cell fraction  256  may be wider or narrower, which in turn will result in the platelet rich plasma fraction  260  being positioned further away in either direction from bent fitting  252 . However, as discussed above in detail with particular reference to  FIGS. 33-34 , the design of centrifuge bags  226  and  226 ′ allow the location of the desired fraction to be shifted until it is in the region of bent fitting  252 . Such shifting can be brought about, for example using centrifuge bag  226 , by withdrawing the red blood cell fraction through inlet tube  248 , or by adding whole blood aliquots through inlet tube  248 . 
     An alternative embodiment of a disposable, flexible centrifuge bag  270  is illustrated in  FIG. 40 . The disposable centrifuge bag  270  has a substantially flat, toroidal- or doughnut-shaped configuration having outer and inner perimeters  271  and  272 , respectively, and comprises radially extending upper and lower sheets  273 ,  274  formed from a substantially flexible material. The upper and lower sheets  273 ,  274  are superimposed and completely sealed together at outer perimeter  271  by an rf weld, heat weld or other comparable method of adhering two surfaces. Inner perimeter  272  defines core  275  of centrifuge bag  270 . In one embodiment of the invention, centrifuge bag  270  further comprises inlet tube  276  sandwiched between upper and lower sheets  273 ,  274  and radially extending from the center of core  275  to the outer perimeter  271 , and outlet tube  278  sandwiched between upper and lower sheets  273 ,  274  and extending across the diameter of core  275  and having first and second distal ends  280 ,  281 . When upper and lower sheets  273 ,  274  are sealed together at inner perimeter  272 , inlet and outlet tubes  276 ,  278  are thereby sealed therebetween. Inlet and outlet tubes  276 ,  278  are each in fluid communication with the interior of centrifuge bag  270  and the environment outside centrifuge bag  270 . Inlet tube  276  and outlet tube  278  are fluidly connected to umbilical cable  228  (not shown), which in this particular embodiment is a dual lumen tubing. Inlet tube  276  is fluidly connected at its proximal end to umbilical cable  228 , preferably by an L-shaped connector (not shown), and outlet tube  278  is fluidly connected at its center to umbilical cable  228  via a T-shaped connector (not shown). 
     The disposable centrifuge bag  270  is formed from a transparent, substantially flexible material, including but not limited to, polyvinyl chloride, polyethylene, polyurethane, ethylene vinyl acetate and combinations of the above or other flexible materials. 
     Upper and lower sheets  273 ,  274  of centrifuge bag  270  are further sealed at two portions between the outer perimeter and the inner perimeter. That is, centrifuge bag  270  further comprises a first C-shaped seal  282  located between the outer and inner perimeters  271 ,  272  and having an first concave indentation or well  283  on the concave side of C-shaped seal  282 , and a second C-shaped seal  284  located between the outer and inner perimeters  271 ,  272  and having an second concave indentation or well  285  on the concave side of C-shaped seal  284 . First and second C-shaped seals  282  and  284  are formed by sealing portions of upper and lower sheets  273 ,  274  together by methods known in the art for sealing two surfaces, including but not limited to rf or heat welding. Ends  288  and  289  of first C-shaped seal  282  are bent inward towards the inner core  275 , and likewise ends  290  and  291  of second C-shaped seal  284  are bent inward towards the inner core  275 . First and second C-shaped seals  282 ,  284  have their concave sides facing each other such that the first and second indentations  283 ,  285  are diametrically opposed to each other. That is, when centrifuge bag  270  is viewed from the top as in  FIG. 40 , first and second C-shaped seals  282 ,  284  are mirror images of each other. First and second C-shaped seals  282 ,  284  together define an outer chamber  292  between the outer perimeter  271  and first and second C-shaped seals  282 ,  284 , wherein the outer chamber  292  has a toroidal configuration and serves as a first processing compartment. First and second C-shaped seals  282 ,  284  together further define an inner chamber  293  between first and second C-shaped seals  282 ,  284  and inner perimeter  272 , wherein the inner chamber  293  has a toroidal configuration and serves as a second processing compartment. The first and second C-shaped seals  282 ,  284  are positioned such that ends  288  and  290  are directly opposite and spaced apart from each other to define a first channel  286  therebetween, and such that ends  289  and  291  are directly opposite and spaced apart from each other to define a second channel  287  therebetween, wherein the first and second channels  286 ,  287  are diametrically opposed and provide fluid communication between the first processing compartment  292  and the second processing compartment  293 . Inlet tube  276  extends through either channel  286  or channel  287 , and the first and second distal ends  280 ,  281  of outlet tube  278  extend into first and second indentations  283 ,  285 , respectively. 
     Centrifuge bag  270  is removably secured between rotor base  204  and rotor cover  206  of rotor  202  in a manner as described above so that centrifuge bag  270  is field in a fixed position relative to rotor base  204  and rotor cover  206  during rotation of the centrifuge rotor  202 . As will be appreciated by those of skill in the art, alternative embodiments of rotor base  204  ( FIG. 15 ) and rotor cover  206  ( FIG. 16 ) will be required to accommodate the design of centrifuge bag  270 . Thus, an alternate embodiment of rotor base  204  comprises raised column  218  comprising first and second grooves which are perpendicular to each other and extend the diameter of the raised base column  218 , such that when rotor  202  is assembled, inlet tube  276  and outlet tube  278  of centrifuge bag  270  are seated in the first and second grooves, respectively, of raised base column  218 . Similarly, an alternate embodiment of cover  206  comprises raised column  220  comprising first and second grooves which are perpendicular to each other and extend the diameter of the raised cover column  220 , such that when rotor  202  is assembled, inlet tube  276  and outlet tube  278  are further seated in the first and second grooves, respectively, of raised cover column  220 . 
     As stated above, inlet and outlet tubes  276 ,  278  are fluidly connected to umbilical cable  228 , which in this particular embodiment is a dual lumen tubing connecting centrifuge bag  270  to source and receiving containers  398 ,  400 , respectively, for the introduction of the fluid to be centrifuged in bag  270  and for the removal of one or more of the separated components from the centrifuge bag  270  during rotation of the centrifuge  20 . Dual lumen tubing  228  comprises inlet lumen  230 , which connects inlet tube  276  with source container  398 , and outlet lumen  232 , which connects outlet tube  278  with receiving container  400 . 
     The fluid or medium to be centrifuged using centrifuge bag  270  may be contained within source container  398 . For example, when the centrifuge  20  of this invention is used to prepare an autologous platelet gel, the fluid (i.e., whole blood), may be withdrawn from the patient during or prior to surgery into source container  398  containing an anticoagulant. The anticoagulated whole blood is introduced to centrifuge bag  270  through inlet tube  276  via inlet lumen  230  after the centrifuge bag  270  has been positioned in the centrifuge rotor  202  and rotation thereof is initiated. 
     Centrifuge bag  270  may be used for the separation and isolation of one or more components dissolved or suspended in a variety of fluid media, including, but not limited to, the separation of cellular components from biological fluids. For example, centrifuge bag  270  is useful for the concentration and removal of platelets from whole blood. Therefore, the following description of the separation of platelets from whole blood using centrifuge bag  270  is merely for purposes of illustration and is not meant to be limiting of the use of bag  270 . The separation of a fluid medium such as whole blood in centrifuge bag  270  may be considered to be a two-stage separation process. The first stage of the separation of platelets from whole blood involves separation of a platelet suspension from the red blood cells. The platelet suspension is typically plasma rich in platelets, and it is commonly referred to as platelet-rich plasma (PRP). However, as used herein, the term “platelet suspension” is not limited to PRP in the technical sense, but is intended to encompass any suspension in which platelets are present in concentrations greater than that in whole blood, and can include suspensions that carry other blood components in addition to platelets. The second stage of the separation comprises separating platelets from the platelet suspension to produce a platelet concentrate. As used herein, the term “platelet concentrate” is intended to encompass a volume of platelets that results after a “platelet suspension” undergoes a subsequent separation step that reduces the fluid volume of the platelet suspension. The platelet concentrate may be a concentrate that is depleted of white blood cells and red blood cells. 
     With reference to  FIG. 41 , stage one of a whole blood separation process using centrifuge bag  270  begins with the introduction of an aliquot of whole blood into centrifuge bag  270  via inlet tube  276  during rotation of the centrifuge  20 . As the aliquot of whole blood enters outer chamber  292  of centrifuge bag  270 , it quickly separates radially under the influence of centrifugal force into various fractions within outer chamber  292  based on the densities of the components of the whole blood, including an outermost fraction containing the red blood cells which pack along the outer perimeter  271  of centrifuge bag  270 , and an inner fraction comprising the platelet suspension. The platelet suspension after centrifugation of the first aliquot of whole blood is represented in  FIG. 41  by ring  294 . Continued infusion of whole blood into the first processing compartment  292  adds an additional volume of red blood cells and consequently pushes the platelet suspension inward as represented by ring  295 . Additional infusions of whole blood will continue to push the platelet suspension further inward, as represented by rings  296  and  297  until the first processing compartment  292  is substantially filled with red blood cells (the remainder of the volume being plasma) such that the platelet suspension is pushed through channels  286  and  287  into second processing compartment  293 . As discussed above, the ends  288 ,  289  and  290 ,  291  of C-shaped seals  282 ,  284 , respectively, bend inward, which both helps to funnel the platelet suspension through channels  286 ,  287  and to minimize the amount of red blood cells that pass through channels  286 ,  287 . The point at which the red blood cells are near the entrance of channels  286 ,  287  may be monitored either visually or by a sensor, as described below in detail. At this point the infusion of additional aliquots of whole blood is terminated, and the second stage of the two-stage separation process begins. 
     During stage two of the separation process, the platelet suspension which was pushed through channels  286 ,  287  into the second processing compartment  293  flow under the influence of centrifugal force towards positions within the second processing compartment  293  that have the greatest radial distances, that is, towards concave wells  283 ,  285 , where the platelets, being the higher density component of the platelet suspension, begin to collect and pack. The platelets can then be withdrawn from concave wells  283 ,  285  through outlet tube  278 . In the above-described two-stage process for the separation of a platelet suspension from whole blood, the first and second C-shaped seals  282 ,  284  thus serve as physical barriers between the red blood cells and the platelets to facilitate the separation and collection of platelets from whole blood. First and second concave wells  283 ,  285  act as reservoirs for containing the platelets as they are separated from the platelet suspension in the second stage of the separation process. 
     After withdrawal of the platelets from the wells  283  and  285 , inlet lumen  230  is disconnected from the whole blood source container, after which the remaining components in centrifuge bag  270  are evacuated through inlet tube  276  by applying suction to inlet lumen  230  and are directed to a disposable container. The inlet lumen  230  is then reconnected to the whole blood source container, and the above-described batch process is repeated as many times as required until the desired quantity of platelets has been harvested. 
     An alternative embodiment of a disposable, flexible centrifuge bag having inner C-shaped seals is illustrated in  FIG. 42  as centrifuge bag  320 . Disposable centrifuge bag  320  has a substantially flat, toroidal- or doughnut-shaped configuration having outer and inner perimeters  322  and  324 , respectively, and comprises radially extending upper and lower sheets  323 ,  325  formed from a substantially flexible material. The upper and lower sheets  323 ,  325  are superimposed and completely sealed together at outer perimeter  322  by an rf weld, heat weld or other comparable method of adhering two surfaces. Inner perimeter  324  defines core  327  of bag  320 . 
     Upper and lower sheets  323 ,  325  of centrifuge bag  320  are further sealed at two portions between the outer perimeter and the inner perimeter. That is, centrifuge bag  320  further comprises a first C-shaped seal  326  located between the inner and outer perimeters  322 ,  324 , and a second C-shaped seal  328  located between the inner and outer perimeters  322 ,  324 . The first and second C-shaped seals  326 ,  328  have their concave sides facing each other such that when centrifuge bag  320  is viewed from the top as in  FIG. 36 , first and second C-shaped seals  326  and  328  are mirror images of each other. First and second C-shaped seals  326 ,  328  together define an outer compartment  348  between the outer perimeter  322  and first and second C-shaped seals  326  and  328 , wherein the outer compartment  348  has a toroidal configuration. First and second C-shaped seals further define an compartment  350  between first and second C-shaped seals  326 ,  328  and inner perimeter  324 , wherein the inner compartment  350  has a doughnut shaped configuration. The ends  330  and  332  of first C-shaped seal  326  are slightly curved inward towards the inner core  327 , and likewise ends  334  and  336  of second C-shaped seal  328  are slightly curved inward towards the inner core  327 . The first and second C-shaped seals  326  and  328  are positioned such that ends  330  and  334  of first and second C-shaped seals  326 ,  328 , respectively, are directly opposite and spaced apart from each other, thereby defining first channel  335  therebetween, and such that ends  332  and  336  of first and second seals  326  and  328 , respectively, are directly opposite and spaced apart from each other, thereby defining second channel  337  therebetween, wherein the first and second channels  335  and  337  are diametrically opposed. First and second channels  335  and  337  provide fluid communication between the outer and inner compartments. 
     Centrifuge bag  320  further comprises an inlet port  340 , in the lower sheet  325  for introducing fluid into outer compartment  348 . Preferably the inlet port  340  is spaced 90 degrees from channel  335  however it could also be positioned at an angle greater or less than 90 degrees from channel  335 . Centrifuge bag  320  further comprises first and second outlet ports  344 ,  346  in lower sheet  325  and positioned within channels  335  and  337  for withdrawing a fluid compartment from centrifuge bag  320 . 
     In a preferred embodiment, centrifuge bag  320  comprises inlet tube  338  secured to the outside surface of upper sheet  323  or lower sheet  325  and radially extending from the center of core  327  towards the outer perimeter  322 , wherein inlet tube  338  is fluidly connected at its distal end to inlet port  340 . Inlet port  340  fluidly connects inlet tube  338  with the outer chamber  348  of centrifuge bag  320 . Inlet tube  338  is fluidly connected at its proximal end to umbilical cable  228 , preferably by an L-shaped connector (not shown). Further, in a preferred embodiment centrifuge bag  320  comprises outlet tube  342  secured to the outside surface of upper sheet  323  or lower sheet  325  and extending across the diameter of core  327 , wherein one end of outlet tube  342  is fluidly connected to first outlet port  344  and the other end of outlet tube  342  is fluidly connected to second outlet port  346 . Outlet tube is fluidly connected at its center to umbilical cable  228  via a T-shaped connector (not shown). 
     In an alternative embodiment of this invention, centrifuge bag  320  comprises inlet tube  338  sandwiched between upper and lower sheets  323 ,  325  and extending radially from the center of core  327  towards outer perimeter  322 , wherein inlet tube  328  is fluidly connected at its distal end to inlet port  340 , and outlet tube  342  sandwiched between upper and lower sheets  323 ,  325  and extending across the diameter of core  327 , wherein one end of outlet tube  342  is fluidly connected to outlet port  344  and the other end of outlet tube  342  is fluidly connected to outlet port  346 . When upper and lower sheets  323 ,  325  are sealed together at inner perimeter  324 , inlet and outlet tubes  338 ,  342  are thereby sealed therebetween. Inlet tube  338  and outlet tube  342  are fluidly connected to umbilical cable  228  (not shown), which in this particular embodiment is a dual lumen tubing. 
     Centrifuge bag  320  is removably secured between rotor base  204  and rotor cover  206  of rotor  202  in a manner as described above so that centrifuge bag  320  is held in a fixed position relative to rotor base  204  and rotor cover  206  during rotation of the centrifuge rotor  202 . As will be appreciated by those of skill in the art, alternative embodiments of rotor base  204  ( FIG. 15 ) and rotor cover  206  ( FIG. 16 ) as discussed above with respect to centrifuge bag  270  will be required to accommodate the design of centrifuge bag  370 . 
     Centrifuge bag  370  may be used for the separation and isolation of one or more components dissolved or suspended in a variety of fluid media, including, but not limited to, the separation of cellular components from biological fluids. For example, centrifuge bag  370  is useful for the concentration and removal of platelets from whole blood. Therefore, the following description of the separation of platelets from whole blood using centrifuge bag  320  is merely for purposes of illustration and is not meant to be limiting of the use of bag  320 . The separation of a fluid medium such as whole blood in centrifuge bag  320  may be considered to be a one-stage separation process. With reference to  FIG. 36 , centrifugation of whole blood begins with the introduction of an aliquot of whole blood into centrifuge bag  320  through inlet port  340  via inlet tube  338  during rotation of the centrifuge  20 . Inlet tube  338  is fluidly connected via inlet lumen  230  of umbilical cable  228  to an anticoagulated whole blood source. As the aliquot of whole blood enters the outer chamber  348  of centrifuge bag  320 , it quickly separates radially within outer chamber  348  into various fractions based on the densities of the components of the whole blood, including an outermost fraction containing the red blood cells which pack along the outer perimeter  322  of centrifuge bag  320 , and inner fractions containing the platelets and plasma. Continued infusion of whole blood adds an additional volume of red blood cells and consequently pushes the fraction containing platelets inward. Additional infusions of whole blood will continue to push the platelet-containing fraction further inward until the chamber  348  is substantially filled with red blood cells (the remainder of the volume being plasma), such that the platelet-containing fraction is pushed into channels  335 ,  337  and into the vicinity of outlet ports  344 ,  346 . As discussed above, the ends of C-shaped seals  326 ,  328  curve slightly inward, which both helps to funnel the platelet-containing fraction into channels  335 ,  337 , and to minimize the amount of red blood cells that flow into channels  335 ,  337 . The point at which the red blood cells are near the entrance of channels  335 ,  337  may be monitored either visually or by a sensor, as described below in detail. As the platelet-containing fraction enters the vicinity of outlet ports  344 ,  346 , the infusion of whole blood is terminated, and suction or other drawing means is applied to outlet tube  342  to withdraw the platelet-containing fraction through outlet ports  344 ,  346 . 
     After withdrawal of substantial portion of the platelet rich plasma, inlet lumen  230  is disconnected from the whole blood source container and connected to a disposal container, after which the remaining components in centrifuge bag  320  are evacuated through inlet port  34  by applying suction to inlet tube  276  and are directed to a disposal container. The inlet lumen  230  is then reconnected to the whole blood source container, and the above-described process is repeated as many times as required until the desired quantity of platelets has been harvested. 
     B. Rigid Centrifuge Container 
     As can be appreciated, it may be desirable to maximize the surface area of separated fraction to be harvested, since this maximizes the amount of the fraction which may be collected without increasing the potential for introducing impurities into the separation (e.g., adjacent, lighter density components may begin moving into the region of the fraction being harvested), and without increasing the size of the centrifuge to an undesirable degree. 
     In order to maximize the amount of the desired component (e.g., platelet rich plasma, white blood cells, or platelet poor plasma) which may be harvested, one embodiment of a centrifuge container of this invention for the separation of components in a fluid medium (e.g., whole blood), shown in  FIGS. 45-52 , is designed to position the desired component (e.g., platelet rich plasma) the platelet rich plasma at a region within the fixed centrifuge container or centrifuge bag so that the desired fraction has a maximum horizontal surface area (i.e., width). Thus, another embodiment of this invention comprises a centrifuge container  500  shown in  FIG. 45 .  FIG. 45  is a side cross-sectional view of a rigid container  500  comprising a rigid, annular body  510  having an axial core  600  that is closed at the top end  610  and opened at the bottom end  620 . Rigid container  500  further comprises an interior collection chamber  580  for receiving and holding the fluid medium to be centrifuged and having an outer perimeter  585  and an inner perimeter  590 . The side, cross-sectional profile of chamber  580  is generally an off-centered “figure eight” or “dumbbell” shape, as shown in  FIG. 46 . As used herein, “figure eight” or “dumbbell” shaped means that the height of section A is approximately equal to the height of section C, and the heights of sections A and C are greater that the height of section B. Furthermore, as used herein, “off-center” means that the width W 1  from the center of section B to outer perimeter  585  is less than the width W 2  from the center of section B to inner perimeter  590  as shown in  FIGS. 45 and 46 . 
     Rigid container  500  further comprises inlet channel  550  extending radially from core  600  to a point near the outer perimeter  585  and is fluidly connected at its distal end with the outer area of chamber  580 . Rigid container  500  further comprises outlet channel  554  extending radially from core  600  to the more central portion of chamber  580  (i.e., the narrow portion or “neck” of the figure eight cross-section) and is fluidly connected at its distal end with chamber  580 . While the inlet and outlet channels  550 ,  554  are shown in  FIG. 45  as being fluidly connected to the top end of chamber  580 , the present invention also includes embodiments wherein both channels  550 ,  554  are in fluid communication with the bottom end of chamber  580 , or wherein channel  550  is in fluid communication with the top end of chamber  580  and channel  554  is in fluid communication with the bottom end of chamber  580 , or vice versa. Inlet and outlet channels  550 ,  554  are fluidly connected to dual lumen tubing  228  having an inlet lumen  230  and an outlet lumen  232 . Rigid container  500  is removably secured to the upper surface  133  of upper bearing assembly  130  with appropriate screws, fasteners or the like (not shown). Inlet lumen  230  may be connected to a source for fluid medium, and outlet lumen  232  may be connected to a suction means for withdrawing the desired fraction from the chamber  580 . 
     The configuration of chamber  580  is specifically designed to maximize the collection of platelet rich plasma by centrifugation of anticoagulated whole blood. More particularly, the shape of chamber  580  increases the width of the platelet rich plasma fraction when viewed from the top and decreases the depth of the platelet rich plasma fraction when viewed from the side, thus allowing the withdrawal of a greater amount of platelet rich plasma. This unique design can be better explained by comparing  FIGS. 44 and 47 .  FIG. 44  shows a side profile of a rigid centrifuge container  500  as shown in  FIG. 43 , having a generally oval profile and containing whole blood that has been separated into four fractions by centrifugation. In  FIG. 44 , width W 3  indicates the relative horizontal width of the platelet rich plasma fraction to be harvested, and D 1  indicates the relative depth of the platelet rich plasma fraction.  FIG. 47  shows a side profile of rigid centrifuge container  580  of this invention having the above-described off-centered figure eight shape and containing whole blood that has been separated into four fractions by centrifugation. In  FIG. 47 , width W 4  indicates the relative horizontal width of the platelet rich plasma fraction  260  to be harvested, and D 2  indicates the relative depth of the platelet rich plasma fraction  260 . Width W 4  is necessarily wider than width W 3  in  FIG. 44 . Thus it can be easily appreciated that upon withdrawal of the platelet rich plasma fraction  260  from the oval shaped container shown in  FIG. 44 , platelet poor plasma fraction  262  will shift closer to the outlet tube  554  relatively quickly. In contrast the dumbbell shaped profile of chamber  580  shown in  FIG. 47  significantly increases the width W 4  while decreasing the average depth D 2 , and therefore a greater portion of the platelet rich plasma fraction  260  can be withdrawn with greater accuracy before the platelet poor plasma fraction  262  reaches the outlet tube  554 . 
     In an embodiment where the platelet rich plasma is to be collected one could design chamber  580  as follows. The configuration of chamber  580 , that is, the relative heights A, B, and C as shown in  FIG. 46 , will be determined based on the typical location of the platelet rich plasma fraction  260  after centrifugation of whole blood. For example, in a rigid centrifuge container  500  as illustrated in  FIG. 45 , having chamber  580  with a 30 ml capacity and a radius of approximately 65 mm measured from its rotational axis to the edge  630 , the platelet rich plasma will collect in chamber  580  at a region at a radial position ranging from about 35 to about 60 mm from the axis. In this region of the chamber  580 , as illustrated in  FIG. 46 , the chamber  580  has a height of about 10 mm such that the horizontal surface area “B” of this region, illustrated in  FIG. 46 , is about 4 mm 2 . Consequently, it can be appreciated that because of the unique configuration of chamber  580 , the surface area of the platelet rich plasma fraction  260  as illustrated in  FIG. 47  may be maximized without undesirably increasing the overall size of the rigid centrifuge container  500 . It will be appreciated by those skilled in the art that various geometric designs may be utilized depending on the fluid medium being centrifuged and the cellular fraction to be collected. The process for harvesting platelets from whole blood using rigid container  500  may be achieved in a manner similar to that described for bag  226   
     Rigid centrifuge container  500  may be, made from any number of rigid, transparent materials that are capable of withstanding typical sterilization conditions, including but not limited to acrylic resins, polycarbonate, or any clear thermal plastic. Preferably rigid container  500  is made of a cost-effective material that is relatively inexpensive to dispose of. 
     C. Centrifuge Rotor Having a Complex Interior Geometry 
     An alternate embodiment of a centrifuge rotor of this invention for holding flexible centrifuge bag  226  is illustrated in  FIGS. 48-52 . Generally and referring to  FIGS. 48 and 49 , the centrifuge rotor  755  is defined by a rotor base  760  ( FIGS. 48 ,  50  and  52 ) having a lower channel  780 , and a rotor cover  770  ( FIGS. 49 and 51 ) having an upper channel  782 . The annular interior chamber  784  ( FIG. 48 ) of rotor  755  is defined by lower and upper channels  780 ,  782 , and has a generally off-centered figure eight side cross-sectional configuration specifically designed to maximize the collection of platelet rich plasma by centrifugation of anticoagulated whole blood, as discussed below in detail. 
     As illustrated in  FIGS. 51 and 52 , rotor base  760  comprises raised annular rim  775  and raised column  786  which is axially disposed in the interior of rotor base  760 . Raised column  786  further has a groove  790  ( FIG. 52 ) extending the diameter of column  786 . The height of rim  775  is equal to the height of column  786 . As illustrated in  FIG. 51 , rotor cover  770  comprises raised annular rim  777  and raised column  788  which is axially disposed in the interior of cover  770 . Raised column  788  further has a groove  792  ( FIG. 52 ) extending the diameter of column  788 . The height of rim  777  is equal to the height of column  788 . Rotor base  760  and rotor cover  770  are preferably made from any number of rigid transparent materials including, but not limited to acrylic resins, polycarbonate, or any clear thermal plastic. 
     When centrifuge rotor  755  is to be assembled for use, flexible, doughnut-shaped centrifuge bag  226  having a center core  242  is placed in rotor base  760  such that center column  786  preferably, but not necessarily, extends through the core of centrifuge bag  226 , and inlet and outlet tubes  248 ,  250  of bag  226  are seated in groove  790 . Rotor cover  770  is superimposed on rotor base  760  such that grooves  790  and  792  are aligned and further so that inlet and outlet tubes  248 ,  250  are seated in groove  792 . In one embodiment, when cover  770  is appropriately secured to base  760  (e.g., with screws, clamps, or the like), rims  775  and  777  are in complete contact with each other, and columns  786  and  788  are preferably in complete contact with each other, thereby creating chamber  784  ( FIG. 48 ). Alternatively when cover  770  is secured to base  760  as described, the inner perimeter of bag  226  is secured between columns  786  and  788  such that the columns do not physically contact each other. 
     When the generally flat, flexible centrifuge bag  226  is contained within chamber  784  prior to the infusion of a fluid medium (e.g., whole blood), it will not fill the entire volume of chamber  784  but rather will have a radially extending, flat shape as centrifuge rotor  755  is spinning. However, after a sufficient volume of the fluid medium (e.g., whole blood) has been introduced into flexible bag  226  through inlet tube  248  such that bag  226  is substantially completely filled, it will be appreciated that filled centrifuge bag  226  will conform to the shape of chamber  784  and consequently will have a off-centered figure eight shaped cross-section. 
     The off-centered figure eight configuration of the chamber  784  is of approximately the same configuration as the rigid bag  500 . Therefore, for the same reasons, the shape of chamber  784  (and consequently the shape of filled bag  226 ), will assume an off-centered figure eight shape wherein the width of the platelet rich plasma fraction is greatly increased relative to the width of a filled bag having an elliptical cross-sectional shape (see, for example,  FIGS. 46 and 47 ). 
     As discussed above, a number of methods may be utilized to gauge the harvesting of the desired fraction (such as, but not limited to, platelet rich plasma) from the centrifuge bag. For instance, the separation of platelet rich plasma fraction may be indicated by visual observation of a concentric ring containing the platelet rich plasma (which will be a less colored fraction) and an outer red-colored concentric ring containing the red blood cells. In this case, when such fraction(s) have been separated, the platelet rich plasma may be withdrawn from centrifuge bag  226  by bent fitting  160  to direct the platelet rich plasma to the appropriate collector. 
     As an alternative to the foregoing, sensors may be incorporated as discussed in detail below to detect the presence of the platelet rich plasma fraction. 
     Based upon the foregoing, it can be appreciated that the centrifugal processing system  10  and the centrifuge rotors and bags of this invention have a plurality of features which are suited to harvesting platelet rich plasma, white blood cells, platelet poor plasma or red blood cells from a patient&#39;s whole blood in accordance with each of the aspects of the present invention. For example, as discussed above, hematocrits (the volume of blood occupied by red blood cells, expressed as a percentage) vary from individual to individual. Thus, depending on the amount of red blood cells present in a particular sample, the exact radial location of various blood components within the centrifuge bag after centrifugation will also vary. The centrifuge bags of this invention overcome this issue by having an inlet tube capable of not only introducing whole blood into the centrifuge bag, but also capable of withdrawing some of all of the red blood cell fraction as needed to shift the location of the fraction to be harvested into the area of the outlet tube. Such features are presented in centrifuge bags  226 ,  270 ,  320  and  500 . Yet another embodiment of the centrifuge bags of this invention which overcomes problems with varying hematocrits is centrifuge bag  226 ′ having multiple outlet tubes. 
     Additionally, the centrifugal processing system  10  effectively provides a closed system which enhances the potential for maintaining a desired degree of sterility associated with the entire procedure since materials can thus be both provided to and removed from the centrifuge bag during rotation of the centrifuge via, for instance, a dual lumen tubing connected to a fluid source (e.g., anticoagulated whole blood withdrawn from a patient before or during surgery) and collection containers (i.e., for the preparation of a platelet gel), without interrupting the process, and thus without significant exposure of the materials to environmental conditions. 
     Moreover, the portable size of the centrifugal processing system  10  in combination with the above-described features of shifting the separated fractions and maximizing the surface area of the harvested fraction allows for increased processing capabilities autologous platelet gel over larger, conventional centrifuges 
     The on-line harvesting capabilities of the centrifugal processing system  10  allows for continuous, dynamic separation and collection of platelet rich plasma, white blood cells, red blood cells and platelet poor plasma, by adjusting the input and removal of fluid medium and separated fractions as described above. Further, the orientation of the flexible and rigid centrifuge bags of this invention and of the contents therein (e.g., being generally radially extending) is not significantly modified in the transformation from separation to harvesting of the various constituents. Moreover, vortexing throughout the contents of the centrifuge bags of this invention is reduced or eliminated since the centrifugal processing system  10  does not have to be decelerated or stopped for addition of fluid medium or removal of the various fractions therefrom. 
     Further, the general orientation of the flexible and rigid centrifuge bags of the invention (e.g., substantially horizontal) is maintained during removal of the desired whole blood fraction similar to the orientation of the centrifuge bags assumed during centrifugation to further assist in maintaining the degree of separation provided by centrifugation. Consequently, the potential is reduced for disturbing the fractions to the degree where the separation achieved is adversely affected. 
     Although the present invention has been described with regard to the separation of whole blood components, it will be appreciated that the methods and apparatus described herein may be used in the separation components of other fluid media, including, but not limited to whole blood with density gradient media; cellular components, or sub-sets of the four whole blood components previously defined. 
     While blood separation and materials handling may be manually controlled, as discussed above, a further embodiment of the present invention provides for the automation of at least portions of the separation and material handling processes. Referring to  FIG. 53 , an automated centrifugal processing system  800  is illustrated that is generally configured to provide automated control over the steps of inputting blood, separating desired components, and outputting the separated components. The following discussion of the processing system  800  provides examples of separating platelets in a blood sample, but the processing system  800  provides features that would be useful for separating other components or fractions from blood or other fluids. These other uses for the processing system  800  are considered within the breadth of this disclosure. Similarly, the specific components discussed for use in the processing system  800  are provided for illustration purposes and not as limitations, with alternative devices being readily apparent to those skilled in the medical device arts. 
     In the embodiment illustrated in  FIG. 53 , the processing system  800  includes a blood source  802  connected with a fluid line  804  to an inlet pump  810 . A valve  806 , such as a solenoid-operated valve or a one-way check valve, is provided in the fluid line  804  to allow control of flow to and from the blood source  802  during operation of the inlet pump  810 . The inlet pump  810  is operable to pump blood from the blood source  802  through the fluid line  818  to a centrifuge  20 . Once all or a select portion of the blood in the blood source  802  have been pumped to a blood reservoir  824  of the centrifuge  820  the inlet pump  810  is turned off and the blood source  802  isolated with valve  806 . The inlet pump  810  may be operated at later times to provide additional blood during the operation of the processing system  800  (such as during or after the removal of a separated component). 
     The centrifuge  20  preferably includes a flexible centrifuge bag, for example  226 ,  226 ′,  270 , or  320 , positioned within the rotor  202  for collecting the input blood, or alternatively rotor  202  may be a rigid container having an off centered figure eight shaped chamber, which may collect blood directly as discussed previously. Thus, while the embodiment described below illustrates a centrifuge having bag  226 , it is to be understood that the alternative centrifuge bags disclosed herein may be used in a similar manner. The centrifuge  20  as discussed above has an internal mid-shaft gear assembly  108  that provides the motive force to rotate the rotor assembly  200 , and particularly the rotor  202 , at a rotation rate that is adequate to create centrifugal forces that act to separate the various constituents or components of the blood in the rotor  202 . The drive assembly  822  may comprise a number of devices useful for generating the motive force, such as an electric motor with a drive shaft connected to internal drive components of the centrifuge  20 . In a preferred embodiment, the drive assembly  822  comprises an electric motor that drives a belt attached to an exterior portion of the centrifuge  20  and more particularly to the timing belt ring  44 . To obtain adequate separation, the rotation rate is typically between about 0 RPM and 5000 RPM, and in one embodiment of the invention, is maintained between about 0 RPM and 5000 RPM. 
     As discussed in detail previously, components of particular densities assume radial positions or belts at differing distances from the central axis A of the rotor  202 . For example, the heavier red blood cells typically separate in an outer region while lower density platelets separate into a region more proximal to the central axis of the rotor  202 . Between each of these component regions, there is an interface at which the fluid density measurably changes from a higher to a lower density (i.e., as density is measured from an outer to an inner region), and this density interface is used in some embodiments of the centrifugal processing system  800  to identify the location of component regions (as will be discussed in more detail below). In a preferred embodiment, the drive assembly  822  continues to operate to rotate the centrifuge  20  to retain the separation of the components throughout the operation of the centrifugal processing system  800 . 
     Once blood separation has been achieved within the rotor  202 , the outlet pump  830  is operated to pump select components from the rotor  202  through outlet lumen  828 . As discussed previously, in relation to the features of the disposable blood centrifuge bag  226 , the centrifuge bag held within the rotor  202  preferably is configured to allow the selective removal of a separated blood component, such as platelets located in a platelet rich plasma region, by the positioning of an outlet lumen  232  a radial distance from the central axis of the centrifuge bag  226 . Preferably, this radial distance or radial location for the outlet lumen is selected to coincide with the radial location of the desired, separated component or the anticipated location of the separated component. In this manner, the outlet pump  830  only (or substantially only) removes a particular component (such as platelets into container  400 ) existing at that radial distance. Once all or a desired quantity of the particular component is removed from the centrifuge bag  226 , operation of the outlet pump  830  is stopped, and a new separation process can be initiated. Alternatively, in a preferred embodiment, additional blood is pumped into the centrifuge by  226  by further operating the inlet pump  810  after or concurrent with operation of the outlet pump  830 . 
     A concern with fixing the radial distance or location of the outlet port is that each blood sample may have varying levels or quantities of different components. Thus, upon separation, the radial distance or location of a particular component or component region within the centrifuge bag  226  varies, at least slightly, with each different blood sample. Additionally, because of the varying levels of components, the size of the component region also varies and the amount that can be pumped out of the centrifuge bag  226  by the outlet pump  830  without inclusion of other components varies with each blood sample. Further, the position of the component region will vary in embodiments of the separation system  800  in which additional blood is added after or during the removal of blood by the outlet pump  830 . 
     To address the varying location of a particular separated component, the centrifugal processing; system  800  preferably is configured to adjust the location of a separated component to substantially align the radial location of the separated component with the radial location of the outlet port. For example, the centrifugal processing system  800  may be utilized to collect platelets from a blood sample. In this example, the centrifugal processing system  800  preferably includes a red blood cell collector  812  connected to the inlet pump  810  via fluid line  814  having an isolation valve  816  (e.g., a solenoid-operated valve or one-way check valve). Alternatively, the pump or syringe may also act as the valve. The inlet pump  810  is configured to selectively pump fluids in two directions, to and away from the centrifuge  820  through fluid line  818 , and in this regard, may be a reversible-direction peristaltic pump or other two-directional pump. Similarly, although shown schematically with two fluid lines  804  and  814 , a single fluid line may be utilized as an inlet and an outlet line to practice the invention. 
     Operation of the inlet pump  810  to remove fluid from the centrifuge bag  226  is useful to align the radial location of the desired separated component with the outlet tube  250  and inlet tube  248  of the centrifuge bag  226 . When it is desired to align platelets or platelet rich plasma with the outlet tube  250 , the inlet tube  248  connected to lumen  232  and  230 , respectively, inlet tube  248  is preferably at a greater radial distance than the outlet tube  250 . When suction is applied to the inlet lumen  230  by inlet pump  810 , red blood cells are pumped out of the centrifuge bag  226  and into the red blood cell collector  812 . As red blood cells are removed, the separated platelets (i.e., the desired component region) move radially outward to a new location within the centrifuge bag  226 . The inlet pump  810  is operated until the radial distance of the separated platelets or platelet region from the central axis is increased to coincide with the radial distance or location of the outlet tube  250  of the centrifuge bag  226 . Once substantial alignment of the desired component region and the outlet tube  250  is achieved, the outlet pump  830  is operated to remove all or a select quantity of the components in the aligned component region. 
     To provide automation features of the invention, the centrifugal processing system  800  includes a controller  850  for monitoring and controlling operation of the inlet pump  810 , the centrifuge  20 , the drive assembly  822 , and the outlet pump  830 . Numerous control devices may be utilized within the centrifugal processing system  800  to effectively monitor and control automated operations. In one embodiment, the controller  850  comprises a computer with a central processing unit (CPU) with a digital signal processor, memory, an input/output (I/O) interface for receiving input and feedback signals and for transmitting control signals, and software or programming applications for processing input signals and generating control signals (with or without signal conditioners and/or amplifiers). The controller  850  is communicatively linked to the devices of the centrifugal processing system  800  with signal lines  860 ,  862 ,  864 ,  866 , and  868  which may include signal conditioning devices and other devices to provide for proper communications between the controller  850  and the components of the centrifugal processing system  800 . 
     Once blood is supplied to the blood source container  802 , the operator pushes the start button and the controller  850  transmits a control signal over signal line  864  to the drive assembly  822 , which may include a motor controller, to begin rotating the centrifuge  20  to cause the components of the blood in centrifuge bag  226  to separate into radially-positioned regions (such as platelet rich plasma regions). After initiation of the centrifuge spinning or concurrently with operation of the drive assembly  822 , the controller  850  generates a control signal over signal line  860  to the inlet pump  810  to begin pumping blood from the blood source container  802  to the centrifuge bag  226  of the centrifuge  20 . In some embodiments of the processing system  800 , the drive assembly  822  is operable at more than one speed or over a range of speeds. Additionally, even with a single speed drive shaft the rotation rate achieved at the centrifuge  20  may vary. To address this issue, the processing system  800  may include a velocity detector  858  that at least periodically detects movement of the centrifuge bag  226  portion of the centrifuge  20  and transmits a feedback signal over signal line  866  to the controller  850 . The controller  850  processes the received signal to calculate the rotation rate of the centrifuge  20 , and if applicable, transmits a control signal to the drive assembly  822  to increase or decrease its operating speed to obtain a desired rotation rate at the centrifuge bag  226 . 
     To determine when separation of the components in the centrifuge bag  226  is achieved, the processing system  800  may be calibrated to account for variations in the centrifuge  20  and drive assembly  822  configuration to determine a minimum rotation time to obtain a desired level of component separation. In this embodiment, the controller  850  preferably includes a timer mechanism  856  that operates to measure the period of time that the centrifuge  20  has been rotated by the drive assembly  822  (such as by beginning measuring from the transmission of the control signal by the controller  850  to the drive assembly  822 ). When the measured rotation time equals the calibrated rotation time for a particular centrifuge  20  and drive assembly  822  configuration, the timing mechanism  856  informs the controller  850  that separation has been achieved in the centrifuge bag  226 . At this point, the controller  850  operates to transmit control signal over signal line  860  to the input pump  810  to cease operation and to the outlet pump  830  over signal line  868  to initiate operation to pump a separated component in the component region adjacent the outlet port of lumen  232  of centrifuge bag  226  through fluid line  828 . In another embodiment where rotation time is utilized by controller  850 , the velocity feedback signal from the velocity detector  858  is utilized by the controller  850  to adjust the rotation time as necessary to obtain the desired level of component separation. For example, the centrifugal processing system  800  can be calibrated for a number of rotation rates and the corresponding minimum rotation times can be stored in a look up table for retrieval by the controller  850  based on a calculated rotation rate. Rotational rates may be varied either manually or automatically to optimize cellular component position and or concentration. 
     Because the location of component separation regions varies during separation operations, a preferred embodiment of the centrifugal processing system  800  includes a sensor assembly  840  to monitor the separation of components within the centrifuge bag and to transmit feedback signals over line  862  to the controller  850 . As will be understood by those skilled in the art, numerous sensor devices exist for detecting the presence of certain components in a fluid, and specifically a blood, sample. Many of these devices comprise a source of radiant energy, such as infrared, laser, or incandescent light, and a compatible radiant energy-sensitive detector that reacts to the received energy by generating an electric signal. Briefly, these radiant energy devices are useful because the detected signal varies in a measurable fashion with variances in the density of the material through which beams of the radiant energy are passed. According to the invention, the sensor assembly  840  may comprise any of these well-known types of radiant energy source and detector devices and other sensor devices useful for measuring the existence of constituents of fluids such as blood. 
     The source and the detector of the sensor assembly  840  are preferably located within the centrifugal processing system  800  to allow monitoring of the centrifuge bag  226  and, particularly, to identify the presence of a particular blood component in a radial position coinciding with the radial position of the outlet port of the centrifuge bag  226 . In one embodiment, the radiation beams from the source are transmitted through a “window” in the centrifuge bag  226  that has a radial location that at least partially overlaps the radial location of the outlet port. During operation of the centrifugal processing system  800 , the feedback signals from the detector of the sensor assembly  840  allow the controller  850  to identify when a density interface has entered the window. This may occur for a number of reasons. The change in density may occur when red blood cells are being removed by operation of the inlet pump  810  to remove fluid from the centrifuge bag  226  via the inlet tube  248 . The change in density may also occur when a denser component is being added to the centrifuge bag  226  causing the particular blood component to be pushed radially inward. In the centrifugation of whole blood, this occurs when additional blood is added by operation of the input pump  810  and red blood cells collect in a region radially outward from the platelet region. 
     To account for differing movement of the density interface, the window of the radiation source may be alternatively positioned radially inward from the location of the outlet tube  250  of the centrifuge bag  226 . By positioning the window inward from the outlet tube  250 , the controller  850  can identify when the outlet pump  830  has nearly removed all of the particular component of the monitored region and/or when the inlet pump  810  has removed a quantity of denser components causing the monitored region to move radially outward. The controller  850  can then operate to send control signals to turn off the outlet pump  830  or the inlet pump  810  (as appropriate) to minimize the amount of undesired components (lower density components) that enter the outlet tube  250 . Alternatively, the sensor assembly  840  may have two radiation sources and detectors, and the second window of the sensor assembly  840  may be located a distance radially outward from the outlet tube  250 . With two sensing windows, the sensor assembly  840  is operable to provide the controller  850  information about a density interface moving radially inward toward the outlet tube  250  (such as when red blood cells are added). In response, the controller  850  can generate a control signal to the inlet pump  810  to operate to pump the denser components, such as red blood cells, out of the centrifuge bag  226 . Two sensing windows also allow the controller  850  to detect a density interface moving outward, which allows the controller  850  to shut off the outlet pump  830  (and/or the inlet pump  810  to stop evacuating processes) and/or to start the inlet pump  810  to add additional blood. 
     To further clarify operation of the processing system  800 ,  FIG. 54  is provided which illustrates the timing and relationship of control signals generated by the controller  850  and the receipt of feedback signals from the sensor assembly  840 . In this embodiment, the radiation detector of the sensor assembly  840  is positioned adjacent outlet tube (inlet to the outlet pump  830 ) in the centrifuge bag  226  to sense density changes in the fluid flowing past the outlet tube  250 . As illustrated, operation of the processing system  800  begins at time t 0 , with the inlet pump  810 , the outlet pump  830 , and the centrifuge drive assembly  822  all being off or not operating. At time t 1 , the controller  850  operates in response to operator input or upon sensing the blood source  802  is adequately filled (sensor not shown) to generate a control signal on line  864  to begin operating the centrifuge drive assembly  822  to rotate the centrifuge bag  226 . In some embodiments, this control signal over line  864  also contains rotation rate information to initially set the operating speed of the drive assembly  822 . Concurrently or at a selected delay time, the controller  850  generates a control signal on line  860  to start the inlet pump  810  in a configuration to pump fluid to the centrifuge bag  226  over fluid line  818 . The sensor assembly  840  provides an initial density feedback signal to the controller  850  on line  862 , which the controller  850  can process to determine an initial or unseparated density adjacent the outlet tube. Alternatively, the controller  850  may be configured to request a feedback signal from the sensor assembly  840  after a set delay period (as measured by the timer mechanism  856 ) to allow separation of the components being pumped into the centrifuge bag  226  (such as the calibrated, minimum rotation time discussed above) into regions. 
     At time t 2 , the controller  850  functions to align the region having the desired density, such as a region comprising a higher density of platelets, adjacent the detector of the sensor assembly  840  (i.e., adjacent the outlet tube). To achieve alignment, the controller  850  transmits a control signal over line  860  to the inlet pump  810  to stop pumping fluid to the centrifuge bag  226 , to reverse pumping directions including shutting valve  806  and opening valve  816 , and to begin pumping components haying a higher density then the particular, desired component from the centrifuge bag  226  to the collector  812 . For example, when the centrifugal processing system  10  is operated to separate and collect platelets or platelet rich plasma, the inlet pump  810  at time, t 2 , is operated to pump out the red blood cell fraction byapplying suction at the inlet tube  248  to the centrifuge bag  226 . At time, t 3 , the density of the fluid adjacent the outlet tube  250  begins to change as denser components are removed by the inlet pump  810 , and the sensor feedback signal being transmitted to the controller  850  changes in magnitude. The sensor feedback signal continues to change in magnitude (either becoming stronger or weaker depending on the particular sensor utilized and the material being collected) until at time t 4 , when the controller  850  processes the feedback signal and determines that the density of the adjacent fluids is within a desired range. This transition can also be thought of as detecting when an interface between two regions of differing densities passes by the location of the detector of the sensor assembly  840 . 
     With the region of the desired, separated component aligned with the outlet tube  250 , the controller  850  operates at time t 4 , to send a control signal over line  860  to stop operations of the inlet pump  810 . Also, at time t 4 , or at any time thereafter, the controller  850  generates a control signal over line  868  to begin operation the outlet pump  830  to apply suction at the outlet tube  250  of the centrifuge bag  226  to remove the desired component, such as the platelet rich plasma fraction, from the centrifuge bag  226 . At time t 5 , the sensor feedback signal again begins to change in magnitude as the density of the fluid near the outlet tube  250  begins to change, such as when platelet poor plasma begins to enter the sampling window of the sensor assembly  840 . At time t 6 , the density of the fluid adjacent the outlet tube  250  and, hence, in the sampling window is outside of a desired density range (e.g., the fluid has less than a predetermined percentage of platelets or other desired fluid component). In response, the controller  850  transmits a control signal on line  868  to halt operations of the outlet pump  830 . Of course, the controller  850  can be operated to transmit the signal to the outlet pump  830  at any time prior to time t 6 , such as at a time after time t 5 , when the density of the adjacent fluid begins to change but prior to time t 6 or based on volume removed. The controller  850  can then operate any time after time t 6 , to halt operation of the centrifuge drive assembly  822 . Further, as discussed above, operations of the separation centrifugal processing system  800  can be repeated with the inlet pump  810  being operated to add additional fluid, e.g., blood, after time t 6 . Alternatively, the inlet pump  810  and the outlet pump  830  may be operated concurrently to add an additional volume of blood with a corresponding new amount of the component being collected after time t 4 , to extend the period of time between detection of the interface at time t 4  and the detection of an out of range density at time t 6 . 
     In the above discussion of the automated processing system  800 , a sensor assembly  840  was shown in  FIG. 53  schematically, and it was noted that the location of a radiant energy source and a detector may be any location within the processing system  800  useful for obtaining an accurate measurement of separating blood components within the centrifuge bag  226 . For example, the source and detector can be both positioned within the centrifuge  20  at a location adjacent the centrifuge bag  226 . In this embodiment, problems may arise with providing proper signal and power line connections to the source and sensor and with accounting for the rotation of the centrifuge and portions of the sensor assembly  840 . Hence, one preferred embodiment of the processing system  800  provides for an externally positioned sensor assembly  840  including source and detector to simplify the structure of the centrifuge  20  while still providing effective density determinations of fluids within the blood reservoir. 
       FIG. 55  illustrates a general side view of the relevant components of this external sensor embodiment of the centrifugal processing system  800 . Generally, the centrifuge  20  comprises a rotor extension portion  880  and a drive portion  881 , which is connected to the drive assembly  822  (connection not shown). Both the centrifuge  20  and the rotor extension portion  880  rotate about a central or rotation axis, C axis , of the centrifuge  20 . As discussed in more detail with respect to the internal gearing features of the centrifuge  20 , the drive portion  881  spins in a ratio of 2 to 1 (or other suitable ratio) relative to the reservoir extension portion  880  to control twisting of inlet and outlet fluid lines to the rotor extension portion  880 . The internal gearing features of the centrifuge  20  also enable the centrifuge  20  to effectively obtain rotation rates that force the separation of components with differing densities while limiting the risk that denser components, such as red blood cells, will become too tightly packed during separation forming a solid, dense material that is more difficult to pump or remove from the centrifuge  20 . 
     Referring again to  FIG. 55 , the rotor extension portion  880  is shown located on the upper end of the centrifuge  20  and includes a centrifuge bag  226  or other receptacle. Preferably, the rotor extension portion  880  is fabricated from a transparent or partially transparent material, such as any of a number of plastics, to allow sensing of fluid densities. The rotor extension portion  880  extends a distance, d over , beyond the outer edge of the centrifuge  20  as measured radially outward from the central axis, c axis . The distance, d over , is preferably selected such that the desired component, such as the platelet rich plasma fraction, to be collected readily separates into a region at a point within the centrifuge bag  226  that also extends outward from the centrifuge  20 . In this regard, the rotor extension portion  880  is also configured so that the centrifuge bag  226  extends within the rotor extension portion  880  to a point near the outer circumference of the rotor extension portion  880 . The distance, d over , selected for extending the rotor extension portion  880  is preferably selected to facilitate alignment process (discussed above) and to control the need for operating the input pump  810  to remove denser components. In one embodiment, the distance, d over , is selected such that during separation of a typical blood sample center of the platelet rich region is about one half the extension distance, d over , from the circumferential edge of the centrifuge  20 . 
     The sensor assembly  840  is entirely external to the centrifuge  20  as shown in  FIG. 55 . The sensor assembly  840  includes a source  882  for remitting beams  884  of radiant energy into and through the rotor extension portion  880  and the included centrifuge bag  226 . Again, as discussed previously, the radiant energy source  882  may be nearly any source of radiant energy (such as incandescent light, a strobe light, an infrared light, laser and the like) useful in a fluid density sensor and the particular type of detector or energy used is not as important as the external location of the source  882 . The sensor assembly  840  further includes a detector  886  that receives or senses beams  888  that have passed through the centrifuge bag  226  and have impinged upon the detector  886 . The detector  886  is selected to be compatible with the source  882  and to transmit a feedback signal in response sensing the energy beams  888 . The detector  886  (in combination with the controller  850  and its processing capacities) is useful for detecting the density of fluids in the centrifuge bag  226  between the source  882  and the detector  886 . Particularly, the sensor assembly  840  is useful for identifying changes in fluid density and interfaces between fluids with differing densities. For example, the interface between a region containing separated red blood cells and a region containing the platelet rich plasma fraction, and the interface between the platelet rich plasma region and a platelet-poor plasma region. 
     With some source and detector configurations, a sampling window is created rather than a single sampling point (although a single sampling point configuration is useful as part of the invention as creating a window defined by a single radial distance). The sampling window is defined by an outer radial distance, dour, from the central axis, ca, and an inner radial distance, d IN . As may be appreciated, for many source and detector configurations the size of the sampling window may be rather small approximating a point and may, of course vary in cross-sectional shape (e.g., circular, square, rectangular, and the like). As discussed previously, it is preferable that the sensor assembly  840  be positioned relative to the reservoir extension portion  880  and the centrifuge bag  226  such that the sampling window created by the source  882  and detector  886  at least partially overlaps the radial position of the region created during separation processes containing a component of particular density, such as platelets. This may be a calibrated position determined through calibration processes of the centrifuge  20  in which a number of blood (or other fluid) samples are fully separated and radial distances to a particular region are measured. The determined or calibrated position can then be utilized as a initial, fixed location for the sensor assembly  840  with the source  882  and detector  886  being positioned relative to the rotor extension portion  880  such that the sampling window overlaps the anticipated position of the selected separation region. Of course, each sample may vary in content of various components which may cause this initial alignment to be inaccurate and operations of the centrifugal processing system  800  may cause misalignment or movement of regions. Hence, alignment processes discussed above preferably are utilized in addition to the initial positioning of the sampling window created by the sensor assembly  840 . 
     In an alternate embodiment, the sensor assembly  840  is not in a fixed position within the separation system  800  and can be positioned during separation operations. For example, the sensor assembly  840  may be mounted on a base which can be slid radially inward toward the centrifuge  20  and radially outward away from the centrifuge  20  to vary the distances, d IN  and d OUT . This sliding movement is useful for providing access to the centrifuge bag  226 , such as to insert and remove a disposable bag. During operation, the sensor assembly  840  would initially be pushed outward from the centrifuge  20  until a new bag was inserted into the centrifuge bag  226 . The sensor assembly  840  could then be slid inward (or otherwise moved inward) to a calibrated position. Alternatively, the centrifugal processing system  800  could be operated for a period of time to achieve partial or full separation (based on a timed period or simple visual observation) and then the sensor assembly  840  slid inward to a position that the operator of the centrifugal processing system  800  visually approximates as aligning the sampling window with a desired region of separated components (such as the platelet rich plasma region). The effectiveness of such alignment could then readily be verified by operating the sensor assembly  840  to detect the density of the fluids in the centrifuge bag  226  and a calculated density (or other information) could be output or displayed by the controller  850 . This alternate embodiment provides a readily maintainable centrifugal processing system  800  while providing the benefits of a fixed position sensor assembly  840  and added benefits of allowing easy relative positioning to obtain or at least approximate a desired sample-window and separation region alignment. 
     In some situations, it may be preferable to not have a rotor extension portion  880  or to modify the rotor extension portion  880  and the sensor assembly  840  such that the extension is not significant to monitoring the separation within the blood reservoir or centrifuge bag  226 . Two alternative embodiments or arrangements are illustrated in  FIGS. 56 and 57  that provide the advantages of an external sensor assembly  840  (such as an external radiation source and detector). With these further embodiments provided, numerous other expansions of the discussed use of an external sensor will become apparent to those skilled in the arts and are considered within the breadth of this invention. 
     Referring to  FIG. 56 , a rotor  202  is illustrated that has no extending portion (although some extension may be utilized) and contains the centrifuge bag  226 . Again, the rotor  202  and centrifuge bag  226  are preferably fabricated from plastics or other materials that allow radiation to pass through to detect changes in densities or other properties of fluid samples within the centrifuge bag  226 . In this embodiment of the sensor assembly  840 , the radiation source  882  and the detector  886  are not positioned on opposing sides of the rotor  202 . Instead, a reflector  885  (such as a mirror and the like) is positioned within the drive portion  881  of the centrifuge to receive the radiation beams  884  from the radiation source  882  and direct them through the portion  880  and centrifuge bag  226 . The detector  886  is positioned within the sensor assembly  840  and relative to the centrifuge  20  to receive the deflected or reflected beams  888  that have passed through the fluid sample in the centrifuge bag  226 . In this manner, the sampling window within the centrifuge bag  226  can be selected to align with the anticipated location of the fraction that is to be collected upon separation. In a preferred embodiment, the sampling window at least partially overlaps with the location of the outlet tube of the blood reservoir or centrifuge bag  226 . 
     In one embodiment, the drive portion is fabricated from a non-transparent material and a path for the beams  884  from the radiation source  884  to the reflector  885  is provided. The path in one preferred embodiment is an opening or hole such as port  154  or  156  ( FIG. 14 ) in the side of the drive portion  881  that creates a path or tunnel through which the beams  884  travel unimpeded. Of course, the opening may be replaced with a path of transparent material to allow the beams to travel to the reflector  885  while also providing a protective cover for the internals of the drive portion  881 . A path is also provided downstream of the reflector  885  to allow the beams  884  to travel through the drive portion  881  internals without or with minimal degradation. Again, the path may be an opening or tunnel through the drive portion leading to the portion  202  or be a path created with transparent materials The beams  884  in these tunnel path embodiments enter the drive portion- 881  one time per revolution of the drive portion  881 , which provides an acceptable rate of sampling. Alternatively, a reflector  885  may readily be provided that extends circumferentially about the center axis of the drive portion  881  to provide a sampling rate equivalent to the rate of beam  884  transmission. Of course, the positions of the radiation source  882  and the detector  886  may be reversed and the angle of the reflector  885  and transmission of the beams  884  may be altered from those shown to practice the invention. 
     A further embodiment of an external sensor assembly  840  is provided in  FIG. 57 . In this embodiment, the radiation source  882  also acts as a radiation detector so there is no need for a separate detector. In this more compact external sensor configuration, the radiation source and detector  882  transmits beams  884  into the rotating drive portion  881  through or over the path in the drive portion  881 . The reflector  885  reflects the beams  884  toward the rotor  202  and the centrifuge bag  226  to create a sampling window within the centrifuge bag  226  in which density changes may be monitored. After passing through the centrifuge bag  226  and included fluid sample, the beams  888  strike a second reflector  887  that is positioned within the rotor  202  to reflect the beams  888  back over the same or substantially the same path through the centrifuge bag  226  to again strike the reflector  885 . The reflector  885  directs the beams  888  out of the drive portion  881  and back to the radiation source and detector  882  which, in response to the impinging beams  888 , transmits a feedback signal to the controller  850  for further processing. 
     In one embodiment, the beams  884  enter the driving portion  881  once during every revolution of the driving portion  881 . The portion  880  is preferably rotating twice for every rotation of the driving portion  881 , as discussed in detail above, and hence, the second reflector  887  is aligned to receive the beams  888  only on every other rotation of the driving portion  881 . Alternatively, a pair of reflectors  887  may be positioned in the rotor  202  such that the beams  888  may be received and reflected back through the centrifuge bag  226  once for every rotation of the driving portion  881 . In yet a further embodiment, the reflector  885  and second reflector  887  may expand partially or fully about the center axis of the centrifuge  20  (with corresponding openings and/or transparent paths in the driving portion  881 ) to provide a higher sampling rate. 
     According to an important feature of the invention, temperature control features are provided in an alternate embodiment of the automated processing system invention  900 , as illustrated in  FIG. 58 . Providing temperature controls within the processing system  900  can take many forms such as controlling the temperature of input fluid samples from the blood source  802 , monitoring and controlling the temperature of fluids in the centrifuge bag  226  to facilitate separation processes, and controlling the operating temperature of temperature sensitive components of the processing system  900 . These components include but are not limited to, red blood cells, white blood cells, plasma, platelet rich plasma or any of these components mixed with other drugs, proteins or compounds. In a preferred embodiment of the invention, a temperature control system is included in the processing system  900  to heat components removed from the centrifuge bag  226  by the outlet pump  830  to a desired temperature range. For example, when the processing system  900  is utilized in the creation of autologous platelet gel, a dispenser assembly  902  is included in the processing system  900  and includes chambers or syringes for collecting and processing platelet rich plasma drawn from the centrifuge  20 . As part of the gel creation process, it is typically desirable to activate the platelets in the harvested platelet rich plasma fraction prior to the use of the gel (e.g., delivery to a patient). The temperature control system is useful in this regard for raising, and for then maintaining, the temperature of the platelets in the dispenser assembly to a predetermined activation temperature range. In one embodiment of the gel creation process, the activation temperature range is 25° C. to 50° C. and preferably 37° C. to 40° C., but it will be understood that differing temperature ranges may readily be utilized to practice the invention depending on the desired activation levels and particular products being processed or created with the processing system  900 . 
     Referring to  FIG. 58 , the temperature control system of the processing system  900  includes a temperature controller  904  that is communicatively linked to the controller  850  with feedback signal line  906 . The controller  850  may be utilized to initially set operating temperature ranges (e.g., an activation temperature range) and communicate these settings over feedback signal line  906  to the temperature controller  904 . Alternatively, the temperature controller  904  may include input/output (I/O) devices for accepting the operating temperature ranges from an operator or these ranges may be preset as part of the initial fabrication and assembly of the processing system  900 . The temperature controller  904  may comprise an electronic control circuit allowing linear, proportional, or other control over temperatures and heater elements and the like. In a preferred embodiment, the temperature controller  904  includes a microprocessor for calculating sensed temperatures, memory for storing temperature and control algorithms and programs, and I/O portions for receiving feedback signals from thermo sensors and for generating and transmitting control signals to various temperature control devices (e.g., resistive heat elements, fan rotors, and other devices well-known to those skilled in the heating and cooling arts). 
     As illustrated, a temperature sensor  908  comprising one or more temperature sensing elements is provided to sense the temperature of the dispenser assembly  902  and to provide a corresponding temperature feedback signal to the temperature controller  904  over signal line  910  (such as an electric signal proportional to sensed temperature changes). The temperature sensor  908  may be any temperature sensitive device useful for sensing temperature and, in response, generating a feedback signal useful by the temperature controller  904 , such as a thermistor, thermocouple, and the like. In a preferred embodiment, the temperature sensor  908  is positioned within the dispenser assembly  902  to be in heat transferring or heat sensing contact with the syringes or other chambers containing the separated product which is to be activated. In this manner, the temperature controller  904  is able to better monitor whether the temperature of the relevant chambers within the dispenser assembly  902  is within the desired activation temperature range. 
     To maintain the chambers of the dispenser assembly  902  within a temperature range, a heater element  913  is included in the temperature control system and is selectively operable by the temperature controller  904  such as by operation of a power source based on signals received from the temperature sensor  908 . The heater element  913  may comprise any number of devices useful for heating an object such as the chambers of the dispenser assembly  902 , such as a fluid heat exchanger with tubing in heat exchange contact with the chambers. In a preferred example, but not as a limitation, electrical resistance-type heaters comprising coils, plates, and the like are utilized as part of the heater element  913 . Preferably, in this embodiment, the resistive portions of the heater element  913  would be formed into a shape that conforms to the shape of the exterior portion of the chambers of the dispenser assembly  902  to provide efficient heat transfer but preferably also allow for insertion and removal of the chambers of the dispenser assembly  902 . During operation of the separation system  900 , the temperature controller  904  is configured to receive an operating temperature range, to receive and process temperature feedback signals from the temperature sensor  908 , and in response, to selectively operate the heater element  913  to first raise the temperature of the chambers of the dispenser assembly  902  to a temperature within the operating temperature range and to second maintain the sensed temperature within the operating range. 
     For example, a desired operating range for activating a gel or manipulating other cellular components and their reactions onto themselves or with agents may be provided as a set point temperature (or desired activation temperature) with a tolerance provided on either side of this set point temperature. The temperature controller  904 , in this example, may operate the heater element  913  to raise the temperature of the chambers of the dispenser assembly  902  to a temperature above the set point temperature but below the upper tolerance temperature at which point the heater element  913  may be shut off by the temperature controller  904 . When the temperature sensed by the temperature sensor  908  drops below the set point temperature but above the lower tolerance temperature, the temperature controller  904  operates the heater element  913  to again raise the sensed temperature to above the set point temperature but below the upper tolerance temperature. In this manner, the temperature controller  904  effectively maintains the temperature of the chambers in the dispenser assembly  902  within a desired activation temperature range (which, of course, may be a very small range that approximates a single set temperature). In one embodiment, the temperature controller is or operates as a proportional integral derivative (PID) temperature controller to provide enhanced temperature control with smaller peaks and abrupt changes in the temperature produced by the heater element  913 . Additionally, the temperature controller  904  may include visual indicators (such as LEDs) to indicate when the sensed temperature is within a set operating range and/or audio alarms to indicate when the sensed temperature is outside the set operating range. 
     In another embodiment, the heater element  913  is configured to operate at more than one setting such that it may be operated throughout operation of the processing system  900  and is not shut off. For example, the heater element  913  may have a lower setting designed to maintain the chambers of the dispenser assembly  902  at the lower end of the operating range (e.g., acceptable activation temperature range) with higher settings that provide heating that brings the chambers up to higher temperatures within the set operating range. In another embodiment, the heater element  913  is configured to heat up at selectable rates (e.g., change in temperature per unit of time) to enhance the activation or other processing of separated liquids in the dispenser assembly  902 . This feature provides the temperature controller  904  with control over the heating rate provided by the heater element  913 . 
     As discussed previously, the invention provides features that combine to provide a compact separation system that is particularly adapted for onsite or field use in hospitals and similar environments where space is limited.  FIG. 59  illustrates one preferred arrangement of the centrifugal processing system  900  of  FIG. 58  that provides a compact profile or footprint while facilitating the inclusion of a temperature control system. An enclosure  916  is included as part of the temperature control system to provide structural support and protection for the components of the temperature control system. The enclosure  916  may be fabricated from a number of structural materials, such as plastic. The enclosure  916  supports a heater housing  918  that is configured to allow insertion and removal of the chambers and other elements of the dispenser assembly  902 . The heater housing  918  has a wall that contains the heater element  913  (not shown in  FIG. 59 ) which is connected via control line  914  to the temperature controller  904 . The temperature sensor  908  (not shown in  FIG. 59 ) is also positioned within the heater housing  918 , and as discussed with reference to  FIG. 58 , is positioned relative to the chambers of the dispenser assembly  902  to sense the temperature of the chambers, and the contained fluid, during operation of the system  900 . A temperature feedback signal is transmitted by the temperature sensor  908  over line  910  to temperature controller  904 , which responds by selectively operating the heater element  913  to maintain the temperature within the heater housing  918  within a selected operating range. 
     Because the separation system  900  includes temperature sensitive components, such as the controller  850 , the temperature control system preferably is configured to monitor and control the temperature within the enclosure  916 . As illustrated, a temperature sensor  920  is included to sense the ambient temperature within the enclosure  916 ′ and to transmit a feedback signal over line  922  to temperature controller  904 . An air inlet  930 , such as a louver, is provided in the enclosure  916  to allow air, A IN , to be drawn into and through the enclosure  916  to remove heated air and maintain the temperature within the enclosure  916  at an acceptable ambient temperature. To circulate the cooling air, a fan  934  is provided to pull the air, A IN , into the enclosure  916  and to discharge hotter air, A OUT , out of the enclosure  916 . The fan  934  is selectively operable by the temperature controller  904  via control signals over line  938 . The size or rating of the fan  934  may vary in embodiments of the invention and is preferably selected based on the volume of the enclosure  916 , the components positioned within the enclosure  916  (e.g., the quantity of heat generated by the separation system  900  components), the desired ambient temperature for the enclosure  916 , and other cooling design factors. 
     In an alternate embodiment of the present invention a dispenser  902 , as shown in  FIG. 60 , is provided, for manipulating the cellular fraction which has been isolated and collected via outlet lumen  232 . In general, the present invention relates to a dispenser  902  which allows for a manual or automated manipulation of a two-phase method for forming an autologous platelet gel  970  composition wherein all of the blood components for the platelet gel  970  are derived from a patient to whom the platelet gel  970  will be applied. 
     The methods of the present invention for preparing an autologous platelet gel  970  composition, discussed in further detail below, are represented in the flow diagrams depicted in  FIGS. 61-63 . As discussed previously, the methods of the present invention begins by forming anticoagulated whole blood  396  which is achieved by collecting a patient&#39;s whole blood  394  in a source container  398  having an anticoagulation agent; such as sodium citrate (citrate) or heparin. Preferably, the whole blood  394  is collected and mixed with a 3.8% solution of sodium citrate (referred to herein as “citrate collection medium”) specifically in a 9:1 ratio of blood to citrate collection-medium. A 3.8% solution of sodium citrate is prepared by adding 3.8 grams of sodium citrate per 100 ml of water. While a 3.8% sodium citrate collection medium is that which is frequently used to collect and preserve blood, the person skilled in this art will recognize that the ratio of sodium citrate to whole blood could be in the range of about 10.9-12.9% mMol final concentration. 
     First, as discussed in detail previously and depicted in  FIG. 61 , platelet rich plasma  260  and/or platelet poor plasma  262  are formed by centrifuging a quantity of anticoagulated whole blood  396  that was previously drawn from the patient. The platelet rich plasma  260  is first drawn from the centrifuge bag  226  and into collection chamber  400 . Collection chamber  400  is preferably a syringe, but any container that will not contact activate the collected fraction is acceptable. The platelet rich plasma  260  can be pumped via outlet pump  803  ( FIG. 53 ) into a collection chamber  400  or the desired fraction can be drawn directly into dispenser  902 . 
     In the preferred embodiment, depicted in  FIG. 62  according to route  951 , the platelet rich plasma  260 , in centrifuge bag  226 , is divided into two portions and stored in vessels  952  and  960 . The first portion is approximately ¼ to ½ of the total volume of platelet rich plasma  260  and is utilized in phase-one to prepare the thrombin, while the second portion of platelet rich plasma  260  is utilized in phase-two vessel  960 . Once the platelet rich plasma  260  or alternatively the platelet poor plasma  262  (shown in  FIG. 61 ) is obtained, the preferred methods to obtain thrombin and then produce the platelet gel compositions in an expedited manner, that is, in less than three minutes, are detailed diagrammatically in routes  951  or  981 , shown in  FIGS. 62 and 63 , respectively and discussed in detail below if, however, a longer clotting time, that is, in a range of two to eight minutes, is desirous the method to obtain the platelet gel composition of the present invention can proceed along the routes  971  and  987 , which are also detailed diagrammatically in  FIGS. 63 and 63 , respectively and discussed in detail below. 
     Phase-one according to the preferred embodiment ( FIG. 62 ) begins by restoring the clot-forming process. To accomplish this, an agent (restoration agent) capable of reversing the effects of the anticoagulation agent is added back into the first portion of the platelet rich plasma  260  stored in vessel  952 . Preferably, the restoration agent can be vessel  952  itself or the restoration agent is contained within vessel  952  prior to the introduction of platelet rich plasma  260 ; however, the restoration agent may also be introduced later. It is furthermore preferable that the contact activator be a material such as but not limited to glass wool  953  or silica, aluminum, diatomaceous earth, kaolin, etc., or non-wettable surfaces such as plastic, siliconized glass, etc. Chemical activators, such as kaolin, can also be used to speed up the clotting time; however, their subsequent removal would also be necessary. In the preferred embodiment, a plastic syringe is the preferred container used to collect the desired fraction. In the presently preferred embodiment of the invention, the reversal of the anticoagulant is accomplished using calcium chloride. However, any substance which is known or found to be functionally equivalent to calcium chloride, such as, calcium gluconate or calcium carbonate, in restoring the coagulation activity of citrated blood may be used in the practice of the present invention. Thus, although calcium chloride is the presently preferred calcium salt for use in the invention, any calcium salt which functions in a similar manner to calcium chloride may be used in the invention. Similarly, although many blood coagulation reactions are currently believed to require calcium ions as cofactors, any substance which is known or subsequently found to be functionally equivalent to calcium in facilitating these coagulation reactions may be used, either individually or in combination with calcium, in the practice of the present invention. If the anticoagulation agent used was heparin, then heparinase or any other suitable anticoagulant reversing compound would be used to reverse the effect of the anticoagulation agent. The concentration of the restoration agent used to reverse the anticoagulation will depend in part, upon the concentration of the anticoagulation agent in the platelet rich plasma  260  and the stoichiometry of the chelating and coagulation reactions. However, the concentration of the restoration agent used to reverse the anticoagulation must be sufficient to achieve clot formation. 
     Upon restoration of the platelet rich plasma  260  as shown in  FIG. 62 , a clot  954  will naturally form. The resulting clot  954  is then triturated by squeezing the clot  954  through glass wool  953  which serves not only as a contact activator but also as a filter, thus expressing thrombin  955 . Alternatively, or in addition a filter  958  having a large micron pore size thereby allowing the removal of clot debris and any activator or solids that are present. Filter  958  is positioned at the outlet  956  of vessel  952 . In the preferred embodiment, the thrombin  955  is then mixed with the second portion of platelet rich plasma (PRP)  260  contained within vessel  960  to form the platelet gel composition  970  of the present invention in less than three minutes and in quantities sufficient for clinical use. 
     Other additives can be added to the above-described process to increase the concentration of thrombin formed by the intrinsic pathway or the extrinsic pathway. 
     As discussed in detail above, restoring the clotting cascade function of citrated plasma by addition of calcium chloride and exposure to an activating agent such as glass wool can generate autologous thrombin. The yield of autologous thrombin by this method however, may be low due to incomplete conversion of prothrombin and the inactivation of generated thrombin by fibrin and antithrombin III. The addition of modifying-agents, such as epsilon aminocaproic acid, to the plasma may improve the yield by reducing the amount of thrombin neutralization. The greatest improvement in thrombin yield, however, will be achieved by providing a thromboplastic material upon which the necessary clotting factors will assemble to maximize the rate of prothrombin conversion. The activated platelet membrane provides such a stimulant surface and also enriches the necessary factor V activity by secreting additional factor V during platelet degranulation. The addition of exogenous lipoprotein and/or thromboplastic material to the plasma environment may also serve to maximize the thrombin generation by activation of both intrinsic and extrinsic clotting cascades. Additional amplification of autologous thrombin generation may also be attained by pretreatment of PRP and/or PPP to block or remove both antithrombin-III and fibrinogen prior to conversion of prothrombin to thrombin. Such modification may be attained by use of appropriate adsorptive agents, antibodies or precipitating reagents. 
     In an alternative embodiment, thrombin  955  is mixed with the platelet poor plasma  262  of phase-two thereby forming the autologous platelet gel composition  972  of the present invention in less than three minutes. 
     A third embodiment of the present invention, route  971 , shown in  FIG. 62 , contemplates collecting the original quantity of platelet rich plasma (PRP)  260  derived from the anticoagulated whole blood  396  in a container, having a wettable surface, such as glass. The platelet rich plasma  260  is then recalcified and the platelet gel composition  974  forms. The desired platelet gel composition  974  will require approximately two to eight minutes to form as opposed to less than a three minute formation as was described in the preferred embodiment. 
     In the fourth embodiment depicted diagrammatically by route  981  in  FIG. 63 , the platelet poor plasma  262 , rather then the platelet rich plasma  260 , is divided into two portions, as discussed previously in the preferred embodiment. The first portion, used in phase-one, which is approximately ¼ to ½ the original volume is stored in a vessel  952  having a wettable surface, then the restoration agent, preferably calcium chloride, is added directly to the platelet poor plasma  262 . Surface activation of the restored platelet poor plasma  262  occurs as result of the vessel&#39;s surface and/or the glass wool  953  or other surface or chemical activators and a clot  962  thus forms. The resulting clot  962  is triturated, as described previously, and the thrombin  955  is collected. Thrombin  955  is then mixed with the platelet rich plasma  260  of phase-two thereby forming the platelet gel sealant composition  973 . 
     In the fifth embodiment, thrombin  955  is mixed with the platelet poor plasma  262  of phase-two thereby forming the platelet gel composition  975  in less than three minutes. 
     The sixth embodiment follows route  987 , shown in  FIG. 63  wherein the original quantity of platelet poor plasma  262  is collected in a container having a wettable surface, such as glass. The platelet poor plasma  262  is then Decalcified and the platelet gel composition forms. 
     The tensile strength of the platelet gel compositions of the present invention can be effected by the addition of calcium ions. Consequently, if a stronger bioadhesive sealant composition is desired using the methods discussed above and disclosed in routes  951  and  981 , in  FIGS. 62 and 62 , respectively, more calcium ions may be added at the time the serum is introduced into the platelet rich plasma  260  or the platelet poor plasma  262 . Alternatively, if the method of preparing the platelet gel compositions follows routes  971  and  987 , depicted in  FIGS. 62 and 63 , respectively, then calcium ions may be introduced directly into the platelet rich plasma  260  or the platelet poor plasma  262  and the platelet gel compositions  974  and  976 , respectively, will form. 
     As discussed in further detail below, the time period necessary for the formation of the platelet gel composition of the present invention is dependent on the quantity of serum added. A 1:4, 1:2 and 3:4 ratio of serum to platelet rich plasma or platelet poor plasma results in the formation of the platelet gel composition in approximately 90, 55 and 30 seconds, respectively. Furthermore, due to the fact that thrombin is autocatalytic, it is important that the serum be used within five hours of preparation, preferably within two hours and ideally immediately. Alternatively, the serum can be chilled or frozen indefinitely. 
     The platelet gel compositions of this invention may be used for sealing a surgical wound by applying to the wound a suitable amount platelet rich plasma or platelet poor plasma. Moreover, due to the fact that the platelet gel compositions of the present invention have been prepared solely from blood components derived from the patient that is to receive the platelet gel there is a zero probability of introducing a new blood transmitted disease to the patient. The methods of the present invention may be further modified so that the formed platelet gel composition functions not only as a haemostatic agent, but also as an adjunct to wound healing and as a matrix for delivery of drugs and proteins with other biologic activities. For example, it is well known that fibrin glue has a great affinity to bind bone fragments which is useful in bone reconstruction, as in plastic surgery or the repair of major bone breaks. Consequently, in keeping with the autologous nature of the platelet gel composition of the present invention autologous bone from a patient can be ground or made into powder or the like, and mixed into the platelet rich plasma obtained in phase-two of the methods of the present invention. Autologous thrombin is then mixed in with the platelet rich plasma and bone fragments in an amount sufficient to allow the resulting gel to be applied to the desired locale where it congeals. Other materials that may be utilized are, but not limited to, gelatin collagen, degradable polymers, hyaluronic acid, carbohydrates and starches. 
     In instances where the desired platelet gel composition of the present invention is to further function as a delivery device drugs and proteins with other biologic activities the method of the present invention may be modified as follows. Prior to adding the thrombin, obtained in phase-one, to the platelet rich plasma of phase-two a wide variety of drugs and proteins with other biologic activities may be added to the platelet rich plasma of phase-two. Examples of the agents to be added to the platelet rich plasma prior to the addition of the serum include, but are not limited to, analgesic compounds, such as Lidocaine, antibacterial compounds, including bactericidal and bacteriostatic compounds, antibiotics (e.g., adriamycin, erythromycin, gentimycin, penicillin, tobramycin), antifungal compounds, anti-inflammatories, antiparasitic compounds, antiviral compounds, anticancer compounds, such as paclitaxol enzymes, enzyme inhibitors, glycoproteins, growth factors (e.g. lymphokines, cytokines), hormones, steroids, glucocorticosteroids, immunomodulators, immunoglobulins, minerals, neuroleptics, proteins, peptides, lipoproteins, tumoricidal compounds, tumorstatic compounds, toxins and vitamins (e.g., Vitamin A, Vitamin E, Vitamin B, Vitamin C, Vitamin D, or derivatives thereof). It is also envisioned that selected fragments, portions, derivatives, or analogues of some or all of the above may be used. 
     A number of different medical apparatuses and testing methods exist for measuring and determining coagulation and coagulation-related activities of blood. These apparatuses and methods can be used to assist in determining the optimal formulation of activator, that is, thrombin, calcium and plasma necessary to form the platelet gel composition of the present invention. Some of the more successful techniques of evaluating blood clotting and coagulation are the plunger techniques illustrated by U.S. Pat. No. 4,599,219 to Cooper et al., U.S. Pat. No. 4,752,449 to Jackson et al., and U.S. Pat. No. 5,174,961 to Smith, all of which are assigned to the assignee of the present invention, and all of which are incorporated herein by reference. 
     Automated apparatuses employing the plunger technique for measuring and detecting coagulation and coagulation-related activities generally comprise a plunger sensor cartridge or cartridges and a microprocessor controlled apparatus into which the cartridge is inserted. The apparatus acts upon the cartridge and the blood sample placed therein to induce and detect the coagulation-related event. The cartridge includes a plurality of test cells, each of which is defined by a tube-like member having an upper reaction chamber where a plunger assembly is located and where the analytical test is carried out, and a reagent chamber which contains a reagent or reagents. For an activated clotting time (ACT) test, for example, the reagents include an activation reagent to activate coagulation of the blood. A plug member seals the bottom of a reagent chamber. When the test commences, the contents of the reagent chamber are forced into the reaction chamber to be mixed with the sample of fluid, usually human blood or its components. An actuator, which is a part of the apparatus, lifts the plunger assembly and lowers it, thereby reciprocating the plunger assembly through the pool of fluid in the reaction chamber. The plunger assembly descends by the force of gravity, resisted by a property of the fluid in the reaction chamber, such as its viscosity. When the property of the sample changes in a predetermined manner as a result of the onset or occurrence of a coagulation-related activity, the descent rate of the plunger assembly there through is changed. Upon a sufficient change in the descent rate, the coagulation-related activity is detected and indicated by the apparatus. 
     Using the methods discussed above; cartridges were assembled with serum obtained from either platelet rich plasma or platelet poor plasma, and CaCl 2  in the reagent chambers. Clotting time tests were performed by the automated process with either platelet rich plasma (PRP) or platelet poor plasma (PPP) dispersed into the reaction chambers of the cartridges. In the first experiment, the results of which are represented in  FIG. 64 , the amount of serum, the type of plasma from which the serum was derived, and the type of plasma the serum was mixed with were tested to determine the shortest clotting times. The ratios of serum to platelet rich plasma or platelet poor plasma that were studied included 1:4, 1:2, and 3:4. In the second set of experiments, the results of which are represented in  FIGS. 66 and 67 , the actual gel time for the platelet gel of the present invention was compared to the clotting time in the cartridge, wherein there is a 0, 30, or 60 minute delay of adding the serum from its generation. The third set of experiments, the results of which are represented in  FIGS. 68 and 69 , studied the effect of calcium addition on actual gel time versus clotting time in the cartridge. The final set of experiments, the results of which are represented in  FIG. 65 , studied the effect of adding calcium on clotting times. 
     Although clotting times varied among donors, comparisons of clotting times for individual donors show significant effects of the serum to plasma ratio and the calcium concentration. For all donors, the shortest clotting times occurred for the 3:4 ratio, with clotting times that were 47% shorter than those for the 1:4 ratio. Although the difference in clotting times for the 3:4 ratio and the 1:2 ratio was not statistically significant, the clotting times were consistently shorter using the 3:4 ratio for all donors. These results demonstrate that clotting times may be shortened by increasing the serum to platelet rich plasma ratio. Similarly, clotting times were significantly affected by the amount of calcium added, with the shortest clotting times obtained when no calcium was added, suggesting that the serum contained levels, of calcium that were sufficient to recalcify the citrated platelet rich plasma. Preliminary results from the scale-up experiments suggest that experimental clotting times in the cartridges correlate with actual gel times. 
     The invention is further illustrated by the following non-limited examples. All scientific and technical terms have the meanings as understood by one with ordinary skill in the art. The specific examples which follow illustrate the methods in which the bioadhesive sealant compositions of the present invention may be prepared in a clinical setting and are not to be construed as limiting the invention in sphere or scope. The methods may be adapted to variation in order to produce compositions embraced by this invention but not specifically disclosed. Further, variations of the methods to produce the same compositions in somewhat different fashion will be evident to one skilled in the art. 
     EXAMPLES 
     The examples herein are meant to exemplify the various aspects of carrying out the invention and are not intended to limit the invention in any way. 
     Example 1 
     Preparation of Bioadhesive Sealant Composition Using Platelet Rich Plasma and Serum 
     6 cc&#39;s of platelet rich plasma are drawn into receiving chamber  961  and 3 cc&#39;s per PRP or PPP are drawn into receiving chamber  957  which further contains 0.33 cc&#39;s of 10% calcium chloride and glass wool. Clotting of the contents will occur in two to eight minutes in receiving chamber  957 . The clot is then squeezed through optional filter  958  and the serum, produced therefrom, is added to the platelet rich plasma contained in receiving chamber  961  by either mixing or spraying the two components. The platelet rich plasma and the serum will gel within approximately three minutes. 
     The application of the gel using the syringe-type devices  902  as described above maybe less than desirable for may applications. Consequently, in an alternate embodiment the inactive blood component and thrombin can be mixed and/or injected into a mold having a desired geometric shape. The mold may be constructed of a material having a wettable surface, such as, but not limited to plastic. In particular, platelet gel of the present invention may be used to temporarily fill, cavities such as but not limited to holes left in the gum from tooth extraction and/or holes left in tissue or bone as a result of injury or surgical procedures. The present invention provides a simpler way of introducing platelet gel for specific uses, by providing that the platelet gel be pre-shaped or molded into a beneficial shape prior to being inserted into a cavity. In the case of tooth extraction the platelet gel may be shaped so as to achieve a basic conical shape. Other shapes such as, but not limited to rods, and rectangles are contemplated by this invention. The ability to cause the gel to be more, or less, solid and thus malleable may be achieved during the activation sequence of the gel formation. 
     The foregoing description is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and processes shown as described above. Accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention as defined by the claims which follow. 
     The foregoing description is considered as illustrative only of the principles of the invention. The words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of one or more stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, or groups thereof. Furthermore, since a number of modifications and changes will readily will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and process shown described above. Accordingly, all suitable modifications and equivalents may be resorted to falling within the scope of the invention as defined by the claims which follow.