Abstract:
A device for applying and measuring fluid pressure in the lumen of a syringe in communication with a tubular member attached to a needle inserted into the body of a disk found in the spinal column of the back. A pressure transducer is integrally mounted in the plunger of the syringe under the plunger tip, such that the force applied by the plunger to the fluid in the syringe is transmitted to the transducer and the resulting electronic signal is converted to a display value aiding the physician in diagnosing diseased disks in the back. Other uses of pressure applying monitoring syringes for other applications in communication with the body also benefit from the disclosed syringe construction, such as percutaneous translumenal angioplasty (PTA) procedures.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. application Ser. No. 10/769,634, filed Jan. 30, 2004, pending, which claims the benefit of U.S. Provisional Application Ser. No. 60/468,398, filed May 5, 2003, under 35 U.S.C. § 119(e), the contents of which are hereby incorporated in their entirety by this reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to an infusion syringe apparatus for applying and monitoring fluid pressure applied to the intervertebral disk of the spinal column, or more specifically, monitoring of the pressure applied through a needle or cannula through the annulus fibrosus of the disk and into the nucleus pulposus thus allowing the diagnosis of diseased or ruptured disks. The field may further include fluid pressure-inducing syringes and methods involved in percutaneous translumental angioplasty (PTA) procedures.  
         [0004]     2. State of the Art  
         [0005]     Infusers utilized in diskography and balloon angioplasty are well known and established in medical practice. The tools typically applied to angioplasty have found application in other fields as well, including opening diseased carotid arteries, improving or reestablishing blood flow to the extremities of diabetics, and similar procedures. Similar tools have been used in the field of pain diagnosis and management related to orthopedic procedures related to the spine.  
         [0006]     The number of failed or ineffectual spine surgeries has driven the development of new techniques for verifying the location of damage or injury in the vertebral column. Typically these procedures involve the insertion of a curved or specifically shaped cannula or needle under the transverse process of the vertebra and around the inferior articular process and penetrate the annulus fibrosus. Application of fluid pressure to the nucleus pulposus will either go undetected, create relief from chronic pain, or induce a pain episode due to the pinching of a nerve. By the application of this technique to suspect vertebral disks, a physician can identify the pain locus and, thus, use the appropriate intervention to provide relief for the patient. This process is typically performed utilizing ionic contrast media, typically made from ionically bound iodine. This media allows the physician to view the procedure on a fluoroscope, which aids in needle positioning and visual diagnosis. Diagnosis is based on the ability, or inability, of the end of inter-vertebral disks to contain the contrast media when it is injected under pressure into the nucleus pulposus of the disk.  
         [0007]     Typically, any syringe with a mechanism for measuring pressure has been used to measure the patency of the inter-vertebral disk. However, such syringes typically utilize a transducer mounted at the distal end of the syringe barrel which is in communication with the fluid path of the syringe. The presence of a non-transparent transducer and associated fixtures adjacent the fluid path prevents clear vision of bubbles in the contrast media or other imperfections that may be of concern in interventional procedures. Such devices are described in U.S. Pat. Nos. 5,021,046 and 5,084,060. Also, many such devices are awkward to use, are unduly complex or fail to provide a flexible fluid pressure adjustment.  
       SUMMARY OF THE INVENTION  
       [0008]     The present instant invention includes a hand-operated syringe for applying pressure to a fluid within the syringe which pressurized fluid interacts, directly or indirectly, with some physiology of the human body.  
         [0009]     The syringe has a barrel, which may be constructed from a rigid material and, optionally, may be transparent. A plunger adapted to slide within the barrel and to apply pressure to fluid within the barrel may be configured to have two operative motions: 1) a first, sliding motion induced by direct hand motion, e.g., thumb force, at the proximal end of the plunger or some plunger extension attached generally axially to the proximal end of the plunger whereby a rapid increase or decrease in the fluid pressure can be controllably caused to occur within the syringe barrel and 2) a second motion wherein the plunger is not freely slidable but has threads which interact with an adjustment mechanism wherein the adjustment mechanism is engageable and disengageable to permit minute axial motion of the plunger to be made and thus adjust the applied fluid pressure in controlled micro pressure adjustments.  
         [0010]     The adjustment mechanism includes means whereby the threads on the plunger may be rapidly (instantaneously) disengaged to permit the plunger to slide freely thereby instantaneously releasing the fluid pressure within the syringe barrel. The adjustment mechanism engages threads on the plunger or on a casing (sleeve) associated with and enveloping at least a portion of the plunger&#39;s external surface.  
         [0011]     Various features of the syringe enable a user to completely operate the syringe with a single hand, leaving the user&#39;s other hand free to perform other tasks.  
         [0012]     A further feature of the syringe is a pressure monitoring system whereby the pressure of the fluid within the barrel may be observed and, by appropriate adjustment of the plunger, such pressure controllably increased, decreased, or released. The pressure monitoring system of the syringe may provide a user with one or more warnings when the pressure reaches a threshold value.  
         [0013]     A pressure sensitive transducer is fitted to communicate directly, or indirectly, with the fluid within the syringe barrel. Such transducers have conventionally been attached to the barrel generally at or near the distal end of the barrel, as illustrated in U.S. Pat. Nos. 5,021,046, 5,009,662, and 5,004,472 to Wallace (hereinafter collectively referred to as “the Wallace Patents”). While such positioning of the pressure sensitive transducer is acceptable for many purposes, the transducer and its associated fittings are not transparent and block the vision of a syringe operator of the fluid within that portion of the barrel adjacent the transducer. This may be very disadvantageous if air bubbles exist within the fluid within the syringe barrel or within the tubing leading to a patient&#39;s body especially where the fluid is intended to enter a portion of the body such as occurs with fluid injection into a spinal disk.  
         [0014]     A significant advantage is realized by attaching the transducer to the distal end (pressure tip) of the plunger and having at least a part of the electronics which are part of the pressure-monitoring apparatus contained within the plunger. A tip of the plunger in which the pressure transducer is positioned may be configured to cover, but accurately transmit pressure to, the pressure sensitive transducer.  
         [0015]     Placement of the transducer and, optionally, electronics on the plunger is especially useful inasmuch as the electronics may emit a wireless signal to cause a pressure reading to occur on a remote display, i.e., a display located on the exterior of the syringe barrel, a remote display not attached to the syringe barrel, including a display positioned at or near the proximal end of the syringe plunger or an extension attached thereto, or a display which is remote from the entire syringe.  
         [0016]     The display may alternatively interact with the electronics associated with the pressure transduced by an electrical conductor. For example, the pressure transducer may communicate, by wires, with electronics or a display that is permanently secured to a proximal end of the plunger, or with a electronics or a display that is configured to be detachably coupled to the syringe plunger.  
         [0017]     The electronics may be configured to ensure that the pressure sensitive transducer is initially exposed to an appropriate amount of pressure and, if not, indicate that there is a problem with the syringe.  
         [0018]     A memory element may be associated with the electronics to store and facilitate transfer of data generated by use of the pressure sensing transducer. In addition, or alternatively, the electronics of a syringe according to the present invention may be provided with a communication element that facilitates the transmission of data generated by the pressure sensing transducer to external electronic devices, such as computers.  
         [0019]     Other features and advantages of the present invention will become apparent to those in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0020]      FIG. 1  is a perspective view of a syringe of the present invention;  
         [0021]      FIG. 2  is a perspective view of the proximal portion of the syringe of  FIG. 1 ;  
         [0022]      FIG. 3  is an exploded view of a plunger of the syringe and a rotatable sleeve that encases the plunger;  
         [0023]      FIGS. 4A and 4B  are exploded views of components associated with the distal end of the plunger;  
         [0024]      FIG. 5  is an exploded view that includes a perspective view of a tip that is associated with the distal end of the plunger to shield a pressure transducer of the syringe while accurately transmitting fluid pressure to the pressure transducer;  
         [0025]      FIGS. 6A-6C  include several views of a clamshell locking mechanism for a syringe of the present invention;  
         [0026]      FIG. 7  is a cross-sectional perspective view of the syringe of  FIG. 1 ;  
         [0027]      FIG. 7A  is a schematic representation of exemplary electronics that may be associated with a syringe according to the present invention;  
         [0028]      FIGS. 8A-8C  are perspective views of a syringe with a streamlined block-shaped head containing a display element of a syringe that incorporates teachings of the present invention;  
         [0029]      FIG. 9  is a cross-sectional view of a plunger having electronics that transmit a wireless signal to a display element located at a proximal end of the plunger;  
         [0030]      FIG. 10  is a perspective view of the syringe of  FIGS. 8A-8C  with fanciful display holder; and  
         [0031]      FIG. 11  is an exploded view of a plunger that includes a reusable electronics and display module which is detachable from the remainder of the syringe. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]      FIG. 1  is an external perspective view of a syringe  10  that incorporates teachings of the present invention. Syringe  10  includes an elongate barrel  14  and a plunger  11  disposed within barrel  14 .  
         [0033]     Barrel  14 , which may be configured similarly to other syringe barrels that are known in the art, includes a connection element  20 , such as a luer lock or a slip socket type connection element, at a distal end  14   d  thereof. By way of example only, connector  20  may be configured to secure a bonded extension line to barrel  14 , in pressure-tight fluid communication therewith. Barrel  14  may also include rings or other grasping elements  15   a  and  15   b  at or near the proximal end  14   p  thereof. Grasping elements  15   a  and  15   b  may be held by the index finger and the middle finger of a health care professional (e.g., a physicial or technician) or other individual who is using syringe  10 .  
         [0034]     Plunger  11  may have a ring or other grasping element  12  at the proximal end  11   p  thereof. Grasping element  12  of plunger  11  may be configured to facilitate manipulation of plunger  11  (e.g., longitudinal movement of plunger  11  through barrel  14  and, thus, the fluid pressure generated by syringe  10 ) with the thumb or other digit of an individual who is using syringe  10 , or with automated apparatus for controlling the operation of syringe  10 .  
         [0035]     In the illustrated embodiment of syringe  10 , grasping elements  12 ,  15   a , and  15   b  are positioned in a triangular arrangement, in which they are in close proximity to one another. Such an arrangement facilitates operation of syringe  10  with a single hand of an individual (e.g., the index finger, thumb, and middle finger of one hand, as previously described). By allowing an individual to operate syringe  10  and, thus, to perform any procedure in which fluid pressure is directly or indirectly applied to any human body part, including a spinal disk or an artery, with a single hand, the individual is free to use his or her other hand to accomplish additional tasks, particularly those associated with the procedure being performed.  
       The Plunger  
       [0036]     With reference to  FIG. 3 , the majority of plunger  11  is an elongate, at least partially hollow element, which has an outer surface  27  and includes an inner bore  26  that is located for communication with a distal end  11   d  of plunger  11 . Additionally, plunger  11  may include a somewhat annular end cap  19  at distal end  11   d  thereof, which is configured to retain a pressure transducer  24  and transducer retainer  31  in place relative to inner bore  26 , while allowing for the communication of fluid pressure from the exterior (at least at distal end  11   d ) of plunger  11  to pressure transducer  24 .  
         [0037]     Pressure transducer  24  may comprise any transducer or group of transducers that is suitable for accurately measuring fluid pressures within one or more ranges that may be encountered by use of syringe  10 . Exemplary transducers that may be employed as pressure transducer  24  include those described in the aforementioned Wallace patents, the disclosure of each of which is hereby incorporated herein in its entirety by this reference.  
         [0038]     A quantity of gel  24 G of a type known in the art (e.g., a silicone gel) may also be disposed within an aperture  19 A of end cap  19  and over a pressure-sensing region  24 P of pressure transducer  24  to provide some protection thereto. Of course, gel  24 G is of a type that accurately transmits fluid pressure present at distal end  11   d  of plunger  11  to pressure-sensing region  24 P and may, therefore, also be referred to as a “force transmitting gel.” 
         [0039]     Transducer retainer  31  is a small, somewhat annular element which is configured to be securely positioned relative to inner bore  26  and end cap  19  and which includes features that are configured to be secured pressure transducer  24  and which includes an outer in position within inner bore  26  during movement of plunger  11  and when high fluid pressures are present within the lumen of barrel  14  ( FIG. 1 ).  
         [0040]     As shown in  FIGS. 4A and 4B , end cap  19  includes a detent  33  at a distal end  19   d  thereof. Detent  33  is configured to receive corresponding features on the interior of a rubber plunger tip  32 , which seals against an inner surface of barrel  14 . As depicted, plunger tip  32  includes an aperture  32   a  therethrough to facilitate the communication of fluid pressure to pressure transducer  24 .  
         [0041]     Alternatively, with reference to  FIG. 5 , a plunger tip  32 ′ that covers a pressure-sensing region  24 P of pressure transducer  24  may be positioned over distal end  11   d  of plunger  11  ( FIG. 3 ), such as over the illustrated end cap  19  that is to be secured to distal end  11   d . Plunger tip  32 ′ includes a somewhat rigid sealing element  32 S′ at the outer periphery thereof, which surrounds a central element  32 C′.  
         [0042]     Rigid sealing element  32 S′ of plunger tip  32 ′ is configured to be secured to an end of plunger  11 . Without limiting the scope of the invention, rigid sealing element  32 S′ may be configured to be secured to end cap  19 , as illustrated. Accordingly, rigid sealing element  32 S′ may include an internally protruding ridge (not shown) that is configured to be inserted into and engaged by detent  33  of end cap  19 . Additionally, rigid sealing element  32 S′ of plunger tip  32 ′ is configured to seal against an inner surface of barrel  14  ( FIG. 1 ).  
         [0043]     Central element  32 C′ of plunger tip  32 ′ is configured to be disposed over, to substantially shield, and to accurately transmit fluid pressure to pressure-sensing region  24 P of pressure transducer  24  and, optionally, gel  24 G located thereover. In the illustrated example, central element  32 C′ is disposed over an aperture  19 A of end cap  19 , through which fluid pressure is communicated to pressure-sensing region  24 P. Central element  32 C′ may comprise the majority of a distal surface  32   d ′ of plunger tip  32 ′ (e.g., about 60% to about 70% of the area of distal surface  32   d ′). By way of example only, central element  32 C′ may be a pliable element that substantially shields pressure transducer  24  from fluids that are present at distal end  1   d  of plunger  11  ( FIG. 3 ). The thickness of such an embodiment of central element  32 C′ and the material (e.g., silicone) from which such a central element  32 ′ is formed are together configured to accurately transmit fluid pressure that is present at distal end  1   d  of plunger  11  to pressure-sensing region  24 P of pressure transducer  24 .  
         [0044]     Other arrangements for securing a pressure transducer  24  to a plunger of a syringe may also be utilized and, thus, are also within the scope of the present invention.  
       Electronics  
       [0045]     Turning to  FIG. 7 , which is a perspective, sectional view of syringe  10  taken along the central longitudinal axis of plunger  11  and barrel  14  thereof, inner bore  26  may extend along substantially the entire length of plunger  11 . Additionally, plunger  11  may include an enlarged, hollow region  37  at proximal end  11   p  thereof with an interior  37 I that communicates with inner bore  26 . It is in this space that an electronics assembly  38  may be incorporated to connect pressure transducer  24  to a display element  39  ( FIGS. 8A through 8C ), which may be located at proximal end  11   p  of plunger  11 .  
         [0046]     Wires (not shown) may extend through inner bore  26  to connect pressure transducer  24  with corresponding elements of the electronics assembly, as known in the art. Alternatively, inner bore  26  may facilitate wireless communication between pressure transducers and corresponding elements of the electronics assembly, as described in further detail hereinafter.  
         [0047]     Electronics assembly  38  may, as shown in  FIG. 7A , include one or more microcontrollers  38 C or other processing elements of a type known in the art, which receive signals from pressure transducer  24 , process the received signals, then output a signal that causes display element  39  to display a numeric indicator of the pressure that has been sensed at distal end  11   d  of plunger  11  by pressure transducer  24 . Electronics assembly  38  also includes a power source  38 B, such as the depicted battery, which comprises a battery having a voltage (e.g., 3 V) sufficient for operating microcontroller  38 C, display element  39 , and other elements that are part of or otherwise associated with electronics assembly  38 .  
         [0048]     Communication between power source  38 B and other electronic elements may be controlled by a switch of a known type. Alternatively, a power inhibitor  38 I, which is formed from electrically insulative material (e.g., plastic, paper, plastic-coated paper, ceramic, glass, etc.) may be positioned between power source  38 B and a contact (not shown) to power source  38 B. When power inhibitor  38 I is removed, electrical communication between power source  38 B and the contact and, thus, electronic components of syringe  10  ( FIG. 7 ) in communication with the contact is established.  
         [0049]     Each time power is initially provided to microcontroller  38 C, such as when power is initially provided to microcontroller  38 C, microcontroller  38 C may be programmed to enter a “zero loop.” In the “zero loop,” microcontroller  38 C determines whether less than a minimum threshold or more than a maximum threshold in differential pressure (e.g., relative to atmospheric pressure, which is equal to zero) is being measured by pressure transducer  24  ( FIG. 7 ). As an example, and not to limit the scope of the present invention, the maximum threshold may be set at about 4 to about 4½ psi, which accommodates the typically 2½ psi variation between atmospheric high and low pressures, as well as variations in pressure at different elevations. Such programming of microcontroller  38 C may permit microcontroller  38 C to receive pressure signals from pressure transducer  24  for a given period of time (e.g., ten seconds), to provide a more accurate sample of the measured pressure. If the fluid pressure that has been measured by pressure transducer  24  exceeds the maximum threshold, microcontroller  38 C shuts down, causes display element  39  to shut down, or go “dark” or “blank,” and restarts, automatically reentering the “zero loop.” When the fluid pressure that is initially measured following provision of power to microcontroller  38 C is at or below the maximum threshold, microcontroller  38 C may output some indication that pressure transducer  24  has been calibrated, such as by causing display element  39  to show the characters “CAL.” Programming of this type prevents inaccurate pressure measurements that may be caused by accidentally or by misuse of syringe  10  and provide a user of syringe  10  with an indication of the existence of a problem.  
         [0050]     An improper initial pressure may be caused by a variety of factors, including, without limitation, if gel  24 G ( FIG. 5 ) sticks to an adjacent area of plunger tip  32  ( FIGS. 5A and 5B ) (which may result in a lower-than-actual) pressure reading by pressure transducer), leaving a cap over connection element  20  ( FIG. 1 ) of barrel  14  ( FIG. 3 ), the presence of bubbles in a fluid within the lumen of barrel  14 , a premature build-up of pressure within barrel  14  (e.g., by using syringe  10  before power is provided to microcontroller  38 C), or otherwise. In reaction to the repeated initialization and shutting down of microcontroller  38 C as a result of the detection of an undesirable fluid pressure as a “zero loop” is being effected, a user may prompted to evaluate syringe  10  and its various components and correct the problem, then restart microcontroller  38 C.  
         [0051]     The display element  39  ( FIGS. 8A through 8C ) of syringe  10  ( FIG. 7 ) that communicates with microcontroller  38 C may comprise any suitable type of display known in the art. By way of nonlimiting example, display element  39  may comprise one or more groups of light emitting diodes (LEDs), each of which may be illuminated in a variety of combinations to form a corresponding variety of characters (e.g., numbers, letters, etc.). As another example, display element  39  may comprise a liquid crystal display of a known type, which likewise includes elements that may be stimulated into displaying combinations of lines that form a variety of different characters. Of course, any other type of display that would be suitable for displaying pressure information and any other desired information that has been processed and output by microcontroller  38 C (e.g., in the form of characters, images, etc.) may also be used in a syringe  10  of the present invention without departing from the scope of the present invention.  
         [0052]     In addition to processing pressure signals that have been received from pressure transducer  24  ( FIG. 7 ), a microcontroller  38 C of electronics assembly  38  that incorporates teachings of the present invention may be programmed to cause any displayed characters to flash when it may be desirable to catch the attention of an individual who is operating syringe  10 . Alternatively or additionally, microcontroller  38 C may transmit signals to other output elements (not shown), such as audio outputs, vibratory outputs, or the like, to provide a caution or warning an individual who is using syringe  10 . Such signals may be provided merely for information purposes, or for safety purposes. For example, if the fluid pressure measured at distal end  11   d  of plunger  11  by pressure transducer  24  exceeds a threshold value (e.g., 125 psi, which is approaching the upper limit of pressure that should be encountered during discography), microcontroller  38 C may cause characters of display element  39  (or images or a backlight on any other type of display element), which may show a value representative of the measured pressure, to repeatedly flash.  
         [0053]     In some embodiments of syringe  10 , electronics assembly  38  may include a memory element  38 M in communication with microprocessor  38 C. Memory element  38 M may, by way of example only, comprise a flash-type memory (i.e., flash EEPROM) associated with microprocessor  38 C. Such a memory element  38 M may be an internal element, which is permanently associated with microprocessor  38 C, or an external element, which is configured to temporarily communicate with microprocessor  38 C by way of a communication element  38 P (e.g., a USB port), then be removed therefrom and used elsewhere. Of course, communication elements  38 P that communicate with microcontroller  38 C may also be used for any other suitable purpose, including for establishing communication between microcontroller  38 C and a processing element (e.g., a processor) of a computer (e.g., for further evaluation of transmitted data, to transfer data from memory element  38 M for storage on a centrally accessible file, etc.).  
         [0054]     Internal memory elements  38 M may be used with syringes  10  that include reusable electronics assemblies  38 . External memory elements  38 M are particularly useful when transfer of the data stored thereon is desirable, or when syringe  10 , including electronics assembly  38  and display element  39  thereof, is disposable.  
         [0055]     A further embodiment of syringe according to the invention incorporates a wireless transmission of pressure information from the pressure transducer to the read-out display at the proximal end of the syringe. The transducer analog output may be introduced to a wireless transmitter to transmit an analog signal to the distal end of the syringe where a wireless receiver receives said signal, converts it to a digital signal which is introduced directly into the digital read-out display.  
         [0056]     The wireless transmitter may be an infra-red processor/transmitter which receives the analog electrical signal, converts it into an infra-red analog signal which is emitted from an infrared (IR) emitter, which has a battery associated therewith. The IR analog signal is transmitted through the body of the syringe preferably through an open channel to an IR analog receiver/converter at the proximal end of the syringe. Alternatively, the electrical signal may be converted into a digital IR or other digital wireless signal to be received by an appropriate receiver. An optical fiber may be advantageously used for precise IR transmission from the IR transmitter to the IR receiver. Further, a digital signal may be sent via an electrical conductor between the transducer/transmitter and the receiver/display.  
         [0057]     The IR signal may pulses that flash at a rate which is indicative of a particular pressure measurement by pressure transducer  24  ( FIGS. 3 through 5 ), or that are embedded with data and, thus, pulse in a manner that is indicative of the embedded data (e.g., somewhat like Morse Code).  
         [0058]     The disclosure of U.S. Pat. Nos. 5,215,523 and 5,387,194 to Williams/Call et al., the disclosures of both of which are hereby incorporated herein in their entireties by this reference, especially with respect to means and systems for wireless transmission of signals produced by a pressure transducer. Also, incorporated herein is U.S. Pat. No. 5,021,046 to Wallace, especially the disclosure relating to pressure transducers.  
         [0059]     Also, wireless transmission of pressure transducer information by radio signals may be utilized within the syringe for the purposes of the invention. However, radio signals may interfere with various other equipment in an operating room-type of environment and would generally be contraindicated where such a syringe was to be utilized upon a patient having a pacemaker.  
         [0060]      FIGS. 8A through 8C  are perspective views of a syringe with a pressure display head located in a display holder having a thumb aperature located between the display and the plunger.  
         [0061]      FIG. 8A  is a perspective view of a syringe  10 ′ with a pressure display head located in a display holder having a thumb aperature located between the display and the plunger. This particular syringe may incorporate the wired connection between the pressure transducer and the pressure display or a wireless transmission system such as that illustrated in  FIG. 9 .  
         [0062]      FIGS. 8B and 8C  show an elevational view and plan view, respectively, of syringe  10 ′ (infuser) of  FIG. 8A . The display-holding portion  37 ′ of syringe  10 ′ is unique in appearance, as can be seen in  FIGS. 8A, 8B  and  8 C. Additionally, the style, shape and juxtaposition of the various elements of the syringe further provide a syringe  10 ′ of a distinctive appearance.  
         [0063]      FIG. 8C  shows the bottom of the display holder, assuming that the surface in which the display is embedded, is denoted the top surface, which is visible in  FIGS. 8A and 8B .  
         [0064]     The syringe  10 ′ of  FIGS. 8A, 8B , and  8 C has the thumb preferably inserted in thumb aperture  12 ′ from the bottom so that the display  39  will face upwards to the technician operating syringe  10 ′.  
         [0065]     This particular syringe may incorporate the wired connection between the pressure transducer and the pressure display or a wireless transmission system such as that illustrated in  FIG. 9   
         [0066]     An embodiment of the invention is shown in  FIG. 9  illustrating in perspective view a hollow plunger  11  having a pressure sensing transducer  24  located at or near plunger tip  32  (distal end), which transducer is electrically connected to an electronics system  40  which wirelessly transmits its output signal (IR or radio frequency (RF)) to a remote receiver/pressure display  41  system. Display  39  may be located at or near the proximal end of said plunger or at a remote location separate from said plunger, e.g., attached to an external surface of said syringe or entirely separate and remote from said syringe, e.g., on a support which positions said pressure display visible to one or more members of a team involved in an infusion procedure.  
         [0067]     The signal transmitted from said electronics system to said display may be an analog or digital signal. If the signal is an analog signal then the pressure display includes a receiver mechanism which receives said signal and converts the analog signal to a digital signal suitable for being displayed as a pressure in millimeters of mercury, pounds per square inch or other useful pressure units. The display mechanism may further have a memory device whereby the total infusion procedure is recorded in terms of elapsed time and regular (substantially continuously, if desired) pressure recordings so that a history of the entire infusion procedure may be later downloaded for permanent storage.  
         [0068]     A substantially hollow plunger having an internal pressure sensing mechanism, e.g., pressure transducer, in the tip which is in direct or indirect contact with fluid of a syringe being pressurized has many advantages, many of which have been enumerated herein. One such advantage is that a direct pressure reading may be displayed in a display incorporated in the proximal end of the plunger. Also, in a structure such as described herein, a fluid, preferably liquid, may be contained within the hollow plunger to contact a dynamic (diaphragm) type-pressure influenced mechanism and conduct the received pressure through said fluid, preferably liquid, to a pressure transducer/display in the proximal end of said plunger.  
         [0069]     In such a structure the pressure experienced at the tip of the plunger is transmitted by a fluid conductor to a pressure transducer or other pressure metering means, e.g., an analog pressure meter, at the proximal end of the plunger. Such a structure permits all the electronics necessary for a digital display, e.g., pressure transducer, analog/digital converter and digital signal receiving display to be directly coupled to one another and located at or near the proximal end of the hollow plunger.  
         [0070]     The display at the proximal end of the syringe may be incorporated into a housing of the varying shapes and designs shown herein which accommodate functional purposes. The shape of the display housing shown in  FIGS. 8A through 8C  is particularly fanciful to provide a smooth aesthetic appearance while not diminishing its attributes as a display holder and thumb engagement device. A further perspective view of the syringe of  FIGS. 8A through 8C  is shown in  FIG. 10 . The view is at an oblique angle from the rear of the syringe.  
         [0071]      FIG. 11  illustrates another embodiment of syringe  10 ″ according to the present invention, which includes wires  46  that extend from the pressure transducer  24  thereof. Modular electronics  38 ″ may be “plugged into” and “unplugged” from an electrical connector  44 , or plug, of known type of syringe  10 ″. Electrical connector  44  may be positioned adjacent to distal end  11   d  of plunger  11  in a relatively fixed position.  
         [0072]     Electrical connector  44  includes pins or receptacles  45  that communicate with one or more wires  46 . Wires  46 , in turn, communicate with corresponding contacts (not shown) of a pressure transducer  24 .  
         [0073]     Modular electronics  38 ″ also includes an electrical connector  47 , which is configured complementarily to electrical connector  44  and, thus, includes receptacles or pins  48  that are positioned and configured to cooperate and electrically communicate with corresponding pins or receptacles  45  of electrical connector  44 . Receptacles or pins  48  have wires  49  coupled thereto, which establish communication with one or more of components (e.g., microcontroller  38 C, power source  38 B, etc.) of an electronic assembly  38  of modular electronics, such as the exemplary electronic assembly  38  depicted in  FIG. 7A .  
         [0074]     By way of example only, electrical connectors  44  and  47  may comprise electronic (e.g., computer) communication ports of known type that are configured to mate with one another.  
         [0075]     As modular electronics  38 ″ may be uncoupled from syringe  10 ″, modular electronics  38 ″ may be used repeatedly, with a plurality of disposable syringes  10 ″. Additionally, modular electronics  38 ″ may be coupled with a communication port of a computer or other electronic device to facilitate programming of one or more elements (e.g., microcontroller  38 C) of electronic assembly  38 , data transfer (e.g., from memory element  38 M of electronic assembly  38 ), or for any other reason to establish communication between one or more components of electronic assembly  38  and an external electronic device.  
       Elements for Positioning the Plunger  
       [0076]     With returned reference to  FIGS. 1 through 3 , syringe  10  may additionally include means for adjusting the position of plunger  11  within barrel and, thus, for controlling the amount of pressure generated by syringe  10 . The means for adjusting may be configured to provide for fine adjustments of the position of plunger  11  and, thus, of the pressure generated by syringe  10 , as well as for larger adjustments.  
         [0077]     Fine adjustments of the position of plunger  11  within barrel  14  may, for example, be accomplished with the depicted rotatable sleeve  16 , which is an elongate, hollow, cylindrical element that is disposed, as a sleeve, over and may be supported by at least a portion (e.g., a smooth portion) of outer surface  27  of plunger  11 . After rotatable sleeve  16  is slid over plunger  11 , a friction reduction washer  30  may be placed over outer surface  27  of plunger  11 , adjacent to distal end  16   d  of rotatable sleeve  16 , to act as a friction reducing bearing between rotatable sleeve  16  and end cap  19  and, thus, to facilitate the substantially free rotation of rotatable sleeve  16  relative to end cap  19 . Rotatable sleeve  16  includes threads  13  on an exterior surface thereof and a control element  23 , such as the depicted wheel, at a proximal end  16   p  thereof.  
         [0078]     Threads  13  may be engaged by corresponding features (not shown) of a locking mechanism  17 , which is associated with and remains in a substantially fixed location relative to proximal end  14   p  of barrel  14 . Locking mechanism  17  includes a housing  17 H and a locking element  17 L. Apertures  25 H and  25 L of housing  17 H and locking element  17 , respectively, accommodate rotatable sleeve  16 . Housing  17 H is secured in place relative to proximal end  14   p  of barrel (e.g., by being molded integrally therewith, bonded thereto, etc.). Locking element  17 L is associated with housing  17 H and may be moved relative thereto.  
         [0079]     As shown in  FIG. 2 , housing  17 H is configured to captivate locking element  17 L in such a way that locking element  17 L may slide laterally relative housing  17 H and radially relative to barrel  14 . In the illustrated example, opposite ends of locking element  17 L are exposed through housing  17 H to facilitate movement thereof. Aperture  25 H of housing  17 H has dimensions that facilitate the substantially free longitudinal movement of rotatable sleeve  16  and, thus, the plunger  11  therein transversely thereto. Aperture  25 L of locking element  17 L may comprise a keyhole-shaped opening, which may include two overlapping circular apertures, one having a larger diameter than the other. The smaller side of aperture  25 L has dimensions that facilitate engagement of threads  13  of rotatable sleeve  16 , while the dimensions of larger side of aperture  25 L are configured not to engage threads  13  and, thus, allow substantially free travel of plunger  11  longitudinally through barrel  14 .  
         [0080]     Locking element  17 L may be placed in a locked, or set, position by causing an interior rib  18 , which is located at an edge of the smaller side of aperture  25 L, to engage threads  13  of rotatable sleeve  16  (e.g., by insertion within a groove of threads  13 ). When in an unlocked, or released, position, interior rib  18  disengages threads  13  of rotatable sleeve  16 , permitting substantially longitudinal movement of rotatable sleeve  16  and, thus, plunger  11  through barrel  14 .  
         [0081]     When locking mechanism  17  is in a locked position (e.g., slid to one side), fine, or minute, adjustments of the position of plunger  11  within barrel  14  and, thus, associated fine or minute adjustments to volume or pressure within the lumen of barrel  14  may be made by use of control element  23 . For example, if control element  23  comprises a wheel which is positioned and configured to be rotated by the thumb of an individual (and, thus, may also be referred to herein as a “thumbwheel”), displacement of plunger  11  relative to barrel  14  may be generated by rotation of control element  23 . Rotation of control element  23  in a direction that forces rotatable sleeve  16  against a flange, such as that provided by a proximal edge  19   p  ( FIG. 4B ) of end cap  19 , against which distal end  16   d  of rotatable sleeve abuts, thereby forcing plunger  11  distally along the length of barrel  14 . As fluid pressure within the lumen of barrel  14  may exert force on plunger  11 , rotation of control element  23  and, thus, rotatable sleeve  16  in the opposite direction (i.e., such that rotatable sleeve  16  moves proximally relative to barrel  14 ), plunger  11  may move proximally relative to barrel  14 . The axial advancement or retraction of plunger  11  effected by rotation of control element  23  is very slight, thus, minute adjustments of fluid pressure are readily accomplished. The ability to achieve such precise adjustment of fluid pressure is desirable in a number of medical procedures, including, but not limited to, discography and angioplasty procedures.  
         [0082]     When locking mechanism  17  is in an unlocked position (e.g., slid to the other side), plunger  11  may be substantially freely moved along the length of barrel by placing force on proximal end  11   p  thereof (e.g., as an individual places his or her thumb within the depicted grasping element  12 , then moves his or her thumb). Thus, larger adjustments of the position of plunger  11  may be made when locking mechanism  17  is in an unlocked position.  
         [0083]     When fluid pressure within the lumen of barrel  14  increases, positioning of locking mechanism  17  in an unlocked position, so as to release threads  13 , allows the fluid pressure to force plunger  11  proximally through barrel  14 , facilitating a rapid, substantially instantaneous reduction of pressure (e.g., to zero additional pressure exerted by syringe  10 ) within barrel  14  and, thus, within a portion of the body of a subject with which the lumen of the barrel  14  is in fluid communication. This feature is desirable since many procedures may require a substantially instantaneous release of fluid pressure to prevent or minimize damage to a body part that is being treated or investigated.  
         [0084]     While a particular embodiment of slide-lock mechanism has been illustrated and described herein, other locking mechanisms may be also effectively utilized on syringes that incorporate teachings of the present invention. For example, a two-piece clam-shell, spring-loaded mechanism, such as that shown in  FIGS. 6A through 6C , can be usefully employed. Two clam-shaped elements  34  and  35  are hinged at their closed ends and spring-biased to be in a “closed” position, as shown in  FIG. 6A . A rotatable cam  36 , which has an elongate cross-section taken transversely to the length thereof, is positioned between clam-shaped elements  34  and  35 , at the open ends thereof. While the smaller dimension of rotatable cam  36  separates clam-shaped elements  34  and  35 , they remain in the “closed” position. When the rotatable cam is rotated, larger dimensions thereof separate the open ends of clam-shaped elements  34  and  35 , forcing them apart from one another and into an “open” position, as shown in  FIGS. 6B and 6C . When clam-shaped elements are in the “open” position, a threaded rotatable sleeve  16  or a threaded plunger  11 ′ may slide freely therebetween.  
         [0085]     Alternative mechanisms for locking and unlocking threaded rotatable sleeve  16  ( FIGS. 1 through 3 ) or a threaded plunger ( FIGS. 6A through 6C ) in a fixed position to provide minute pressure adjustment may be also employed without departing from the scope of the present invention, including, without limitation, the locking mechanisms that are disclosed in U.S. Pat. Nos. 5,860,955, 5,433,707, and 5,685,848, the disclosures of which are hereby incorporated herein in their entireties by this reference.  
         [0086]     Having a rotatable sleeve  16  that may be engaged or disengaged by a locking mechanism (e.g., locking mechanism  17  ( FIGS. 1 and 2 ) or locking mechanism  17 ′ ( FIGS. 6A through 6C ) permits minor axial adjustments of plunger  11  without requiring that plunger  11  itself be rotated. Thus, any features of syringe  10 , such as pressure readout display  39  ( FIGS. 8A through 8C ), that are affixed at proximal end  11   p  of plunger  11  remain in a constant position (and, in the case of pressure readout display  39 , in a continuously visible position).  
         [0087]     If, however, pressure transducer  24  ( FIGS. 3 through 5 ) and its associated electronics (not shown) are integrated into a plunger, with the electronics being configured to transmit wireless signals to remote processing or display apparatus, then the plunger  11 ′ ( FIGS. 6A through 6C ) itself may be threaded, at least near its proximal end  11   p , for engagement with a suitable locking mechanism (e.g., locking mechanism  17  ( FIGS. 1 and 2 ) or locking mechanism  17 ′ ( FIGS. 6A through 6C ) and, thus, rotated to accomplish minute axial adjustment of the position of plunger  11  along the length of barrel  14 . The grasping element  12  associated with such a plunger  11  may be configured (e.g., a ring with an enlarged open diameter) to facilitate operation of plunger with an individual&#39;s thumb regardless of slightly offset rotation of grasping element  12 .  
         [0088]     Syringes  10  that include grasping elements  12  (e.g., a ring), electronics, and/or displays  39  (an of course, wireless connections of rotatable connection elements) that are secured in position relative to proximal end  11   p  of plunger  11  in such a way that they substantially freely rotate relative to proximal end  11   p  are also within the scope of the present invention.  
         [0089]     Referring again to  FIG. 1 , it is currently preferred that an individual who uses syringe  10  be able to control the position (i.e., locked or unlocked) of locking mechanism  17  with the same hand that he or she is using to hold or operate other features of syringe  10 . For example, the individual may use his or her thumb to set (i.e., lock) or release (i.e., unlock) locking mechanism  17 , while holding grasping elements  15   a  and  15   b  with the index finger and middle finger of the same hand. The location of control element  23  vis-a-vis grasping elements  12 ,  15   a , and  15   b  may likewise readily permit an individual using syringe  10  to remove his or her thumb to from grasping element  12  and place it upon control element  23  to rotate control element  23  to achieve minute fluid pressure adjustments, further facilitating continuous one-handed operation of syringe  10 .  
         [0090]     Use of a syringe  10  that incorporates teachings of the present invention facilitates control over the pressure generated or measured thereby with a single hand, while the individual operating syringe  10  may use his or her other hand to perform other tasks. For example, in discography procedures, the individual&#39;s free hand may be used to position a stylus that communicates with syringe  10 , while the hand that holds syringe  10  is used to inject additional fluorescent media to provide additional illumination on a fluoroscope and, thus, a better idea of the actual location an end of the stylus.  
         [0091]     Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some of the presently preferred embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions and modifications to the invention as disclosed herein which fall within the meaning and scope of the claims are to be embraced thereby.