Abstract:
An improved radial expansible retractor and a method of minimally invasive surgery, by opening a channel in the brain or other soft tissue of a patient, by inserting the radial expansible retractor into the body of the patient, and by widening the channel at a continuous and gentle rate. The use of the improved radial expansible retractor renders surgical procedures, including neurosurgical procedures, shorter, less traumatic, and more reliable, reducing risk and the need for subsequent surgery and reducing recovery time. Procedures are carried out with real time monitoring of the retracted brain perfusion pressure. A plurality of improved radial expansible retractors may be used in a single operation. The improved radial expansible retractor allows access to areas of the brain previously almost impossible to access.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to apparatus and techniques for performing minimally invasive surgery and, in particular to a retractor device for minimally invasive surgery. 
         [0002]    Minimally invasive surgical techniques are becoming increasingly widespread in many different surgical fields. An area in which such techniques would appear to be particularly relevant is neurosurgical removal of Space-Occupying lesions (SOL), Intra Cerebral Hemorrhages (ICH), Intra Ventricular Hemorrhages (IVH), Intra Axial Brain Tumors (IABT), Intra Ventricular Brain Tumors (IVBT), and Other Brain lesions (OBL) and Brain Pathological Conditions (BPC). 
         [0003]    In accordance with current methods, following initial imaging for locating a brain lesion, die skull is trepanned so as to remove a bone flap exposing an opening in the skull surface, an opening of from 1 cm×1 cm tip to 5 cm×5 cm, after which retractors are inserted into the brain tissue or lobes, and used to move and draw back brain tissue or lobs in the region of the lesion, thereby exposing the brain tissue for removal. 
         [0004]    In cases in which the region of the lesion to be removed cannot be reached, a retractor is inserted into the brain tissue and is opened slowly in order to create a channel in the brain tissue enabling access to the lesion. 
         [0005]    After a procedure which can take many hours, the retractor is removed and the bone flap is replaced 2D or 3D Ultrasound Imaging (USI) is performed once again so as to ensure that the entire lesion has, in fact, been removed. 
         [0006]    Existing brain retractors allow only one dimensional retraction of the brain tissue, elevating Brain Retraction Pressure (BRP) to more than 20 mg Hg causing post-operation brain edema, or severe scarring. Known current neurosurgical intervention may cause the following complications: 
         [0007]    a. infarction of brain tissue due to the localized pressure to which the retracted portions of the brain are subjected; 
         [0008]    b. bleeding upon insertion of the retractors; 
         [0009]    c. if several retractors need to be inserted, the pressure on the brain tissue is uneven, the lesion may not be properly exposed, possibly leading to a need to perform supplementary surgery in order to remove any remaining tumor tissue; or 
         [0010]    d. insertion of the retractors and separation of the brain lobes are performed manually; these motions are thus inherently uneven, and are liable to cause trauma to the brain tissue. 
         [0011]    Procedures are very lengthy and a number of surgical procedures are not carried at all out due to risk factors, or cannot be carried out successfully using current techniques. These include among others treating hemorrhage in the 4th ventricle or lateral ventricle, treating intra-ventricular hemorrhage, simultaneous removal of multiple metastases, direct treatment of brain abscess, and directly applied chemotherapy or radiotherapy of pathological tissue. 
         [0012]    Edema caused by use of the retractor entails an increase in Intracranial Pressure (ICP), affecting the value of Cerebral Perfusion Pressure (CPP), which also depends on Mean Blood Pressure (MBP), according to the following association: 
         [0000]    
       
      
       CPP=MBP−ICP  
      
     
         [0013]    The CPP must be within the range of 50-120 mm Hg. Increased dislocation and pressure on the brainstem could cause cessation of breathing and death of the patient. 
         [0014]    The evolution of means of opening working channels includes the following generations: The first generation used a manually opened retractor, which was also held open manually. This type of retractor also generally included two arms which open and move away from each other in linear motion. This method has several main disadvantages, including the opening applying uneven pressure on brain tissue, the retractor&#39;s force is exerted only in the single direction or single dimensional of the linear opening. Furthermore, the retractor, which is hand-held by the human operator, is insufficiently stable, and any slight tremor of the operator&#39;s hands could damage brain tissue. 
         [0015]    The second generation used the Yasargil retractor, which is the most common means used at present. 
         [0016]    Prof. Yasargil (now living and working in the USA) is a Turkish medical scientist and neurosurgeon. He is the inventor of the Yasargil retractor, a self-retaining brain retractor, which avoids the need for manual holding of the brain retractor. 
         [0017]      FIG. 1  of the prior art illustrates a Yasargil retractor  10 . As shown in this illustration, the head of the patient  100  is on the operation table  13 , to which retractor holder  14  is attached, also including arms  12  holding a pair of spatulas  11  which are inserted in to the head when they are both close to each other and are slowly distanced from each other to enlarge the canal which was created in order to enable a view of the Space Occupation Lesion (SOL) designated for treatment, and performing the treatment itself. 
         [0018]    In spite of the significant improvement that this means provides over the previous generation, it still does not provide sufficient uniformity of the pressure applied on the brain tissue. 
         [0019]    The third generation is the present inventor&#39;s First Radial Expansible Retractor (FRER) for minimally invasive surgery, described in PCT/IL00/00387, filed Jul. 4, 2000, which has significant improvements which can benefit patients. 
         [0020]      FIG. 2   a  of the prior art illustrates side view of a FRER  300 . FRER  300  includes a FRER planar base  21 , a FRER upper plate  22 , a FRER lower plate  23  having a FRER central opening  25 , FRER linear drive elements  24 , FRER longitudinal ribs  26  comprising a FRER expansible needle shaped retractor  27 , which are parallel to FRER axis  29  which is perpendicular to FRER planar base  21 , and a FRER probe  28 . 
         [0021]      FIG. 2   b  of the prior art is a lateral cross-section view of the FRER  300  of  FIG. 2   a , showing the FRER expansion mechanism  31  which serves to generate the opening and closing motions of the FRER expansible needle shaped retractor, also including the FRER linear drive elements  24  and FRER outer cogwheel  32 , and FRER inward facing pluralities of teeth  33  and the FRER longitudinal ribs  26 . 
         [0022]    It is of utmost importance for the retractor&#39;s opening rate to be controlled and the mechanism controlling the opening rate must be able to allow a nonlinear opening rate. Initially, the brain&#39;s resistance to the opening retractor is relatively small, and increases at a linear rate as the opening increases. A suitable opening rate at this stage is approximately 10 microns per second. Once the opening has reached a diameter of approximately 20 to 30 mm, the brain&#39;s resistance is no longer linear, and the larger the diameter, the faster the resistance increases, therefore, at this stage the opening rate must be slower, within a range of 3 to 5 microns per second, in order to prevent damage to brain tissue. Achieving such a change of rate in an opening mechanism based on cogwheels is possible only by means of changing the manual rotation rate of the external rotating wheel. 
         [0023]    In addition, an entirely different method was demonstrated in the Cincinnati Children&#39;s Hospital Medical Center in Ohio by Dr. Crone, in which a sausage-like balloon was inserted into the brain, was gradually inflated mid kept in the brain for several days. The balloon was inflated slowly, spreading and creating a safe pathway, afterwards the inflation was ceased and the balloon was removed from the brain, leaving a gap in the brain which could be used as a working channel. 
         [0024]    This method requires anesthetizing the patient more than once, thus increasing the risk to his life. 
         [0025]    There is thus a widely recognized need for, and it would be highly advantageous to have, a radial expansible retractor for minimally invasive surgery which enables opening a channel while exerting force on the surrounding tissue as uniformly as possible when inserted into brain tissue, while achieving a continuous opening rate and value suitable for the respective CPP at every stage of the opening. 
       SUMMARY OF THE INVENTION 
       [0026]    It is an objective of the present invention to provide the means to open a channel in the brain or any other organ of a patient, through which the area designated for treatment can be seen, and through which surgical tools can be inserted for treatment, such as extracting a tissue sample for biopsy, or performing excision or suction of tissue for the purpose of removing a cancerous tumor etc. According to the present invention, a retractor of improved performance with regard to the performance of standard retractors is used and enables performance of medical procedures in previously unattainable depths in the brain, and in a patient-friendly manner in comparison with the insertion of standard retractors into the brain, which results in less brain damage to recovering patients, as well as a lower post-operation death rate. 
         [0027]    The retractor according to the present invention is connected stably to a device which can be attached to die operation table on which the patient is prone. After drilling a hole of a suitable diameter in the skull, in the case of brain surgery, the retractor is inserted into the patient&#39;s brain under the surveillance of an imaging system such as MRI or any other of sufficient resolution to prevent damage to brain neural fibers. After insertion into the required depth and location, the retractor is opened gently, at a suitable opening rate and force. The retractor is composed of several ribs of a suitable length creating a lateral cross section shaped compatibly with the desired cross section of the channel. Usually, when the retractor is closed, the ribs form the shape of a closed cylinder with walls of a sufficient width to ensure the necessary structural integrity, with each rib serving as a segment of the cylinder&#39;s section. For example, when the cylinder&#39;s section is circular, and the number of ribs is eight, each rib will have a cross section of a circular arc with an opening angle of 45 degrees. This structure of the retractor prevents the formation of non-uniform pressures on the different brain areas coming into contact with the retractor. 
         [0028]    Gentle and continuous opening of the retractor is of special importance, and is achieved by gentle rotation of a disc grooved with a single groove for each rib, with a pin at the base of each rib which is inserted in the respective groove, and thus forced to move radially according to the state of the grooved disc. The forced radial motion is achieved by the disposal of the base of the rib in an adjacent channeled disc, such that rotational movement, around a joint perpendicular central rotational axis, alters the angular relation between discs, the grooved disc and the channeled disc. 
         [0029]    Control of the rotational velocity of the grooved disc can be manual or by means of a suitable engine, assisted by a mechanical system for transmission of continuous and gentle motion. 
         [0030]    When the retractor opens, a gap is created between the ribs, causing the creation of non-uniform pressures on the brain tissue; therefore the retractor includes a flexible sleeve external to the ribs, which stretches during opening. In the center of the retractor, between the ribs, there is a probe at whose tip in the retractor entry direction there is a half-elliptical or similarly shaped dome. This dome facilitates assembling the flexible sleeve onto the retractor ribs, and serves as the retractor&#39;s spearhead when inserting the retractor into the tissue. 
         [0031]    Due to both the force exerted by the flexible sleeve on the ribs and the pressure of the tissue into which the retractor is inserted when opening as the ribs are distanced from each other at their base near the grooved disc, their opening near the spearhead is little or nonexistent, and the retractor assumes a shape resembling a pyramid, so that when opening is completed, therefore when opening is completed a cylinder, whose cross section has geometrical dimensions and form conforming to the retractor&#39;s cross section, is gently inserted through the base of the retractor, so that the retractor&#39;s ribs are gradually pushed away from each other until they are all parallel. This cylinder and the flexible sleeve can be composed of translucent materials which enable performing a visual survey of the tissue surrounding the retractor, by means of illumination of a suitable wavelength. Furthermore, samples can be collected from various depths of brain tissue, namely Multi Level Biopsy (MLB) of the tissue surrounding the retractor can be performed through perforations in the wall of the cylinder and the flexible sleeve. 
         [0032]    When sufficient opening is achieved, the probe can be removed from the retractor. Note that an ultrasound probe can be used instead of a simple mechanical probe to assist in guiding the retractor during insertion. 
         [0033]    According to the present invention, the retractor can be manufactured with ribs of a fixed length in several models and sizes, varying in rib length, rib cross section shape, and/or the initial diameter of the ribs when closed and maximal diameter to which the ribs can be opened. Furthermore, models can be manufactured in which ribs of a certain length are interchangeable with ribs of another length. 
         [0034]    According to the present invention, the grooves dictate the opening rate for a fixed rotation speed of the external rotating wheel, and the form of the grooves&#39; curve is determined according to the need. 
         [0035]    Opening the retractor is safest when done with real-time monitoring of the Brain Tissue Retraction Pressure (BTRP). When the BTRP increases, the operator lowers the opening rates, and if the BTRP approaches a critical value, the operator will completely cease from opening for the necessary time interval, or even reverse and close the retractor slightly. This is done mainly to avoid damage to the Blood Brain Barrier (BBB) in order not to leave hemorrhaging as a result of torn capillary blood vessels in the brain. 
         [0036]    At the end of the medical procedure, the retractor is gently closed and then pulled out. 
         [0037]    Changing the direction of insertion of the improved radial expansible retractor is possible, whether in a direct path or a curved path according to the shape of the anatomical section of the operation field. Changes in the angle of insertion and in the form of curvature can be carried out during insertion simultaneously in the x, y and z planes, with 6 degrees of freedom of movement in the device at any time. The shape of the channel can be altered to accommodate curved access areas, as a tube can be made from metal that is malleable and retains a first shape until manipulated into a new shape. 
         [0038]    The tubular opening into the depths of the brain and to other organs allows for the use of endoscopes, laparoscopes, ultrasound aspirators, laser, cryogenic techniques, and possibly even au operating microscope. Different types of coagulation and bleeding cessation devices can be inserted. Focused radiation of different types can be applied via the opening and directed onto pathological tissue with minimal damage to surrounding healthy tissue. 
         [0039]    Neurosurgical operations have multiple applications, including but not restricted to removal of blood clots in the brain including in areas that are difficult to access such as the 4th ventricle, lateral ventricle, etc. Neuro-navigation and intra-ventricular deep brain surgery and general brain tumor therapy are possible by means of minimally invasive procedures, drastically reducing operating time and vastly improving recovery process. Double or multiple insertion of the device is possible to work independently and simultaneously in different areas of the brain. With the aid of an endoscope and light, tumors are easily removed. Negative pressure can be applied in the event of intra-ventricular hemorrhaging to alleviate pressure in the aqueduct, to prevent hydrocephalus, to suction and clean out ventricles and remove blood clots. Suction can be either contact or non-contact. Multiple metastases can be removed by a plurality of retraction devices being inserted into different areas of the brain. Ventricular peritoneal shunt that is currently inserted blindly causing damage by accidentally entering the brain ventricle can now be guided from the occipital boom to drain fluid. Procedures can be carried out under ME. 
         [0040]    For operation of the improved radial expansible retractor, the required size of the opening of the skull is much smaller than in prior art procedures, and the time needed to perform surgery is greatly reduced, speeding up post-operative recovery and reducing post-operative complications. 
         [0041]    Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
         [0042]    According to the present invention there is provided a radial expansible retractor for minimally invasive surgery for opening a channel in the brain and in any other soft tissue of a patient, by inserting part of the radial expansible retractor into the body of the patient, and by widening the channel at a continuous and gentle rate, the radial expansible retractor including: (a) a grooved disc having a central perforation, a cylindrical surface at the circumference of the grooved disc, and at least three grooves wherein the grooved disc defines an imaginary orthogonal coordinate system having X, Y, and Z axis, wherein the Z axis substantially passes through the center of the central perforation of the grooved disc, and wherein toe grooved disc substantially lays on an imaginary plane, perpendicularly to the Z axis, wherein each of the grooves have an continuous curved shape on a plane perpendicular to the Z axis, wherein each of the grooves has three dimensional geometrical shape and size; (b) a channeled disc disposed at a position relative to the grooved disc, having at least three channels, wherein the channeled disc substantially lays on an imaginary plane, perpendicularly to the Z axis, and wherein the Z axis substantially passes through the center of the central perforation of the channeled disc, wherein each of the channels has three dimensional geometrical shape and size, wherein each of the channels has a direction on a plane perpendicular to the Z axis, along a radial, wherein the radial starts at the Z axis, wherein the grooved disc can rotate at certain angle limits around the Z axis and thereby changing the position of the channeled disc relative to the grooved disc; (c) at least three ribs defining a channel having a cross sectional size, wherein each of the ribs has a base, a leading edge, and a cross section shape, wherein each of the ribs is laid substantially in parallel to the Z axis; and (d) at least three carriers wherein each of the carriers is connected to the base of one of the ribs, so that each of the ribs is connected to one of the carriers, wherein each of the carriers has three dimensional geometrical shape and size, conforming to the geometrical shape and size of the channels, wherein each of the carriers includes: (i) a pin having three dimensional geometrical shape and size, conforming to the geometrical shape and size of the grooves, wherein each of the carriers is located inside one of the channels, and wherein each of the pins is located inside one of the grooves, so that a change of a relative position of the channeled disc relative to the grooved disc, which is expressed in a change of the angle between them on the plane perpendicular to the Z axis, causes a change of distance of each of the ribs from the Z axis, while the change of distance can be performed gently and continuously. 
         [0043]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (e) a cover disc having a central perforation and a cylindrical wall, and wherein the Z axis substantially passes through the center of the central perforation of the cover disc, wherein the channeled disc and the cover disc together form a package inside which a grooved disc is disposed. 
         [0044]    According to further features in preferred embodiments of the present invention the radial expansible retractor, further including: (f) at least tree bolts, wherein the each of the rib bases and each of the rib carriers has a hole and wherein each one of the bolts connect one of the rib carriers to one of the rib bases, so that each one of the rib bases is connected to one of the rib carriers and each one of the rib carriers is connected to one of the rib bases. 
         [0045]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (g) a tooth rail disposed on the cylindrical surface at the circumference of the grooved disc. 
         [0046]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (h) a handle housing disposed on the cover disc and on the channeled disc; and (i) a worm, wherein the worn is positioned inside the handle housing, adjacent to the tooth rail such that when the worm performs rotational movement around an imaginary axis on a plane perpendicular to Z axis, it transmits mechanical movement to the tooth rail, thus granting rotational movement to the grooved disc around Z axis. 
         [0047]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (j) a shaft disposed on the worm, inside the handle housing; (k) a front sleeve disposed around the shaft, inside the handle housing; and (l) an inner bearing disposed around the shaft, inside the handle house. 
         [0048]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (m) a rotating wheel disposed on the shaft. 
         [0049]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (m) an engine disposed on the shaft. 
         [0050]    According to the present invention the radial expansible retractor further including: (m)
       an adaptor disposed on the handle housing.       
 
         [0052]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (n) a central rod having tail and head, wherein the head has a dome shape, wherein the central rod can be inserted between the ribs and pulled out from between them; (o) a tubule, wherein the tubule can be inserted between the ribs and pulled out from between the ribs and pulled out from between them; and (p) a flexible sleeve, wherein the flexible sleeve can be pulled over the ribs and pulled off of them. 
         [0053]    According to further features in preferred embodiments of the present invention the tubule is composed of a translucent material and has at least one perforation, and wherein the flexible sleeve is composed of a translucent material. 
         [0054]    According to further features in preferred embodiments of the present invention each of the ribs cross section shape is circular. 
         [0055]    According to further features in preferred embodiments of the present invention each of the ribs cross section shape is of a segment of a cylindrical wall, while the combination of all of the cross section shapes can form a cross section shape of a cylindrical wall, and wherein each of the ribs has an internal surface, and an external surface. 
         [0056]    According to further features in preferred embodiments of the present invention the cylindrical wall shape is circular. 
         [0057]    According to further features in preferred embodiments of the present invention the cylindrical wall shape is oval. 
         [0058]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (m) at least one pressure sensor disposed on the external surface. 
         [0059]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (m) at least one pressure sensor disposed on the external surface. 
         [0060]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (m) at least one pressure sensor disposed on the external surface. 
         [0061]    According to further features in preferred embodiments of the present invention the radial expansible retractor has at least eight ribs, wherein the grooved disc has at least eight grooves, and wherein the channeled disc has at least eight channels. 
         [0062]    According to further features in preferred embodiments of the present invention each of the grooves&#39; continuous curves shape has the same curved shape. 
         [0063]    According to further features in preferred embodiments of the present invention at least one of the grooves&#39; continuous curves has a shape differing from that of at least one of the other grooves&#39; continuous curves. 
         [0064]    According to further features in preferred embodiments of the present invention each of the grooves&#39; continuous curves has a first end and a second end, wherein the groove&#39;s continuous curve has a first angle measured between the continuous curve&#39;s direction at the first end and the direction of a radius starting at Z axis passing through the first end, wherein the groove&#39;s continuous curve has a second angle measured between the continuous curve&#39;s direction at the second end and the direction of a radius starting at Z axis passing through the second end, and wherein the second angle is at least three degrees larger, and at most eight degrees larger, than the first angle. 
         [0065]    According to further features in preferred embodiments of the present invention the radial expansible retractor further including: (in) at least one subsystem for real time measurement and monitoring of the brain retraction pressure (BRP), the subsystem for measurement of the pressure on tissue including: (i) a folded bag disposed in a gap formed between two adjacent the labs; (ii) an air pipeline connected to the folded bag; (iii) an air pressure source connected to the pipeline; and (iv) an air pressure gauge connected to the pipeline, wherein the flexible sleeve has a window and wherein the folded bag is disposed facing the flexible sleeve window. 
         [0066]    According to further features in preferred embodiments of the present invention the subsystem for measurement of the pressure on tissue, her including: (v) an electrical power source; (vi) electrical wires connected to the power source; (vii) a miniature control light bulb connected to the electrical wires; and (viii) two electrical contact elements connected to the electrical wires and attached to the insides of the folded bag such that when the folded bag is not inflated both of the contact elements touch each other and the miniature control light bulb is switched on, and when the folded bag is inflated both of the contact elements are separated from each other and the miniature control light bulb is switched off. 
         [0067]    According to the present invention there is provided a method of minimally invasive surgery, including the steps of: (a) providing a radial expansible retractor for minimally invasive surgery for opening a channel in the brain of a patient, by inserting the radial expansible retractor into the brain of the patient, and by widening the channel at a continuously and gentle rate, the radial expansible retractor including: (i) a grooved disc having a central perforation, a cylindrical surface at the circumference of the grooved disc, and at least three grooves wherein the grooved disc defines an imaginary orthogonal coordinate system having X, Y, and Z axis, wherein the Z axis substantially passes through the center of the central perforation of the grooved disc, and wherein the grooved disc substantially lies on an imaginary plane, perpendicularly to the Z axis, wherein each of the grooves has an continuous curved shape on a plane perpendicular to the Z axis, wherein each of the grooves has three dimensional geometrical shape and size; (ii) a channeled disc disposed at a position relative to the grooved disc, having at least three channels wherein the channeled disc substantially lies on an imaginary plane, perpendicularly to the Z axis, and wherein the Z axis substantially passes trough the center of the central perforation of the channeled disc, wherein each of the channels have three dimensional geometrical shape and size, wherein each of the channels has a direction on a plane perpendicular to the Z axis, along a radial, wherein the radial starts at the Z axis, wherein the grooved disc can be rotated at certain angle limits around the Z axis thereby changing the position of the channeled disc relative to the grooved disc; (iii) at least three ribs defining a channel having a cross sectional size, wherein each of the ribs has a base, a leading edge, and a cross section shape, wherein each of the ribs is laid in parallel to the Z axis; and (iv) at least three carriers wherein each of the carriers is connected to the base of one of the ribs, so that each of the ribs is connected to one of the carrier, wherein each of the carriers has three dimensional geometrical shape and size, conforming to the geometrical shape and size of the channels, wherein each of the carriers includes: (A) a pin having three dimensional geometrical shape and size, conforming to the geometrical shape and size of the grooves, wherein each of the carriers is located inside one of the channels, and wherein each of the pins is located inside one of the grooves, so that a change of a relative position of the channeled disc relative to the grooved disc, which is expressed in a change of the angle between them on the plane perpendicular to the Z axis, causes a change of distance of each of the ribs from the Z axis, while the change of distance can be performed gently and continuously; and (v) a cover disc having a central perforation and a cylindrical wall, and wherein the Z axis substantially passes trough the center of the central perforation of the cover disc, wherein the channeled disc and the cover disc together form a package inside which a grooved disc is disposed; (b) forming an opening in an exterior of a body portion located in proximity to a tissue portion sought to be surgically removed; (c) inserting the radial expansible retractor ribs through the opening, through a body tissue so as to reach the tissue portion sought to be surgically removed; and (d) expanding the radial expansible retractor ribs by distancing them from one another in linear radial movement from a joint center to cause a lateral multi-axial displacement of adjacent tissue so as to expose the tissue portion sought to be surgically removed. 
         [0068]    According to further features in preferred embodiments of the present invention the method of minimally invasive surgery further including the steps of: (e) removing the tissue portion sought to be surgically removed by direct contact. 
         [0069]    According to the features in preferred embodiments of the present invention the method of minimally invasive surgery further including the steps of: (e) removing the tissue portion sought to be surgically removed by non-contact suction. 
         [0070]    According to the present invention there is provided a method of Minimally Invasive Surgery (MIS), including die steps of: (a) providing a radial expansible retractor for minimally invasive surgery for opening a channel in the brain of a patient, by inserting the radial expansible retractor into the brain of the patient, and by widening the channel at a continuously and gentle rate, the radial expansible retractor including: (i) a grooved disc having a central perforation, a cylindrical surface at the circumference of the grooved disc, and at least three grooves wherein the grooved disc defines an imaginary orthogonal coordinate system having X, Y, and Z axis, wherein the Z axis substantially passes through the center of the central perforation of the grooved disc, and wherein the grooved disc substantially lies on an imaginary plane, perpendicularly to the Z axis, wherein each of the grooves has an continuous curved shape on a plane perpendicular to the Z axis, wherein each of the grooves has three dimensional geometrical shape and size; (ii) a channeled disc disposed at a position relative to the grooved disc, having at least three channels wherein the channeled disc substantially lies on an imaginary plane, perpendicularly to the Z axis, and wherein the Z axis substantially passes through the center of the central perforation of the channeled disc, wherein each of the channels has three dimensional geometrical shape and size, wherein each of the channels has a direction on a plane perpendicular to the Z axis, along a radial, wherein the radial start at the Z axis, wherein the grooved disc can be rotated at certain angle limits around the Z axis and thereby changing the position of the channeled disc relative to the grooved disc; (iii) at least three ribs defining a channel having a cross sectional size, wherein each of the ribs has a base, a leading edge, and a cross section shape, wherein each of the ribs is laid in parallel to the Z axis; and (iv) at least three carriers wherein each of the carriers is connected to the base of one of the ribs, so that each of the ribs is connected to one of the carrier, wherein each of the carriers has three dimensional geometrical shape and size, conforming to the geometrical shape and size of the channels, wherein each of the carriers includes: (A) a pin having three dimensional geometrical shape and size, conforming to the geometrical shape and size of the grooves, wherein each of the carriers is located inside one of the channels, and wherein each of the pins is located inside one of the grooves, so that a change of a relative position of the channeled disc relative to the grooved disc, which is expressed in a change of the angle between them on the plane perpendicular to the Z axis, causes a change of distance of each of the ribs from the Z axis, while the change of distance can be performed gently and continuously; and (v) a cover disc having a central perforation and a cylindrical wall, and wherein the Z axis substantially passes through the center of the central perforation of the cover disc, wherein the channeled disc and the cover disc together form a package inside which a grooved disc is disposed; (b) forming an opening in the exterior of a body portion located in proximity to a tissue portion in which hemorrhaging has occurred; (c) inserting an radial expansible retractor ribs through the opening, through body tissue so as to reach the hemorrhage to be suctioned out; (d) expanding the radial expansible ribs by distancing them from one another with linear radial movement from a joint center to cause a lateral multi-axial displacement of adjacent tissue so as to expose the hemorrhage; and (e) removing the hemorrhage by a suction. 
         [0071]    According to further features in preferred embodiments of the present invention the method of minimally invasive surgery further including the steps of: (i) providing another radial expansible retractor for minimally invasive surgery for opening a channel in the brain of a patient; (j) forming another opening in an exterior of a body portion located in proximity to a tissue portion where hemorrhaging has occurred; (k) inserting another radial expansible retractor ribs through the another opening, through body tissue so as to reach the hemorrhage to be suctioned out; (l) expanding the other radial expansible retractor ribs by distancing them from one another in linear radial movement from a joint center to cause a lateral multi-axial displacement of adjacent tissue so as to expose a hemorrhage; and (j) removing the hemorrhage. 
         [0072]    According to further features in preferred embodiments of the present invention the method of minimally invasive surgery further including the steps of: (e) monitoring pressure exerted on the radial expansible retractor, at least at one point of contact with a tissue during a surgical procedure, allowing a surgeon to minimize the gaps between the radial expansible retractor ribs to lower pressure, if necessary. 
         [0073]    According to further features in preferred embodiments of the present invention the method of minimally invasive surgery further including the steps of: (f) monitoring pressure exerted on the radial expansible retractor, at least at one point of contact with a tissue during a surgical procedure, allowing a surgeon to minimize the gaps between the radial expansible retractor ribs to lower pressure, if necessary. 
         [0074]    According to further features in preferred embodiments of the present invention the folded bag is a folded polyethylene bag. 
         [0075]    According to further features in preferred embodiments of the present invention the electrical power source of the subsystem for measurement of the pressure on tissue, is a battery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0076]    The invention is herein described, by way of example, only, with reference to the accompanying drawings, wherein: 
           [0077]      FIG. 1  of the prior art illustrates a Yasargil retractor. 
           [0078]      FIGS. 2   a  and  2   b  of the prior art are schematic illustrations of the present inventor&#39;s first radial expansible retractor. 
           [0079]      FIGS. 3   a ,  3   b , and  3   c  are schematic illustrations of a preferred embodiment of an improved radial expansible retractor in a close mode according to the present invention. 
           [0080]      FIG. 4   a  is a schematic perspective view illustration of a preferred embodiment of an improved radial expansible retractor in an open mode according to the present invention. 
           [0081]      FIG. 4   b  is a schematic perspective view illustration of a flexible sleeve of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
           [0082]      FIG. 5   a  is a schematic top view illustration of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
           [0083]      FIGS. 5   b , and  5   c  are lateral section schematic illustrations of the improved radial expansible retractor of  FIG. 5   a.    
           [0084]      FIGS. 6   a ,  6   b , and  6   c  are schematic perspective view illustrations of a cover, a grooved disc, and a channeled disc, respectively, of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
           [0085]      FIG. 7   a  is a geometrical description of the principle of granting radial movement to a rib. 
           [0086]      FIG. 7   b  is a geometrical description of the principle of granting radial movement to ribs creating an oval aperture form, of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
           [0087]      FIGS. 7   c  and  7   d  are schematic top view illustrations of a grooved disc and a channeled disc, respectively, of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
           [0088]      FIG. 8  is an exploded view of an improved radial expansible retractor according to the present invention. 
           [0089]      FIGS. 9   a  and  9   b  a are schematic perspective view illustrations of a rib and of a rib base, respectively, of an improved radial expansible retractor according to the present invention. 
           [0090]      FIGS. 9   c ,  9   d , and  9   e  are schematic cross sections of the ribs. 
           [0091]      FIG. 10   a  is a schematic illustration of a subsystem for Brain Tissue Retraction Pressure (BTRP) measurement of the tissue which is in contact with the improved radial expansible retractor, according to the present invention. 
           [0092]      FIG. 10   b  is a schematic cross section of a component of the subsystem for BTRP measurement of the tissue according to the present invention. 
           [0093]      FIG. 10   c  is a schematic illustration of a component of the subsystem for BTRP measurement of the tissue disposed between the ribs of the retractor according to the present invention. 
           [0094]      FIG. 11  is a schematic illustration of an improved radial expansible retractor, with an opening engine mechanism according to the present invention. 
           [0095]      FIG. 12  is a schematic illustrations of an improved radial expansible retractor stationed during operation according to the present invention, in action. 
           [0096]      FIG. 13  is an illustration of a procedure to remove intra-ventricular hemorrhage from the lateral ventricle or to remove intra-ventricular hemorrhage from the fourth ventricle, using the improved radial expansible retractor, according to the present invention. 
           [0097]      FIG. 14  shows a multi-portal approach to intra-ventricular hemorrhaging and intra-cerebral hemorrhaging with the improved radial expansible retractor being inserted from two separate sites easily accessing the hemorrhage and removing it by suction, according to the present invention. 
           [0098]      FIG. 15  shows a multi-portal removal of intra-ventricular lesions with an aspirator inserted into the expanded cannel from one side and an endoscope inserted via a second cannel, both through separated improved radial expansible retractor, according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0099]    The present invention is an Improved Radial Expansible Retractor (IRER) for Minimally Invasive Surgery (MIS). 
         [0100]    The principles and operation of an IRER according to the present invention may be better understood with reference to the drawings and the accompanying description. 
         [0101]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. 
         [0102]    Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The materials, dimensions, methods, and examples provided herein are illustrative only and are not intended to be linking. 
         [0103]    The following list is a legend of the numbering of the application illustrations:
         11  spatula     12  arm     13  operation table     14  Yasargil retractor holder     21  FE-R planar base     22  FRER upper plate     23  FRER lower plate     24  FRER linear drive elements     25  FRER central opening     26  FRER longitudinal rib     27  FRER expansible needle shaped retractor     28  FRER probe (can also include ultrasound probe)     29  FRER axis     32  FRER outer cogwheel     33  FRER outward facing pluralities of teeth     40  pressure sensor     41  rib     41   a  rib leading edge     41   b  rib external surface     41   c  rib internal surface     42  rib base     43  rib base hole     44  rib carrier     45  rib carrier pin     46  rib carrier hole     47  rib carrier bolt     48  central rod     48   a  central rod tail     48   b  central rod head dome     49  tubule     49   a  tubule perforation     50  flexible sleeve     50   a  flexible sleeve window     51  cover disc     51   a  cover central perforation     51   b  cylindrical wall of cover disc     51   c  protuberances     51   d  cover disc bolt holes     52  grooved disc     52   a  grooved disc central perforation     52   b  groove     52   c  external surface     52   d  depression     53  channeled disc     53   a  channeled disc central perforation     53   b  channel     53   c  channeled disc bolt holes     53   d  protrusion     60  handle housing     61  rotating wheel     62  measure wheel     63  shaft     64  front sleeve     65  worm     66  inner bearing     67  tooth rail     68  adaptor bolt     69  adaptor     70  fixation bolt     71  engine     81  holder device     82  lock     83  skull clamp     84  endoscope     85  doctor eye     86  suction device     90  folded bag     91  air pressure source     92  pipeline     93  air pressure gauge     94  electrical power source     95  miniature control light bulb     96  electrical wire     97  electrical contact element     98  subsystem for measurement of the pressure on tissue     99  aspirator     100  patient head     101  lateral ventricle     102  fourth ventricle     103  hemorrhage     104  Intra Cerebral Hemorrhage (a) (ICH)     105  Intra Ventricular Hemorrhage (IVH)     106  Intra Cerebral Hemorrhage (b) (ICH)     107  Intra Ventricular Lesions (IVL)     200  Yasargil retractor     300  First Radial Expansible Retractor (FRER)     400  Improved Radial Expansible Retractor (IRER)       
 
         [0191]    Referring now to the drawings,  FIGS. 3   a ,  3   b , and  3   c  are schematic illustrations of a preferred embodiment of an improved radial expansible retractor  400  in a closed mode according to a preferred embodiment of the present invention. 
         [0192]      FIG. 3   a  is a perspective view,  FIG. 3   b  is a top view, and  FIG. 3   c  is a side view. 
         [0193]    The illustrations show ribs  41  touching each other, and in the illustrated case, forming a hollow cylinder with walls of a thickness which, combined with the material composing ribs  41 , grants the necessary strength for channel dilatation within tissue. 
         [0194]    The quantity of ribs  41  can vary, in the preferred embodiment shown in this illustration and in those following; there are eight. The shape of the lateral section of the formed cylinder can also vary, in the preferred embodiment shown in this illustration and those following; it is circular, unless specifically noted otherwise. 
         [0195]    In the center between the ribs  41  there is a central rod  48  whose end facing the retractor&#39;s direction of insertion has a half-elliptical or similarly shaped dome  48   b . This dome facilitates pulling the flexible sleeve onto the retractor ribs and serves during insertion of the retractor into tissue, as the spearhead leading the retractor. The tail of the central rod  48   a  protrudes above the cover  51  and enables removal of the central rod  48   a  when the aperture of the ribs  41  is sufficiently wide. 
         [0196]    Improved radial expansible retractor  400  is equipped with an adaptor  69  which, by means of fixation bolt  70 , can connect the retractor to the arm of a holder device. The adaptor  69  and the handle house  60  form the retractor base, which contains a mechanism transmitting gentle rotational mechanical movement from rotating wheel  61  to a grooved disc not shown in these illustrations, within a casing whose bottom is a channeled disc  53  and is closed at the top with cover  51 . 
         [0197]    Rotating wheel  61 , according to the embodiment shown in the illustration is rotated by the operator&#39;s right hand. An improved radial expansible retractor  400  can be manufactured such that the rotating wheel  61  is disposed to enable rotation by the operator&#39;s left hand. 
         [0198]    A measuring wheel  62  marked with measurement lines can be disposed next to rotating wheel  61 . 
         [0199]    According to another preferred embodiment of the present invention, in lieu of manual operation, the rotational movement is generated by an engine. 
         [0200]      FIG. 5   b  shows central perforation  51   a  in cover  51 . The center of central perforation  51   a  can be the origin of an imaginary orthogonal coordinate system, fixed to the improved radial expansible retractor  400 , with imaginary longitudinal axis Z, and with imaginary X and Y axes defining an imaginary plane, perpendicular to the imaginary longitudinal axis Z. The origin of such an imaginary orthogonal coordinate system can also be in other locations, such as the center of grooved disc central perforation  52   a , or the center of channeled disc central perforation  53   a , ( 52   a  and  53   a  are not seen in the present figure). Rib bases  42 , in this case eight, can be seen through central perforation  51   a.    
         [0201]      FIG. 3   c  is marked with section line a-a. 
         [0202]      FIG. 4   a  is a schematic perspective view illustration of a preferred embodiment of an improved radial expansible retractor  400  in an open mode according to the present invention. 
         [0203]    The illustration shows a state in which the eight ribs  41  are distanced from each other, and tubule  49  passes between them. Tubule  49  can be translucent and its walls can have perforations  49   a  in its walls, for the purpose of illuminating the surrounding tissue with light in the visible range or any other wavelength range, by means of a light source for viewing the state of the tissue, and for performing Multi Level Biopsy (MLB). 
         [0204]    Insertion of the tubule  49  between the ribs  41  is done after fall opening is completed gently and at a sufficiently gentle rate to ensure prevention of any undesired increase in pressure on the surrounding tissue. The lateral section of tubule  49  conforms to the lateral section of the aperture formed by the open ribs  41  and the geometrical dimensions of tubule  49  conform to the specific aperture of the ribs  41 , such that when the tubule  49  is inserted, the ribs  41  are gradually distanced from each other for their entire lengths until they are parallel to each other. 
         [0205]    Prior to removal of die improved radial expansible retractor  400 , tubule  49  is removed and a closing process is performed in which the ribs  41  are drawn closer to each other, preferably to the point of touching each other and once again forming a closed shape. 
         [0206]      FIG. 4   b  is a schematic perspective view illustration of a flexible sleeve  50  of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
         [0207]    The flexible sleeve  50  is pulled over the ribs  41  and expands as the ribs grow further apart. The lateral section of the flexible sleeve  50 , in working mode, is determined by combining its elastic qualities, the pressure exerted upon it by the surrounding tissue, the shape of the ribs  41 , and the shape of the tubule  49 , after it is inserted between the ribs  41 . 
         [0208]    Tubule  49  and the flexible sleeve  50  are disposable, minimizing infections. The ribs  41  may be disposable, too. 
         [0209]      FIG. 5   a  is a small-scale schematic top view illustration of a preferred embodiment of an improved radial expansible retractor  400  according to the present invention, marked with cross section line b-b. 
         [0210]      FIG. 5   b , is a schematic cross section illustration of the improved radial expansible retractor  400  of  FIG. 5   a  along line b-b. 
         [0211]    The illustration also shows cover  51 , including cover central perforation  51   b , grooved disc  52 , channeled disc  53 , and ribs  41 . 
         [0212]      FIG. 5   c  shows an enlarged segment of  FIG. 5   b  clearly showing rib carrier  44  disposed within channel  53   b  of the channeled disc  53 , with the rib carrier pin  45  disposed within groove  52   b  of the grooved disc  52  whose center has a perforation  52   a  (not shown in the present figure) of a suitable diameter for inserting the tubule and performing the medical procedure. A series of similar perforations  51   a ,  52   a , and  53   a  (not shown in the present figure) can be found in the centers of the cover  51 , the grooved disc  52 , and the channeled disc  53  respectively, with the centers of these three perforations disposed on a single axis. The rib carrier  44  connects to rib base  42  which is the integral base of arm  41 , by means of rib carrier bolt  47 . 
         [0213]      FIG. 6   a  is a schematic perspective view illustration of cover  51  in whose center is perforation  51   a  of a suitable diameter for inserting the tubule and performing the medical procedure, of a preferred embodiment of an improved radial expansible retractor according to the present invention. 
         [0214]    Cover disc  51  can have a cylindrical wall  51   b  over part of its circumference, and this wall can have protuberances  51   c  for connection to channeled disc  53  shown in detail in  FIG. 6   c , furthermore there can be holes  51   d  in cover disc  51  designated for fitting connective bolts into them. 
         [0215]      FIG. 6   b  is a schematic perspective view illustration of grooved disc  52 , of a preferred embodiment of an improved radial expansible retractor according to the present invention, in whose center is perforation  52   a , of a suitable diameter for inserting the tubule and performing the medical procedure, and grooves  52   b , in the present case eight, designated to grant continuous forced movement to the rib carrier pin. 
         [0216]    Grooves  52   b  can run the entire depth of the grooved disc, or a partial depth and at a suitable width, all conforming to the dimensions of the rib carrier pin. 
         [0217]    Along the circumference of the grooved disc  52 , there is an external surface  52   c , a part of which can be shaped as a depression  52   d  designated and suitable for connection of a tooth rail to it. 
         [0218]      FIG. 6   c  a is a schematic perspective view illustration of channeled disc  53  of a preferred embodiment of an improved radial expansible retractor according to the present invention, in whose center is perforation  53   a , of a suitable diameter for inserting the tubule and performing the medical procedure, and channels  53   b , in the present case eight, designated to grant continuous forced movement to the rib carrier  44  (not shown in the present figure). The channels  53   b  are completely straight, and are pointed in the directions of the radiuses from a joint center of the channeled disc  53 . Their dimensions conform to those of rib carrier  44 , and they are designated to enable strictly radial movement of rib carrier  44  with regard to the aforementioned center. 
         [0219]    The channeled disc  53  can be designed and manufactured in a structure of optimal volume and weight. 
         [0220]    Combination of the channeled disc  53  and the cover  51  is done by means of geometrically conforming both to each other, together forming a casing suitable for carrying grooved disc  52  and granting it smooth rotational movement. Closure of the casing can use suitable protuberances and depressions and part of the structures of the channeled disc  53  and the cover  51  as well as small bolts. Channeled disc  53  has bolt holes  53   c.    
         [0221]      FIG. 7   a  is a geometrical illustration showing the principle of granting the rib with radial motion. The illustration shows two angular relations between the groove  52   b  and the channel  53   b . In the first state, the channel  53   b  is at an angle of a 1  to an arbitrary reference line, and in the second state, the channel  53   b  is at an angle of a 2  to the same reference line. The angles are measured from a joint center. 
         [0222]    Seeing as the rib carrier pin  45  at the base of the rib is forced to be in the groove, and the base of the rib is forced to be in the channel, in the first state the rib carrier pill  45  is at a radius of r 1  from the center, and in the second state the rib carrier pin  45  is at a radius of r 2  from the same center. Namely, the connected rib carrier pin  45  and the rib carrier  44 , as well as the rib connected to them are, in each state, at a different distance from the center, which is the center of rotation between the grooved disc and the channeled disc, and seeing as the channel  53   b  is radial, the rib&#39;s motion will also be radial. 
         [0223]    As explained in the summary, it is of utmost importance for the retractor&#39;s opening rate to be controlled, and the mechanism controlling the opening rate must be able to allow a nonlinear opening rate. 
         [0224]    The velocity of the radial movement of rib carrier pin  45  for a fixed rotational speed of groove  52   b  depends upon several factors, including the distance from the center of rib carrier pin  45  at the given time. The larger this distance, the larger the radial velocity, and the more perpendicular the tendency angle of groove  52   b , namely the closer to the radius direction, the larger the radial velocity, while the more horizontal the tendency angle of groove  52   b , namely the closer to the direction tangent to the rotational movement, the smaller the radial velocity. 
         [0225]    In the case shown in the illustration, the tendency angle between radius r 1  and groove  52   b  at their intersection point is y 1  while the tendency angle between radius r 2  and groove  52   b  at their intersection point is y 2  while y 1 &lt;y 2 . 
         [0226]      FIG. 7   b  is a geometrical description of the principle of granting radial movement to the ribs forming a not-circular aperture form. The illustration shows four grooves  52   b  out of eight, which are responsible for the movement of four ribs. As shown, each of the grooves has a different curve, and each groove ends at a different distance from the center. This difference necessarily results in different movement of each of the ribs, forming a lateral section which is not circular. 
         [0227]      FIG. 7   c , is a schematic top view illustration of a grooved disc  52  of a preferred embodiment of an improved radial expansible retractor according to the present invention. The illustration shows the central perforation  52   a , eight grooves  52   b , and a depression  53   d  designated to enable good connection of the disc to the tooth rail. 
         [0228]    In this case, the curves of all of the grooves  52   b  are identical and therefore the aperture of the ribs will be circular, Design and selection of the groove curve can be done by means of either trial and error or analytical calculations. The factors affecting the desired curve also include: geometrical location possibilities, depending on the dimensions of the grooved disc  52  and the width of the groove  52   b , the desired radial velocity for each distance of the rib from the center, and tendency angle limitations of the groove  52   b  curve to allow moving rib carrier  44  to require no more than reasonable force. 
         [0229]      FIG. 7   d  is a schematic top view illustration of a channeled disc  53  of a preferred embodiment of an improved radial expansible retractor according to the present invention. The illustration shows the central perforation  53   a , eight radial channels  53   b , and two protrusions  53   d  suitable for the movement of tooth rail  67  along with the grooved disc  52 . 
         [0230]      FIG. 8  is an exploded view of a preferred embodiment of an improved radial expansible retractor  400  according to the present invention. The illustration shows the following parts of the improved radial expansible retractor  400 : 
         [0231]    The rib carrier bolt  47  designated to carry the rib carrier  44  to the rib  41 , the cover disc  51  and the channeled disc  53 , creating in unison a packaging which allows limited rotation movement of the grooved disc  52  and the tooth rail  67  designated to connect to the grooved disc, preferably to a depression in its circumference, while the tooth rail  67  has teeth facing outwards designated to gain motive force for rotational movement of the grooved disc  52 , the central rod  48 , the fixation bolt  70 , and the adaptor  69 , which is designated to adapt the packaging formed by the cover disc  51  and the channeled disc  53 , and serves as a housing for some of the rotational movement transmission components and adjacent components also including the rotating wheel  61 , which is the first component initiating the motion, by force of the operator&#39;s hand, the measure wheel  62 , the shaft  63  which is connected to rotating wheel  61  and transmits the rotational movement to worm  65  which is connected to shaft  63  which has a spiral tooth in dimensions suitable to the dimension of the teeth of the tooth rail  67  such that the improved radial expansible retractor  400  has the spiral tooth of worm  65 , combined with the teeth of the tooth rail  67 , assembled to it, therefore the rotational movement initiated by rotating wheel  61  moves the grooved disc  52  rotationally around a rotational axis perpendicular to that of the rotating wheel  61 . Shaft  63  rotates within front sleeve  64  and inner bearing  66 . 
         [0232]    The friction in the motive system is suitable for gentle transmission of motion and sufficient for the pressure on the ribs  41  created by the tissue does not close them undesirably. 
         [0233]      FIG. 9   a , is a schematic perspective view illustration of a rib  41  of a preferred embodiment of an improved radial expansible retractor  400  according to the present invention. At one end of rib  41 , the rib&#39;s base  42  is disposed, into which the rib base hole  43  is perforated, enabling connection by means of a bolt to the rib carrier  44 . Rib  41  is formed as an elongated rod whose cross section can have many various geometrical shapes, also including the shape of a section of the wall of a cylinder, as in the present embodiment. 
         [0234]    Rib  41  has a leading edge  41   a  and an external surface and an internal surface, such that as shown in  FIG. 9   c , on the external surface of rib  41 , a pressure sensor  40  can be disposed, enabling real time measurement of the CPP. 
         [0235]      FIG. 9   b , is a schematic perspective view illustration of a rib base  42  of a preferred embodiment of an improved radial expansible retractor  400  according to the present invention. Its shape conforms for connection to the rib&#39;s base  42  and it includes rib carrier hole  46 , and rib carrier pin  45 . 
         [0236]    This preferred embodiment enables exchanging rib  41  with another rib as necessary, for example a rib of a different length, cross section, etc. 
         [0237]    According to another preferred embodiment, the rib and the rib base, including the pin, are made as a single part. 
         [0238]      FIG. 9   c  is a schematic cross section of ribs  41  along the section line a-a as marked in  FIG. 3   c . The center of the illustration shows eight ribs  41  in closed mode, touching each other and forming a closed shape, in this case of a circular cylinder, namely each rib  41  has a cross section in the shape of a 45-degree segment of a circular cylinder wall. The perimeter of the illustration shows an opened mode of the ribs  41 , after they have been distanced from each other, in this specific case at an identical distance of opening. Rib  41  has a rib internal surface  41   c , and a rib external surface  41   b.    
         [0239]      FIG. 9   d  is a schematic cross section of ribs  41  along the section line a-a as marked in  FIG. 3   c . The center of the illustration shows eight ribs  41  in nearly closed mode, almost touching each other, and forming a closed shape, in this case of an elliptical cylinder, namely each rib  41  has a cross section of a segment of an elliptical cylinder wall, in the specific case shown in the illustration different ribs of the eight differ from each other in cross section shapes. 
         [0240]      FIG. 9   e  is a schematic cross section of ribs  41  along the section line a-a as marked in  FIG. 3   c . The center of the illustration shows eight ribs  41  in nearly closed more, almost touching each other, while each of the ribs  41  has a circular cross section. 
         [0241]      FIG. 10   a  is a schematic illustration of a subsystem for BTRP measurement of the tissue  98  according to the present invention. 
         [0242]    Knowing the level of pressures exerted by the retractor on the tissue it comes into contact with, when performing a medical procedure and especially when the ribs  41  are open, is extremely important. According to the present invention, folded bags  90  can be disposed in various places along the retractor inserted between tissues or into tissue. The location of a folded bag  90  monitor depression on the external surface of a rib  41  or between the ribs, namely between the tubule  49  and flexible sleeve  50 , in which case the folded bag  90  is inserted into place only after insertion of the tubule  49  between the ribs  41 . The subsystem for measurement of the pressure on the tissue  98  includes one or more folded bags  90 , which can be of polyethylene or any other suitable material. Pipeline  92  is connected to the folded bag  90  for the purpose of filling it with air, and pipeline  92  is also connected to air source, or any other suitable fluid, pressure source  91 , which can be a compressed air container or a pump etc. In addition, there is a pressure gauge  93  connected to the pipeline. 
         [0243]    Pressure measurement is started by increasing the pressure of the air in the folded bag  90  by means of the pressure source  91 . As soon as the pressure in the bag  90  equals the pressure exerted on the folded bag  90  by the tissue with which it is in contact, the pressure gauge  93  gives a reading. 
         [0244]    A miniature control light bulb  95 , which indicates lack of pressure measurement, can optionally be added to the subsystem for measurement of the pressure on the tissue  98 . The light is connected to electrical wire  96 , and is supplied from an electrical power source  94 . At each end of electrical wire  96 , disposed within folded bag  90 , there is an electrical contact element  97 . When the elements  97  touch each other, the electrical circuit is closed and miniature control light bulb  95  goes on. This state occurs when there is no air pressure in folded bag  90 , meaning that the pressure on the tissue  98  is not being measured at the moment. 
         [0245]      FIG. 10   b  is a schematic cross section illustration of the folded bag  90  of  FIG. 10   a  along line c-c. The illustration shows both electrical contact elements  97  attached to the insides of the folded bag  90 , when they are separated from each other seeing as folded bag  90  has internal air pressure and is inflated. In this case miniature control light bulb  95  is off. 
         [0246]      FIG. 10   c  is a schematic cross section along the section line a-a as marked in  FIG. 3   c  through folded bag  90  which is disposed between the ribs  41  according to the present invention. 
         [0247]    Folded bag  90  is disposed in the gap formed between two adjacent ribs  41  which are external to the tubule  49  facing a window of flexible sleeve  50   a . The location facing the window of flexible sleeve  50   a  ensures that pressure exerted by the flexible sleeve  50  will not be mistakenly measured. 
         [0248]    Additional folded bags  90  can be disposed between other ribs  41 , as well as in other sections along the ribs  41 , to enable collection of pressure data from numerous points. 
         [0249]      FIG. 11  is a schematic illustration of an improved radial expansible retractor  400 , equipped with an opening engine  71  mechanism, according to another preferred embodiment of the present invention. Engine  71  provides the necessary rotational moment for operation of the improved radial expansible retractor  400 , which can be controlled manually by the operator and can also be controlled automatically by a control system which also receives input of real time pressure data. 
         [0250]      FIG. 12  is a schematic illustration of a preferred embodiment of an improved radial expansible retractor  400  according to the present invention, in action. 
         [0251]    The improved radial expansible retractor  400  is easily affixed to existing skull clamps and holder devices for use in neurosurgery. 
         [0252]    The drawing illustrates the compatibility of the improved radial expansible retractor  400  with existing skull holding mechanisms. The improved radial expansible retractor  400  is securely held in place by a skull clamp joined to a holder device  81  locked by means of lock  82 . 
         [0253]    An endoscope  84 , through which the doctor&#39;s eye  35  looks, is inserted into the canal together with a suction device  86  to access and remove, for example, an intracerebral hemorrhage (a) (ICH)  104 . 
         [0254]    As the improved radial expansible retractor  400  can come in many sizes, there is wide range of surgical specialties that can apply the device in their surgical procedures including general surgery, orthopedic surgery, ENT, vascular surgery, gynecology, urology, pediatric surgery, biopsy, and robotic technique. Cardiac surgery can make use of the device for insertions between the ribs and the insertion of an endoscope into the coronary artery to carry out bypass surgery without the need to cut and open the sternum. Multiple bone fractions can be reset using the device to realign bones and insert plates minimizing incision size and blood loss. The device allows for easy access for abdominal laparoscopic cholecystectomy. Chemotherapy can be applied directly to pathological cells with minimal damage to surrounding healthy cells. 
         [0255]      FIG. 13  is an illustration of the procedure to remove intraventricular hemorrhage from the lateral ventricle  101  or to remove intraventricular hemorrhage from the fourth ventricle  102 , using the improved radial expansible retractor  400  to access the hemorrhage  103 . The device allows access to areas of the brain previously almost impossible to access. 
         [0256]      FIG. 14  shows a multi-portal approach to intraventricular hemorrhaging  105  and intracerebral hemorrhaging (b)  106  with the improved radial expansible retractor  400  being inserted from two separate sites a and b to easily access the hemorrhage and suction it out. 
         [0257]      FIG. 15  shows a multi-portal removal of intra-ventricular lesions  107  with an aspirator  99  inserted into the expanded canal from one side and an endoscope  94  inserted via a second canal, both through separated improved radial expansible retractor  400 . 
         [0258]    Some of the advantages of the improved radial expansible retractor according to the present invention follow: 
         [0259]    It offers minimally invasive surgical solutions for many patients who at present face a bleak outlook. 
         [0260]    There will be a drastic reduction in brain damage caused by lengthy and uncontrolled retraction of brain tissue. 
         [0261]    It will shorten the time of operation. Operations that presently take 9-12 hours will take 1-2 hours. 
         [0262]    Minimal openings in the skull will be no more than 10 to 20 mm. 
         [0263]    Multiple tumors and metastases ran be removed in one surgical procedure, entering the brain at different points, with easier access and minimal damage to surrounding tissue. 
         [0264]    Treatment of brain tumors with radiation applied via the retractor working channel directly to pathological cells will greatly reduce peripheral tissue damage and increase survival rates. 
         [0265]    Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.