Abstract:
An elongated patient support table [ 22 ] with a horizontal patient support surface has a contoured radiolucent table extension assembly [ 26, 126 ] connected thereto in cantilever fashion for supporting the head and upper torso of a patient [ 27 ]. An outer end of the extension assembly [ 26, 126 ] has a reduced width compared to the support table [ 22 ] to enable extendable movement of the radiolucent extension assembly [ 26, 126 ] into a scanning zone defined by a central opening [ 112 ] of a diagnostic unit such as a CT scanner [ 20 ]. The table extension assembly [ 26, 126 ] supports the patient [ 27 ] via an inboard radiolucent horseshoe headrest [ 32, 132 ] and an outer tool support [ 54, 122 ] for holding an outer stabilization device [ 66, 166 ] such as a radiolucent skull clamp [ 74, 174 ]. The combination of the support table [ 22 ] with the radiolucent table extension assembly [ 26, 126 ] and the inner and outer stabilization devices [ 32, 132, 66, 166 ] support the patient [ 27 ] in a desired position during successive scanning or surgical procedures. With an imaging system [ 24 ] operatively connected to the CT scanner [ 20 ], the table extension assembly [ 26, 126 ] permits a neurosurgeon to conveniently obtain updated images of the scanned region after performing a stereotactic operative procedure, thereby to immediately and easily determine if any follow-up procedures are necessary before closing up the surgical incision.

Description:
This application is a continuation of PCT application Ser. No. PCT/US98/18405, entitled “Radiolucent Table Extension And Method,” filed on Sep. 3, 1998, which in turn claims priority to U.S. application Ser. No. 08/922,969, filed on Sep. 3, 1997, and issued on Dec. 5, 1999 as U.S. Pat. No. 6,003,174, and U.S. Provisional Application Serial No. 60/083,014, filed on Apr. 24, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to beds and more particularly, to an improved surgical operating table. 
     BACKGROUND OF THE INVENTION 
     With current medical practices, it is common for a patient to undergo a diagnostic scanning procedure, which is normally performed in a separate suite containing the scanning machine and dedicated to scanning procedures. The scanning machine may be a CT, MRI, or other scanning device. Thereafter, the scan data is utilized in a surgical planning process, which conventionally takes place at a location, for example, an office or an operating room. In some surgical procedures, the scanning data is utilized with a system for post processing the scan data acquired during imaging. Further, the imaging system may be located in a surgical suite, and the surgical planning performed before and during surgical procedure utilizing the imaging system and scan data. 
     During the scanning procedure, the patient must maintain a perfectly still and motionless posture, and while most often, the patient simply lies on a scanning support table, in some situations, the patient may be supported in the desired scanning position with pads, straps or other supports. Further, the support on which the patient rests is normally radiolucent, that is, transparent to the scanning device, so that the support does not compromise the utility of the scanned image. Further, the patient support used for scanning normally translates with respect to the imaging device. Translation of the patient support permits the patient to be moved into the scanning field or zone of the scanning machine. 
     After the scanning process is completed, often the patient is then moved to an operating room which requires either that the patient walk, or be carried, for example, by transferring the patient from the scanning table to an operating table. Alternatively, as illustrated in U.S. Pat. No. 5,475,884, the patient may be supported on a portable support plate, which is easily moved between the scanning table and the operating table. The scan data is often used in a post processing imaging system for surgical planning purposes both prior to and during surgery. If during or after a surgical process, it is desired to scan a patient again, the patient must be moved from the operating room to the scanning suite, transferred to and from the operating table to the scanning table, and after scanning, transferred back to the operating table and returned to the operating room. The above process is cumbersome, time consuming and potentially risky for the patient. 
     Some newer scanning machines are substantially reduced in size. One such machine is shown in FIGS. 2 and 3 of U.S. Pat. No. 5,499,415, which show an annular-shaped scanner mounted on a wheel-supported frame, to enable the scanner to be used at multiple sites. Consequently, such scanning machines do not require their own suite or room, but instead, they may be used within the operating suite itself. Thus, in an operating room, the patient may be scanned; the surgical planning performed; an operative procedure executed; and the patient scanned again to determine the current status of the operative procedure. Based on the new scanned images, the operative procedure can be continued and the above process repeated as necessary. 
     A limitation of the current state-of-the-art is that the posture of the patient during the scanning process is often different from the patient&#39;s posture during surgery. If a patient is positioned in one posture on a scanning table during the scanning process, and then is moved to an operating table, that motion of the patient may cause the position of the target to change with respect to the body surface. During surgery, this problem is compounded by tissue shifts attendant to the opening of body cavities, removal of body fluid or tissues and tissue retractions. Thus, while such motion may be small, any motion of the target will reduce or compromise the utility of the preoperative scan data. 
     The solution to these problems is to scan the patient in the operating room during surgery while the patient is maintained in the surgical posture. 
     While current scanning tables are radiolucent and provide a translation to move the patient into the scanning machine, such scanning tables do not have the accessories required to attach, support and stabilize surgical instrumentation and to properly support the patient&#39;s body in the desired surgical posture. Further, while operating tables contain numerous accessories and couplings to which surgical instrumentation may be attached and supported, most operating tables are not compatible with scanning instrumentation. Thus, as presently known, scanning tables cannot be used as operating tables, and generally, operating tables are inappropriate for use as scanning tables. 
     It is an object of this invention to overcome the above-described limitations in the prior art, by facilitating the function of supporting a patient in a desired position in a manner which readily accommodates successive surgical or scanning procedures. 
     SUMMARY OF THE INVENTION 
     The present invention achieves the above-stated objective with a radiolucent table extension that connects to a surgical table and permits a patient to be positioned on the table in a posture suitable for successive surgical or scanning procedures, with the head and the upper torso of the patient supported on the table extension and the radiolucent table extension including additional cooperative components such as a radiolucent horseshoe headrest and a radiolucent skull clamp to positively hold the patient relative to extension. The radiolucent table extension is cantilevered from one end of the surgical table and it is shaped so that it may be moved in a relative manner into a toroidal shaped scanning zone of an upright annular scanning machine. This permits the patient to be scanned in the desired surgical posture. This radiolucent table extension is especially useful for those procedures in which it is desirable to maintain the patient in a desired position during successive scanning or surgical procedures. 
     By operatively connecting the toroidal scanner to an imaging system, so that the imaging system may store data representative of scans of the patient taken in the scanning zone, and by supporting the patient with the extension and fixing the position of the patient with the horseshoe headrest and the skull clamp, this invention facilitates the positioning of the patient during successive scans, thereby assuring the accuracy of the scanned data. This helps the surgeon to know almost immediately whether the surgical procedure accomplished its objective, or whether a subsequent surgical procedure may be necessary. 
     According to the principles of the present invention and in accordance with the preferred embodiments, a radiolucent table extension has a first end adapted to be attached to one end of a table. The table extension includes a contoured radiolucent member designed to support an upper torso and head of a patient with the rest of the patient&#39;s body being further supported by an adjacently located surface of the table. The member has a sufficiently narrow width to permit it to be extended, in cantilever fashion, into a scanning zone of portable CT scanning system. A tool support extends along a periphery of the member and is designed to receive and support at least one outboard stabilization device, such as a skull clamp, to positively hold the patient in a fixed position relative to the member. The extension also includes at least one inboard stabilization device. More specifically, inboard of the periphery a radiolucent horseshoe headrest also provides stabilized support for the patient. Therefore, the patient can be supported on the radiolucent table extension in the desired posture. The patient can then be conveniently scanned before a surgical procedure. After surgery, a subsequent scanning procedures may be performed if necessary or desired. Thus, the table extension has the advantage of not requiring that the patient be moved with respect to the table extension between successive scanning and surgical procedures. 
     Moreover, with updated scanned images readily available for viewing via the imaging system, the surgeon can review the results of a surgical procedure to determine if a particular operation has been completely successful. For example, if the objective of the surgery was to completely remove a hematoma from the brain, a follow-up scan may enable the surgeon to use the imaging system to determine if the entire hematoma has been removed. If a subsequent scan shows that some of the “target” remains, then the surgeon can perform another surgical procedure, using the imaging system if desired, to achieve 100% removal of the target. Thus, this overall system facilitates successive scanning and surgical procedures, and the table extension assembly makes it possible to use this system more effectively, by assuring accurate and repeatable positioning of the patient. 
     In one aspect of the invention, a hinge mechanism mechanically couples the radiolucent member to an operating table, thereby permitting the table extension to be pivoted or rotated with respect to the table. Thus, the patient&#39;s head and upper torso may be raised or lowered and supported in any desired position to facilitate the scanning and operative procedures. 
     In a further aspect of the invention, the tool support extends along the periphery at one end of the table, but in another aspect of the invention, the tool support extends along the periphery including the lateral edges of the table. Thus, a wide variety of surgical instruments may be connected to the table extension to facilitate many different surgical procedures. 
     In still another aspect of the invention, the table extension includes a radiolucent horseshoe headrest removably mounted to the radiolucent member, inboard of the peripheral edge, and it is tiltable with respect to the member. This horseshoe headrest may surround a portion of an opening in the member, when viewed from above. The removable, tiltable horseshoe headrest optimizes versatility for the neurosurgeon in positioning a patient. 
     If desired, the tool support may be detachable from an external edge of the member. This enables a surgical drape, shaped in a bag-like form, to extend over the head of an intubated patient stabilized in position by the radiolucent horseshoe headrest. The headrest resides “inboard” of the peripheral edge with the patients&#39; head and upper torso supported relative to the member. 
     Thereafter, the tool support can be connected to the edge of the member, with the drape sandwiched therebetween, and the skull clamp attached “outboard” to the tool support. This places the tooling connected to the tool support, i.e., the skull clamp, within the sterile field. This arrangement represents an advantageous option for some types of surgical and/or scanning procedures. For one thing, the drape is more closely confined to the table extension so that the surgeon and other hospital attendants can readily determine visually that the table extension and the patient can be extended within the scanning zone of the scanner without impediment. For some procedures, this arrangement also simplifies connection of the skull clamp. 
     These and other objects and advantages of the present invention will become more readily apparent during the following detailed description taken in conjunction with the drawings herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a portion of an operating table including a radiolucent table extension assembly in accordance with the principles of the present invention. 
     FIG. 2 is a top plan view of the radiolucent table extension assembly of FIG.  1 . 
     FIG. 3 is a side view in elevation of the radiolucent table extension assembly of FIG.  1 . 
     FIG. 4 is a cross-section view taken along the line  4 — 4  of FIG.  2 . 
     FIG. 5 is a cross-section of view taken along the line  5 — 5  of FIG.  2 . 
     FIG. 6 is a top plan view of an alternative embodiment of the radiolucent table extension assembly in accordance with the principles of the present invention. 
     FIG. 7 is a perspective view of yet another alternative embodiment of a table extension assembly in accordance with the present invention. 
     FIG. 8 is a top plan view of the table extension assembly shown in FIG. 7, but with additional hardware shown, namely an inboard horseshoe headrest. 
     FIG. 9 is a side view of the table extension of FIG. 8, but also showing an outboard stabilization device, in this case a skull clamp, secured to the tooling support outboard of the edge of the table extension. 
     FIG. 10 is a side view, similar to FIG. 9, showing the inboard horseshoe headrest tilted relative to the table extension assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a portable CT scanning system  20  is located in an operating suite with an operating table  22 . The CT scanning system may be either a mobile system such as that commercially available from Analogic of Peabody, Massachusetts or a stationary scanning system such as that commercially available from General Electric Medical Systems of Milwaukee, Wisconsin. The operating table  22  may be one of many commercially available tables, for example, an operating table commercially available from Amsco of Erie, Pa., MDT Diagnostic Co. of N. Charleston, N.C., or other suppliers. The operating table has a lateral rail  23  extending along each side of the table to which retractors, clamps and other devices may be attached and stablely supported. A stereotactic image processing system  24 , for example, the MAYFIELD-ACCISS image processing system, commercially available from Ohio Medical Instrument Company, Inc. of Cincinnati, Ohio is operatively connected to the scanner  20  and responsive to scan data provided by the CT system  20 , to provide selected images on a display screen of the scan data along selected planes. To facilitate the use of the operating table  22  with the CT system  20 , one end of the operating table is used to support a radiolucent table extension, or table extension assembly,  26  in accordance with the present invention. Use of an imaging system  24  of this type is described in U.S. Pat. No. 5,695,501, which is expressly incorporated by reference herein, in its entirety. 
     Referring to FIG. 2, the table extension  26  includes a support member or plate  28  made of radiolucent material, for example, wood, carbon graphite, etc, and the table extension  26  has a length to normally support the upper torso and head of a patient  27 , the upper torso being defined as the portion of the patient&#39;s body above the waist including the head. As shown in FIG. 4, the patient support member  28  has a curved cross-sectional profile and has a laminated construction with a center layer of mahogany between two outer layers of carbon graphite, although the invention also contemplates molding the member  26  as one integral piece. The curve is normally a circular arc having a relatively large radius, for example,  28  inches, to generally conform to the shape of a patient. The support member  28  may have a length up to about  52  inches, although most procedures can be accommodated with a shorter-length, such as  36  inches. The outer or distal end  30  of the support member  28  includes a horseshoe headrest  32  that is generally U-shaped and filled with a gel to comfortably and properly support the patient&#39;s head. The headrest  32  surrounds an opening  34  within the support member  28 . The opening  34  is sized to receive the face of a patient lying on the support member  28  in a prone position. The distal end  30  is narrower than the inner or fixed end  36 , and the narrow profile of the distal end  30  of the support plate  28  facilitates positioning the distal end  30  in scanner  20  even if the table or the scanner  20  is tilted. The support member  28 , when viewed from the top as shown in FIG. 2, has a profile that flares outward from the distal end  30  to the fixed end  36 . The width of the support member  28  at the fixed end  36  is generally greater than the distance between the holes  46  and is normally equal to the width of the operating table  22 . 
     Referring to FIG. 5, the support member  28  is secured at its fixed end  36  within a slot  38  of an attachment base  40 . Fasteners, for example, screws  42  are used to clamp and secure the support plate  28  within the attachment base  40 . The attachment base  40  is mechanically linked to support shafts  44 , which extend longitudinally from the fixed end of the support base  40  and are sized to fit into holes  46  of the table  22 . Thus, the support plate  28  provides an extension of and is cantilevered from the end  23  of the table  22 . 
     Referring to FIGS. 1-3, an instrument or tool support or rail  54  is attached to the periphery of the distal end  30  of the support plate  28 . The tool support  54  may be made from a “DELRIN®” acetal polymer material, a polyethersuylfone (“PES”) material or a carbon graphite. An inner directed side  56  of the tool support  54  includes a slot  58  for receiving the portion of the periphery  60  of the support plate  28 . The support plate  28  may be secured in the slot  58  using fasteners or adhesives or both. The slot  58  is curved with respect to a radius sweeping a vertical plane that is generally perpendicular to and extends across the width of the support plate  28 . An outer directed side  62  of the tool support  54  includes a second slot  64  that is generally parallel to a longitudinal center line of the tool support  54 . Thus, when viewed from the end of the support plate  28 , that is, looking to the left in FIG. 3, the slot  64  will appear generally as a straight slot. The slot  64  permits medical instruments, such as stabilization devices  66 , for example a skull clamp, retractors, clamps, supports, etc., also collectively referred to as “tools” herein, to be supported, selectively moved with respect to the distal end  30  of the support plate  28  to desired positions and locked or secured in place. In the illustrated embodiment, the slot  64  has a dovetail shape that matches a mating dovetail on the tool to be mounted and secured to the tool support  54 . For example, the tool support  54  may receive one end  68  of a transitional element  70 . The other end  72  of the transitional element  70  is rotatably coupled to a swivel adapter  74 . The swivel adapter, in turn, is coupled to a skull clamp  76 . The skull clamp  76  is normally manufactured from radiolucent materials, for example, as described in U.S. Pat. No. 5,276,927 issued to the assignee of the present invention. 
     As shown in FIG. 3, the support plate  28  is often used in a generally horizontal position such that the top of the operating table  22  is generally in line with the support plate  28 . However, numerous surgical procedures require that the support plate  28  be tilted or pivoted up or down with respect to the end  25  of the table  22 . The tilting or pivoting of the support plate  28  is accomplished by the mechanism illustrated in FIG.  5 . The attachment base  40  includes a pair of housings  86  connected to a lower surface  41  at a location near the ends of the attachment base  40  (FIG.  4 ). The attachment base  40  and housings  86  may be cast or made from aluminum. The support shafts  44  are rigidly connected at one end to respective cross-shafts  88  that are rotatably mounted within the lateral side walls  90  of the housings  86 . The cross-shafts  88  extend through brass bushings (not shown) mounted in the lateral side walls  90  and function as pivot pin in a hinge. The support shafts  44  function as fixed hinge members, and the housings function as movable hinge members. A ratchet wheel  92  is fixed at the center of each of the cross-shafts  88 , and each ratchet wheel has notches  94  between teeth  96 . The support shafts  44 , crossshafts  88 , and ratchet wheels  92  are normally made from stainless steel. 
     Pawls  98  are shaped to mate with and fit into the notches  94  of respective ratchet wheels  92 . Each pawl  98  is mounted on the end of a release shaft  100  that extends through a bore  102  of a respective housing  86 . With the pawls  98  in the position illustrated in FIG. 5, they function to securely support their respective housings  86  and the support plate  28  in a generally horizontal position. A spring  104  provides a bias to forcibly maintain the pawls  98  within the slots  94 . The pawls  98  and release shafts  100  are normally made of stainless steel. 
     As shown in FIG. 4, a release shaft or bar  106 , normally made of aluminum or stainless steel, extends between the shafts  100  and the housings  86 . By pulling on the bar  106 , the shafts  100  move to the right as viewed in FIG. 5; and the pawls  98  are pulled out of engagement with respective ratchet notches  94 . Once the pawls  98  are disengaged from the notches  94 , the support plate  28 , attachment base  40 , and housings  86  are freely rotatable relative to respective stationary ratchet wheels  92 , cross-shafts  88  and support shafts  44 . Thus, the support plate  28  may be pivoted with respect to an axis of rotation  108  in the generally clockwise or counter-clockwise direction until the support plate  28  is at its desired angular position as shown in phantom in FIG.  5 . Normally, the support plate  28  may be pivoted approximately 60° above and below its illustrated horizontal position. When the bar  106  is released, the springs  104  push their respective pawls  98  into the closest ratchet notches  94 , thereby securing the support plate with the desired angle or tilt. 
     In use, referring to FIG. 1, the scanning system  20  and operating table  22  are brought into a surgical suite. The scanning system  20  has a toroid shape scanning element  110  with a central opening  112  defining an enclosed or encircled scanning zone with which the portion of the patient to be scanned is axially aligned. The scanning element  110  further has the capability of rotating or tilting within its base  114  with respect to a diametric horizontal axis. The distal end  30  of the support plate  28  is narrowed so that it can extend into the opening  112  without interference. If necessary, the head section (not shown) of the table  22  is removed therefrom, and the radiolucent table extension  26  is mounted to the table by inserting the support bars  44  into mating bores  46  on the end surface  47  of the table  22 . The patient  116  is then positioned on the table in a posture suitable for a surgical procedure. The length of the support plate  28  is sized such that the patient&#39;s upper torso and head are accessible for scanning and surgical procedures. The portion of the patient&#39;s anatomy on which the surgical procedure is to be performed may be stabilized by various clamps and restraining devices, for example, the skull clamp  76 . Further, the support plate  28  or the scanning element  110  may be tilted so that the desired posture and/or scanning plane is achieved. 
     When the desired surgical posture is achieved, normally the patient will have already been scanned; and the surgical planning and procedure can be performed. Thereafter, a portion of the radiolucent table extension  26  is then moved into the opening  112 , for a follow-up scan. The extent to which the extension  26  is moved into the opening  112  depends on what portion of the head or upper torso is to be scanned. The initial alignment of the table extension may be determined by visual inspection; and thereafter, a scan made to determine exactly whether and to what extent the table extension may be out of alignment. Alternatively, the scanner may be equipped with LED&#39;s or other sources of light providing beams of light with which the table extension can be aligned. In another embodiment, the table  22  may have an alignment tab  124  (FIG. 1) which is moved into an alignment slot  126  on the scanner  110 . When the tab  124  is properly seated in the slot  126 , the table is properly aligned with the scanner  110 . The scanning process is executed by the scanning machine moving the scanning element  110  incrementally in an axial direction and with each increment, a scan is taken. Thereafter, the extension  26  and the patient are removed from within the scanning element  110 , either by moving the scanning machine  20  or the operating table  22 . The scan data is then used in association with the imaging systems  24  to plan the surgical procedure. The surgical procedure is then performed, and thereafter, the patient may be moved back into the scanning machine  20 , and the scanning process repeated. The scanning and imaging system may be used to gauge the effectiveness of the surgical procedure; and if necessary, further procedures performed. The above process may be executed any number of times with the patient remaining in the desired position on the same patient support. 
     Thus, the above-described operating table and radiolucent table extension has a significant advantage of not only being able to support a patient during a scanning process, but also support the patient in the identical posture during a surgical procedure. The radiolucent table extension permits an operating table that is normally nonradiolucent and inappropriate for scanning purposes to be used with a scanning machine. Further, the table extension may be tilted to accommodate different desired surgical postures and is sized and shaped to readily fit within the opening of a scanning element, whether in a horizontal or tilted position. Further, not only does the table position permit successive scanning and operative procedures on the upper torso and head of a patient, but the radiolucent table extension  26  readily supports the patient in a prone, or supine position. 
     Referring to FIG. 6, an alternative embodiment of the support plate  118  has an distal end  120  that is curved to generally follow the profile of the headrest  32 . Further a tool support  122  extends along the periphery of the support plate  118  to a location at which the width of the support plate  118  begins to flare outwardly toward the width of the fixed end  32 . Other than its length, the construction and function of the tool support  122  is substantially identical to the tool support  54  described earlier. 
     According to a further variation of this embodiment, as shown in FIGS. 7-10, a radiolucent table extension assembly  126  includes a tool support  122  removably connected to the peripheral edge at a distal end  120  of the support member  128 . The support member  128  is preferably pivotal relative to a table (not shown) to which is connected. This is done by incorporating a pivot mechanism (not shown) into the table extension assembly  126  or even into the table itself, as with surgical tables commercially available from Midmark of Dayton, Ohio, which are built so as to tilt relative to horizontal. With such tube, the support member  128  is simply plugged via pins  129  into the table (not shown) which is already oriented at a desired angle. The support member  128  may have an inner portion  128   a  which is contoured to the body of the patient and an outer portion  118   b  which is generally flat. The tool support  122  may removably secure to the support plate  128  via a pair of hand-tightenable knobs  124 . The member  128  includes an opening  134 , and a radiolucent horseshoe headrest  32  or  132  resides inboard of, and generally in alignment with, a portion of the opening  134  as shown in FIGS. 8-10. This configuration enables a baglike surgical drape (not shown) to be placed over a patient who is supported on the support member  128  by the horseshoe  132 , and in an intubated condition, and then the tool support  122  connected to the distal end  120  to confine the drape within the edge of the support member  128 , between the support member  128  and the tool support  122 . Phantom line  130  in FIG. 9 illustrates an example of where this drape would be located. The patient  27  may be supported on the support member  128  in a face up or face down position. In a face down position, the hole  134  may be used for routing of one or more intubation tubes (not shown) or other medical instruments to the patient  27 . 
     This results in locating the tool support  122  outside the drape  130 , in the surgical field. This is also true for any other attendant hardware or assembly components  166  connected thereto, such as a skull clamp  174 . For some types of surgical procedures, this draping arrangement may be preferable during surgical or scanning procedures. At least with respect to scanning, this configuration helps to assure that no structure will impede movement of the table extension assembly  126  into the scanning zone. 
     With this embodiment, i.e., the tool support  122  and the outer stabilization device  166 , in this case the skull clamp  174 , connected “outboard” of the outer edge of the support member  128 , it is also possible to hold the head of the patient with a removably connected, tiltable horseshoe  132  located inboard of the edge of the support plate member  128  (FIGS. 8,  9 ). FIG. 10 shows the headrest  132  tilted relative to the support member  128 . With the tiltable horseshoe headrest  132 , there is a first connection piece  132   a  which mounts to an inside edge of the opening  134  and a pair of mirror image headrest pieces  132   b  and  132   c  (FIG. 8) which connect to each other in a common plane and tilt relative to the piece  132   a . This tilting feature gives the surgeon additional versatility in positioning the patient. Both the connector piece  132   a  and the second headrest pieces  132   b  and  132   c  are made of radiolucent material so as to not create artifacts during scanning. 
     FIGS. 8-10 show outer tooling  166 , specifically a skull clamp  174 , along with an inner device such as a horseshoe headrest  132  connected to the tool support  122 . Preferably the tooling or devices  166  are radiolucent and positively hold the patient in a fixed position relative to the support member  128 , so that the patient remains in a desired position during successive surgery and scanning procedures. This is done with the inboard headrest  132  and/or an outer stabilization device  166 , to affirmatively hold the patient  27  in a fixed position relative to the support plate  118 . This structural capability facilitates convenient positioning of the patient  27  during successive scanning or surgical procedures, thereby enabling the surgeon to conveniently and easily perform follow-up procedures. 
     While the invention has been illustrated by the description of several embodiments and while the embodiments have been described in considerable detail, there is no intention to restrict nor in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those who are skilled in the art. For example, the support plate  28  may be made of other radiolucent materials and may or may not have a laminated construction. Further, when viewed in a cross-section taken across its width as shown in FIG. 4, the support plate  28  has a curvature; however, the support plate  28  may also be constructed to be flat without such a curvature. Further, while the radiolucent table extension is particularly useful with nonradiolucent operating tables, it may also be used with radiolucent operating tables. 
     The tool support  54  has been described as an edge strip with a slot  64  having a dovetail shape for receiving and supporting tools; however, as will be appreciated, other configurations of the tool support are anticipated by the invention. For example, the slot  64  may have other shapes. Further, the slot  64  may be replaced by round, square or other shaped holes or coupling elements which are shaped to receive mating elements on tools, thereby supporting and holding the respective tools in a desired position. In addition, the tool support  54  may be a strip extending along the edge of the periphery of the plate  28  without the slot  64  but providing a hard surface for clamping purposes, for example, for using C-clamps to secure tools to the strip. While the tool support  54  is described and illustrated as having a slot  58  for receiving an edge of the plate  28 , the tool support  54  can be attached to the plate  28  in other ways. For example, the slot  54  may be on the upper or lower surfaces of the plate  28 , or the tool support  54  can be attached to the upper or lower surfaces, or the edge, of the plate  28 . In addition, even though the tool support  54  has been described as being made from a radiolucent material, under some circumstances, for example, if the tool support is outside the scan field, the tool support  54  may be made of a nonradiolucent material, for example, metal. 
     As will be appreciated, the horseshoe-shaped gel filled headrest  32  illustrated and described may have other embodiments. For example, the headrest may be circular or another shape, may be filled with a different material, or may be thicker so that the patient&#39;s head is supported fully above the upper surface of the support plate  28 . The headrest  132  shown in FIGS. 8-10 represents only one of these possible variations. Further, the opening  34  may have other configurations. For example, the opening  34  may be replaced by, or supplemented by, one or a plurality of holes of any shape for various purposes, for example, ventilating the patient, access for tubes and other equipment, drainage, or openings through which the patient can see or the patient&#39;s eyes can be seen. As will be appreciated, separate inserts or built-in hole covers may be used to fill or cap the holes when they are not being used. 
     As will be appreciated, the aligning tab  124  may be located on the scanner  20 , and the slot  126  located on the table  22 . In addition, other alignment devices and procedures may be used. For example, the scanner  20  may have a built-in aligning system or the imaging system may be used to align the table  22  to the scanner  20 . 
     Therefore, the invention in its broadest aspects is not limited to the specific details shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.