Trajectory guide method and apparatus for use in magnetic resonance and computerized tomographic scanners

A surgical method and apparatus for accurately aligning the trajectory of, guiding of, and introducing or withdrawal of an instrument includes a base with a movable member. The base has a tubular shape. Positioned near the first end of the base is a seat. The seat is dimensioned to receive a movable member. A positioning member is used to move the movable member. The initial position of the movable member is determined using a scanning device, such as a CT scanner, frameless stereotaxy device or an MRI device. The movable member is elevated above the patient so that a burr hole does not have to be made in the patient to do the above described procedure. The second end has an opening therein and the tubular body is positioned between the seat and the second end. A flange near the second end is used to attach the base to the patient. The flange may also engage a plastic ring such that it can rotate or swivel with respect to the ring. The ring is attached to a flexible adhesive patch so which may be attached to the body. A portion or the entire positioning stem may be doped to make the positioning stem detectable by x-radiation and by the CT scanner. Arched bails can also be attached to the base for adjusting the trajectory alignment. An adapter externalizes burr holes and eliminates the need for burr hole. The externalizer forms a substitute burr hole away from the skull or body so tools which usually work only within a burr hole can be used without having to make a burr hole.

FIELD OF THE INVENTION
 The present invention is related to a surgical working platform. More
 specifically, the present invention relates to a platform and method for
 using the same for facilitating the alignment of surgical and
 observational instruments, and for the passing of said instruments into a
 patient using a drill hole. The present invention may be adapted for use
 in a MR scan or CT scan environment.
 BACKGROUND OF THE INVENTION
 In the treatment of some diseases or defects associated with a patient, it
 has been found necessary to access specific targets within a patient. In
 the treatment of some diseases of or defects of human beings, it has been
 found necessary to access specific portions of the brain. Currently there
 are several methods for inserting surgical and observational instruments
 into a patient's brain.
 U.S. Pat. No. 3,055,370 issued to McKinney et al. shows one currently used
 method for placing a surgical instrument to access a specific portion of
 the brain. The surgical instrument of the U.S. Pat. No. 3,055,370 patent
 includes a ball which has a bore. The direction of the bore can be
 changed. The instrument has an elongated tube of a specific length. A
 stylet is inserted within the tube to access the globus pallidus and
 perform a pallidotomy. An opening or burr hole is made in the skull at a
 specific landmark on the skull. Next, X-rays are taken in the fore-and-aft
 (AP) and lateral positions, and the line of the bar is projected
 downwardly by a ruler both in the fore-and-aft (AP) and lateral positions,
 so that the direction of the needle can be determined before it is
 inserted. When the direction of the longitudinal axis of the tubular
 member is determined to be satisfactory, a holder is threaded further into
 a tap to force a surface against a ball and lock a tubular member into
 place. Alignment of the trajectory is not measurable along a specific line
 occurring at the intersection of two planes. Alignment is dependent on
 placement of the burr hole at a specific location to determine one plane.
 X-rays are used to determine another plane-based use of common landmarks
 on the skull. The end result is that an educated guess is being used to
 position the stylet at the globus pallidus for the pallidotomy. One
 shortcoming with the method of using X-ray imaging to direct a surgical or
 observational instrument, is that many of the destinations within a
 patient are not viewable via X-ray. Another shortcoming relates to the
 slight shifting of intracranial contents, once a burr hole is placed and
 the dura and arachnoid are penetrated. Once cerebrospinal fluid is
 released via the burr hole, the intracranial contents (i.e. brain) may
 shift one or more millimeters. In such a case, the calculated trajectory
 is no longer accurate. Hence, there is an inherent inaccuracy with the
 described scheme.
 Several other methods are also used to place instruments, catheters, or
 observational tools into patients. Like the method discussed above, most
 surgical procedures are performed through craniotomy flaps or craniotomy
 burr holes. A burr hole is an round opening in the skull having a diameter
 of about 14 mm. The diameter is a standard length in most parts of the
 world. Currently, the Europeans use a slightly different standard diameter
 of about 15 mm. Needles or probes are typically passed through the burr
 hole into the brain using framed stereotaxy, frameless stereotaxy or
 freehand without stereotaxy. Many instruments used for doing various
 operations attach to the burr hole. Many use an outside thread that grips
 the inner diameter of the burr hole.
 The freehand method depends very heavily on the knowledge and judgment of
 the surgeon. In the freehand method, the surgeon determines the insertion
 point with a couple of measurements from a known landmark. The surgeon
 then looks at the measured point, makes adjustments, determines the angle
 of insertion and then inserts the surgical instrument or tool.
 In framed stereotaxy, a ring frame is mounted to the patient's skull by
 multiple (typically three or four) pins or screws. This ring frame is used
 to determine a three dimensional data set. From this data set, Cartesian
 coordinates are calculated for both the lesion, the location of the pins
 or screws, and the fiducial marks on the frame. The ring frame fits into a
 large frame. A large frame is then attached to the patient in the
 operating suite. The large frame provides known positions and guides the
 surgical or observational instruments. The large frame is used to position
 the instrument to be introduced into the patient through a burr hole so
 that it intersects the target. In frameless stereotaxy, the ring frame is
 replaced with several markings on the patient's skull which can be used to
 determine several known positions. The large frame is replaced by a
 camera. The camera is usually infrared or some such device. Multiple
 sensors readable by the camera are placed on the instrument. For example,
 the surgical instrument or tool is provided with one or more light
 emitting diodes ("LEDs") which are tracked by the camera. The position of
 the surgical instrument can be calculated from the information from the
 LEDs on the surgical instrument or observational tool.
 U.S. Pat. Nos. 4,955,891 and 4,805,615, both issued to Carol, each discuss
 the use of stereotaxy surgery with computerized tomographic ("CT")
 scanning. CT scanning is used to determine the exact position of a lesion
 or specific portion of the brain. After the exact position of the lesion
 or specific portion of the brain is determined, a phantom fixture is set
 up. The phantom fixture replicates the position of the ring frame on the
 patient. A phantom target is set up. The phantom fixture and target are
 typically determined outside the operating suite. Within the operating
 suite, the instrument can then be positioned on the phantom fixture such
 that it intersects the target. The information from the phantom fixture
 can then be used to initially position the instrument in the operating
 suite. Most procedures require forming a burr hole in the patient's head.
 Loss of fluid from the burr hole results in a shifting of the contents of
 the cranial cavity. The burr hole is typically made in the operating suite
 after the phantom frame and target have been set up. As a result, a
 subsequent CT scan is necessary especially in the case when the target is
 small, thereby requiring accurate placement of the instrument.
 U.S. Pat. No. 4,998,938 issued to Ghajar et al. shows another surgical
 device for facilitating the insertion of an instrument into a patient's
 cranial cavity through a burr hole. The device includes a guide having an
 end configured to pass into the burr hole. There is a separate locking
 member. A body member includes alignment markings to help with insertion
 of a catheter or stylet. Unlike U.S. Pat. No. 3,055,370, there is no
 movable member for adjusting the path of the guide.
 The methods currently in use all have a number of shortcomings. One of the
 shortcomings is that all of the techniques require initially making
 craniotomy flaps or craniotomy burr holes in the patients skull or body. A
 burr hole of about 14 mm is made in the skull. Needles or probes are
 typically passed through the burr hole into the brain during a typical
 procedure, such as a biopsy or laser ablation of a tumor. The burr hole
 formed is large and it takes a fair amount of surgical time to make. In
 addition to the surgical time, the forming of the burr hole results in
 shifting of the contents within the cranial cavity. It would be
 advantageous if a surgical tool would allow surgical procedures to be
 performed without the formation of a burr hole. In addition, it would be
 advantageous if tools that attached or required a burr hole could be
 adapted so that the surgical procedure would not require formation of the
 burr hole in the patient's skull. The formation of a burr hole is a time
 consuming portion of an operation.
 Most of the techniques currently used to place a surgical instrument or
 observational tool within a patient employ a limited amount of accuracy.
 In particular, current framed, frameless, and freehand methods compute or
 predict trajectories on the basis of imaging data or anatomic landmarks
 that do not account for the slight, but real shifting of the brain upon
 opening the cranium and meninges to the level of the subarachnoid space.
 This inherent inaccuracy inherently limits the success of these various
 methodologies. In other words, these systems do not use any means of
 updating the data files to include data obtained following the placement
 of a surgical burr hole and opening of the meninges. In addition, all the
 methods require large amounts of judgment on the part of the surgeon
 placing the surgical instrument or tool, and in particular, offer no
 direct feedback on the success or failure of the trajectory to reach the
 target. Very few of the techniques use an imaging or scanning apparatus to
 aid in the placement of the surgical instrument or observational tool. The
 only one that does requires a phantom frame and target to be set up to
 simulate the real geometry. In short, none of the apparatuses appear to
 use an imaging or scanning apparatus as extensively as they could be used
 to minimize the time and effort needed to accurately place a surgical
 instrument into a patient, and to offer immediate data on the success or
 failure of the trajectory to reach the target. It would be advantageous if
 more accurate methods could be developed which could use either MR or
 computerized tomographic ("CT") scanners. Both MR or CT scanners are
 widely available worldwide. Even though CT scanning equipment has the
 disadvantage of patient exposure to x-radiation, a method for accurate
 placement of an instrument using CT scanning equipment would be even more
 widely available to patients around the world than a similar MR method.
 SUMMARY OF THE INVENTION
 An externalizer eliminates the need for always making a burr hole when
 placing an instrument within the skull of the patient. In one embodiment,
 the externalizer is integral with a positioning stem. In another
 embodiment, the externalizer forms a universal burr hole away from the
 patient's body. This embodiment is an adapter which can accommodate any
 tool which previously required a burr hole. The externalizer forms a
 substitute burr hole away from the skull or body of the patient. The
 result is that any instrument that normally requires a burr hole, can now
 be used with the externalizer. The making of a burr hole within the
 patient's skull is now optional. Many procedures can now be accomplished
 by making a screw or drill opening in the patient's body. The drill or
 screw opening is much smaller than a burr hole. This procedure requires
 much less time and results in less shifting of contents within the cranial
 cavity since there is less fluid loss.
 A surgical method and apparatus for accurately aligning the trajectory of,
 guiding of, and introducing or withdrawal of an instrument using CT
 scanning equipment is also disclosed. The apparatus is doped with barium
 or another dopant so that it is CT visible. The apparatus includes a base
 which has a movable member movably attached to the base. The movable
 member has a passage therein which forms a portion of the trajectory path.
 The movable member also includes a guide stem which has an opening
 therein. The guide stem is attached to said movable member such that the
 opening in the guide stem substantially aligns with the passage in the
 movable member. The movable member can include either an integral guide
 stem for holding the positioning stem or a removably attached guide stem.
 In the case of the former, a positioning stem is inserted into the opening
 of the integral guide stem for purposes of trajectory alignment. In the
 case of the latter, the removably attached guide stem can be removed and
 replaced with a positioning stem. A portion or the entire positioning stem
 may be doped to make the positioning stem detectable by x-radiation and by
 the CT scanner. The base of the trajectory guide includes two arched bails
 which are used to adjust the trajectory alignment.
 In operation, the positioning stem is initially positioned. A CT scan is
 performed to locate the positioning stem and the target. The line formed
 by the positioning stem is determined by the CT scanning system. Another
 line between the end of the positioning stem nearest the patient and the
 target is then determined by the computer of the CT scanning system. The
 second line between the end of the positioning stem nearest the patient
 and the target corresponds to or is coaxial with the trajectory. The
 computer of the CT scanning system determines the difference between these
 lines and produces an adjustment that the surgeon must make to reposition
 the positioning stem so that it aligns with the trajectory corresponds to
 a line passing through the opening in the ball and guide stem. The
 adjustment corresponds to the grid increments or markings on two arched
 bails of the trajectory guide. Another scan is done to confirm alignment.
 If not aligned, several of the above steps are repeated until alignment is
 attained.
 Advantageously, widely available CT scanning devices used for diagnostic
 purposes can be employed to place an instrument within the body of a
 patient. There is no need for framed stereotaxy or unframed stereotaxy,
 two procedures which require large amounts of time to perform. Procedures
 that formerly required many hours can now be performed in substantially
 less amounts of time with the trajectory guide. Other procedures which
 required a burr hole can also be performed in less time.
 Although frameless stereotaxy is not required, if the equipment for
 frameless stereotaxy is available, the procedure associated with
 positioning the positioning stem is simpler when compared to the CT only
 method.
 The externalizer can be used with CT scanning equipment, frameless
 stereotaxy equipment or with MR equipment. The various equipment is used
 to align the positioning stem or instrument with a target within the body.
 The externalizer can also be used to perform procedures with or without a
 burr hole. The externalizer adapter also provides this option for
 instruments which normally require the formation of a burr hole.
 An externalizer can also be adapted for use on other portions of the body.
 The body portal type externalizer is usually used to direct surgical
 instruments to larger targets within the body. The body portal type
 externalizer features an angled or vertical base that swivels or rotates
 within a plastic ring. The plastic ring is merged with an adhesive patch
 that is used to attach the body portal type externalizer to the body. The
 angled base allows surgical instruments to be passed through the
 externalizer without interfering with nearby objects, such as a magnet, in
 an operating suite. The alternative vertical base is an option for an open
 magnet MR device. The swivel or ability to rotate the base allows the
 surgeon or technician access from a comfortable position with respect to
 the body portal. An incision is made in the patient and the body portal
 type externalizer is placed over the incision. The adhesive patch seals
 the area. After the instrument is removed and the procedure is completed,
 the body portal type externalizer is removed and the incision is stitched
 or bandaged.

DESCRIPTION OF THE EMBODIMENT
 In the following detailed description of the embodiment, reference is made
 to the accompanying drawings which form a part hereof, and in which is
 shown by way of illustration specific preferred embodiments in which the
 invention may be practiced. These embodiments are described in sufficient
 detail to enable those skilled in the art to practice the invention, and
 it is to be understood that other embodiments may be utilized and that
 structural, logical and electrical changes may be made without departing
 from the spirit and scope of the present invention. The following detailed
 description is, therefore, not to be taken in a limiting sense, and the
 scope of the present invention is defined only by the appended claims.
 Within some parts of a patient, it is critical to very accurately place a
 surgical instrument. For example, in neurosurgery, it is very critical to
 have instruments, such as catheters or needles, placed very accurately
 within the cranium or head of a patient. FIG. 2 shows a side view of a
 patient on which a trajectory guide 200 is being used. The trajectory
 guide 200 includes a base unit 210, a movable member 220, a locking member
 230 and a guide stem 240. The base unit 210 is attached to the skull of
 the patient. In the particular embodiment shown, the attachment is made by
 way of bone screws. A burr hole is not required in the patient. In this
 particular embodiment, the movable member 220 is held away from the
 patient's body such that a burr hole is not required.
 The movable member 220 has a passage therein 222 which is shown in FIG. 2
 as dotted lines. The guide stem 240 also has an elongated opening 242
 therein. The opening 242 is also shown as dotted lines in FIG. 2. The
 passage 242 in the guide stem 240 and the opening 222 in the movable
 member or ball 220 form a line or a trajectory 260 which, when the guide
 stem 240 and movable member 220 are positioned correctly, intersects with
 a target 270 within the patient. The guide stem 240 and movable member or
 ball 220 form the first part of the trajectory 260. The base unit 210
 includes a seat 218 or socket which allows the movable member 220 to move
 freely. The seat is positioned away from a flange 214 on the base 210. The
 seat 218 is elevated with respect to the flange 214. Below the seat is an
 opening through which instruments may pass. The elevated seat 218 and
 opening below serve as a substitute for a burr hole in the skull.
 After aligning the opening 242 and the opening 222 to form the trajectory
 260, a twist drill is then used to make a small opening in the patient.
 The twist drill is passed through the opening 242 and opening 222 along
 trajectory 260. After a drill hole is formed in the patient, a surgical
 instrument or observational tool can be inserted into the opening 242 of
 the guide stem 240 and passed through the passage in the movable member
 220 and through the drill hole formed along the trajectory 260. Further
 insertion of the surgical instrument or observational tool into the
 patient for a selected distance will strike or place the tool near or at
 the target 270. The opening 242 in the guide stem 240 and the passage 222
 in the movable member 220 guide a surgical instrument along the trajectory
 260 to the target 270. Of course, the movable member 220 is locked into
 place by locking member 230 before a surgical instrument 280 is placed
 through the opening 242 in the guide member 240.
 FIG. 3 shows an exploded isometric view of the trajectory guide 200 with a
 guide member installed. As shown in FIG. 3, the trajectory guide 200 is
 comprised of a base 210, a movable member 220, a locking member 230, and
 the guide member 240. The guide member 240 may be threadably attached or
 the guide member can be made integral with the movable member 220. The
 base 210 includes a cylindrical portion 212 and a flange 214. The flange
 looks like a series of ears. Each of the ears of the flange 214 includes a
 plurality of countersunk screw openings 215, 216, and 217. The countersunk
 screw openings 215, 216, and 217 receive bone screws which are screwed
 into the skull bone or the bone of a patient. The flange 214 also includes
 markings 219 used to position the guide member 240. As shown in FIG. 3,
 the markings 219 are in the form of a grid having an x-axis and a y-axis.
 The cylindrical portion 212 fits within the burr hole 250 in the patient.
 The base also includes a semi-spherical seat 218 on the end of the base
 opposite the flange 214. The flange 214 is in a plane away from the seat
 218. Although not shown in FIG. 3, there is an opening in the base 210
 having a first end which terminates at the seat 218 and another end which
 terminates at the bottom of the base 210. This opening is essentially a
 substitute burr hole.
 As shown in FIG. 3, the movable member 220 is essentially a spherical
 member or a ball. The spherical member or ball fits within the seat 218.
 The spherical member or ball moves freely within the seat 218. The
 ball-shaped movable member 220 also has an opening therein 222. The
 opening passes through the ball shaped movable member. One end of the
 opening may have a set of internal threads therein, which can be used to
 receive mating threads which are placed onto the guide stem or member 240
 or positioning stem (discussed with respect to FIG. 4).
 The locking member 230 also has an opening therethrough. The locking member
 230 includes a cylindrical bottom portion 232 and a flange 234. The
 opening through the locking member 230 has sufficient space to allow
 movement of movable member 220 when the locking member is in an unlocked
 or untightened position. Although not shown in FIG. 4, the bottom of the
 cylindrical portion 232 of the locking member 230 includes a set of
 internal threads. The set of internal threads engage a set of external
 threads on the base unit 210 (shown in FIG. 7b). As will be detailed
 later, when the internal threads of the locking member 230 are engaged
 with the threads on the base 210, a portion of the locking member engages
 the movable member 220 to fix the movable member and the passage 222
 therethrough at a fixed position.
 A guide stem or guide member 240 is also shown in FIG. 3. The guide stem
 has an elongated opening 242 therein. The elongated opening passes through
 the length of the guide stem 240. One end of the guide stem includes a set
 of external threads which engage the internal threads of the spherical,
 movable member 220. When the external threads of the guide stem 240 engage
 the internal threads of the movable member 220, the opening 242 is
 substantially aligned with the passage 222 in the movable member. The
 opening 242 and passage 222 form the first part or guide for the
 trajectory 260 to the target 270 within the patient. It should be noted
 that the movable member 220 need not necessarily be a spherical element,
 although the spherical shape allows the ball to have a universal joint
 type swivel action which is preferred. As mentioned previously, the
 movable element 220 and the guide stem 240 can be formed as one piece.
 This would eliminate the need for the threaded end of the guide stem 240
 and the threaded inner diameter 222 of the movable member 220.
 In addition, the locking member 230 can be formed in most any shape. A
 flange 234 is useful in that it allows additional leverage for tightening
 or loosening the locking member. Any shape capable of being turned or
 placed into a locking position with respect to the movable member 220 is
 acceptable.
 Positioning Member
 Now turning to FIG. 4, an exploded isometric view of the trajectory guide
 200 with a positioning member 400 is shown. The positioning member 400 may
 also be referred to as a positioning stem. Many of the parts of the
 trajectory guide 200 shown in FIG. 4 are the same as those shown in FIG.
 3. In the interest of time, a discussion of the common elements will not
 be repeated. Several of the basic elements will be numbered for the
 purposes of this discussion. The difference between FIGS. 3 and 4 is that
 the guide stem or guide member 240 has been replaced with the positioning
 stem 400. The positioning stem 400 includes an end 410 which carries
 threads for engaging internal threads within the passage 222 in the
 movable element 220.
 Movable Member
 FIGS. 5a and 5b show the movable member which will now be discussed in
 slightly more detail. FIGS. 5a and 5b show that the movable member 220 is
 substantially spherical in shape. The movable member 220 has an opening
 222 therein. The opening 222 includes a smaller diameter portion 223 and a
 larger diameter portion 224. The inside surface of the larger portion 224
 of opening 222 is threaded as indicated by reference numeral 225. The
 larger diameter portion 224 and the threads 225 receive the external
 threaded portion of either the positioning stem 400 or the guide stem 240.
 The smaller diameter portion 223 of the opening 222 is of a sufficient
 diameter to allow an instrument, such as a needle, probe, catheter,
 endoscope, or electrode to pass through the opening. The movable member
 220 is made of a biocompatible material such as delrin.
 FIGS. 6a and 6b show a side and top view of the base 210 of the trajectory
 guide 200. The base 210 includes the cylindrical portion 212 and the
 flange 214. The flange 214 includes ears with countersunk openings 215,
 216, and 217 as well as the seat 218 which receives the movable member
 220. It should be noted that the flange 214 can be of any shape. As shown,
 the seat 218 is in a plane substantially parallel to the plane of the
 flange 214. The seat 218 is elevated with respect to the flange 214. The
 seat 218 is on one end of the base 210 and the flange 214 is on the
 opposite end of the base 210. Between the seat and the flange is an
 opening 600 which includes an internally threaded portion 610. The
 internally threaded portion 610 is dimensioned so as to receive the
 threads of either the positioning stem 400 or the guide stem 240. The
 flange 214 may include a first arched bail 910 and a second arched bail
 920 (arched bails are shown in FIGS. 9 and 10) which are used to align the
 positioning stem 400 so that it defines a trajectory 260 which intersects
 the target 270 within the patient. It should be noted, that although the
 flange 214 is shown as having a triangular shape, the flange could be most
 any shape.
 Now turning to FIGS. 7a and 7b, the locking member of the trajectory guide
 200 will now be discussed. The locking member 230 includes the cylindrical
 portion 232 and a flange 234. The external surface of the flange 232 is
 threaded to form a threaded external surface 700. The threads associated
 with the externally threaded surface 700 are dimensioned so as to engage
 the internally threaded surface 600 of the base 210. The locking member
 230 also includes an opening 710 which passes through the locking member
 230. The locking member also has a locking surface 720. In this particular
 embodiment, the locking surface 720 is flat so that it engages a flat face
 on the movable member 220. The flanges 234 are extended so that the
 threads of the threaded surface 700 can be easily engaged with the
 internal threads 600 of the base 210. It is contemplated that other
 geometric shapes could be used for the locking member and that other
 locking surfaces could be employed.
 Integral Guide Stem and Movable Member
 FIG. 8 shows an isometric view of a movable element 820 that has a ball end
 810 and a guide stem end 830. The movable element 820 fits within the base
 210 and locking member 230. As shown, the movable element 820 has a
 passageway 822 therein which traverses the length of the movable element
 820. In other words, the passageway 822 passes through the guide stem end
 830 and through the ball end 810. FIG. 8 also shows a positioning stem
 400. The positioning stem 400 is dimensioned so that it fits snugly within
 the passageway 822.
 The various guide stems and positioning stems shown in FIGS. 2-8 can be
 used with any type of body scanner. The positioning stems can be provided
 with MR viewable portions and positioned with the aid of an MR imaging
 device similar to the one discussed in the U.S. patent application
 entitled "Surgical Instrument Trajectory Guide Method and Apparatus" filed
 Aug. 28, 1997 and having Ser. No. 08/919,649. The guide stems shown in
 FIGS. 2-8 can also be adapted for use with a CT scanner. CT scanners are
 widely available around the world.
 CT Scanner
 FIG. 1 is a block diagram of a patient scanning system 100. The specific
 scanning system shown is a computerized tomography ("CT") system. An CT
 scanning system 100 includes a computer 102. The computer 102 includes a
 central processing unit ("CPU") 104 and memory 106. The CPU 104 and memory
 106 has the capacity to perform multiple calculations used to determine
 images as well as positions of various organs, or portions or within an
 image field. The computer 102 controls an image data processing portion
 110. The computer 102 also reconstructs an image along a desired plane. An
 X-ray tube 120 is pulsed at many times per second. Across from the x-ray
 tube are a plurality of detectors 130. Most commonly, the detectors 130
 are photo diodes.
 The data is interpreted and placed on a display 140 associated with the
 computer of the CT system 100. The computer 102 and the CPU 104 and memory
 106 can use data acquired from the CT system 100 to build up images of a
 portion of the patient which is being subjected to x-radiation. The images
 are typically referred to as slices. For example, a horizontal slice and a
 vertical slice can be made of the portion of the body or patient being
 imaged. The computer can also recalculate and build other slices for use
 by doctors and radiologists having any selected orientation needed to
 facilitate study of various items within a patient. For example, lesions
 can be found within the body as well as certain organs. Different slices
 can be requested to facilitate study of these targets. From the data
 acquired, the position of the lesions or organs can also be very
 accurately determined using a Cartesian or polar coordinate system.
 In operation, x-ray beams of a computerized tomography scanner pass through
 a human body or an object and are collected with an array of detectors;
 the beam is rotated to produce the equivalent of a "slice" through the
 area of interest. The x-ray information collected during the rotation is
 then used by a computer to reconstruct the "internal structures," and the
 resulting image is displayed on a television screen. This technique
 represents a noninvasive way of seeing internal structures, and has in
 many ways revolutionized diagnostic approaches. In the brain, for example,
 computerized tomography can readily locate tumors and hemorrhages, thereby
 providing immediate information for evaluating neurological emergencies.
 Basically, the scanner gantry is composed of an x-ray tube, an array of
 detectors opposite the tube, and a central aperture in which the person
 (or object) is placed. X-rays are generated in short bursts, usually
 lasting 2-3 ms; the x-ray beam contains an "invisible image" of the
 internal structures. The role of the detectors is to collect this
 information, which is then fed into a computer. The computer reconstructs
 the image from the information collected by the detectors. In order to
 obtain enough information to calculate one image, the newer scanners can
 take as many as 90,000 readings (300 pulses and 300 detectors). CT
 scanning devices are widely available throughout the world. The above
 description of the CT scanning device 100 is simply for demonstrative
 purposes.
 For use with CT scanning system 100, the positioning stem 400 of FIG. 4 is
 modified by doping with a dopant that is detectable with x-radiation. The
 dopant can be a liquid carrying barium which is housed with a tubular
 cavity of the position stem. The dopant can also be made within the
 material of the positioning stem. Since it is detectable, the positioning
 stem 400 is viewable as a result of the CT scan. One dopant which could be
 used is barium. The entire positioning stem 400 or selected portions of
 the positioning stem may be doped so as to produce a detectable image on
 the display 180 of the CT scanning device 100. For example, rather than
 dope the entire positioning stem 400, the ends 420 and 430 of the
 positioning stem may be doped. The two ends of the positioning stem could
 be detected by the CT scanning device 100 and used to define a line
 corresponding to the current trajectory through the opening 222 in the
 movable member 220.
 Now turning to FIG. 9, the further modification of the device shown in FIG.
 4 will be discussed. The modifications provide for an alignment instrument
 which can be used where only CT scanners are available. In the
 alternative, if CT scanning equipment is available, it can be used as an
 alternative to more expensive methods, such as MR scanning. The
 positioning stem 400 is doped as discussed above. A ring 950 is attached
 to the cylindrical portion 212 of the base 210. The ring 950 moves with
 repsect to the cylindrical portion 212. Attached to the ring 950 is a
 first arched bail 910 and a second arched bail 920. The arched bails 910
 have physical markings 912 thereon. The arched bail 920 has physical
 markings 922 thereon. At least one of the bails 910 or 920 is also doped
 at least three points so that the three points determine a plane viewable
 on a CT scan. The arched bails 910 and 920 are secured to the flange 214
 with a fastener which can be securely tightened to prevent movement of the
 bail 910 and 920. The bails 910 and 920 are also made so that they extend
 a distance above the movable member 220 to allow clearance for the locking
 member 230.
 Also for use with a CT scanning system 100, the positioning stem 400' of
 the trajectory guide 200', shown in FIG. 8 is doped with a dopant that is
 detectable with x-radiation. Since it is detectable, the positioning stem
 400' is viewable as a result of the CT scan. One dopant which could be
 used is barium. The entire positioning stem 400' or selected portions of
 the positioning stem may be doped so as to produce a detectable image on
 the display 180 of the CT scanning device 100. For example, rather than
 dope the entire positioning stem 400', the ends 420' and 430' of the
 positioning stem may be doped. The two ends of the positioning stem could
 be detected by the CT scanning device 100 and used to define a line
 corresponding to the current trajectory through the opening guide member
 end 830 and the opening 822 in the ball end 220.
 The first end 420 and the second end 430' of the positioning stem 400' do
 not need to be doped with the same material. This may enable the computer
 102 associated with the CT scanning device to more easily discern end 420'
 from end 430'. In this embodiment, the positioning stem 400' is inserted
 into the guide stem end 830. The movable member 820 and more specifically
 the opening 822 in the movable member 820 is moved until it is aligned to
 the desired trajectory 260 to the target 270. Once aligned, a locking
 member 230 (not shown in FIG. 8 to more clearly illustrate this
 embodiment) locks the ball end 810 in place. The positioning stem 400' is
 removed and the surgical instrument is passed into the guide member end.
 In still another embodiment, portions of the movable member 820 are doped
 with a dopant that makes it x-radiation readable and viewable. Movable
 member 820 includes a ball as well as an extended guide stem end 830. All
 or part of the guide stem end 830 may be doped. The ends of the opening
 822 in the movable member 820 may also be doped. The ends could then be
 used in locating the line or trajectory 260 defined by the opening 822. In
 this embodiment, there would be no real need for positioning stem 400'.
 When the movable member 820 is determined to be properly aligned, the
 movable member 820 would be locked into place and the surgical instrument
 or tool would be passed directly into the opening 822.
 FIG. 10 shows the trajectory guide 200' having a base 210 that has a ring
 950. The arched bail 910 and the arched bail 920 are attached to the ring
 950. The arched bails are attached to the ring 950 so that they can be
 rotatably moved with respect to the base 210. The bails 910 and 920 can
 then be rotated with respect to the ring 950. The attachment also allows
 them to be tightened so the bails 910 and 920 stay in one position. The
 bails 910 and 920 are positioned so that there is clearance so the locking
 member 230 can be loosened to adjust the position of the at least one of
 the bails 910 or 920. At least one of the bails 910 or 920 includes a CT
 readable portion that defines a plane. Preferably, one edge of the bail,
 910 or 920, will be readable via CT scan. The edge of the bail 910 or 920
 will be an arcuate line which defines a plane. The bail 910 will have
 markings 912 and the bail 920 will have markings 922. The bails 910 and
 912 would enable a person to reposition the movable member 820 to make
 adjustments to the trajectory guide so that the opening 822 in the movable
 member aligns with the trajectory 260.
 Method for Using CT Scans and Trajectory Guide
 In operation, a patient undergoes a CT scan with a CT scanning device 100
 to locate a particular organ within a patient or to locate lesions or any
 other target 270 within the patient. It should be noted that targets are
 not necessarily limited to being within the head of a patient. There can
 also be other areas of a patient where it would be critical to accurately
 place a surgical or observational tool. In addition, it should also be
 noted that the patient need not necessarily be human. A patient may
 include any living animal.
 Once the target 270 is found and located using the CT scanning system 100,
 the base 210 of the trajectory guide 200 can be attached to the patient.
 The base is affixed to the patient in an area near the target 270. The
 computer 102 of the scanning device 100 is used to determine the exact
 location of the target 270. The exact location can be found in any type of
 coordinate system, although normally a Cartesian coordinate system is
 used. Once the base 210 is attached to the patient, the remaining portions
 of the trajectory guide 200 are attached to the base 210. In other words,
 the movable member 220, the locking guide, the locking member 230 and a
 positioning stem 400 are added to form a complete trajectory guide 200.
 Now turning to FIG. 11, as shown by step 1100, the positioning stem 400 or
 400' is initially positioned. As depicted by step 1102, a CT scan is
 performed to initially locate the positioning stem 400 or 400' and the
 target 270. The line or trajectory formed by the positioning stem 400 or
 400' is read by the CT scanning system 100. The trajectory 260 is
 determined by determining a line between the end 430 or 430' of the
 positioning stem 400 or 400' nearest the patient and the target 270. The
 computer 102 determines the difference between the trajectory 260 and the
 line formed by the doped positioning stem 400, 400'. The computer 102
 determines the adjustment that the surgeon must make to reposition the
 positioning stem 400 or 400' so that it corresponds to the trajectory 260.
 The adjustment corresponds to the increments 912, 922 on the arched bails
 910, 920 attached to the base 210.
 The computer 102 also determines the plane corresponding to the edge of one
 of the bails 910 or 920. The computer can then output an adjustment that
 can be made by the surgeon or person doing the procedure. Given the plane
 defined by the edge of one of the arched bails 910 or 920, the position of
 the other bail 920 or 910 can be determined.
 The physician is instructed to leave one bail 910 in a fixed position. In
 fact, one bail 910 could remain in a fixed position. The edge of the other
 bail 910 is moved to a mark 912 on the fixed bail 910. The edge with the
 markings 922 is moved to a mark 912. The bail 920 is then secured into
 position. The surgeon then moves the positioning stem 400 or 400' to a
 mark 922 on the second bail 920 to reposition the positioning stem 400 or
 400' so that it corresponds to the trajectory 260. This series of steps
 corresponds to the step of adjusting the position of the positioning stem
 so the trajectory aligns with the target 1104.
 The instrument is then inserted using the guide stem. In the instance of
 the trajectory guide 200, the positioning stem is replaced by the guide
 stem. In the instance of the trajectory guide 200', the positioning stem
 400' is removed and then the instrument is placed in the movable member.
 The instrument is inserted to a selected distance into the patient, as
 depicted by step 9. The selected distance is the distance to the target
 270 along the trajectory 260.
 Another CT scan is then done, as depicted by step 1106, to confirm that the
 instrument is at the target 270. If the instrument has not reached the
 target 270, the needle is inserted another selected distance (step 1105).
 The procedure for repositioning the positioning stem 400 or 400' may be
 modified slightly depending on the size of the target 270 and whether a
 burr hole opening will be made. The trajectory guides 200 and 200' do not
 need a burr hole, but they can be used with burr holes. If a burr hole is
 formed, the contents within the cranium shift may shift slightly as a
 result of fluid loss through the burr hole. If the target 270 is large,
 such as a tumor, it may not be necessary to recheck the trajectory 260. If
 the target is small, it may require a recheck of the trajectory even if
 only a twist drill opening is made in the skull.
 Frameless Stereotaxy Environment
 In an environment where there are detectors for light-emitting diodes
 ("LEDs"), the trajectory guide 200 as shown in FIG. 4 or the trajectory
 guide 200' as shown in FIG. 8 can be used to accomplish this procedure.
 FIG. 12 shows the positioning guide 400 of the trajectory guide 200
 provided with two or more LEDs 1210 and 1220 which are located along the
 length of the positioning stem 400. Rather than use the arched bails 910
 and 920 to reposition the positioning stem 400, one or more LED detectors
 1230 and 1240 are used to locate the LEDs 1210 and 1220. The step of
 adjusting the position of the positioning stem 1104 so that it aligns with
 the trajectory 260 to the target 270 is accomplished by moving the
 positioning stem 400 manually until the LEDs 1210 and 1220 form a line
 which is collinear with the trajectory 260. The computer 102 determines
 the trajectory 260 by determining the formula for a line between the
 target 270 and the end of the positioning stem 400 closest to the patient.
 The positioning stem 400 is moved until the LEDs 1210 and 1220 are aligned
 with the trajectory 260. The positioning stem can be moved manually
 (directly or remotely) or by automated control, such as under control of a
 computer. The LED's position can be determined by the detectors 1230 and
 1240 at a relatively high frequency rate such that movement of the
 positioning stem 400 can be monitored in real time. Once the LEDs 1210 and
 1220 are aligned with the trajectory 260, the computer 102 will output a
 signal indicating that the positioning stem 400 is correctly positioned.
 The same procedure would be followed for a trajectory guide 200'. The
 positioning stem 400' would be provided with the LEDs 1210 and 1220. Once
 the positioning stem 400' is correctly positioned, a signal from computer
 102 indicates the correctly positioned positioning stem 400'. The movable
 member 820 is then locked into position. The positioning stem 400' is
 removed and the instrument is passed into the opening 822 in the movable
 member 820.
 Of course, this procedure may be modified slightly depending upon the
 particulars of the procedure. The trajectory guides 200 and 200' do not
 need a burr hole, but can be used with burr holes. If a burr hole is
 formed during the procedure, the contents of the cranium shift slightly as
 a result of fluid loss through the burr hole. If the target 270 is large,
 such as a tumor, it may be unnecessary to recheck the trajectory 260. If
 the target is small, such as when the target is the globus pallidus
 interna, it may be necessary to recheck the trajectory before inserting a
 tool or an instrument to the target 270. Once the trajectory 260 is
 determined, the instrument or tool is inserted a selected distance into
 the trajectory guide 200 or 200'. The selected distance is equal to the
 distance between the trajectory guide and the target 270. The position of
 the instrument or tool can then be checked using x-radiation to determine
 if the tool or instrument has reached the target 270.
 Magnetic Resonance Imaging Procedure
 The trajectory guide 200 or 200' can also be used in an MR imaging
 environment. In such an environment, the positioning stem 400 or 400' is
 provided with a dopant that can be read by an MR imaging device. The
 procedure set forth above for the frameless stereotaxy environment is
 similar to the procedure used here. The MR imaging device is used to
 determine the position of the positioning stem 400 and to determine the
 trajectory between the portion of the positioning stem nearest the patient
 and the actual target 270. The positioning stem 400 is moved either
 manually or with the aid of a remote device. The positioning stem 400 is
 moved until it is positioned so that it is collinear with the trajectory
 260 between target 270 and the end of the positioning stem 400 nearest the
 patient.
 The basic procedure set forth in FIG. 11 varies at a step 1104, which is to
 adjust the position of the positioning stem. When using CT scanning
 equipment only, the positioning stem 400 is adjusted using the arched
 bails 910 and 920. When the trajectory guide is used in an MR environment,
 the MR scanning device is used to locate the position of the positioning
 stem 400. In either environment, the positioning stem 400 may be used in
 association with frameless stereotaxy, in which case LED detectors are
 used to find the position of the positioning stem. Once the positioning
 stem is properly located collinearly with the trajectory 260, the
 instrument is inserted through the trajectory guide 200 or 200' toward the
 target 270 to a specific distance. Another scan is then taken to confirm
 that the instrument is at the target. These are the steps as shown and
 described previously and correspond to steps 1106 and 1108 in FIG. 11.
 FIG. 13 shows a remote controlled version of trajectory guide 200' that
 could be used under MR guidance. The remote device includes a remote
 positioner 1320 which either duplicates the trajectory guide 200' or the
 movement of the trajectory guide 200'. The replica trajectory guide 1320
 is manipulated until the positioning stem 400' is located collinearly with
 the trajectory 260 to the target 270. (The trajectory 260 and the target
 270 are shown in FIG. 2.) The positioning stem 400' is then removed from
 the trajectory guide 200' and an instrument is placed into the trajectory
 guide 200'. Attached to the instrument is a block 1310 and a locking
 collar 1312. A rod member 1314 is attached between the block 1310 and the
 locking collar 1312. The locking collar 1312 holds the instrument by
 coiling around the stem of a surgical instrument or tool. Pulling a
 plunger 1330 causes the locking collar to move toward the block 1310,
 thereby inserting the tool or instrument through the trajectory guide 200'
 to the target 270. Once the instrument tip reaches the target 270 within
 the patient, the locking collar and block can be removed and the
 procedure, such as a biopsy or laser ablation, can be performed.
 Burr Hole Externalizer Adapter for Other Tools
 Turning now to FIGS. 14-16, the burr hole externalizer will be detailed.
 FIG. 14 is a top view of a burr hole extension apparatus 1400. FIG. 15 is
 a side view of the burr hole externalizer 1400. The burr hole externalizer
 1400 is made of a tubular body 1410 with a set of flanges 1420, 1422, and
 1424 attached thereto. The tubular body 1410 is approximately 1 cm in
 height. The tubular body 1410 has a height that allows clearance between
 the tubular body and the tool to allow insertion of the tool into the
 patient's body. The tubular body 1410 has a flange end 1412 and a burr
 hole end 1414. The flanges 1420, 1422, and 1424 are used to attach the
 burr hole externalizer 1400 to the patient. The flanged end 1412 is the
 end of the burr hole externalizer 1400 that contacts the patient. The burr
 hole end 1414 is positioned a distance from the patient's body. The burr
 hole externalizer 1400 basically provides a substitute opening for a burr
 hole that used to have to be made in the patient. The burr hole end 1414
 of the tubular body is dimensioned so that it replicates a burr hole. The
 inner diameter of the burr hole end 1414 is the same as a standard burr
 hole. It should be pointed out that the Europeans have one standard
 diameter and the rest of the world has another standard diameter. The burr
 hole end 1414 may also include an inside thread 1416 so that tools which
 thread into a burr hole can also thread into the burr hole end 1414 of the
 externalizer 1400. It should be noted that an inside thread is not
 necessary. Thus the externalizer 1400 can also be thought of as a
 universal adapter for tools that normally are attached to a burr hole.
 In operation, a physician/surgeon will initially position the burr hole
 externalizer 1000 onto the patient's body. For the sake of example, the
 physician surgeon will initially position the externalizer on the
 patient's head. The burr hole externalizer is held in place using several
 bone screws. The bone screws pass through openings in each of the flanges
 1420, 1422, and 1424. A selected tool is then attached to the burr hole
 end 1014 of the burr hole externalizer 1400. The tool attached can be a
 trajectory guide such as described above or such as described in U.S.
 patent application Ser. No. 08/919,649 filed Aug. 28, 1997 and entitled
 "Surgical Instrument Trajectory Guide Method and Apparatus". The tool can
 be any tool that previously required attachment to a burr hole in the body
 of the patient. The advantages associated with using the burr hole
 externalizer 1400 stem from the fact that the surgeon no longer has to
 make a burr hole in the patient. Not having to make a burr hole means that
 the procedure takes less time. It also results in less fluid loss from the
 spine and the cranium which results in less shifting of the target or
 contents of the head. In addition to several small bone screws, the only
 opening made in the patient's body is a small twist drill hole. A twist
 drill hole has a diameter of approximately 2 mm. This is much smaller than
 the 12-15 mm burr hole previously discussed above. A drill hole of this
 small size can be made with a minor incision or scalp or upper body area
 and with minimal trauma. Thus, there is less trauma and less discomfort
 for the patient when the burr hole externalizer is used.
 FIG. 16 is a top view of another embodiment of the burr hole externalizer
 1400. Most of the components are the same and are numbered the same as the
 externalizer 1400 shown in FIG. 14. The difference is that the flanges are
 replaced with a first headband 1610 and a second headband 1612. This
 produces four long legs when compared to the externalizer 1400 shown in
 FIG. 14. Three elongated legs could also be used to provide adequete
 attachment of the externalizer to the patient's body. In the ends of each
 head band are openings for body screws. The body screws may not have to be
 used to secure the burr hole externalizer 1400 to the patient. It should
 be noted that the embodiments shown are just two examples of ways of
 attaching the burr hole externalizer 1400 to the patient. There are many
 ways of stably attaching the burr hole externalizer 1400. In addition,
 although a burr hole is normally used for entering the cranial cavity,
 this externalizer 1400 could easily be used for similar operations on
 other portions of the patient's body. Procedures that formerly required
 many hours can now be performed in substantially less amounts of time with
 the burr hole externalizer and the trajectory guide 200.
 Many uses are contemplated for this new trajectory guide 200. For example,
 a surgical instrument can be used to access certain portions of the body
 of the patient. Using the head of a human patient as an example, the
 trajectory guide 200 can be used to deliver an instrument to an area of
 the brain for biopsy. An instrument can also be used to access the
 ventricular area of the brain and cerebrospinal fluid for placement of a
 ventricular shunt or drain. The trajectory guide can also be used to
 enable a neurosurgeon to perform ventricular endoscopy. The instrument in
 such endoscopy typically includes a fiber optic for viewing a portion of
 the brain. The instrument can be rigid or flexible. The trajectory guide
 200 can also be used in treating or researching various other disorders or
 diseases of the brain, such as Alzheimer's disease, multiple sclerosis,
 Huntington's chorea, Parkinson's disease and other neurodegenerative
 diseases. The globus pallidus is one key to controlling the tremors that
 patients with Parkinson's disease have. In some treatments, electrodes are
 used to deliver electrical signals to this organ to reduce or eliminate
 the effect of Parkinson's disease. In addition, a surgical instrument can
 be used to perform a pallidotomy (i.e., lesion the globus pallidus).
 Similarly, other targets include the thalamus and subthalamic nucleus.
 Depending on the surgeon, additional targets could be considered,
 including nuclear and non-nuclear regions of the brain stem. Another
 surgical procedure is the removal of tumor material in the brain. The
 tumor can be located and eliminated using an instrument delivered with the
 help of the trajectory guide 200. Still other procedures are removal of
 lesions which are formed in the brain due to strokes or other medical
 conditions.
 Other Uses of the Trajectory Guide
 Described above are procedures associated with the head and brain. There
 are numerous other surgical procedures that can also be performed on other
 than the brain that would benefit from accurate placement of a surgical
 tool. In particular, it is anticipated that cardiac and pulmonary
 conditions will be ameliorated by minimally invasive therapies that can be
 made possible with the trajectory guide. In such procedures, the
 trajectory guide is more of a body portal and may or may not be used to
 lock into a specific trajectory toward a target. Moreover, such procedures
 may require use of more than one trajectory guide or may require a
 multiple body portal configuration in which each of the portals include
 one or more trajectory guides. In such therapies, surgical instruments or
 observational tools may be inserted to enable the surgeon in performing
 surgical procedures. Similarly, probes may be delivered to specific
 targets or general targets by the trajectory guide for the performance of
 cryotherapy, laser therapy, radio frequency ablation, microwave
 interstitial therapy, focussed ultrasound therapy and other therapies.
 These therapies are all currently done on various parts of the body in
 conjunction with an imaging device, such as the CT scanning device 100.
 The trajectory guide 200 makes delivery of the instruments to the various
 targets easier in all of these therapies. In addition, the use of the burr
 hole externalizer 1000 further speeds procedures that require the entry of
 tools into the patient's body.
 FIGS. 17-21 show a trajectory guide 1700 which can be used as a body
 portal. FIG. 17 is an end view of a patient positioned within a MR scanner
 1700. The patient has a body portal type trajectory guide 1710 attached
 and positioned on their body. FIG. 18 is a side view of a patient
 positioned within a conventional MR scanner 1700. As shown in FIG. 18, the
 body portal type trajectory guide is positioned at an angle with respect
 to the body of the patient so that the total overall height of the body
 portal type trajectory guide 1710 will fit within the conventional MR
 scanner 1700. The movable element 820, if positioned perpendicular with
 respect to the body, may interfere with the MR scanner 1700. Most
 certainly if the movable element 820 is positioned perpendicular with
 respect to the body, a surgical instrument could not be placed within the
 movable element 820. A surgical instrument such as a catheter extends
 through a longitudinal opening or passageway 822 in the movable element
 820. When perpendicular to the patient, there would not be enough room
 between the MR scanner 1700 and the surgical instrument being placed
 within the passageway 822 of the movable element 820. It should be noted
 that the body portal type trajectory guide 1710 may be equipped with a
 movable element 820 or a guide member 240 or a positioning member 400. The
 movable member 820 is rotatable with respect to the patient so that a
 surgical instrument may be placed within the movable member 820 from any
 position the surgeon may take with respect to the patient. In a scanning
 environment that has an open magnet, an angled base is not necessary. The
 base for the body portal type positioner could be made with a vertical
 surface or a surface substantially parallel to the patient's body.
 FIGS. 19-21 show the body portal type trajectory guide 1710 in more detail.
 FIG. 19 is a side view of the body portal type trajectory guide 1710 and
 FIG. 20 is a cutaway side view of the body portal type trajectory guide
 1710. The movable element 820 includes passageway 822. The movable element
 820 also has a guide stem end 830 and a base end 810. The base end 810 is
 ball shaped. The body portal type trajectory guide 1710 includes a base
 1720 which has an opening or passageway 1722 therein. The passageway 1722
 allows the surgical instrument to pass into the body of the patient and to
 a target 270 within the patient. At one end of the passageway 1722 is a
 cup 1724. The cup 1724 is dimensioned such that the cup grips the ball end
 810 of the positioning member 820. The cup 1724 may also include portions
 which extend beyond the largest diameter of the ball end 810 to further
 grip the ball end 810 of the movable member 820. The base 1720 also
 includes an angled portion 1726 and a flat base portion 1728. The flat
 base portion 1728 is circular and includes a first flange 1730 and a
 second flange 1732. A plastic ring 1740 includes a finger 1742 which
 engages the slot between the first flange 1730 and the second flange 1732
 of the flat base. The plastic finger 1742 engages the slot between the
 first flange 1730 and the second flange 1732 so that the base 1720 can
 rotate or swivel with respect to the plastic ring 1740. The plastic ring
 1740 is merged or attached to a flexible adhesive patch 1750. The flexible
 adhesive patch is made from a flexible material which can conform to
 various body portions or parts of a patient. An adhesive material is
 placed on one side of the flexible adhesive patch. The adhesive is placed
 on surface 1752 which is opposite the side of the flexible adhesive patch
 1750 closest to the angled base portion 1726. The flexible adhesive patch
 1750 is made of a biocompatible material such as might be used to affix a
 colostomy bag to a patient or a similar material. FIG. 21 shows an
 embodiment that includes a quick locking mechanism 2000. The base is
 provided with a high pitch thread. The locking mechanism 2000 is provided
 with a matching high pitch thread. The locking mechanism 2000 is also
 provided with a single arm or knob 2010 for turning the locking mechanism
 2000 with respect to the threaded base portion. The knob 2010 is
 positioned away from the patient so that the surgeon has easy access to
 the knob 2010. Because a high pitch thread length is used, the knob needs
 to be turned only slightly to lock the movable element 820 into position
 with respect to the base.
 FIG. 21 is a top view of the body portal type trajectory guide 1710. The
 movable member 820 includes the guide stem end 830 and the ball end 810
 which is positioned within the cup 1724. The base is angled through the
 angled base portion 1726 and is attached to the flat base portion 1728.
 The flat base portion is attached to the plastic ring portion 1740 which
 in turn is merged with a flexible body patch 1750.
 In operation, the body portal type trajectory guide 1710 is used as
 follows. Initially, the surgeon determines the approximate location of the
 target 270 within the body of the patient. An incision is made in the
 patient near the target 270. The body portal type trajectory guide 1710 is
 then placed over the incision so that the passageway 1722 in the base 1720
 is positioned over the incision that is made in the patient. The
 passageway 1722 is roughly aligned with a line between the target and the
 incision within the patient. The flexible adhesive patch 1750 is attached
 to the patient to seal the incision as well as to provide a stable
 attachment point for the body portal type trajectory guide 1710. The
 movable member 820 can be repositioned with respect to the cup 1724 within
 the base 1720 of the trajectory guide 1710. The entire base 1720 can be
 moved with respect to the plastic ring 1740 and the flexible adhesive
 patch 1750. By moving the base with respect to the flexible adhesive
 patch, a surgeon is afforded the flexibility to work from a variety of
 positions with respect to the patient and with respect to the MR scanner
 which is positioned around the patient. Initially, the physician will
 roughly position the base 1720 with respect to the target. The base 1720
 can be rotated with respect to the plastic ring and flexible adhesive
 patch to enable the surgeon to take any position with respect to the
 incision and the patient. The movable member 822 can then be moved to
 assure that the surgical instrument that will be placed within the opening
 or passageway 822 in the movable member 820 will intersect with the target
 270. The movable member can be equipped with RF micro coils to aid in
 positioning the movable member, similar to those described in U.S. patent
 application Ser. No. 08/919,649 filed Aug. 8, 1997 and entitled "Surgical
 Instrument Trajectory Guide Method and Apparatus".
 It should be noted that the body portal type trajectory guide 1710 will be
 used when the targets 270 are relatively large. In other words, a
 trajectory guide 1710 can be used to take a biopsy of a liver, which is a
 relatively large organ. Thus, if the guide member 820 is slightly out of
 position, the sample will come from just a slightly different portion of
 the liver but will still be valid. Although a locking member could be
 provided, the body portal type trajectory guide 1710 shown does not
 feature a locking member for the movable member 822. The cup 1724 holds
 the ball end 810 of the movable member 820 tightly such that it will not
 move under most conditions. As stated before, the body portal type
 trajectory guide 1710 is used on relatively large targets 270 and,
 therefore, slight movement of the movable member due to respiratory
 excursion will not affect the placement of the surgical instrument within
 the large target 270. Once the surgical instrument has been inserted
 through the passageway 822 and the passageway 1722 and to the target 270
 and the operation has been performed, the surgical instrument is removed.
 The body patch 1750 can then also be removed. By removing the body patch
 1750, the entire trajectory guide 1710 is also removed. The incision is
 then sewn or bandaged by the surgeon to end the operation. The main
 advantages of the body portal type trajectory guide 1710 is that the
 operation can be done relatively quickly in either a CT or MR environment.
 The body patch 1750 also keeps the area clear and clean. Operations that
 used to be difficult or impossible or used to take large amounts of time
 can now be performed easily and efficiently.
 There are many other uses contemplated for the body portal type trajectory
 guide 1710. The trajectory guide 1710 can be used to biopsy or provide
 therapy to organs in or near the abdomen or pelvis. Among the uses are
 liver biopsies, renal biopsies, pancreatic biopsies, adrenal biopsies. In
 addition, some procedures require both a biopsy as well as a therapy. The
 biopsy needle is used first and then an instrument used in therapy is
 substituted for the biopsy needle. The instrument for applying therapy
 includes instruments for thermal ablation, and instrument for providing
 shunts to various organs such as TIPS (transjugular intraheptic portal
 systemic shunts). The trajectory guide 1710 can also be used to conduct
 biliary drainages, and used to conduct other biopsies and treatments at or
 near the abdomen of the pelvis. The trajectory guide 1710 can also be used
 for procedures on the back and near the spine of a patient. Nerve blocks,
 epidural injections, facet injections, sacroiliac joint injections, and
 spinal cordotomy are just a few of the procedures possible with the
 trajectory guide 1710. Non-brain treatments and biopsies in the head and
 neck can also be accomplished using the trajectory guide 1710. Trigeminal
 neuralgia can be treated using the trajectory guide 1710. Biopsies of the
 pleura, the lung, and the mediastinurn and removal of emphazematious blebs
 to reduce the volume of the lung can be done percutanously using the
 trajectory guide. The trajectory guide 1710 can also be used for fetal
 surgery such as for division of fetal hydrocephalus, and for treatment of
 fetal hydronephrosis. These are just a sampling of the possible procedures
 that can be done using the body portal type trajectory guide 1710.
 Numerous other procedures will be accomplished using this device. In
 addition, the device rise to other future surgical procedures.
 It is to be understood that the above description is intended to be
 illustrative, and not restrictive. Many other embodiments will be apparent
 to those of skill in the art upon reviewing the above description. The
 scope of the invention should, therefore, be determined with reference to
 the appended claims, along with the full scope of equivalents to which
 such claims are entitled.