EP2693972A1

EP2693972A1 - Head fixation system and method

Info

Publication number: EP2693972A1
Application number: EP12768498.3A
Authority: EP
Inventors: Genius Dacpano; Mark Grant; Salman Qureshi
Original assignee: Monteris Medical Corp
Current assignee: Monteris Medical Corp
Priority date: 2011-04-08
Filing date: 2012-04-05
Publication date: 2014-02-12
Also published as: EP2693972A4; JP2014519859A; JP5933901B2; CN104254296A; WO2012137179A1

Abstract

A head fixation system comprises a platform, a fixation ring rotatably coupled to a ring mount extending from an upper surface of the platform, wherein the fixation ring includes a plurality of slots extending around a circumference thereof, a head support structured for insertion into a first one of the slots in the fixation ring, a first fixation post having a first fixation pin for engagement with a patient's skull, wherein the first fixation post is structured for insertion into a second one of the slots in the fixation ring, a second fixation post having a second fixation pin for engagement with the patient's skull, wherein the second fixation post is structured for insertion into a third one of the slots in the fixation ring, and an MRI coil including a top coil member and a bottom coil member removably mounted to the platform, wherein the MRI coil is rotatable relative to and independent of the fixation ring.

Description

HEAD FIXATION SYSTEM AND METHOD

FIELD OF THE INVENTION

[0001] The present invention is related to surgical working platforms. More specifically, the present invention relates to a head fixation system and method for using the sarrie which facilitates the alignment of surgical and observational instruments into a patient.

BACKGROUND OF THE INVENTION

[0002] Each year roughly 200,000 patients are diagnosed with brain tumors in the United States. Roughly 17,000 of these tumors are "benign," meaning that the tumor mass is not cancerous. However, the other roughly 183,000 of these tumors are "malignant" (i.e., cancerous), meaning that they are capable of causing or contributing to patient death. Approximately 10% of cancerous brain tumors are "primary" tumors, meaning that the tumors originate in the brain. The primary tumors typically consist of brain tissue with mutated DNA that aggressively grows and displaces or replaces normal brain tissue. The most common of the primary tumors are known as gliomas, which indicate cancer of the glial cells of the brain. In most instances, primary tumors appear as single masses. However, these single masses can often be quite large, irregularly- shaped, multi-lobed and/or infiltrated into surrounding brain tissue. Primary tumors are generally not diagnosed until the patient experiences symptoms, such as headaches, altered behavior, sensory impairment, or the like. However, by the time the symptoms develop the tumor may already be large and aggressive.

[0003] One well known treatment for cancerous brain tumors is surgery. In particular, surgery involves a craniotomy (i.e., removal of a portion of the skull), dissection, and total or partial tumor resection. The objectives of surgery include removal or lessening of the number of active malignant cells within the brain, and a reduction in the pain or functional impairment due to the effect of the tumor on adjacent brain structures. However, by its very nature, surgery is highly invasive and risky. Furthermore, for some tumors surgery is often only partially effective. In other tumors, the surgery itself may not be feasible, it may risk impairment to the patient, it may not be tolerable by the patient, and/or it may involve significant cost and recovery.

[0004] Another well known treatment for cancerous brain tumors is stereotactic radiosurgery (SRS). In particular, SRS is a treatment method by which multiple intersecting beams of radiation are directed at the tumor such that the point of intersection of the beams receives a lethal dose of radiation, while tissue in the path of any single beam remains unharmed. SRS is non-invasive and is typically performed as a single outpatient procedure. However, confirmation that the tumor has been killed or neutralized is often not possible for several months post- treatment. Furthermore, in situations where high doses of radiation may be required to kill a tumor, such as in the case of multiple or recurring tumors, it is common for the patient to reach the "toxic threshold" prior to killing all of the tumors, where further radiation is inadvisable.

[0005] More recently, the treatment of tumors by "heat" (also referred to as hyperthermia or thermal therapy) has been developed. In particular, it is known that above 57°C all living tissue is almost immediately and irreparably damaged and killed through a process called coagulation necrosis or ablation. Malignant tumors, because of their high vascularization and altered DNA, are more susceptible to heat-induced damage than normal tissue. Various types of energy sources may be used, such as laser, microwave, radiofrequency, electric, and ultrasound sources. Depending upon the application and the technology, the heat source may be extracorporeal (i.e., outside the body), extrastitial (i.e., outside the tumor), or interstitial (i.e., inside the tumor).

[0006] Interstitial thermal therapy (ITT) is a process designed to heat and destroy a tumor from within the tumor. One advantage of this type of therapy is that the energy is applied directly to the tumor rather than passing through surrounding normal tissue. Another advantage of this type of therapy is that the energy deposition is more likely to be extended throughout the entire tumor.

[0007] One exemplary ITT process begins by inserting an optical fiber into the tumor, wherein the tumor has an element at its "inserted" end that redirects laser light from an exterior source in a direction generally at right angles to the length of the fiber. The energy from the laser thus extends into the tissue surrounding the end or tip and effects heating. The energy is directed in a beam confined to a relatively shallow angle so that, as the fiber is rotated, the beam also rotates around the axis of the fiber to effect heating of different parts of the tumor at positions around the fiber. The fiber can thus be moved longitudinally and rotated to effect heating of the tumor over the full volume of the tumor with the intention of heating the tumor to the required temperature without significantly affecting the surrounding tissue.

[0008] The fiber used in the ITT process may be controlled and manipulated by a surgeon with little or no guidance apart from the surgeon's knowledge of the anatomy of the patient and the location of the tumor. Therefore, it is difficult for the surgeon to effect a controlled heating which heats the entire tumor to a required level while also minimizing damage to the surrounding tissue.

[0009] It is known that the location of tumors and other lesions to be excised can be determined using a magnetic resonance imaging system. Although these imaging systems have been helpful to assist the surgeon in determining a location of the tumor to be excised, use of the imaging systems ended once the location of the tumor was mapped out for the surgeon. In particular, previous excision procedures required the removal of the patient from the imaging system prior to commencing treatment. However, movement of the patient, together with the partial excision or coagulation of some of the tissue, can significantly change the location of the tumor to be excised. As a result, any possibility of providing controlled accuracy in the excision is eliminated.

[0010] It is also known that magnetic resonance imaging systems can be used by modification of the imaging sequences to determine the temperature of tissue within the image and to determine changes in that temperature over time.

[0011] U.S. Pat. No. 4,914,608 (LeBiahan) assigned to U.S. Department of Health and Human Services issued Apr. 3, 1990, discloses a method for determining temperature in tissue.

[0012] U.S. Pat. No. 5,284,144 (Delannoy) also assigned to U.S. Department of Health and Human Services and issued Feb. 8, 1994, discloses an apparatus for hyperthermia treatment of cancer in which an external, non-invasive heating system is mounted within the coil of a magnetic resonance imaging system. The disclosure is speculative and relates to initial experimentation concerning the viability of MRI measurement of temperature in conjunction with an external heating system. The disclosure of the patent has not led to a commercially viable hyperthermic treatment system.

[0013] U.S. Pat. Nos. 5,368,031 and 5,291 ,890 assigned to General Electric relate to an MRI controlled heating system in which a point source of heat generates a predetermined heat distribution which is then monitored to ensure that the actual heat distribution follows the predicted heat distribution to obtain an overall heating of the area to be heated. Again this patented arrangement has not led to a commercially viable hyperthermia surgical system.

[0014] U.S. Pat. No. 4,671 ,254 (Fair) assigned to Memorial Hospital for Cancer and Allied Diseases and issued Jun. 9, 1987, discloses a method for the non surgical treatment of tumors in which the tumor is subjected to shock waves. This type of treatment does not incorporate a monitoring system to monitor and control the effect of the shock waves.

[0015] U.S. Pat. No. 5,823,941 (Shaunnessey), not assigned, and issued Oct. 20, 1998, discloses a specially modified endoscope designed to support an optical fiber. The optical fiber emits light energy and may be moved longitudinally and rotated angularly about its axis to direct the energy. The device is used for excising tumors, and the energy is arranged to be sufficient to effect vaporization of the tissue to be excised. The gas formed during the process is removed by suction through the endoscope. An image of the tumor is obtained by MRI, which is thereafter used to program a path of movement of the fiber to be taken during the operation. Again, there is no feedback during the procedure to control the movement of the optical fiber, and the operation is wholly dependent upon the initial analysis. This arrangement has not achieved commercial or medical success.

[0016] U.S. Pat. No. 5,454,807 (Lennox) assigned to Boston Scientific Corporation and issued Oct. 3, 1995, discloses a device for use in irradiating a tumor with light energy from an optical fiber. A cooling fluid is supplied through a conduit within the fiber to apply surface cooling and to prevent surface damage while allowing increased levels of energy to be applied to deeper tissues. Once again, this arrangement does not provide feedback control of the heating effect.

[0017] U.S. Pat. No. 5,785,704 (Bille) assigned to MRC Systems GmbH and issued Jul. 28, 1996, also discloses a particular arrangement of a laser beam and lens for use in irradiation of brain tumors. In particular, this arrangement uses high speed pulsed laser energy for a photo-disruption effect, but does not disclose methods of feedback control of the energy.

[0018] Kahn, et al. in Journal of Computer Assisted Tomography 18(4):519-532, July/August 1994; Kahn, et al. in Journal of Magnetic Resonance Imaging 8: 160- 164, 1998; and Vogl, et al. in Radiology 209: 381-385, 1998, all disclose a method of application of heat energy from a laser through a fiber to a tumor where the temperature at the periphery of the tumor is monitored during the application of the energy by MRI. McNichols, RJ et al. in Lasers in Surgery and Medicine, 34:48-55, 2005, disclose energy control by an MRI feedback monitoring arrangement in a paper entitled "MR Thermometry-Based Feedback Control of LITT at 980 nm." Additionally, the paper of Vogl discloses a cooling system supplied commercially by Somatex of Berlin, Germany for cooling the tissues at the probe end. The system is formed by an inner tube containing the fiber mounted within an outer tube. Cooling fluid is passed between the two tubes and inside the inner tube in a continuous stream.

[0019] While highly effective in certain applications, the use of ITT to treat brain tumors has been limited by the inability to focus the energy exclusively and precisely on the tumor so as to avoid damage to surrounding normal brain tissue. This is complicated by the fact that many brain tumors are highly irregular in shape.

[0020] Focused laser interstitial thermal therapy (f-LITT) is the next general refinement of laser-based thermal therapy technologies. In particular, f-LITT enables precise control over the deposition of heat energy, thereby enabling the physician to contain cell damage exclusively to within a tumor mass of virtually any size and shape. However, there is a need for an apparatus that allows the physician to precisely fix the position of the patient's head while at the same time avoiding interference with the trajectory guide instrument that is typically used to guide the heat generating treatment probe into the tumor mass.

[0021] Therefore, a heretofore unaddressed need exists to establish a head fixation device that is capable of precisely fixing the position of the patient's head to allow unobstructed access to the point of entry into the patient's head regardless of where that point of entry lies. The head fixation device should preferably allow independent rotation with respect to an MRI coil surrounding the patient's head. Furthermore, the head fixation system should preferably be usable in combination with a customizable MRI coil having two or more interchangeable coil sections in order to adapt to various trajectory lines and points of entry into the patient's head.

BRIEF SUMMARY OF THE INVENTION

[0022] The present invention solves the foregoing problems by providing a head fixation system including a platform, a fixation ring rotatably coupled to a ring mount extending from an upper surface of the platform, wherein the fixation ring includes a plurality of slots extending around a circumference thereof, a head support structured for insertion into a first one of the slots in the fixation ring, a first fixation post having a first fixation pin for engagement with a patient's skull, wherein the first fixation post is structured for insertion into a second one of the slots in the fixation ring, a second fixation post having a second fixation pin for engagement with the patient's skull, wherein the second fixation post is structured for insertion into a third one of the slots in the fixation ring, and an MRI coil including a top coil member and a bottom coil member removably mounted to the platform, wherein the MRI coil is rotatable relative to and independent of the fixation ring.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a perspective view of an exemplary trajectory guide that may be used in combination with the head fixation system of the present invention. [0024] FIG. 2 illustrates that first step in a planning process in which an MRI scan depicts the identification of a tumor in a patient's brain.

[0025] FIG. 3 illustrates a second step in a planning process depicting a visual display produced by planning software showing a patient's head and the location of the tumor identified in FIG. 2.

[0026] FIGS. 4A-D illustrate step three in a planning process in which a virtual trajectory guide is place over a user-selected point of entry.

[0027] FIGS. 5A-D illustrate step four in a planning process in which the virtual trajectory guide is adjusted to establish a desired trajectory.

[0028] FIGS. 6A-D illustrate step five in a planning process in which a patient's head with a trajectory guide is displayed within a virtual head fixation system.

[0029] FIG. 7A is a perspective view of an exemplary embodiment of a head system in accordance with the present invention.

[0030] FIG. 7B is a perspective view of an exemplary embodiment of a head fixation system including head fixation device, MRI coil and transfer bed.

[0031] FIG. 7C is a perspective view of an MRI coil that is operable in conjunction with the head fixation device of the present invention.

[0032] FIGS. 8A - 8D illustrate the head fixation device operably coupled to a patient's head.

[0033] FIGS. 9-13 illustrate the head fixation system of FIGS. 7A-7C being used in operation.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Generally speaking, the present invention encompasses a system and method for orienting and securing a patient's head in preparation for performing a surgical procedure that requires trajectory alignment. More particularly, the present invention includes an adjustable head fixation system that enables a surgeon to select almost any point of entry on a patient's head (and thus, any trajectory) and attach a suitable trajectory guide without the risk of interference with the MRI coil surrounding the patient's head. While reference is made to brain tumors and brain surgery, those of skill in the art will appreciate that the system and method in accordance with the invention is designed for use with any surgery in which head fixation is desirable.

[0035] Prior to describing the head fixation system in detail, one exemplary embodiment of a trajectory guide that may be used during a procedure in combination with the head fixation system will be discussed. Several optional "planning" steps leading up to the procedure will also be discussed.

[0036] FIG. 1 is a perspective view one exemplary embodiment of a trajectory guide 10, which generally includes a base plate 11 , a plurality of feet 12 attachable to the skull or other body part of a patient, and a plurality of adjustable, telescoping legs 14 equal in number to the plurality of feet 12. As illustrated in FIG. 1 , the trajectory guide 10 may be oriented to define a trajectory line T for tools or instruments that require alignment. Tools or instruments may include, but are not limited to, probes, catheters, biopsy needles, drills, and the like.

[0037] The base plate 11 of the trajectory guide 10 includes a top clamp 16 and a bottom clamp 18 hingedly coupled together by hinge means 19, which may include a first hinge portion 20 extending from the top clamp 16 that is structured to mate with a second hinge portion 22 extending from the bottom clamp 18. The first and second hinge portions 20 and 22 may be coupled together via any suitable connection means, such as a pin 24 or similar connection device. Furthermore, the top clamp 16 and the bottom clamp 18 may be locked together in a closed position with a clamp lock 25 after the trajectory is determined.

[0038] The top and bottom clamps 16 and 18 each include an opening that is structured to allow a ball joint moveable member 26 to be moveably and rotatably seated therebetween. The ball joint moveable member 26 may include an adapter receiving member 28 and a central receiving lumen (not shown in FIG. 1 ) extending through the adapter receiving member 28 and the ball joint moveable member 26. The adapter receiving member 28 of the ball joint moveable member 26 may be structured to receive a center ball adapter 30 therein that may in turn be structured to receive and interface with various tools.

[0039] As illustrated in FIG. 1 , the center ball adapter 30 passes through the ball joint moveable member 26 from the top and includes a tubular portion 32 and an interface portion 34 structured to mate with the adapter receiving member 28 of the ball joint moveable member 26. A first fastening means 36 may be coupled to the adapter receiving member 28 that is operable to secure the center ball adapter 30 to the ball joint moveable member 26 after it has been inserted therethrough. Particularly, the first fastening means 36 may be any suitable fastening means including, but not limited to, a thumb screw or the like. After fully inserting the center ball adapter 30 into the adapter receiving member 28 of the ball joint moveable member 26, the thumb screw may be tightened to lock it in place. Thereafter, the user may remove the center ball adapter 30 by simply loosening the thumb screw and sliding the adapter 30 from within the adapter receiving member 28.

[0040] The center ball adapter 30 may include a lumen 38 extending through the tubular portion 32 and the interface portion 34 that is structured to receive a surgical tool. The diameter of the lumens in various center ball adapters may vary depending upon the size of the probe and/or instrument that the lumen is designed and structured to receive. Additionally, the center ball adapter 30 may include a second fastening means 40 that is operable to secure the tool in place once it has been positioned within the lumen 38. As will be appreciated by one of ordinary skill in the art, the second fastening means 40 may be similar to the first fastening means 36 previously described.

[0041] As illustrated in FIG. 1 , each of the adjustable, telescoping legs 14 may include a ball joint end 42 and a hinged end 43. A length of each leg 14 may be adjusted and the leg locked at a desired length with a leg cam lock 44 after the trajectory is determined.

[0042] As further illustrated in FIG. 1 , the trajectory guide 10 may optionally include a web assembly 45 designed to assist with the proper spacing and alignment of the feet 12 during the placement of the trajectory guide 10 on the patient.

[0043] In order to determine the proper placement of the trajectory guide 10 on the patient as well as the desired trajectory of the guide (i.e., the length/orientation of the legs and the orientation of the ball joint movable member), several planning steps may be performed. Exemplary but non-limiting planning steps that are performed using a custom software program will now be described.

[0044] In a first planning step as illustrated in FIG. 2, various MRI scans are taken and uploaded into planning software. Then, a desired point of entry is determined by the surgeon in a second planning step. As illustrated in FIGS. 3A - 3D, the planning software may be designed to display a depiction of the patient's head as well as the location of the tumor 300 therein. Various points of possible entry 310 are also displayed. The planning process continues at step three where a "virtual" trajectory guide is placed over the user-selected point of entry and displayed to the surgeon as illustrated in FIGS. 4A - 4D. Subsequently, as illustrated in FIGS. 5A - 5D, the legs and the ball joint movable member on the virtual trajectory guide are adjusted to establish a desired trajectory to the tumor in a fourth planning step. Finally, in a fifth planning step, the patient's head and trajectory guide may be displayed within a "virtual" head fixation system as illustrated in FIG. 6 to determine a desired location for the fixation posts/pins and a desired fixation ring orientation as will be described in further detail below.

[0045] As will be appreciated by one of ordinary skill in the art, because the surgical planning is performed in a "virtual" environment using software, it may be completed days or even weeks before the actual surgery.

[0046] After the surgical planning is complete, the surgeon may then or at any time thereafter proceed with the actual surgical procedure by physically positioning the patient in the head fixation system.

[0047] FIG. 7A is a perspective view illustrating one exemplary but non- limiting embodiment of a head fixation system 100 in accordance with the present invention. As illustrated in FIG. 7A, the head fixation system 100 generally includes a platform 102, a head fixation ring 104 rotatably coupled to a ring mount 106 extending from an upper surface of the platform 102, a head support 108, and a plurality of fixation posts 1 10. The head fixation ring 104 includes a plurality of slots 1 12 extending around a circumference thereof. As illustrated in FIG. 7A, the head support 108 is removably received by a first one of the slots 1 12, a first fixation post 1 10A is removably received by a second one of the slots 1 12, and a second fixation post 1 10B is removably received by a third one of the slots 1 12. The first, second, and third slots 1 12 may be any of the slots around the circumference of the head fixation ring 104 depending on the desired trajectory, and may optionally be selected in the software planning process as described above. As will be appreciated by one of ordinary skill in the art, the head fixation system 100 may include fewer or more fixation posts than shown. For example, in one exemplary alternative embodiment the head fixation system 100 includes four fixation posts.

[0048] The first fixation post 1 10A includes a plurality of fixation pin apertures 1 16A along its length adapted to receive one or more fixation pins 1 14A, 1 14B. Fixation pins 1 14A, 1 14B may be threadably received by fixation pin apertures 1 16A, 1 16B respectively thus providing a variety of "penetration depths" to set the fixation pins. After being received by a fixation pin aperture, a first adjustable fixation pin 114A extends inwardly toward a center of the head fixation ring 104. In addition to the adjustability of the "penetration depth" of the fixation pin 1 14A, the plurality of fixation pin apertures 1 16A, 1 16B on fixation post 1 1 OA, 1 10B provides the surgeon with a variety of fixation pin placement options. Similarly, the second fixation post 1 10B includes a second adjustable fixation pin 1 14B that may be removably and adjustably received by one of said plurality of fixation pin apertures 1 16B along the length of the post 1 10B. As noted above, any number of fixation posts may be utilized depending on the nature of the surgery.

[0049] The head fixation ring 104 is removably and rotatably positioned within ring mount 106. The head fixation ring4 104 is rotatable with respect to platform 102 as indicated by the arrow 1 18 to adjust the angular position of the patient's head. The head fixation ring 104 may be locked in the desired position using one or more ring locking devices 120. In one exemplary embodiment the ring locking devices 120 may include a retractable pin or pins (not shown) that is received by one or more of a plurality of apertures 122 along an outer circumferential edge of the head fixation ring 104.

[0050] Platform 102 may be integrally coupled to patient board 105. Alternatively, platform 102 may be detachably coupled to patient board 105 by hinges or like mechanisms known to those of skill in the art. Yet alternatively, platform 102 may simply lie adjacent to patient board 105 depending on the surgery required. Handles 107 facilitate the transfer of the patient and the system in accordance with the invention while in use.

[0051] As further illustrated in FIG. 7A, the head fixation system 100 includes a coil support 124 integrally or non-integrally/detachably coupled to platform 102. Coil support 124 is structured to removably receive an MRI coil thereon. One exemplary coil 125 is illustrated in FIGS. 7B and 7C. The coil 125 includes a bottom coil member 127 and an interchangeable top coil member, such as top coil members 129A and 129B illustrated in FIG. 7C. As will be appreciated by one or ordinary skill in the art, the top coil member 129A is preferably used for trajectories that extend from the top of the head, while the top coil member 129B is preferably used for trajectories extending from the forehead or sides of the head. In order to operably couple the top coil member 129A or 129B to the bottom coil member 127, the top coil members 129A and 129B are provided with alignment pins 131 and electrical connectors 133 that are structured to mate with corresponding pin slots 135 and electrical receptacles 137 in the bottom coil member 127. The bottom coil member 127 includes a connector 143 that operably couples to an MRI cable to link the coil 125 to the MRI system.

[0052] With reference to FIGS. 7A and 7B, a first end 139 of the bottom coil member 127 is structured to engage with a first coil track portion 126 while a second end 141 of the coil is structured to engage with a second coil track portion 128. The first and second coil track portions 126 and 128 allow the coil 125 to rotate relative to and independent of the head fixation ring 104. When rotated to the desired position, the coil 125 may be "locked" with one or more coil locking devices 130, such as by way of example friction locks, pins, screws or other means known to those of skill in the art.

[0053] FIGS. 8-13 illustrate one exemplary process for physically attaching the patient's head to the head fixation system 100 described above. Particularly, the process begins with the head fixation ring 104 being positioned around the head of a patient P as illustrated in FIG. 8. This may be performed with the fixation ring 104 either coupled to the ring mount 106 with the patient lying on the patient transfer board 105 or alternatively with the fixation ring 104 decoupled from the ring mount 106 and the patient standing or sitting. Then, as illustrated in FIG. 9, the first and second fixation posts 11 OA and 110B are inserted into the appropriate slots 112 in the head fixation ring 104 and the first and second fixation pins 114A and 114B are attached to the patient's head. As will be appreciated by one of ordinary skill in the art, the fixation pins may comprise any suitable attachment means such as, for example, a threaded shaft. If the head fixation ring 104 was not previously coupled to the ring mount 106 (i.e., the fixation ring 104 was decoupled from the ring mount 106 when attached to the patient's head), then the next step involves positioning the patient P on the platform 102 and locking the fixation ring 104 into the ring mount 106. Subsequently, the head fixation ring 104 is rotated as illustrated in FIG. 10 to provide access to the mounting location (and point of entry) for the trajectory guide 10.

[0054] In the next step of the process, the surgeon attaches the trajectory guide 10 to the head of the patient P based on the information derived during the surgical planning steps as illustrated in FIG. 11. As will be appreciated by one of ordinary skill in the art, the head fixation ring 104 may be rotated further if necessary to avoid any potential interference between the treatment probe/instrument that will be used and the MRI bore. Once the trajectory guide 10 is attached to the patient's head, the patient may be transported to the MRI room and transferred to the MRI table.

[0055] The process continues with attachment of the MRI coil 125 to the patient platform 102 as illustrated in FIG. 12. As will be appreciated by one of ordinary skill in the art, top coil member 129B was required in the illustrated example due to the orientation of the trajectory guide 10 on the patient's head. Once the coil 125 is assembled, the surgeon may visually verify that a minimum distance D is maintained between the trajectory guide 10 and the MRI bore B as illustrated in FIG. 13. Finally, the surgeon may take MRI scans to confirm the trajectory and continue with the treatment/procedure.

[0056] The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above disclosure.

[0057] The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope.

Claims

What is claimed is:

1. A head fixation system comprising: a platform having an upper and lower surface; a ring mount operably coupled to said upper surface of said platform; a fixation ring rotatably coupled to said ring mount, the fixation ring including a plurality of fixation ring slots extending around a circumference thereof; a first fixation post receivable into a first one of the fixation ring slots; and a second fixation post receivable into a second one of the slots in the fixation ring.

2. The head fixation system of claim 1 further comprising a head support structured for insertion into a third one of the fixation ring slots. ¹

3. The head fixation system of claim 1 further wherein said fixation posts include at least one fixation post aperture therethrough.

4. The head fixation system of claim 3 further comprising at least one fixation pin receivable by said at least one fixation post aperture for engagement with a patient's skull.

5. The head fixation system of claim 3 wherein said at least one fixation post aperture includes a plurality of fixation post apertures.

6. The head fixation system of claim 5 further comprising a plurality of fixation pins receivable by at least one of said plurality of apertures.

7. The head fixation system of claim 1 further comprising a transfer board detachably coupled to said platform.

8. The head fixation system of claim 1 further comprising a coil support coupled to said platform.

9. The head fixation system of claim 1 wherein said ring mount further comprises first and second coil tracks.

10. The head fixation system of claim 1 further comprising an MRI coil having a top coil member and a bottom coil member removably mounted to the platform, wherein the MRI coil is rotatable relative to and independent of the fixation ring.

11. The head fixation system of claim 9 further comprising an MRI coil having a top coil member rotatably engageable with said first coil track and a bottom coil member rotatably engageable with said second coil track.

12. The head fixation system of claim 1 wherein said head fixation ring includes a plurality of fixation ring apertures circumferentially position on an edge thereof.

13. The head fixation system of claim 12 further comprising one or more ring locks receivable by one or more of said plurality of fixation ring apertures.

14. The head fixation system of claims 10 and 11 wherein said top coil member includes one or more alignment pins mateable with corresponding pin slots on said bottom coil member.

15. The head fixation system of claims 10 and 11 wherein said bottom coil member includes connector means for connecting said MRI coil to an MRI system.

16. The head fixation system of claim 10 wherein said coil support further comprises one or more coil locking devices for locking said MRI coil in position.

17. A head fixation system comprising: a platform having an upper and lower surface; a ring mount operably coupled to said upper surface of said platform; a fixation ring rotatably received by said ring mount, the fixation ring including a plurality of fixation ring slots extending around a circumference thereof; a first fixation post receivable into a first one of the fixation ring slots, said first fixation post including a first fixation pin for engagement with a patient's skull; and a second fixation post receivable into a second one of the slots in the fixation ring, said second fixation post including a second fixation pin for engagement with a patient's skull; and an MRI coil rotatably received by and removably mounted to the platform, wherein the MRI coil is rotatable relative to and independent of the fixation ring.

18. The head fixation system of claim 17 further comprising a head support structured for insertion into a third one of the fixation ring slots.

19. The head fixation system of claim 17 further wherein said fixation posts include at least one fixation post aperture therethrough.

20. The head fixation system of claim 19 further comprising at least one fixation pin receivable by said at least one fixation post aperture for engagement with a patient's skull.

21. The head fixation system of claim 19 wherein said at least one fixation post aperture includes a plurality of fixation post apertures.

22. The head fixation system of claim 21 further comprising a plurality of fixation pins receivable by at least one of said plurality of apertures.

23. The head fixation system of claim 17 further comprising a transfer board detachably coupled to said platform.

24. The head fixation system of claim 1 further comprising a coil support coupled to said platform.

25. The head fixation system of claim 17 wherein said ring mount further comprises first and second coil tracks.

26. The head fixation system of claim 25 wherein the MRI coil includes a top coil member and a bottom coil member rotatably received by said first and second coil tracks.

27. The head fixation system of claim 17 wherein said head fixation ring includes a plurality of fixation ring apertures circumferentially position on an edge thereof.

28. The head fixation system of claim 27 further comprising one or more ring locks receivable by one or more of said plurality of fixation ring apertures.

29. The head fixation system of claim 10 wherein said coil support further comprises one or more coil locking devices for locking said MRI coil in position.

30. A method of using a head fixation system comprising: providing a head fixation system including a fixation ring having a plurality of fixation ring slots extending around a circumference thereof, a first fixation post receivable into a first one of the fixation ring slots, said first fixation post including at least one fixation pin; a second fixation post receivable into a second one of the fixation ring slots, said second fixation post including at least one fixation pin; positioning the head fixation ring about a patient's head; adjustably inserting said first fixation post into said first one of the fixation ring slots; adjustably inserting said second fixation post into said second one of the fixation ring slots; positioning said fixation pins against the patient's head to secure said fixation ring against the patient's head.

31. A method of using a head fixation system comprising: positioning a trajectory guide on a patient's head to establish a trajectory for a point of entry; providing a head fixation device including a platform having an upper and lower surface, the platform including MRI coil receiving tracks; a ring mount operably coupled to said upper surface of said platform; a fixation ring rotatably coupled to said ring mount, the fixation ring including a plurality of fixation ring slots extending around a circumference thereof; a first fixation post receivable into a first one of the fixation ring slots; and a second fixation post receivable into a second one of the slots in the fixation ring, wherein the fixation posts include one or more fixation pins; positioning the fixation ring about a patient's head; adjusting the first and second fixation posts in the fixation ring slots; securing the fixation posts to the patient's head with the fixation pins; locking the fixation ring in the ring mount; rotating the fixation ring to provide access to the point of entry; attaching an MRI coil to the platform by positioning the MRI coil in the MRI coil receiving tracks; taking MRI scans to confirm the trajectory.