Repeat fixation for frameless stereotactic procedure

What is claimed is:

1. A medical method comprising the steps, not necessarily in order, of:

positioning a patient for a first medical procedure;

attaching a mechanically free locator to the patient, the locator having at least 3 LEDs thereon and being in registry with a portion of the patient;

using the LEDs a first time to get precise positioning information relative to at least part of the patient;

performing a first medical procedure on the patient;

after the first medical procedure, removing the locator from the patient;

at a later time after the removing of the locator, re-attaching the locator to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached;

after the re-attaching step, using the LEDs a second time to get precise positioning information relative to the at least part of the patient; and

after the re-attaching step, performing a second medical procedure on the patient and

wherein the attaching and re-attaching of the locator is non-invasive and wherein the locator is a bite plate with an external portion connected thereto, and the LEDs are on the external portion, and wherein the attaching includes using a mold of dental impression material to bring the bite plate in registry with teeth of the patient, and wherein the re-attaching uses the mold to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached.

2. The medical method of claim 1 wherein the first medical procedure is an imaging of at least a portion of the patient.

3. The medical method of claim 4 wherein the second medical procedure is a remedial procedure treating at least one problem precisely localized in the first medical procedure.

4. The medical method of claim 3 wherein the second medical procedure uses a probe inserted in the patient for treatment of the patient.

5. The medical method of claim 3 wherein the second medical procedure includes radiotherapy.

6. A medical method comprising the steps, not necessarily in order, of:

positioning a patient for a first medical procedure;

attaching a mechanically free locator to the patient, the locator having at least 3 LEDs thereon and being in registry with a portion of the patient;

using the LEDs a first time to get precise positioning information relative to at least part of the patient;

performing a first medical procedure on the patient;

after the first medical procedure, removing the locator from the patient;

at a later time after the removing of the locator, re-attaching the locator to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached;

after the re-attaching step, using the LEDs a second time to get precise positioning information relative to the at least part of the patient; and

after the re-attaching step, performing a second medical procedure on the patient and

wherein both the first and second medical procedures include radiotherapy.

7. A system for medical procedures, the system comprising:

a locator attachable to a patient, having at least 3 LEDs thereon, and having a registration portion for registration with a portion of a patient's body, the registration portion allowing removal of the locator from the patient and re-attachment to the patient with an identical orientation relative to the portion of the patient as when the locator was previously attached, the locator being mechanically free such that a patient is positionable without applying forces to the locator during patient positioning;

a positioner independent of the locator and operable to secure at least the portion of the patient in a desired position; and

a sensing subsystem for sensing the positions of the LEDs when the patient is in the desired position and wherein the locator is non-invasive and wherein the locator is a bite plate with an external portion connected thereto, and the LEDs are on the external portion, and the bite plate has dental impression material for fabrication of a mold to bring the bite plate in registry with teeth of the patient, and the mold is operable to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached.

8. A system for medical procedures, the system comprising:

a locator attachable to a patient, having at least 3 LEDs thereon, and having a registration portion for registration with a portion of a patient's body, the registration portion allowing removal of the locator from the patient and re-attachment to the patient with an identical orientation relative to the portion of the patient as when the locator was previously attached, the locator being mechanically free such that a patient is positionable without applying forces to the locator during patient positioning;

a positioner independent of the locator and operable to secure at least the portion of the patient in a desired position; and a sensing subsystem for sensing the positions of the LEDs when the patient is in the desired position and further comprising a radiotherapy apparatus for applying radiation treatment to a patient, the positioner and sensing subsystem allowing proper positioning of the patient for applying radiation treatment.

9. A medical method comprising the steps, not necessarily in order, of:

positioning a patient for a first medical procedure;

attaching a locator to a patient, the locator having at least 3 fiducial markers thereon and being in registry with a portion of the patient;

using fiducial markers a first time to get precise positioning information relative to at least part of the patient;

performing a first medical procedure on the patient;

after the first medical procedure, removing the locator from the patient;

at a later time after the removing, re-attaching the locator to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached;

after the re-attaching step, using fiducial markers a second time to get precise positioning information relative to the at least part of the patient; and

after the re-attaching step, performing a second medical procedure on the patient; and

wherein the locator is a bite plate with an external portion connected thereto, and the fiducial markers are on the external portion, and wherein the attaching includes using a mold of dental impression material to bring the bite plate in registry with teeth of the patient, and wherein the re-attaching uses the mold to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached and wherein the second medical procedure uses a probe inserted in the patient for treatment of the patient.

10. A medical method comprising the steps, not necessarily in order, of:

positioning a patient for a first medical procedure;

attaching a locator to a patient, the locator having at least 3 fiducial markers thereon and being in registry with a portion of the

patient;

using fiducial markers a first time to get precise positioning information relative to at least part of the patient;

performing a first medical procedure on the patient;

after the first medical procedure, removing the locator from the patient;

at a later time after the removing re-attaching the locator to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached;

after the re-attaching step, using fiducial markers a second time to get precise positioning information relative to the at least part of the patient; and

after the re-attaching step, performing a second medical procedure on the patient; and

wherein the locator is a bite plate with an external portion connected thereto, and the fiducial markers are on the external portion, and wherein the attaching includes using a mold of dental impression material to bring the bite plate in registry with teeth of the patient, and wherein the re-attaching uses the mold to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached and wherein the fiducial markers used the first time are objects other than LEDs and the fiducial markers used the second time are LEDs put on the external portion at locations of the objects.

11. A medical method comprising the steps, not necessarily in order, of:

positioning a patient for a first medical procedure;

attaching a locator to a patient, the locator having at least 3 fiducial markers thereon and being in registry with a portion of the patient;

using fiducial markers a first time to get precise positioning information relative to at least part of the patient;

performing a first medical procedure on the patient;

after the first medical procedure, removing the locator from the patient;

at a later time after the removing, re-attaching the locator to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached;

after the re-attaching step, using fiducial markers a second time to get precise positioning information relative to the at least part of the patient; and

after the re-attaching step, performing a second medical procedure on the patient; and

wherein the locator is a bite plate with an external portion connected thereto, and the fiducial markers are on the external portion, and wherein the attaching includes using a mold of dental impression material to bring the bite plate in registry with teeth of the patient, and wherein the re-attaching uses the mold to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached and wherein the fiducial markers used the first and second times are LEDs, wherein the using of the fiducial markers the first and second times utilizes a sensing subsystem for sensing the positions of the LEDs, and wherein, before performing each of the first and second medical procedures, the patient is positioned using a positioner independent of the locator to secure at least the portion of the patient in a desired position.

12. A system for medical procedures, the system comprising:

a locator attachable to a patient, having at least 3 fiducial markers thereon, and having a registration portion for registration with a portion of a patient's body, the registration portion allowing removal of the locator from the patient and re-attachment to the patient with an identical orientation relative to the portion of the patient as when the locator was previously attached, the locator being mechanically free such that a patient is positionable without applying forces to the locator during patient positioning;

a positioner independent of the locator and operable to secure at least the portion of the patient in a desired position; and

a sensing subsystem for sensing the positions of the fiducial markers when the patient is in the desired position; and

wherein the locator is a bite plate with an external portion connected thereto, and the fiducial markers are on the external portion, and the bite plate has a mold to bring the bite plate in registry with teeth of the patient, and the mold is operable to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached and wherein the fiducial markers includes three LEDs which uniquely define a plane.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

The present invention relates to device, system and method for stereotactic medical procedures. More specifically, it provides for repeated accurate positioning (fixation) of a patient or part of a patient for carrying out medical procedures which are done at different times.

Various medical procedures involve repeated treatments at different times. For example, application of radiation is sometimes used for treating brain tumors or other conditions. Although a single application of radiation may sometimes be used, under many circumstances there are sound medical reasons to use repeated application of radiation at different times.

The treatment of a radiation therapy patient can be broken down into four stages. These are (1) diagnostic evaluation, (2) treatment planning, (3) simulation and (4) treatment. Our repeat fixation device is applicable to the latter three phases of the treatment process. In the first stage of diagnostic evaluation the physician decides which tissues are at risk of disease and should be targeted. The patient may undergo many diagnostic tests including angiography, computerized tomography (CT) and magnetic resonance (MR) imaging. After the physician is satisfied that they have identified the tissues at risk, the patient then undergoes a process known as treatment simulation. This process involves obtaining a set of images such as plane films, digital images, CT, MRI, and ultrasound images. These radiographs allow the physician to select a specific path for each radiation beam which only includes the tissues at risk and excludes normal tissues. Because the tissues the physician has targeted are often radiographically transparent the physician routinely relies upon radiographic landmarks to infer the proper beam alignment. These same landmarks are subsequently imaged on similar radiographs taken with the therapeutic x-ray beam prior to administering the radiation treatment. These pretreatment radiographs, which are known as therapy portal films, allow the physician to judge the appropriate alignment of the treatment beam and the patients anatomy. The frequency at which these portal films are repeated is dependent upon the complexity of the patient setup and the proximity of the beam to critical structures (such as a patient's optic nerve).

A routine course of radiation therapy may span anywhere from 10 to 64 fractions over a period of two to six weeks. The number of treatments dependent upon the specifics of the particular disease. For each fraction the patient must be repositioned at the teletherapy unit and aligned relative to the radiation beam.

There exists a clinical situation in which the target tissues cannot be adequately localized by their proximity to radiographically opaque structures as required by the above simulation procedure. Arteriovenous malformations, acoustic neurinomas and other small intracranial targets are examples of such clinical entities. To enable the identification, and subsequent treatment of such targets, a new and very powerful technique known as radiotherapy has been developed. (Radiosurgery is usually considered to be a single fraction radiotherapy treatment, meaning a single treatment, although it may also be more broadly interpreted. Multiple radiotherapy treatments are often called high precision radiotherapy or fractioned stereotactic radiotherapy.) This technique allows small intracranial targets to be identified and treated to a very high degree of precision.

The radiosurgical technique uses stereotactic principles for targeting, localization and treatment. The procedure begins with a stereotactic reference system being fixed to the patient's skull. This reference system remains fixed relative to all intracranial points throughout the entire radiosurgical procedure. All diagnostic exams, such as angiography, CT and MR scanning include a set of fiducial markers which allow all points within the image to be localized relative to the stereotactic reference frame.

Once the target tissues have been identified the path of radiation beams can be mathematically computed. The computer algorithms, which support this procedure, allow the clinician to evaluate the amount of dose which would be deposited within the patient if the simulated beams were actually x-ray beams were applied along the proposed paths. In an attempt to arrive at a treatment plan which adequately confines the radiation dose to the target tissues while limiting the dose to all normal tissues the beams of radiation are modified, eliminated or new beams added to the plan. Once a plan with an acceptable dose distribution has been arrived at the information on beam trajectory is transferred to the radiotherapy treatment unit. A single fraction of radiation is then given to the patient and the stereotactic frame is removed. The entire length of the procedure, from frame application through treatment, usually spans 6 to 8 hours.

The present inventors' prior U.S. patents listed below, assigned to the assignee of the present application and hereby incorporated by reference disclose techniques for providing stereotactic radiosurgery with a high degree of precision:

______________________________________ U.S. Pat. No. Issue Date Title ______________________________________ 5,027,818 July 2, 1991 DOSIMETRIC TECHNIQUE FOR STEREOTACTIC RADIOSURGERY 5,189,687 February 23, 1993 APPARATUS FOR STEREOTACTIC RADIOSURGERY ______________________________________

The techniques of the inventors' above patents allow the patient to be precisely positioned relative to radiation beams of stereotactic radiosurgery to within 0.2 mm plus or minus 0.1 mm. Although this works very well for single fraction therapy, there exist clinical settings where fractionating the total dose, i.e. dividing the dose into many small fractions, would yield additional therapeutic advantage. In the radiotherapy procedure, once the reference frame has been removed from the patient the relationship between intracranial target points and the reference system is lost. Because the above procedure would require the reference frame to remain fixed to the patient's skull through the entire course of treatment, which may last several weeks, this approach is considered inappropriate for fractionated therapy. Alternately, each fractional treatment would require a laborious and time-consuming procedure to redetermine patient position for second and subsequent treatments.

There exist several different techniques for non-invasive repeat fixation. These methods can be broken down into three basic categories. These are bite plate systems, contour realignment systems and mask systems. All of these systems have design flaws which can lead to unacceptable, and undetectable, positional errors.

The mask techniques have been used in radiation therapy for over three decades. In these system a custom mask, which snugly fits either the face or the entire head, is fabricated. For high precision radiotherapy the mask is then attached to a stereotactic reference frame, similar to the frame used for any stereotactic procedure. Prior to each diagnostic exam the patient is placed into the mask/frame system and normal stereotactic fiducial systems are used for image registration.

Mask immobilization and repositioning systems have been used extensively in radiation therapy. From multiple reports in the literature mask systems appear to have a repeat fixation tolerance no better than 3 to 5 mm. It is our opinion that this level of accuracy is unacceptable for fractionated radiotherapy.

Bite plate systems have also been used in radiotherapy for several decades. This technique requires the fabrication of a customized bite plate. The plate fits snugly onto the patient's teeth. As with the mask/frame systems, the bite plate is fixed to a stereotactic reference frame which then accepts the routine set of fiducial markers for both plane film radiography, CT and MR scanning. The primary disadvantage of this system is that the bite plate is used for both localization and patient fixation. The bite plate not only provides the reference for stereotactic localization, but it also is the mechanism which is used to move the patient into position. Moving the patient by use of the bite plate produces torque on the bite plate-teeth interface. An analysis of this approach reveals that very small movements in the bite plate position, relative to the patient's teeth, can result in large translations and rotations of the intracranial targets. Since no method of alignment verification has ever been developed, these errors go undetected.

An alternate system for patient positioning uses the patient's own anatomical contours as the stereotactic reference system. In this approach a CT or MR scan is taken and a three dimensional reconstruction of the patient's surface is obtained. These contours act as the reference system for stereotactic localization.

The usual diagnostic exams are carried out and the treatment is then planned using the same stereotactic principles used in routine radiotherapy. The target is identified and the patient's surface contour coordinates are measured relative to the isocenter. The patient is placed at the teletherapy treatment unit and the surface contours are again obtained through the use of surface digitization. A set of algorithms then calculate the translations as well rotations required to reposition the patient's target over the teletherapy units isocenter. The accuracy of such systems under clinical test conditions have been shown to be approximately two to three mm.

When performing fractionated radiotherapy, accuracy in applying the radiation is very important. Some tumors or other conditions require that the radiation be concentrated in relatively small volumes. Misalignment of the radiation beam may cause an insufficient amount of radiation to be applied to the tumor or other target. Further, such misalignment may increase the likelihood and/or degree of damage to healthy tissue adjacent the tumor or other target.

Fractionated radiotherapy may be imprecise if the tumor or other target cannot be localized with a sufficient degree of accuracy. However, this need for proper localization is the same need which one has when performing single dose radiotherapy and this need is addressed by the present inventors' incorporated by reference patents. The additional factor in fractionated radiotherapy is the need to easily and accurately repeat a position of the patient. If the position of the patient was accurate relative to the first treatment, the repositioning should normally cause the patient to assume the exact same position (relative to the treatment mechanism) for the second and subsequent treatments. However, if the second or other subsequent treatment is performed with the patient only slightly moved from the first treatment position, this will introduce inaccuracies. The repeat fixation techniques discussed above have the indicated disadvantages.

More generally, the need for repeat fixation of a patient or portion of a patient exists outside of radiotherapy. In the general case, one wishes to perform a first medical procedure on a patient with a precise localization of portions of the patient, and, at some later time, perform a second medical procedure on the patient with a precise localization of portions of the patient. One can repeat laborious and time-consuming localization steps for the second medical procedure, but this increases medical costs and complexity. As used herein, a medical procedure is a procedure for diagnostic and/or remedial purposes.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide a new and improved method and system for repeat fixation in performing medical procedures.

A more specific object of the present invention is to provide for highly precise non-invasive repeat fixation.

A further object of the present invention is to provide repeat fixation in which a locator is mechanically independent from any structures used for positioning the patient. That is, any structure used to position the patient does not move the locator except by way of the patient.

Yet another object of the present invention is to provide repeat fixation for stereotactic radiotherapy.

A further object of the present invention is to provide repeat fixation which allows relatively fast relocalization of a patient after an initial localization.

Yet another object of the present invention is to provide repeat fixation which minimizes or avoids the disadvantages of prior techniques discussed above.

The above and other features of the present invention which will be more readily understood when the following detailed description is considered in conjunction with the accompanying drawings are realized by a medical method including the steps, not necessarily in order, of: positioning a patient for a first medical procedure; and attaching a mechanically free locator to a patient, the locator having at least 3 LEDs (light emitting diode) thereon and being in registry with a portion of the patient. As used herein, a mechanically free locator is one which is used for localization without being rigidly fixed to a structure other than possibly a portion of a patient. LEDs are used a first time to get precise positioning information relative to at least part of the patient.

A first medical procedure is performed on the patient. After the first medical procedure, the locator is removed from the patient. At a later time, the locator is re-attached to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached. After the re-attaching step, the LEDs are used a second time to get precise positioning information relative to the at least part of the patient. After the re-attaching step, a second medical procedure is performed on the patient.

Preferably, the attaching and re-attaching of the locator is non-invasive. As used herein, non-invasive shall mean that no holes need to be created in a patient and no patient tissue needs to be removed in order to attach and re-attach the locator.

More specifically, the locator is a bite plate with an external portion connected thereto, and the LEDs are on the external portion. The attaching includes using a mold of dental impression material to bring the bite plate in registry with teeth of the patient, and wherein the re-attaching uses the mold to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached.

In one technique of the invention, the first medical procedure is an imaging of at least a portion of the patient and the second medical procedure is a remedial procedure treating at least one problem precisely localized in the first medical procedure. The second medical procedure may use a probe inserted in the patient for treatment of the patient or the second medical procedure includes radiotherapy.

In another aspect of the invention, both the first and second medical procedures include radiotherapy.

The using of the LEDs the first and second times utilizes a sensing subsystem for sensing the positions of the LEDs. Before performing the second medical procedure, the patient is positioned using a positioner independent of the locator to secure at least the portion of the patient in a desired position.

The present invention may alternately be described as a system for medical procedures, the system including a locator attachable to a patient, having at least 3 LEDs thereon, and having a registration portion for registration with a portion of a patient's body. The registration portion allows removal of the locator from the patient and re-attachment to the patient with an identical orientation relative to the portion of the patient as when the locator was previously attached. The locator is mechanically free such that a patient is positionable without applying forces to the locator during patient positioning. The system has a positioner independent of the locator and operable to secure at least the portion of the patient in a desired position. A sensing subsystem is operable for sensing the positions of the LEDs when the patient is in the desired position. The locator is non-invasive. The locator is more specifically a bite plate with an external portion connected thereto, and the LEDs are on the external portion, and the bite plate has dental impression material for fabrication of a mold to bring the bite plate in registry with teeth of the patient, and the mold is operable to bring the bite plate in registry with teeth of the patient with an identical orientation relative to the teeth as when the bite plate was previously attached.

The system further includes a radiotherapy apparatus for applying radiation treatment to a patient, the positioner and sensing subsystem allowing proper positioning of the patient for applying radiation treatment. The system further includes an imaging subsystem for imaging the patient.

The present invention may further be described as a medical method comprising the steps, not necessarily in order, of: positioning a patient for a first medical procedure; attaching a locator to a patient, the locator having at least 3 fiducial markers thereon and being in registry with a portion of the patient; using fiducial markers a first time to get precise positioning information relative to at least part of the patient; and performing a first medical procedure on the patient. After the first medical procedure, the locator is removed from the patient. At a later time after the removal of the locator, the locator is re-attached to the patient, the locator again being in registry with the portion of the patient and having an identical orientation relative to the portion of the patient as when the locator was previously attached. After the re-attaching step, fiducial markers are used a second time to get precise positioning information relative to at least part of the patient. After the re-attaching step, a second medical procedure is performed on the patient. The locator is a bite plate with an external portion connected thereto, and the fiducial markers are on the external portion, and wherein the attaching includes using a mold of dental impression material to bring the bite plate in registry wi