Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-06-20
2004-04-20
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06725079
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magnetic resonance imaging. More particularly it relates to a device and method for determining the position, direction, and/or rotational angle of a pointing device used with an imaging system and in particular with a magnetic resonance imaging apparatus.
BACKGROUND OF THE INVENTION
When performing a medical scanning procedure, precision in localization of different objects or areas within the patient's tissue is of crucial importance. This is especially true for surgical procedures performed in a closed body area, when visualization of the target is impossible (i.e. within the patient's head, stomach etc.). One example is brain surgery, where knowledge of the exact localization of various anatomies allows planning of the procedure and avoiding unnecessary damage to healthy surrounding tissue. Recent diagnostic methods such as computerized tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), nuclear medical apparatus and other medical scanning methods allow accurate pre-operative diagnosis. Nevertheless, these pre-operative pictures are of limited relevance once a surgical procedure is performed since they depend on the coordinates of the patient, which might change during the course of operation due to reasons such as a shift in the patient's position.
To overcome this problem, stereotactic surgery and navigation are commonly used and are based on pre-operative images and on rigid markers fixed to the patient. Still, registration of the patient is always needed to compare pre-operative scans and the current situation during surgery. Moreover, any changes occurring during surgery are not accounted for.
Registration of the patient as a reference for determining the position of surgical instruments or probes is known.
In U.S. Pat. No. 5,782,765 (Jonkman), titled MEDICAL POSITIONING SYSTEM, filed in 1996, and incorporated herein by reference, there was disclosed a method and apparatus for positioning a probe inside a patient including a plurality of transmitter/receiver nodes arranged around the patient for communicating with the probe and generating navigation signals, a system for generating one or more positional signals in response to the navigational signals, and a system for collecting and analyzing those positional signals to determine the location of the medical instrument inside the patient's body. The transmitting/receiving nodes may be arranged on a flexible blanket which is wrapped around and adhered to the patient's body or over a table supporting the patient's body.
U.S. Pat. No. 5,871,455 (Bucholz), entitled SYSTEM FOR INDICATING THE POSITION OF A SURGICAL PROBE WITHIN A HEAD ON AN IMAGE OF THE HEAD, filed in 1995, suggested a similar approach. There was disclosed a system for determining a position of a probe relative to an object such as a head of a body of a patient. The head includes a surface such as a forehead having a contour. Cross sectional images of the head are scanned and stored as a function of the forehead contour. If the forehead contour does not appear in the scan images, then the position of the forehead contour relative to the scan images is determined with an optical scanner and a ring. During surgery, the optical scanner also determines the position of the forehead relative to the ring. An array for receiving radiation emitted from the probe and from the ring generates signals indicating the position of the tip of the probe relative to the ring. A stereotactic imaging system generates and displays an image of the head corresponding to the measured position of the tip of the probe. The system may also display scan images from different scanning technologies which scan images correspond to the same position in the head (See also U.S. Pat. No. 5,383,454).
In U.S. patent application Ser. No. 09/545,383 (Katznelson, et al), entitled SYSTEM AND METHOD OF INTERACTIVE POSITIONING, filed Apr. 7, 2000 and incorporated herein by reference, there was disclosed a positioning system for determining the relation between a coordinate set of a scanning apparatus and a coordinate set of a tracking system so as to allow determining the position of a selected target on an image of a patient acquired by the scanning apparatus in the coordinate set of the tracking apparatus and vice versa, the system comprising:
Reference point means positioned in predetermined location relative to the coordinate set of the scanning apparatus;
Tracking means adapted to detect and determine the position of said reference points means, relative to the coordinate set of the tracking means;
Processing means adapted to communicate with said tracking means and adapted to determine the relation between the coordinate set of the scanning apparatus and the coordinate set of the tracking means, and adapted to translate the coordinates of the target on the image acquired by the scanning apparatus to corresponding coordinates on the coordinate set of the tracking means.
However, there are several sources of distortion that affect the accuracy of translation of the coordinate set of the tracking means to the target on the image acquired by the scanning apparatus, which is assumed here to be a magnetic resonance imaging (MRI) device.
First of all, distortion can occur due to the difference between the geometry of the tracking system and that of the image.
The tracking coordinates are Euclidian (having three orthogonal axes where the unit of measurement is constant) whereas the image is only approximately Euclidean. Mapping between the two becomes increasingly inaccurate as the tracking device (pointer) is moved away from the center of the image volume. This inaccuracy can be globally corrected by measuring the magnetic field and the gradient field. However for greater accuracy, local corrections are required. For example, when moving to a given point on an imaged object, increasingly local corrections are required as the pointer moves in absolute space closer and closer to the target on the image.
It is therefore desirable that there be a means for generating local corrections for any subvolume of the imaging volume.
Another limitation of the correction is that it becomes invalid if there are changes in environmental factors over time. Such factors include the effect of movement of ferromagnetic devices and of changes in temperature.
Each time that such an environmental change occurs, it can cause a change in the distortion in the image and therefore a new correction must be generated. It is sometimes inconvenient or even impossible to generate new corrections each time such an environmental change creates the need for one. For example, when MRI is used during surgery, the patient would have to be moved so that the correction could be generated.
Therefore it is also desirable that there be a way to easily correct for discrepancies in the mapping of the tracked point to the image.
The incorporation of magnetic resonance imaging (MRI) techniques in surgical procedures is known for some years now. Interventional MRI (iMRI), also referred to as intraoperative MRI, allows surgeons to obtain a practically real time image of the patient's body part under surgery and to receive immediate feedback on the outcome of the operation carried out.
Israel Pat. Appl. No. 119558 (Katznelson et al.) filed Nov. 4, 1996, incorporated herein by reference, discloses a compact, transportable, intra-operative MRI System, which includes a host computer coupled to a central electronics system which may be coupled to different MRI probes.
Compact MRI systems for performing local imaging of specific body parts or organs may use a hollow tube-like magnet assembly or other assemblies, such as two opposing magnets, such as described in U.S. Pat. No. 5,900,793 (Katznelson et al.), filed Jul. 23, 1997 incorporated herein by reference.
U.S. Pat. No. 5,735,278 (Hoult et al.), filed Mar. 15, 1996, disclosed an apparatus for use in surgical procedure comprising an operating table for receiving a patient for su
Katznelson Ehud
Zuk Yuval
Eitan, Pearl, Latzer & Cohen Zedek LLP
Jain Ruby
Jaworski Francis J.
Odin Medical Technologies Ltd.
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