Image analysis – Applications – Biomedical applications
Reexamination Certificate
1999-02-16
2003-05-06
Mehta, Bhavesh (Department: 2625)
Image analysis
Applications
Biomedical applications
C128S922000, C378S021000, C378S062000, C382S132000, C382S173000, C600S414000, C600S424000, C600S426000
Reexamination Certificate
active
06560354
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to an apparatus and method for the registration of images to physical space by the use of a weighted combination of points and surfaces. The present invention is more particularly directed to the registration of images of patients' body parts to the actual patients' body parts for surgery although it is applicable to any use in which a geometrical transformation represents rigid-body motion or approximate rigid-body motion. Such images can be taken by X-ray computed tomography (CT) or the like.
Registration is the determination of a one-to-one mapping or transformation between the coordinates in one space and those in another such that points in the two spaces that correspond to the same anatomic point are mapped to each other. Registration of multimodal images makes it possible to combine different types of structural information [such as X-ray computed tomography (CT) and magnetic resonance (MR) images] and functional information [such as positron emission tomography (PET) and single photon emission tomography (SPECT)] for diagnosis and surgical planning. Registration of images acquired with the same modality at different times allows quantitative comparison of serial data for longitudinal monitoring of disease progression/regression and postoperative follow up.
Registration of preoperative images with the physical space occupied by the patient during surgery is a fundamental step in interactive, image-guided surgery techniques. Surgical navigation systems use the image-to-physical transformation to track in real time the changing position of a surgical probe on a display of the preoperative images. Stereotactic procedures use the transformation to direct a needle (stereotactic biopsy) or energy (stereotactic radiosurgery) to a surgical target (e.g., tumor) located in the images.
Many methods have been used to register medical images. Image-guided stereotactic surgical procedures have been performed since the early 1970's using stereotactic frame systems. Such systems generally include a reference frame that provides rigid skull fixation using pins or screws and establishes a stereotactic coordinate system in physical space, a method for stereotactic image acquisition, and a system for mechanical direction of a probe or other surgical instrument to a defined intracranial point. Most current systems relate image space to the physical coordinate space established by the reference frame by attaching a localizing system consisting of N-shaped fiducials during image acquisition. Frames permit neurosurgeons to perform biopsies and to resect deep-seated and previously inaccessible lesions.
Frame-based techniques, however, have several limitations. The frames are bulky and may interfere with the surgical exposure. Patients complain about the weight of the frame and the pain associated with its application. The surgeon is typically limited to target points on a linear trajectory. Perhaps most importantly, frame-based stereotactic systems do not provide real-time feedback to the surgeon about anatomic structures encountered in the surgical field.
To address such limitations, a number of frameless stereotactic systems have been developed over the last decade. Of the many frameless methods that have been used to register medical images, it appears that point-based and surface-based techniques are the most useful for image-to-physical registration. There is mounting evidence that voxel-intensity-based methods might be the easiest and most accurate way to perform mono- and multi-modality image-to-image registration, but their use for image-to-physical registration is probably rather limited until higher quality three-dimensional (3-D) intraoperative images become readily available. Point-based registration involves determining the coordinates of corresponding points in different images and/or physical space and computing the geometrical transformation that best aligns those points, generally in a least-squares sense. Many investigators have performed point-based image-to-physical registration using external anatomic landmarks (e.g., internal and external canthi, nasion), skin-affixed markers, or bone-implanted markers; a recent survey cites more than 70 publications devoted to point-based registration. Surface-based registration involves determining corresponding surfaces in different images and/or physical space and computing the geometrical transformation that best matches those surfaces. Researchers have performed surface-based image-to-physical registration using the skin or the outer skull surface. Points and surfaces can be easily and accurately acquired in physical space using 3-D probes (e.g., articulated mechanical, electromagnetic, ultrasonic, optical), stereo video cameras, and/or laser range-finders.
Most previously reported registration techniques that align three-dimensional (3-D) image volumes by matching geometrical features such as points, curves, or surfaces use a single type of feature. Patents have been issued for the idea of point-based registration using bone-implanted markers (e.g., G. S. Allen, “Method and Apparatus for Imaging the Anatomy,” U.S. Pat. No. 5,016,639, May 1991) and surface-based registration (e.g., C. A. Pelizzari and G. T. Y. Chen, “Means to Correlate Images from Scans Taken at Different Times Including Means to Determine the Minimum Distances between a Patient Anatomical Contour and a Correlating Surface,” U.S. Pat. No. 4,977,505, December 1990). An example of a surface commonly used for registration is the skin-air interface.
A technique has been developed to use multiple features simultaneously (C. R. Meyer, G. S. Leichtman, J. A. Brunberg, R. L. Wahl, and L. E. Quint, “Simultaneous usage of homologous points, lines, and planes for optimal, 3-D, linear registration of multimodality imaging data,”
IEEE Transactions on Medical Imaging
, 14: 1-11, 1995). However, that method uses points, lines, and planes and is accordingly less general and less useful than is desired, since lines are special cases of curves and planes are special cases of surfaces.
SUMMARY OF THE INVENTION
It will be readily apparent from the above discussion that a need still exists in the art for a method and apparatus for 3-D image registration that provides high accuracy while minimizing the need for invasive techniques and other sources of patient discomfort.
Accordingly, it is an object of the invention to allow accurate 3-D image registration without the need for frames and with only minimal need for markers.
Another object of the invention is to allow 3-D image registration using a combination of points and surfaces.
Yet another object of the invention is to allow 3-D image registration which is not limited to points, lines and planes.
Still another object of the invention is to allow 3-D image registration through weighting of the various features to be registered.
A still further object of the invention is to allow 3-D image registration while avoiding the above-noted deficiencies in the prior art.
To achieve the above and other objects, the present claimed invention is directed to a 3-D image registration method that uses a weighted combination of multiple geometrical features simultaneously. The method uses an algorithm, called a weighted geometrical feature (WGF) registration algorithm, which has the capability of using points, curves (e.g., line segment sets), and surfaces (e.g., triangle sets). The result of the registration is a transformation function which is used in guiding surgical operations. The present invention is further directed to an apparatus for carrying out the algorithm and performing the surgical operations in accordance with the transformation function.
The main idea of the present invention can be summarized briefly as follows:
1) If extrinsic markers (e.g., skin-affixed or bone-implanted markers) are to be used for registration, first attach such markers to the patient in the region of the anatomy to be imaged and registered.
2) Acquire a 3-D image (
Fitzpatrick J. Michael
Maciunas Robert J.
Maurer, Jr. Calvin R.
Blank Rome LLP
Desire Gregory
Mehta Bhavesh
University of Rochester
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