Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-04-28
2002-11-19
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S427000, C600S429000, C600S431000, C606S130000
Reexamination Certificate
active
06484049
ABSTRACT:
BACKGROUND
The present invention relates to medical and surgical imaging, and in particular to intraoperative or perioperative imaging in which images are formed of a region of the patient's body and a surgical tool or instrument is applied thereto, and the images aid in an ongoing procedure. It is of a special utility in surgical procedures such as brain surgery and arthroscopic procedures on the knee, wrist, shoulder or spine, as well as certain types of angiography, cardiac procedures, interventional radiology and biopsies in which x-ray images may be taken to display, correct the position of, or otherwise navigate a tool or instrument involved in the procedure.
Several areas of surgery have required very precise planning and control for the placement of an elongated probe or other article in tissue or bone that is internal or difficult to view directly. In particular, for brain surgery, stereotactic frames to define the entry point, probe angle and probe depth are used to access a site in the brain, generally in conjunction with previously compiled three-dimensional diagnostic images such as MRI, PET or CT scan images which provide accurate tissue images. For placement of pedicle screws in the spine, where visual and fluoroscopic imaging directions cannot capture an axial view necessary to center the profile of an insertion path in bone, such systems have also been useful.
When used with existing CT, PET or MRI image sets, these previously recorded diagnostic image sets themselves define a three dimensional rectilinear coordinate system, by virtue of their precision scan formation or the spatial mathematics of their reconstruction algorithms. However, it may be necessary to correlate the available fluoroscopic views and anatomical features visible from the surface or in fluoroscopic images with features in the 3-D diagnostic images and with the external coordinates of the tools being employed. This is often done by providing implanted fiducials, and adding externally visible or trackable markers that may be imaged, and using a keyboard or mouse to identify fiducials in the various images, and thus identify common sets of coordinate registration points in the different images, that may also be trackable in an automated way by an external coordinate measurement device, such as a suitably programmed off-the-shelf optical tracking assembly. Instead of imageable fiducials, which may for example be imaged in both fluoroscopic and MRI or CT images, such systems can also operate to a large extent with simple optical tracking of the surgical tool, and may employ an initialization protocol wherein the surgeon touches or points at a number of bony prominences or other recognizable anatomic features in order to define the external coordinates in relation to the patient anatomy and to initiate software tracking of those features.
Generally, systems of this type operate with an image display which is positioned in the surgeon's field of view, and which displays a few panels such as a selected MRI image and several x-ray or fluoroscopic views taken from different angles. The three-dimensional diagnostic images typically have a spatial resolution that is both rectilinear and accurate to within a very small tolerance, e.g., to within one millimeter or less. The fluoroscopic views by contrast are distorted, and they are shadowgraphic in that they represent the density of all tissue through which the conical x-ray beam has passed. In tool navigation systems of this type, the display visible to the surgeon may show an image of the surgical tool, biopsy instrument, pedicle screw, probe or the like projected onto a fluoroscopic image, so that the surgeon may visualize the orientation of the surgical instrument in relation to the imaged patient anatomy, while an appropriate reconstructed CT or MRI image, which may correspond to the tracked coordinates of the probe tip, is also displayed.
Among the systems which have been proposed for effecting such displays, many rely on closely tracking the position and orientation of the surgical instrument in external coordinates. The various sets of coordinates may be defined by robotic mechanical links and encoders, or more usually, are defined by a fixed patient support, two or more receivers such as video cameras which may be fixed to the support, and a plurality of signaling elements attached to a guide or frame on the surgical instrument that enable the position and orientation of the tool with respect to the patient support and camera frame to be automatically determined by triangulation, so that various transformations between respective coordinates may be computed. Three-dimensional tracking systems employing two video cameras and a plurality of emitters or other position signaling elements have long been commercially available and are readily adapted to such operating room systems. Similar systems may also determine external position coordinates using commercially available acoustic ranging systems in which three or more acoustic emitters are actuated and their sounds detected at plural receivers to determine their relative distances from the detecting assemblies, and thus define by simple triangulation the position and orientation of the frames or supports on which the emitters are mounted. When tracked fiducials appear in the diagnostic images, it is possible to define a transformation between operating room coordinates and the coordinates of the image.
In general, the feasibility or utility of a system of this type depends on a number of factors such as cost, accuracy, dependability, ease of use, speed of operation and the like. Intraoperative x-ray images taken by C-arm fluoroscopes alone have both a high degree of distortion and a low degree of repeatability, due largely to deformations of the basic source and camera assembly, and to intrinsic variability of positioning and image distortion properties of the camera. In an intraoperative sterile field, such devices must be draped, which may impair optical or acoustic signal paths of the signal elements they employ to track the patient, tool or camera.
More recently, a number of systems have been proposed in which the accuracy of the 3-D diagnostic data image sets is exploited to enhance accuracy of operating room images, by matching these 3-D images to patterns appearing in intraoperative fluoroscope images. These systems may require tracking and matching edge profiles of bones, morphologically deforming one image onto another to determine a coordinate transform, or other correlation process. The procedure of correlating the lesser quality and non-planar fluoroscopic images with planes in the 3-D image data sets may be time-consuming, and in those techniques that rely on fiducials or added markers, the processing necessary to identify and correlate markers between various sets of images may require the surgeon to follow a lengthy initialization protocol, or may be a slow and computationally intensive procedure. All of these factors have affected the speed and utility of intraoperative image guidance or navigation systems.
Correlation of patient anatomy or intraoperative fluoroscopic images with precompiled 3-D diagnostic image data sets may also be complicated by intervening movement of the imaged structures, particularly soft tissue structures, between the times of original imaging and the intraoperative procedure. Thus, transformations between three or more coordinate systems for two sets of images and the physical coordinates in the operating room may require a large number of registration points to provide an effective correlation. For spinal tracking to position pedicle screws it may be necessary to initialize the tracking assembly on ten or more points on a single vertebra to achieve suitable accuracy. In cases where a growing tumor or evolving condition actually changes the tissue dimension or position between imaging sessions, further confounding factors may appear.
When the purpose of image guided tracking is to define an operation on a rigid or bony structure near the surfac
Gregerson Gene
Kapur Tina
Lin Faith
Seeley Teresa
Dellapenna Michael A.
GE Medical Systems Global Technology Company LLC
Lateef Marvin M.
Lin Jeoyuh
McAndrews Held & Malloy Ltd.
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