Our group has developed and tested a noninvasive image registration technique that does not require a special imaging study following the application of a head frame or radiological markers on the patient. This registration method involves performing automatic alignment between segmented scalp reconstructions from CT or MRI fitted with arc surfaces traced with the RegulusTM NavigatorTM. This paper will present a quantitative analysis of this technique compared to other stereotactic and image-guided registration techniques. This noninvasive surface alignment technique has been found to be a viable, quick and accurate method of performing image-guided registration.
A three-dimensional magnetic field digitizer has been interfaced the COMPASS Stereotactic System to act as a measuring device aiding in computer-assisted volumetric procedures. Reference points on the stereotactic headholder are used to create a transformation matrix to convert the digitizer coordinates to stereotactic coordinates, allowing the location of the stylus to be displayed on CT and reconstructed tumor volume images to maintain the surgeon''s orientation. This technology is an adjunct to and employs treatment planning software of the system to calculate a target and determine a safe trajectory to a lesion. Environmental effects of the magnetic field have been studied to determine overall accuracy and reliability of the system. A device was developed to map the magnetic field in efforts to compensate for environmental effects. The device has been utilized on five procedures. We have found it to be a useful tool in aiding the surgeon in locating the surgical field preoperatively and maintaining orientation intraoperatively.
Display of three-dimensionally rendered images derived from radiological data sets is often suggested to be useful for surgical and radiation treatment planning in neurosurgery. Nevertheless, physicians will often note (off the record) that these rendered images are ''just a pretty picture'' and are not clinically useful. This paper will discuss our three-dimensional rendering and quantitative analysis software and its primary use in evaluating and utilizing frameless stereotactic methodologies. A variety of concepts and techniques will be discussed. Specifically, a computer graphic and statistical-based technique will be presented that enables timely and measurable image registration between radiological image space and the coordinate system of computer-driven surgical devices in the operating room. This technique may be utilized to maintain a surgeon''s orientation and to quantitatively and graphically monitor the position of probes and instruments in the surgical field. Three-dimensional quantitative results of phantom testing will be presented. Correlation to and validation against stereotactic imaging calculations using the compass stereotactic system will also be discussed. These computer graphic/statistical-based techniques are applicable for evaluating the accuracy of any frameless stereotactic device including, but not limited to robotic arms, spark gap, LED and magnetic field digitizers.
This study demonstrates that the detection of LC test patterns for MR imaging QC programs can be successfully developed and that their response can model the human visual detection system of expert MR QC readers.
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