Abstract
The system consists of an inverted U-shaped frame with right angled corners, so mounted that it can be adjusted vertically, antero-posteriorly and made to rotate on an axis ("the axis of the frame") formed by its free ends. The frame carries an arc probe carrier whose probe holder slides on an arc which is centered on the axis of the frame. The centre of the probe holder and axis of fram lie in one plane "The plane of probe". After positioning the patient in the frame on the CT table, using either table indexing or laser positioning light, the plane of the probe is brought in the CT plane of the target. Once in this CT plane, direct measurements can be obtained so as to bring the axis of the frame passing through the target and centering the arc on the target. The frame can then be rotated to any desired angle and the probe holder can be moved to any position on the arc without altering the direction of the probe with respect to the target. As the structures in the probe plane are constructed of plastic, it can be used within the scanner with practically no artifacts, and direct measurements can be obtained without any calculations. This system can be used in any total body scanner with standard features and no special computer programming is necessary. This is a simple and truly CT-oriented stereotactic system with a high degree of accuracy.