Abstract: Repeat fixation for medical procedures is accomplished using a non-invasive locator, specifically a bite plate. The bite plate has at least three fiducial markers on it. The fiducial markers may be LEDs, radiopaque markers for angiography or computerized tomography (CT) imaging or magnetic resonance markers for magnetic resonance (MR) imaging. By detecting the position of the markers, the position of features within the patient (such as a brain tumor or other intracranial target to which radiation is to be applied) can be determined with great precision. Since the bite plate has been molded to uniquely fit to the patient's teeth, it may be removed after an initial imaging of the patient. The bite plate may then be re-attached one or more times to the teeth and the location of the features will be in a known position relative to the sensed markers.

Abstract: Stereostactic radiosurgery apparatus for eliminating misalignments due to mechanical inaccuracies and sag of a linear accelerator radiation-emitting head which is swung through an arc comprises a guiding and support structure with a first bearing system for accurately rotating a collimator through a precise arc in a vertical plane with respect to a predetermined center point in the plane corresponding to a treatment location, a second gimbal bearing system for coupling the collimator to the head so that the rotating head can drive the collimator through its arc while mechanically uncoupling the head from the collimator by eliminating torques and forces on the collimator which would be exerted by mechanical inaccuracies or sag of the head, and a third bearing system for rotatably supporting a stereotactic floorstand for rotation about a vertical axis which intersects the center point.

Abstract: Stereotactic radiosurgery is facilitated by a technique for computing the doses at various points within the patient's body. In particular, the doses are computed at a relatively high density of points within a fine dose grid and at a relatively low density of points within a coarse dose grid. In that fashion, the user can quickly obtain necessary information about the radiation dose distribution before implementation of a proposed treatment plan. An advantageous technique of locating the intersection between the radiation beam and the contour or other surface of the patient is also provided. The method is especially well suited for use with a particular structure which allows one to utilize relatively narrow beam widths as a result of great mechanical accuracy.

Abstract: A belt and buckle assembly in which first and second ends of a belt are adapted to be interconnected and the belt has means for receiving and releasably retaining a buckle member; and a plurality of buckle members, each having means for attachment to the belt, such that one of a plurality of available buckles may be selectively attached to the belt and subsequently removed and replaced by a second of the buckles.