Frameless method of stereotaxic localization with DSA.

Abstract

To improve a method of stereotaxic localization with digital subtraction angiography that does not require use of a localization frame fixed to the patient's skull during examination. An independent, low-cost, stereotaxic computing system was devised. Software programs used magnetic resonance images, computed tomographic scans, and digitized radiographs of plastic bone implants with head landmarks to establish reference trihedrons in each imaging system, transpose target coordinates from one system to another, adjust surgical instruments, help plan radiation surgery, and compute and display isodose curves. The geometric distortions of the image intensifier were corrected. Distortion problems of the conic projection were solved, and three-dimensional localization was achieved with only two associated front and lateral views. Accuracy to within 1 mm was achieved for the three coordinates. This frameless stereotaxic localization technique is highly accurate and reliable. The system allows maximum automation of examination procedures.