Conformal Stereotactic Radiosurgery With Multileaf Collimation.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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This paper outlines and implements a method of producing dose distributions that conform to any arbitrary, irregularly shaped target by means of dynamic conformal collimation using a multileaf collimator. The method may be summarized in three steps production of the treatment plan localization of the target and the calculation of three dimensional dosimetry. Provision is made for volumetric evaluation of dosimetry with dose volume histograms and complication probability functions. Treatment plans follow the standard of non- conformal stereotactic radiosurgery with several non-intersecting parasagittal arcs. Target localization begins with identification and contouring of target axial dimensions using diagnostic CT scans. A system for processing these target contours has been produced using the Beams Eye View technique. Projected target Cross sectional areas at each gantrytable position are found by graphical search and each leaf of the collimator is set to position. The localization results are then sent to dosimetry calculation for the production of isodose plots on the three principal planes, individual field cross plots, dose volume histograms, and complication probability functions. The three dimensional dosimetry technique developed here is termed the modified negative field method. Dosimetry from cases previously treated using the University of Florida Stereotactic Radiosurgery System are compared with the developed method and also with a rotating collimator system that has been described in the literature. It is shown that the method developed herein provides better conformation and homogeneity in dose throughout the target volume than those techniques used at present.
- Medicine and Medical Research