Comparison of radiosurgery treatment modalities based on physical dose distributions

Abstract

As a means of selecting the optimal stereotactic radiosurgery (SRS) treatment modality, a comparison of physical dose distributions to defined targets and nontarget brain tissue has been made for a group of test cases selected to represent a range of treatment-planning situations from small, nearly spherical volumes to large irregular volumes. Plans were developed for each case using photon beams from the Leksell Gamma Unit (LGU), multiarc bremsstrahlung photon beams from a linear accelerator (linac) and proton beams, with the objective of encompassing the target as closely as possible with the prescription isodose line, and minimizing dosage to normal tissue within the bounds of standard clinical practice. Dose-volume histograms (DVHs) were calculated for target and for nontarget brain tissue and compared for the various modalities. In general, protons delivered less dosage to normal brain than other modalities for large and peripheral lesions and LGU plans were more successful at conforming to highly irregular shapes than conventional linac plans. Differences were observed to depend on treatment modality, target characteristics (shape, size and location), and the amount of effort expended on treatment planning and the time allotted for treatment implementation.