COMPARISON OF RADIOSURGERY TREATMENT MODALITIES BASED ON PHYSICAL DOSE DISTRIBUTIONS

Purpose: 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 gro up of test cases selected to represent a range of treatment-planning s ituations from small, nearly spherical volumes to large irregular volu mes, Methods and Materials: Plans were developed for each case using p hoton 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 t he prescription isodose line, and minimizing dosage to normal tissue w ithin 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, Results: In general, protons deli vered 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, Conclusions: D ifferences were observed to depend on treatment modality, target chara cteristics (shape, size and location), and the amount of effort expend ed on treatment planning and the time allotted for treatment implement ation, (C) 1998 Elsevier Science Inc.