title: Comparison of two methods to compute the absorbed dose to water for photon beams.
abstract: Cross-validation was performed between an in-house dose-to-water (D(water)) calculation method used at Virginia Commonwealth University and the VMC++ D(water) calculation during particle transport. The effect of Monte Carlo statistical precision was observed. The results of the two calculations on homogeneous phantoms with densities varying from 0.3 g cm(-3) to 2.95 g cm(-3) were compared. Depth and field size dependence were tested. D(water) calculations were compared in a bone-lung-bone phantom to observe how the calculations differed in steep density gradients. The methods were compared for five prostate and five head-and-neck (H/N) patient cases as well. In all phantom tests, the differences between the two D(water) calculations were less than 1%. The largest differences in patient cases was a prostate case in which 1% of the voxels with doses greater than 50% of the maximum dose had a systematic difference corresponding to 1.16% of the maximum dose. All differences were clinically insignificant.
authors: Department of Radiation Oncology, Virginia Commonwealth University Medical Center, Richmond, VA, USA. gardnerjk@vcu.edu
authors: Joseph K
authors: JK
authors: Gardner
authors: Jeffrey V
authors: JV
authors: Siebers
authors: Iwan
authors: I
authors: Kawrakow
mesh_terms: D000042:Absorption; D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D017785:Photons; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D014867:Water
chemical_list: D014867:Water