title: COMS eye plaque brachytherapy dosimetry simulations for 103Pd, 125I, and 131Cs.
abstract: Monte Carlo (MC) simulations were performed to estimate brachytherapy dose distributions for Collaborative Ocular Melanoma Study (COMS) eye plaques. Brachytherapy seed models 200, 6711, and CS-1 Rev2 carrying 103Pd, 125I, and 131Cs radionuclides, respectively, were modeled and benchmarked against previously published values. Calculated dose rate constants MClambda were 0.684, 0.924, and 1.052 cGy h(-1) U(-1) (+/- 2.6%, k = 1 uncertainty) for models 200, 6711, and CS-1 Rev2, respectively. The seeds were distributed into 10, 12, 14, 16, 18, 20, and 22 mm-diameter COMS eye plaques. Simulations were performed in both heterogeneous and homogeneous environments, where the latter were in-water and the former included the silastic seed carrier insert and gold-alloy plaque. MC-based homogenous central axis dose distributions agreed within 2% +/- 1% (+/- 1 s.d.) to hand-calculated values. For heterogeneous simulations, notable photon attenuation was observed, with dose reduction at 5 mm of 19%, 11%, and 9% for 103Pd, 125I, and 131Cs, respectively. A depth-dependent correction factor was derived to correct homogenous central-axis dose distributions for plaque component heterogeneities, which were found to be significant at short radial distances.
authors.affiliation: Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA. cmelhus@tuftsmedicalcenter.org
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Melhus
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Rivard
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D002588:Cesium Radioisotopes / Q000627:therapeutic use*; D003198:Computer Simulation; D004867:Equipment Design; D005123:Eye / Q000528:radiation effects; D005134:Eye Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D010165:Palladium / Q000627:therapeutic use*; D017785:Photons; D011868:Radioisotopes / Q000627:therapeutic use*; D011874:Radiometry / Q000379:methods*; D012984:Software; D013997:Time Factors
chemical_list: D002588:Cesium Radioisotopes; D007457:Iodine Radioisotopes; D011868:Radioisotopes; D010165:Palladium