title: Report on the dosimetry of a new design 125Iodine brachytherapy source.
abstract: Dosimetric measurements were performed to characterize a new 125I source that is a variant design of an existing source, designated as MED3631-A/S, and that has application in interstitial brachytherapy. The new source, designated as MED3631-A/M, has centralized radio-opaque markers. In the original MED3631-A/S source, the radio-opaque markers are separated. Thermoluminescent dosimeters were placed in phantom to measure transverse axis and angular dose profiles over a range of distances from 0.5 to 7 cm. The data were analyzed in terms of parameters recommended by AAPM Task Group No. 43. Tabular data evaluated in liquid water are provided for the dose-rate constant, lambda, radial dose function, g(r), the anisotropy function, F(r,theta), the anisotropy factor, phi(an)(r), the point-source approximation anisotropy constant, phi(an). The dose-rate constant was determined by an absolute method using a Cobalt-60 reference and by relative measurements using calibrated 125I source(s). Values of the dose-rate constant are provided for both the 1985 and 1999 NIST air-kerma strength standards. The new source is comparable to both the MED3631-A/S and the model 6702 125I source designs, demonstrating equivalent radial dose function, g(r). Differences in the value of the dose-rate constant, lambda, and the anisotropy of the dose distributions in phantom are discussed in light of the improved isotropy of the new design, the MED3631-A/M source, and the uncertainty involved in the dose measurement using a Cobalt-60 reference.
authors.affiliation: Department of Radiation Oncology, University of California, Los Angeles 90095-6951, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Wallace
authors.forename: J J
authors.initials: JJ
authors.lastname: Fan
mesh_terms: D016880:Anisotropy; D055592:Biophysical Phenomena; D001703:Biophysics; D001918:Brachytherapy / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D019047:Phantoms, Imaging; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted
chemical_list: D007457:Iodine Radioisotopes