Title :
On the dosimetric influences of air-kerma strength calibration geometry and internal source structure for 103Pd and 125 I brachytherapy sources
Author :
Williamson, J.F.
Author_Institution :
Radiat. Oncology Center, Washington Univ. Sch. of Med., St. Louis, MO, USA
Abstract :
Monte Carlo photon-transport simulation techniques are used to study the influence of the new wide-angle free-air chamber (WAFAC) on low energy interstitial source dosimetric parameters. For sources containing radio opaque components with sharp corners, or low density components coated with high density materials, oblique filtration unexpectedly induces primary photon flux anisotropy near the transverse plane at typical calibration distances. Thus, the dose-rate constant may vary as much as 11% with the solid angle subtended by the SK measurement instrument. For the Model 200 103Pd source, and by extension, other “thin radio opaque layer” seeds, the WAFAC renders the absolute dose-rate distribution near the seed independent of this dense layer and its thickness
Keywords :
calibration; dosimetry; iodine; palladium; radiation therapy; radioactive sources; 125I; I; Model 200 103Pd source; Pd; SK measurement instrument; absolute dose-rate distribution; air-kerma strength calibration geometry; brachytherapy sources; internal source structure; primary photon flux anisotropy; therapeutic nuclear medicine; thin radio opaque layer seeds; transverse plane; typical calibration distances; Anisotropic magnetoresistance; Calibration; Coatings; Geometry; Instruments; Monte Carlo methods; NIST; Resins; Solid modeling; Titanium;
Conference_Titel :
Engineering in Medicine and Biology Society, 2000. Proceedings of the 22nd Annual International Conference of the IEEE
Conference_Location :
Chicago, IL
Print_ISBN :
0-7803-6465-1
DOI :
10.1109/IEMBS.2000.900751
