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Chemical dosimetry in the near‐zone of brachytherapy sources
Author(s) -
Hasson Brian F.
Publication year - 1998
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598432
Subject(s) - dosimeter , dosimetry , scanner , monte carlo method , brachytherapy , materials science , nuclear medicine , optics , medical physics , physics , radiation therapy , medicine , radiology , mathematics , statistics
The treatment of neointimal‐hyperplasia, prostate cancer with125 I seed implants, and transition zone effects in three‐dimensional conformal therapy has spurred the development of new dosimeters for evaluating steep dose‐gradient regions. This thesis describes two dosimetry systems to accurately measure the radial dose in the near‐zone (<5 mm) of clinically used137 Cs and192 Ir sources. A custom‐made polymer gel dosimeter was designed and implemented for this project. This dosimeter evaluated with a high field strength small‐bore MR (Magnetic Resonance) scanner provided precise measurement of the dose in the near‐zone. A second system consisted of gaf‐chromic film and a custom‐built precision scanner. The scanner, using a 670 nm diode laser and precision built micrometers, provided precise scanning of the gaf‐chromic film. The gaf‐chromic film dosimetry system gave results that were in good agreement (2%) with the polymer gel dosimeter for the radial dose in the near‐zone of clinically used137 Cs and192 Ir sources. The radial dose data from both dosimetry systems agreed to within 3% with Monte Carlo data at radial distances of less than 5 mm from the center of single137 Cs and192 Ir sources. This project has extended the reliable data in the near‐zone to 1 mm for192 Ir . Both dosimeters were shown to be satisfactory for near‐zone dosimetry, and provide an empirical benchmark for the Monte Carlo theorist.