Calibration of gamma-ray-emitting brachytherapy sources

New national air-kerma-strength standards for I-125 and Pd-103 brachytherapy seeds

“…Multiple drops/measurements were done with the re-entrant chamber to effectively randomize the seed orientation to average over any anisotropy of seed emissions or chamber response. With the long-term stability of the re-entrant chamber checked by a long-half-life 226 Ra source (see [ 19 ]), the calibrated re-entrant chamber would serve as the secondary standard for subsequent routine measurements. The stated uncertainties, expanded with a coverage factor of 2 to approximate that expected at the 95 % confidence level, for the transferred measurements are 3 % for the 6702 seed and 4 % for the 6711 seed [ 11 ].…”

“…The stated uncertainties, expanded with a coverage factor of 2 to approximate that expected at the 95 % confidence level, for the transferred measurements are 3 % for the 6702 seed and 4 % for the 6711 seed [ 11 ]. For subsequent re-entrant seed calibrations, the uncertainty in the measurement of the unknown is added, with the typical result for the expanded (95 % confidence level) uncertainty of 5 % for the 6702 seed and 6 % for the 6711 seed [ 19 ].…”

Comprehensive QA for radiation oncology: Report of AAPM Radiation Therapy Committee Task Group 40

“…Well ionization or reentrant chambers are preferred for conventional strength brachytherapy sources (Berkley et al, 1981;Weaver et al, 1990b), and thimble chambers measuring radiation intensity at a distance are preferred for high dose rate sources (Goetsch et al, 1991). However, thimble chambers have been used successfully for conventional dose rate sources (Loftus, 1980(Loftus, ,1984Berkley et al, 1981;Weaver et al, 1988), and Goetsch reports on a reentrant chamber designed for high dose rate sources (Goetsch et al, 1991). The radiation oncology physicist should identify a single dosimetry system that will be used for brachytherapy calibration-although this need not be the sole use of the system.…”

Dosimetric prerequisites for routine clinical use of photon emitting brachytherapy sources with average energy higher than 50 keva)

“…In regards to determination of source air-kerma strength, calibration services for 137 Cs and 192 Ir LDR sources in the U.S. have long been available from the National Institute of Standards and Technology ͑NIST͒. [8][9][10] Currently, no standard is available from NIST for HDR 192 Ir sources, although some European standards laboratories do offer such a calibration service for selected HDR sources, e.g., the National Physical Laboratory in the UK. The Accredited Dosimetry Calibration Laboratories ͑ADCLs͒ in the United States have adopted the AAPM standard using an in-air method with chambers having calibration coefficients that are directly traceable to NIST air-kerma standards.…”