On the assay of brachytherapy sources

• Published in: Medical physics (Lancaster) 2007-06, Vol.34 (6), p.1975-1982
• Main Authors: Yue, Ning J., Haffty, Bruce G., Yue, Jinfeng
• Format: Article
• Language: English
• Subjects: ACCURACY; assay; BRACHYTHERAPY; Brachytherapy - instrumentation; Brachytherapy - standards; brachytherapy source; DOSIMETRY; DRUGS; Electric measurements; Error analysis; Guidelines as Topic; interstitial brachytherapy; Measurement and error theory; measurement uncertainty; PARTICLE ACCELERATORS; Physicists; Probability theory; Probability theory, stochastic processes, and statistics; Quality Assurance, Health Care - methods; Quality Assurance, Health Care - standards; RADIATION DOSES; Radiation monitoring, control, and safety; RADIATION PROTECTION AND DOSIMETRY; RADIATION SOURCES; Radiation treatment; radioactive sources; Radioisotopes - analysis; Radioisotopes - standards; RADIOLOGY AND NUCLEAR MEDICINE; Radiometry - instrumentation; Radiometry - standards; Radiotherapy Dosage; RECOMMENDATIONS; Reference Standards; Reproducibility of Results; Sensitivity and Specificity; Sources of radioactive nuclei; statistical analysis; Therapeutic applications, including brachytherapy; Ultrasonography; United States; US NRC
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.2734723

In many of brachytherapy procedures, a large amount of radioactive sources are used to deliver desired doses to the target volume. It is both the federal regulation recommendation (US Nuclear Regulatory Commission, 10 CFR 35.432) and recommendations of the American Association of Physicists in Medicine (AAPM) [Kutcher et al. , Med. Phys. 21, 581–618 (1994); Nath et al. , Med. Phys. 24, 1557–1598 (1997)] that users independently verify the sources’ strength. Though the reports of AAPM Task Group 40 [Kutcher et al. , Med. Phys. 21, 581–618 (1994)] and 56 [Nath et al. , Med. Phys. 24, 1557–1598 (1997)] have made specific recommendations on the assay of brachytherapy sources, the relevant statistical significance of the recommendations remain unanswered. In this study, statistical theories were used and a method was presented to quantify the assay process of brachytherapy sources and to evaluate the recommendations. The results showed that the quality of a source assay process was dependent on the measured source strength deviation and number of assayed sources. Its dependence on the total number of sources becomes statistically insignificant if the total number is large enough. It was concluded that the assay process can be determined by the obtained assay information, instead of a preset percentage of total sources. It was further found that the use of manufacturer’s stated strength value may possibly lead to bigger uncertainty in source strength accuracy, unless the manufacturer’s stated strength is the measured mean value of all the ordered sources.