Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Int J Clin Oncol. 2009 Dec;14(6):525-8. doi: 10.1007/s10147-009-0914-3. Epub 2009 Dec 5.
To assure the physical quality of brachytherapy, we investigated the difference between measured and manufacturer's stated source strengths in a single model SourceTech Medical (STM)1251 (125)I seed.
A well-type ionization chamber with a single-seed holder was used to measure the source strength of 2412 (125)I seeds before implant in 34 patients. The air-kerma strength was 0.450 U for all cases. The mean source strength for each patient was measured and compared with the manufacturer's stated value. The deviation from the measured value was compared with the tolerance range of the American Association of Physicists in Medicine (AAPM) TG-56 report's recommendation.
The measured source strength was higher than the manufacturer's stated value, with a median difference of 1% (range, 2% to 5%). Sixteen of the total of 2412 seeds (0.7%) were more than 5% different from the manufacturer's stated value. The median SD from the mean value was 2.2% (range, 1.1% to 2.5%) for all patients.
This is the first report of a single-seed assay performed for the model STM1251 (125)I seed. In this study the manufacturer's stated strength agreed well with the measured value. Nevertheless, the advisability of performing a single-seed assay at every institution should be considered, by referring to the appropriate regulations; for example, those used in the United States.
为了确保近距离放射治疗的物理质量，我们研究了在单模型 SourceTech Medical（STM）1251（125）I 种子中，测量值与制造商声明的源强之间的差异。
使用带有单个种子支架的井型电离室，在 34 名患者植入前测量 2412（125）I 种子的源强。所有情况下空气比释动能强度均为 0.450 U。测量每位患者的平均源强，并与制造商的声明值进行比较。将偏差与美国医学物理学家协会（AAPM）TG-56 报告建议的容差范围进行比较。
测量的源强高于制造商的声明值，中位数差异为 1%（范围为 2%至 5%）。2412 个种子中共有 16 个（0.7%）与制造商的声明值相差超过 5%。所有患者的平均数值的中位标准差为 2.2%（范围为 1.1%至 2.5%）。
这是首次对 STM1251（125）I 种子模型进行单种子测定的报告。在本研究中，制造商声明的强度与测量值吻合良好。然而，应该考虑在每个机构进行单种子测定的可取性，参考适当的规定；例如，在美国使用的规定。
