Karaiskos P, Papagiannis P, Sakelliou L, Anagnostopoulos G, Baltas D
Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, Athens, Greece.
Med Phys. 2001 Aug;28(8):1753-60. doi: 10.1118/1.1384460.
This work provides full dosimetric data for the new selectSeed 125I prostate seed source to be distributed by Nucletron B.V. The AAPM TG-43 dosimetric formalism and the new 1999 NIST air kerma strength calibration standard have been followed. Air kerma strength, dose rate constant, radial dose functions, anisotropy functions, and anisotropy factors were calculated using Monte Carlo simulation. Corresponding calculations were also performed for the commercially available 6711 seed source, which is of similar design, for reasons of comparison. The calculated dose rate constant of the selectSeed was 0.954+/-0.005 cGy h(-1) U(-1) compared to 0.953+/-0.005 cGy h(-1) U(-1) for the 6711 source design. The latter value for the 6711 source suggests that the correction factor proposed by NIST for conversion of dose rate constants to the new 1999 NIST calibration standard may be overestimated by 2-3%. Radial dose functions of the two sources were found in good agreement for radial distances up to 4 cm, the selectSeed being less penetrating at greater radial distances (approximately 4% at 10 cm). The selectSeed source presents similar anisotropy characteristics with the 6711 source design. For both source designs, a distance and polar angle dependent discontinuity of anisotropy function values was observed owing to the dose contribution of radioactivity distributed on the ends of the cylindrical source cores. Variation of dosimetric parameters with possible variation in radioactive silver halide coating thickness of the silver source core of the new source was also investigated.
本研究提供了由Nucletron B.V.公司销售的新型selectSeed 125I前列腺籽源的完整剂量学数据。遵循了AAPM TG - 43剂量学形式主义和新的1999年NIST空气比释动能强度校准标准。使用蒙特卡罗模拟计算了空气比释动能强度、剂量率常数、径向剂量函数、各向异性函数和各向异性因子。出于比较的目的，还对设计相似的市售6711籽源进行了相应计算。selectSeed的计算剂量率常数为0.954±0.005 cGy h(-1) U(-1)，而6711源设计的该值为0.953±0.005 cGy h(-1) U(-1)。6711源的后一个值表明，NIST提出的将剂量率常数转换为新的1999年NIST校准标准的校正因子可能被高估了2 - 3%。发现两种源在径向距离达4 cm时的径向剂量函数吻合良好，selectSeed在更大径向距离处（10 cm时约低4%）穿透性较差。selectSeed源与6711源设计具有相似的各向异性特征。对于两种源设计，由于分布在圆柱形源芯端部的放射性物质的剂量贡献，观察到各向异性函数值存在距离和极角相关的不连续性。还研究了剂量学参数随新源银源芯放射性卤化银涂层厚度可能变化的情况。
