Mauceri T, Biggs P, Beatty J, Flynn D
Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
Med Phys. 1999 Jan;26(1):97-9. doi: 10.1118/1.598481.
Most algorithms developed by various investigators for use in brachytherapy treatment planning have typically been designed to calculate the dose within a 10 cm range of a radiation source. These algorithms predict the dose well at distances < 10 cm from the source but were not developed and should not be utilized to predict the dose at distances > 10 cm. On the contrary, treatment planning systems and manual calculations will produce erroneous results when dose points > 10 cm are calculated using these algorithms. The spread in the data generated by the above algorithms is 16% at 15 cm and 42% at 20 cm. Physical measurements were performed at distances between 5 and 50 cm from a high activity 192Ir source in water. The measured data correlated well with the predicted data from 5 to 10 cm, which had a 5% spread. Beyond 10 cm the measured data fell central to the range of the predicted data, with the spread of the predicted data increasing from 5% to 80% with increasing distance from the source. The measured data was fitted with a model incorporating a buildup factor and an attenuation factor. The best fit values are in reasonable agreement with those obtained by two of the investigators, Thomason and Tripathi.
不同研究者开发的用于近距离放射治疗治疗计划的大多数算法，通常设计用于计算辐射源10厘米范围内的剂量。这些算法在距离源小于10厘米处能很好地预测剂量，但并非为预测距离源大于10厘米处的剂量而开发，也不应被用于此。相反，当使用这些算法计算距离大于10厘米的剂量点时，治疗计划系统和手动计算会产生错误结果。上述算法生成的数据在15厘米处的离散度为16%，在20厘米处为42%。在水中距离高活度192铱源5至50厘米处进行了物理测量。测量数据与5至10厘米处的预测数据相关性良好，预测数据的离散度为5%。超过10厘米后，测量数据落在预测数据范围的中心，随着与源距离的增加，预测数据的离散度从5%增加到80%。测量数据用一个包含积累因子和衰减因子的模型进行拟合。最佳拟合值与研究者托马森和特里帕蒂两人得到的值合理吻合。
