Tagesson M, Ljungberg M, Strand S E
Department of Radiation Physics, Lund University Hospital, Lund, Sweden.
Acta Oncol. 1996;35(3):367-72. doi: 10.3109/02841869609101653.
In systemic radiation therapy, the absorbed dose distribution must be calculated from the individual activity distribution. A computer code has been developed for the conversion of an arbitrary activity distribution to a 3-D absorbed dose distribution. The activity distribution can be described either analytically or as a voxel based distribution, which comes from a SPECT acquisition. Decay points are sampled according to the activity map, and particles (photons and electrons) from the decay are followed through the tissue until they either escape the patient or drop below a cut off energy. To verify the calculated results, the mathematically defined MIRD phantom and unity density spheres have been included in the code. Also other published dosimetry data were used for verification. Absorbed fractions and S-values were calculated. A comparison with simulated data from the code with MIRD data shows good agreement. The S values are within 10-20% of published MIRD S values for most organs. Absorbed fractions for photons and electrons in spheres (masses between 1 g and 200 kg) are within 10-15% of those published. Radial absorbed dose distributions in a necrotic tumor show good agreement with published data. The application of the code in a radionuclide therapy dose planning system, based on quantitative SPECT, is discussed.
在全身放射治疗中，必须根据个体活度分布来计算吸收剂量分布。已开发出一种计算机代码，用于将任意活度分布转换为三维吸收剂量分布。活度分布既可以用解析法描述，也可以描述为基于体素的分布，后者来自单光子发射计算机断层扫描（SPECT）采集。衰变点根据活度图进行采样，衰变产生的粒子（光子和电子）在组织中穿行，直到它们离开患者身体或能量降至截止能量以下。为了验证计算结果，代码中纳入了数学定义的医学内照射剂量学（MIRD）体模和单位密度球体。还使用了其他已发表的剂量学数据进行验证。计算了吸收分数和S值。将该代码的模拟数据与MIRD数据进行比较，结果显示吻合良好。对于大多数器官，S值在已发表的MIRD S值的10% - 20%范围内。球体（质量在1克至200千克之间）中光子和电子的吸收分数在已发表值的10% - 15%范围内。坏死肿瘤中的径向吸收剂量分布与已发表数据吻合良好。本文还讨论了该代码在基于定量SPECT的放射性核素治疗剂量规划系统中的应用。
