Physics Division, Department of Radiation Oncology, The University of California, San Francisco, CA 94115, USA.
J Appl Clin Med Phys. 2010 Jun 3;11(3):3096. doi: 10.1120/jacmp.v11i3.3096.
The purpose is to demonstrate the ability to generate clinically acceptable prostate permanent seed implant plans using two seed types which are identical except for their activity. The IPSA inverse planning algorithms were modified to include multiple dose matrices for the calculation of dose from different sources, and a selection algorithm was implemented to allow for the swapping of source type at any given source position. Five previously treated patients with a range of prostate volumes from 20-48 cm3 were re-optimized under two hybrid scenarios: (1) using 0.32 and 0.51 mGy m2 / h 125I, and (2) using 0.64 and 0.76 mGy m2 / h 125I. Isodose lines were generated and dosimetric indices , V150Prostate, D90Prostate, V150Urethra, V125Urethra, V120Urethra,V100Urethra, and D10Urethra were calculated. The algorithm allows for the generation of single-isotope, multi-activity hybrid brachytherapy plans. By dealing with only one radionuclide, but of different activity, the biology is unchanged from a standard plan. All V100Prostate were within 2.3 percentage points for every plan and always above the clinically desirable 95%. All V150Urethra were identically zero, and V120Urethra is always below the clinically acceptable value of 1.0 cm3. Clinical optimization times for the hybrid plans are still under one minute, for most cases. It is possible to generate clinically advantageous brachytherapy plans (i.e. obtain the same quality dose distribution as a standard single-activity plan) while incorporating leftover seeds from a previous patient treatment. This method will allow a clinic to continue to provide excellent patient care, but at a reduced cost. Multi-activity hybrid plans were equal in quality (as measured by the standard dosimetric indices) to plans with seeds of a single activity. Despite the expanded search space, optimization times for these studies were still under two minutes on a modern day laptop and can be reduced to below one minute in a clinical setting. With the typical cost of a set of PPI seeds on the order of thousands of dollars, it is possible to reduce the cost of brachytherapy treatments by allowing for easier use of seeds left over from a previous patient or unused due to a cancelled treatment.
目的是展示使用两种类型的种子生成临床可接受的前列腺永久种子植入计划的能力，这两种种子除了活性外完全相同。修改了 IPSA 逆规划算法，以包括多个剂量矩阵，用于计算来自不同源的剂量，并实现了选择算法，允许在任何给定源位置交换源类型。对 5 名前列腺体积在 20-48cm3 之间的既往治疗患者进行了重新优化，采用两种混合方案：（1）使用 0.32 和 0.51mGy m2/h125I，（2）使用 0.64 和 0.76mGy m2/h125I。生成等剂量线，并计算剂量学指标 V150Prostate、D90Prostate、V150Urethra、V125Urethra、V120Urethra、V100Urethra 和 D10Urethra。该算法允许生成单同位素、多活性混合近距离治疗计划。通过只处理一种放射性核素，但活性不同，生物学与标准计划保持不变。对于每个计划，V100Prostate 均在 2.3 个百分点内，始终高于临床期望的 95%。所有 V150Urethra 均为零，V120Urethra 始终低于 1.0cm3 的临床可接受值。对于大多数病例，混合计划的临床优化时间仍在一分钟内。可以生成具有临床优势的近距离治疗计划（即获得与标准单活性计划相同的质量剂量分布），同时结合前一位患者治疗中剩余的种子。这种方法将使诊所能够继续提供出色的患者护理，但成本降低。多活性混合计划在质量上（如标准剂量学指标所示）与具有单一活性种子的计划相同。尽管搜索空间扩大，但在现代笔记本电脑上，这些研究的优化时间仍在两分钟内，在临床环境下可以减少到一分钟以下。由于一套 PPI 种子的典型成本在数千美元左右，因此通过允许更容易地使用前一位患者剩余的种子或因治疗取消而未使用的种子，可以降低近距离治疗的成本。
