Systematic study of the iodinated rectal hydrogel spacer material discrepancy on accuracy of proton dosimetry.
Systematic study of the iodinated rectal hydrogel spacer material discrepancy on accuracy of proton dosimetry.
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DOI：
10.1002/acm2.13774
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发表时间：
2022-10
影响因子：
2.1
通讯作者：
Ding, Kai
中科院分区：
文献类型：
--
作者：
Hooshangnejad, Hamed;Han, Dong;Feng, Ziwei;Dong, Liang;Sun, Edward;Du, Kaifang;Ding, Kai
关键词：
直肠水凝胶间隔物的碘化可提高CT的可见度。碘化水凝胶间隔材料对质子剂量测量精度的影响还没有得到充分的研究。我们提出了一项系统的研究，以确定在质子治疗(PT)期间加碘对质子剂量测量精度的影响。为20例前列腺癌患者设计直肠水凝胶间隔器的PT计划。考虑了水凝胶密度的三种变化。首先，以水凝胶真材料(TM)的真实元素组成为基础，通过对隔离基阻止功率比的测量验证，用于方案优化和蒙特卡罗剂量计算。用(1)基于碘化间隔物的CT强度的无材料(NM)覆盖和(2)水材料(WM)覆盖，其中间隔物被水取代，重新计算剂量分布。使用伽马指数(GI)和剂量学指数将计划与地面真实情况进行比较。水凝胶间隔物的碘化影响了质子剂量分布，其中NM方案偏离地面真实情况最多。间隔物的碘化导致CT强度显著增加，并导致治疗计划系统错误地将碘化间隔物作为高密度材料。在靶区附近的结构中，神经血管束显示出最大的剂量差异，最高可达350cGy，约为NM规定剂量的5%。与WM方案相比，NM方案的剂量分布相似性和GI合格率较低。用于碘化间隔的CT强度材料不准确导致了PT剂量计算的误差。我们发现，如果用水取代碘化间隔物，误差可以忽略不计。水密度可用作临床可及且方便的替代材料替代真正的间隔物材料。
Iodination of rectal hydrogel spacer increases the computed tomography (CT) visibility. The effect of iodinated hydrogel spacer material on the accuracy of proton dosimetry has not been fully studied yet. We presented a systematic study to determine the effect of iodination on proton dosimetry accuracy during proton therapy (PT). PT plans were designed for 20 prostate cancer patients with rectal hydrogel spacer. Three variations of hydrogel density were considered. First, as the ground truth, the true elemental composition of hydrogel true material (TM), verified by our measurement of spacer stopping power ratio, was used for plan optimization and Monte Carlo dose calculation. The dose distribution was recalculated with (1) no material (NM) override based on the CT intensity of the iodinated spacer, and (2) the water material (WM) override, where spacer material was replaced by water. The plans were compared with the ground truth using the metrics of gamma index (GI) and dosimetric indices. The iodination of hydrogel spacer affected the proton dose distribution with the NM scenario showing the most deviation from the ground truth. The iodination of spacer resulted in a notable increase in CT intensity and led to the treatment planning systems mistreating the iodinated spacer as a high‐density material. Among the structures adjacent to the target, neurovascular bundles showed the largest dose difference, up to 350 cGy or about 5% of the prescribed dose with NM. Compared to the WM scenario, dose distribution similarity and GI passing ratios were lower in the NM scenario. The inaccurate CT intensity‐based material for iodinated spacer resulted in errors in PT dose calculation. We found that the error was negligible if the iodinated spacer was replaced with water. Water density can be used as a clinically accessible and convenient alternative material override to true spacer material.
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DOI：
10.1016/j.ijrobp.2018.07.184
发表时间：
2018-11-01
期刊：
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