Previous studies have primarily focused on quality of imaging in radiotherapy planning computed tomography (RTCT), with few investigations on imaging doses. To our knowledge, this is the first study aimed to investigate the imaging dose in RTCT to determine baseline data for establishing national diagnostic reference levels (DRLs) in Japanese institutions. A survey questionnaire was sent to domestic RT institutions between 10 October and 16 December 2021. The questionnaire items were volume computed tomography dose index (CTDIvol), dose–length product (DLP), and acquisition parameters, including use of auto exposure image control (AEC) or image-improving reconstruction option (IIRO) for brain stereotactic irradiation (brain STI), head and neck (HN) intensity-modulated radiotherapy (IMRT), lung stereotactic body radiotherapy (lung SBRT), breast-conserving radiotherapy (breast RT), and prostate IMRT protocols. Details on the use of motion-management techniques for lung SBRT were collected. Consequently, we collected 328 responses. The 75th percentiles of CTDIvol were 92, 33, 86, 23, and 32 mGy and those of DLP were 2805, 1301, 2416, 930, and 1158 mGy·cm for brain STI, HN IMRT, lung SBRT, breast RT, and prostate IMRT, respectively. CTDIvol and DLP values in institutions that used AEC or IIRO were lower than those without use for almost all sites. The 75th percentiles of DLP in each treatment technique for lung SBRT were 2541, 2034, 2336, and 2730 mGy·cm for free breathing, breath holding, gating technique, and real-time tumor tracking technique, respectively. Our data will help in establishing DRLs for RTCT protocols, thus reducing imaging doses in Japan.

中文翻译：

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放射成像保护：日本外部放射治疗计划计算机断层扫描时使用的成像剂量研究

以往的研究主要集中在放疗计划计算机断层扫描（RTCT）中的成像质量，而对成像剂量的研究很少。据我们所知，这是第一项旨在调查 RTCT 成像剂量的研究，以确定日本机构建立国家诊断参考水平 (DRL) 的基线数据。2021 年 10 月 10 日至 12 月 16 日期间，向国内放射治疗机构发出调查问卷。调查问卷项目为体积计算机断层扫描剂量指数（CTDIvol）、剂量长度乘积（DLP）和采集参数，包括使用自动曝光图像控制（ AEC）或图像改善重建选项（IIRO）用于脑立体定向照射（脑 STI）、头颈（HN）调强放疗（IMRT）、肺部立体定向全身放疗（肺 SBRT）、保乳放疗（乳房 RT） ）和前列腺 IMRT 方案。收集了有关肺 SBRT 运动管理技术使用的详细信息。因此，我们收集了 328 份回复。对于脑 STI、HN IMRT、肺 SBRT、乳腺 RT 和前列腺，CTDIvol 的第 75 个百分位数为 92、33、86、23 和 32 mGy，DLP 的第 75 个百分位数为 2805、1301、2416、930 和 1158 mGy·cm分别为调强放射治疗 (IMRT)。几乎所有站点使用 AEC 或 IIRO 的机构中的 CTDIvol 和 DLP 值均低于未使用的机构。肺SBRT每种治疗技术中自由呼吸、屏气、门控技术和实时肿瘤跟踪技术的DLP第75个百分位数分别为2541、2034、2336和2730 mGy·cm。我们的数据将有助于建立 RTCT 协议的 DRL，从而减少日本的成像剂量。