Department of Radiologic Technology, National Cancer Center Hospital East, 6-5-1 Kashiwanoha, Kashiwa, 277-8577, Japan.
Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, 7-2-10 Arakawa‑ku, Tokyo, 116‑8551, Japan.
Ann Nucl Med. 2021 Nov;35(11):1177-1186. doi: 10.1007/s12149-021-01656-x. Epub 2021 Jul 21.
Recently, the national diagnostic reference levels (DRLs) in Japan were revised as the DRLs 2020, wherein the body weight-based injection dose optimization in positron emission tomography/computed tomography using F-fluoro-2-deoxy-D-glucose (F-FDG PET/CT) was first proposed. We retrospectively investigated the usefulness of this optimization method in improving image quality and reducing radiation dose.
A total of 1,231 patients were enrolled in this study. A fixed injection dose of 240 MBq was administered to 624 patients, and a dose adjusted to 3.7 MBq/kg body weight was given to 607 patients. The patients with body weight-based injection doses were further divided according to body weight: group 1 (≤ 49 kg), group 2 (50-59 kg), group 3 (60-69 kg), and group 4 (≥ 70 kg). The effective radiation dose of FDG PET was calculated using the conversion factor of 0.019 mSv/MBq, per the International Commission on Radiological Protection publication 106. Image quality was assessed using noise equivalent count density (NEC), which was calculated by excluding the counts of the brain and bladder. The usefulness of the injection dose optimization in terms of radiation dose and image quality was analyzed.
The body weight-based injection dose optimization significantly decreased the effective dose by 11%, from 4.54 ± 0.1 mSv to 4.05 ± 0.8 mSv (p < 0.001). Image quality evaluated by NEC was also significantly improved by 10%, from 0.39 ± 0.1 to 0.43 ± 0.2 (p < 0.001). In no case did NEC deteriorate when the effective dose was decreased. In group 1, the dose decreased by 32%, while there was no significant deterioration in NEC (p = 0.054). In group 2, the dose decreased by 17%, and the NEC increased significantly (p < 0.01). In group 3, the dose decreased by 3%, and the NEC increased significantly (p < 0.01). In group 4, the dose increased by 14%, but there was no significant change in the NEC (p = 0.766).
Body weight-based FDG injection dose optimization contributed to not only the reduction of effective dose but also the improvement of image quality in patients weighing between 50 and 69 kg.
最近，日本修订了全国诊断参考水平（DRLs），即 2020 年 DRLs，首次提出了正电子发射断层扫描/计算机断层扫描（PET/CT）中基于体重的 F-氟-2-脱氧-D-葡萄糖（F-FDG）注射剂量优化。我们回顾性研究了这种优化方法在提高图像质量和降低辐射剂量方面的作用。
本研究共纳入 1231 例患者。624 例患者给予固定注射剂量 240MBq，607 例患者给予按体重调整的 3.7MBq/kg 体重剂量。根据体重，将接受基于体重的注射剂量的患者进一步分为 4 组：组 1（≤49kg）、组 2（50-59kg）、组 3（60-69kg）和组 4（≥70kg）。FDG PET 的有效辐射剂量根据国际辐射防护委员会第 106 号出版物，使用 0.019mSv/MBq 的转换因子计算。图像质量使用噪声等效计数密度（NEC）评估，NEC 通过排除大脑和膀胱的计数来计算。分析了注射剂量优化在辐射剂量和图像质量方面的作用。
基于体重的注射剂量优化使有效剂量显著降低 11%，从 4.54±0.1mSv 降至 4.05±0.8mSv（p<0.001）。NEC 评估的图像质量也显著提高 10%，从 0.39±0.1 提高至 0.43±0.2（p<0.001）。在降低有效剂量的情况下，NEC 并未恶化。在组 1 中，剂量降低了 32%，而 NEC 没有明显恶化（p=0.054）。在组 2 中，剂量降低了 17%，而 NEC 显著增加（p<0.01）。在组 3 中，剂量降低了 3%，而 NEC 显著增加（p<0.01）。在组 4 中，剂量增加了 14%，但 NEC 没有明显变化（p=0.766）。
基于体重的 FDG 注射剂量优化不仅有助于降低有效剂量，还可以改善 50-69kg 体重患者的图像质量。
