After each cycle of [177Lu]-DOTA-TATE peptide receptor radionuclide therapy (PRRT) dosimetry is performed to enable precise calculation of the radiation-absorbed dose to tumors and normal organs. Absorbed doses are routinely calculated from three quantitative single-photon emission computed tomography (SPECT) studies corrected by computed tomography (CT) acquired at t1 = 24 h, t2 = 96 h, and t3 = 168 h after the first cycle of treatment. After following cycles, a single SPECT/CT study is performed. The aim of the present study is to assess the feasibility of a “two time point” quantitative SPECT/CT protocol after the first PRRT cycle and its impact on patient management. Quantitative SPECT/CT data of 25 consecutive patients with metastatic neuroendocrine tumors after PRRT were retrospectively analyzed. Radiation-absorbed doses calculated using the standard protocol with three SPECT/CT studies acquired at (t1, t2, t3) were compared to those obtained from three different “two time point” protocols with SPECT/CT studies performed at (t1, t2), (t1, t3), or (t2, t3). The best agreement for the cumulative doses absorbed by the kidneys, bone marrow, liver, spleen, and tumors with the conventional protocol was obtained with the (t1, t3) protocol with mean relative differences of − 1.0% ± 2.4%, 0.4% ± 3.1%, − 0.9% ± 4.0%, − 0.8% ± 1.1%, and − 0.5% ± 2.0%, respectively, and correlation coefficients of r = 0.99 for all. In all patients, there was no difference in the management decision of whether or not to stop PRRT because of unsafe absorbed dose to risk organs using either the standard protocol or the (t1, t3) protocol. These preliminary results demonstrate that dosimetry calculations using two quantitative SPECT/CT studies acquired at 24 and 168 h after the first PRRT cycle are feasible and are in good agreement with the standard imaging protocol with no change in patient management decisions, while enabling improved patient comfort and reduced scanner and staff time.

中文翻译：

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肽受体放射性核素治疗后的剂量测定：减少后处理研究次数对吸收剂量计算和患者管理的影响。

在[177Lu] -DOTA-TATE肽受体放射性核素治疗（PRRT）的每个周期后，都要进行剂量测定，以精确计算对肿瘤和正常器官的辐射吸收剂量。吸收剂量是通过三个定量单光子发射计算机断层扫描（SPECT）研究常规计算得出的，该研究由在第一个治疗周期后的t1 = 24小时，t2 = 96小时和t3 = 168小时获得的计算机断层摄影（CT）校正。在随后的周期后，将进行一次SPECT / CT研究。本研究的目的是评估第一个PRRT周期后“两个时间点”定量SPECT / CT方案的可行性及其对患者管理的影响。回顾性分析了25例PRRT后连续转移性神经内分泌肿瘤患者的SPECT / CT定量数据。将使用在t1，t2，t3进行的三项SPECT / CT研究的标准方案计算的辐射吸收剂量与在t1，t2进行SPECT / CT研究的三种不同的“两个时间点”方案获得的辐射吸收剂量进行比较。 ，（t1，t3）或（t2，t3）。通过（t1，t3）方案获得了常规方案下肾脏，骨髓，肝脏，脾脏和肿瘤吸收的累积剂量的最佳协议，平均相对差为-1.0％±2.4％，0.4％±分别为3.1％，-0.9％±4.0％，-0.8％±1.1％和-0.5％±2.0％，所有相关系数均为r = 0.99。在所有患者中，由于使用标准方案或（t1，t3）方案对危险器官的吸收剂量不安全，是否停止PRRT的管理决策均无差异。