Rosar Florian, Schön Niklas, Bohnenberger Hendrik, Bartholomä Mark, Stemler Tobias, Maus Stephan, Khreish Fadi, Ezziddin Samer, Schaefer-Schuler Andrea
Department of Nuclear Medicine, Saarland University-Medical Center, Kirrberger Str. Geb. 50, D-66421, Homburg, Germany.
EJNMMI Phys. 2021 May 5;8(1):40. doi: 10.1186/s40658-021-00385-4.
Dosimetry is of high importance for optimization of patient-individual PSMA-targeted radioligand therapy (PSMA-RLT). The aim of our study was to evaluate and compare the feasibility of different approaches of image-based absorbed dose estimation in terms of accuracy and effort in clinical routine.
Whole-body planar images and SPECT/CT images were acquired from 24 patients and 65 cycles at 24h, 48h, and ≥96h after administration of a mean activity of 6.4 GBq [Lu]Lu-PSMA-617 (range 3-10.9 GBq). Dosimetry was performed by use of the following approaches: 2D planar-based dosimetry, 3D SPECT/CT-based dosimetry, and hybrid dosimetry combining 2D and 3D data. Absorbed doses were calculated according to IDAC 2.1 for the kidneys, the liver, the salivary glands, and bone metastases.
Mean absorbed doses estimated by 3D dosimetry (the reference method) were 0.54 ± 0.28 Gy/GBq for the kidneys, 0.10 ± 0.05 Gy/GBq for the liver, 0.81 ± 0.34 Gy/GBq for the parotid gland, 0.72 ± 0.39 Gy/GBq for the submandibular gland, and 1.68 ± 1.32 Gy/GBq for bone metastases. Absorbed doses of normal organs estimated by hybrid dosimetry showed small, non-significant differences (median up to 4.0%) to the results of 3D dosimetry. Using 2D dosimetry, in contrast, significant differences (median up to 10.9%) were observed. Regarding bone metastases, small, but significant differences (median up to 7.0%) of absorbed dose were found for both, 2D dosimetry and hybrid dosimetry. Bland-Altman analysis revealed high agreement between hybrid dosimetry and 3D dosimetry for normal organs and bone metastases, but substantial differences between 2D dosimetry and 3D dosimetry.
Hybrid dosimetry provides high accuracy in estimation of absorbed dose in comparison to 3D dosimetry for all important organs and is therefore feasible for use in individualized PSMA-RLT.
剂量测定对于优化患者个体化的前列腺特异性膜抗原靶向放射性配体治疗（PSMA-RLT）至关重要。我们研究的目的是在临床常规中，从准确性和工作量方面评估和比较基于图像的吸收剂量估计的不同方法的可行性。
在给予平均活度为6.4 GBq的[¹⁷⁷Lu]Lu-PSMA-617（范围3 - 10.9 GBq）后24小时、48小时和≥96小时，从24例患者和65个周期采集全身平面图像和SPECT/CT图像。使用以下方法进行剂量测定：基于二维平面的剂量测定、基于三维SPECT/CT的剂量测定以及结合二维和三维数据的混合剂量测定。根据IDAC 2.1计算肾脏、肝脏、唾液腺和骨转移灶的吸收剂量。
通过三维剂量测定（参考方法）估计的平均吸收剂量，肾脏为0.54±0.28 Gy/GBq，肝脏为0.10±0.05 Gy/GBq，腮腺为0.81±0.34 Gy/GBq，颌下腺为0.72±0.39 Gy/GBq，骨转移灶为1.68±1.32 Gy/GBq。混合剂量测定估计的正常器官吸收剂量与三维剂量测定结果显示出微小的、无统计学意义的差异（中位数高达4.0%）。相比之下，使用二维剂量测定时，观察到显著差异（中位数高达10.9%）。对于骨转移灶，二维剂量测定和混合剂量测定均发现吸收剂量存在微小但显著的差异（中位数高达7.0%）。Bland-Altman分析显示，混合剂量测定与三维剂量测定在正常器官和骨转移灶方面具有高度一致性，但二维剂量测定与三维剂量测定之间存在实质性差异。
与三维剂量测定相比，混合剂量测定在所有重要器官的吸收剂量估计中具有较高的准确性，因此可用于个体化的PSMA-RLT。
