Department of Nuclear Medicine, University of Szeged, Szeged, Hungary;
Ahmanson Translational Theranostics Division, Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California.
J Nucl Med. 2021 Aug 1;62(8):1075-1081. doi: 10.2967/jnumed.120.253476. Epub 2020 Dec 4.
Tc-PSMA I&S is a prostate-specific membrane antigen (PSMA) tracer that can be used for planar and SPECT/CT γ-imaging and radioguided surgery. The primary aim of this study was to estimate the dosimetry of Tc-PSMA I&S using a hybrid method (sequential γ-planar imaging and 1 single SPECT/CT) in healthy volunteers. The secondary aim was to depict the tracer biodistribution and tumor-to-background ratios (TBRs) in patients with prostate cancer (PCa). Dosimetry of Tc-PSMA I&S was investigated in 4 healthy volunteers. Whole-body planar imaging was acquired at 1, 2, 3, 6, and 24 h and SPECT/CT at 6 h after tracer injection. Contours of organs were drawn on all acquisitions to determine organ activity at each time point. Absorbed dose was estimated using 2 methods: independent curve-fitting manual method (Levenberg-Marquardt-based algorithm using dose factors from RAdiation Dose Assessment Resource [RADAR] website) and OLINDA/EXM software (version 2.0; HERMES Medical Solutions). Biodistribution of Tc-PSMA I&S was assessed in 10 patients with PCa on SPECT/CT images at 6 h. Tumor uptake (SUV), and TBR (tumor SUV/background organ SUV) using muscle (T/M), bladder (T/B), and intestine (T/I) as background organs were determined. The mean injected activity of Tc-PSMA I&S was 717 MBq (range: 562-828 MBq). No adverse events related to the injection of Tc-PSMA I&S were reported. The average radiation effective dose was 0.0055 mSv/MBq with the RADAR manual method and 0.0052 mSv/MBq with OLINDA/EXM. Total body effective dose ranged between 3.33-4.42 and 3.11-4.23 mSv, respectively. All PCa patients showed high tracer uptake in primary and metastatic lesions with T/M, T/B, and T/I ranging from 5.29-110, 0.11-7.02, and 0.96-16.30, respectively. Effective doses of Tc-PSMA I&S were comparable to those known for most of the Tc tracers and was lower than for the Ga-labeled and F-labeled agents. Tc-PSMA I&S SPECT/CT showed high TBR in PCa patients. This study can provide required data for translation and approval of Tc-PSMA I&S by regulatory agencies.
Tc-PSMA I&S 是一种前列腺特异性膜抗原（PSMA）示踪剂，可用于平面和 SPECT/CT γ-成像和放射性引导手术。本研究的主要目的是使用混合方法（顺序γ平面成像和 1 次 SPECT/CT）在健康志愿者中估算 Tc-PSMA I&S 的剂量。次要目的是描述前列腺癌（PCa）患者中的示踪剂生物分布和肿瘤与背景比（TBR）。 在 4 名健康志愿者中研究了 Tc-PSMA I&S 的剂量。在注射示踪剂后 1、2、3、6 和 24 小时进行全身平面成像，在 6 小时进行 SPECT/CT。在所有采集物上绘制器官轮廓，以确定每个时间点的器官活性。使用 2 种方法估算吸收剂量：独立曲线拟合手动方法（使用 RAdiation Dose Assessment Resource [RADAR] 网站的剂量因子的 Levenberg-Marquardt 算法）和 OLINDA/EXM 软件（版本 2.0；HERMES Medical Solutions）。在 10 名 PCa 患者的 SPECT/CT 图像上，在 6 小时时评估 Tc-PSMA I&S 的生物分布。使用肌肉（T/M）、膀胱（T/B）和肠（T/I）作为背景器官，确定肿瘤摄取（SUV）和 TBR（肿瘤 SUV/背景器官 SUV）。 Tc-PSMA I&S 的平均注射活性为 717 MBq（范围：562-828 MBq）。未报告与 Tc-PSMA I&S 注射相关的不良事件。使用 RADAR 手动方法的平均辐射有效剂量为 0.0055 mSv/MBq，使用 OLINDA/EXM 的平均辐射有效剂量为 0.0052 mSv/MBq。全身有效剂量范围分别为 3.33-4.42 和 3.11-4.23 mSv。所有 PCa 患者在原发性和转移性病变中均显示出高示踪剂摄取，T/M、T/B 和 T/I 分别为 5.29-110、0.11-7.02 和 0.96-16.30。 Tc-PSMA I&S 的有效剂量与大多数 Tc 示踪剂的有效剂量相当，低于 Ga 标记和 F 标记的制剂。 Tc-PSMA I&S SPECT/CT 在 PCa 患者中显示出高 TBR。本研究可为监管机构对 Tc-PSMA I&S 的翻译和批准提供所需数据。
