Belli Maria Luisa, Mezzenga Emilio, Di Iorio Valentina, Celli Monica, Caroli Paola, Canali Elisabeth, Matteucci Federica, Tardelli Elisa, Grassi Ilaria, Sansovini Maddalena, Nicolini Silvia, Severi Stefano, Cremonesi Marta, Ferrari Mahila, Paganelli Giovanni, Sarnelli Anna
Medical Physics Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy;
Medical Physics Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy.
J Vis Exp. 2020 Apr 24(158). doi: 10.3791/60477.
Peptide-receptor-radionuclide-therapy (PPRT) is a targeted therapy that combines a short-range energy radionuclide with a substrate with high specificity for cancer cell receptors. After injection, the radiotracer is distributed throughout the entire body, with a higher uptake in tissues where targeted receptors are overexpressed. The use of beta/gamma radionuclide emitters enables therapy imaging (beta-emission) and post-therapy imaging (gamma-emission) to be performed at the same time. Post-treatment sequential images permit absorbed dose calculation based on local uptake and wash-in/wash-out kinetics. We implemented a hybrid method that combines information derived from both 2D and 3D images. Serial whole-body images and blood samples are acquired to estimate the absorbed dose to different organs at risk and to lesions disseminated throughout the body. A single 3D-SPECT/CT image, limited to the abdominal region, overcomes projection overlap on planar images of different structures such as the intestines and kidneys. The hybrid 2D+3D-SPECT/CT method combines the effective half-life information derived from 2D planar images with the local uptake distribution derived from 3D images. We implemented this methodology to estimate the absorbed dose for patients undergoing PRRT with Lu-PSMA-617. The methodology could, however, be implemented with other beta-gamma radiotracers. To date, 10 patients have been enrolled into the dosimetry study with Lu-PSMA-617 combined with drug protectors for kidneys and salivary glands (mannitol and glutamate tablets, respectively). The median ratio between kidney uptake at 24 h evaluated on planar images and 3D-SPECT/CT is 0.45 (range:0.32-1.23). The comparison between hybrid and full 3D approach has been tested on one patient, resulting in a 1.6% underestimation with respect to full 3D (2D: 0.829 mGy/MBq, hybrid: 0.315 mGy/MBq, 3D: 0.320 mGy/MBq). Treatment safety has been confirmed, with a mean absorbed dose of 0.73 mGy/MBq (range:0.26-1.07) for kidneys, 0.56 mGy/MBq (0.33-2.63) for the parotid glands and 0.63 mGy/MBq (0.23-1.20) for submandibular glands, values in accordance with previously published data.
肽受体放射性核素治疗（PPRT）是一种靶向治疗方法，它将短程能量放射性核素与对癌细胞受体具有高特异性的底物相结合。注射后，放射性示踪剂分布于全身，在靶向受体过度表达的组织中摄取更高。使用β/γ放射性核素发射体能够同时进行治疗成像（β发射）和治疗后成像（γ发射）。治疗后的序列图像可根据局部摄取及摄取/洗脱动力学进行吸收剂量计算。我们实施了一种结合二维和三维图像信息的混合方法。采集系列全身图像和血样，以估计不同危险器官及全身播散性病变的吸收剂量。仅局限于腹部区域的单一三维SPECT/CT图像克服了诸如肠道和肾脏等不同结构在平面图像上的投影重叠。二维+三维SPECT/CT混合方法将二维平面图像获得的有效半衰期信息与三维图像获得的局部摄取分布相结合。我们应用这种方法来估计接受Lu-PSMA-617肽受体放射性核素治疗患者的吸收剂量。然而，该方法也可应用于其他β-γ放射性示踪剂。迄今为止，已有10名患者纳入了使用Lu-PSMA-617联合肾脏和唾液腺药物保护剂（分别为甘露醇和谷氨酸片）的剂量学研究。平面图像和三维SPECT/CT评估的24小时肾脏摄取量的中位数比值为0.45（范围：0.32 - 1.23）。在一名患者身上测试了混合方法与全三维方法的比较，结果显示相对于全三维方法低估了1.6%（二维：0.829 mGy/MBq，混合：0.315 mGy/MBq，三维：0.320 mGy/MBq）。已证实治疗的安全性，肾脏的平均吸收剂量为0.73 mGy/MBq（范围：0.26 - 1.07），腮腺为0.56 mGy/MBq（0.33 - 2.63），颌下腺为0.63 mGy/MBq（0.23 - 1.20），这些值与先前发表的数据一致。
