Sandblom Viktor, Ståhl Ingun, Olofsson Bagge Roger, Forssell-Aronsson Eva
Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy, University of Gothenburg, SE-413 45, Gothenburg, Sweden.
Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Cancer Center, Sahlgrenska Academy, University of Gothenburg, SE-413 45, Gothenburg, Sweden.
EJNMMI Phys. 2017 Dec;4(1):3. doi: 10.1186/s40658-016-0168-x. Epub 2017 Jan 9.
Patients with somatostatin receptor-expressing neuroendocrine tumours can be treated with intravenously administered Lu-octreotate. Few patients are cured with the present protocol due to the current dose limitation of normal organs at risk, such as the kidneys. By locally administering Lu-octreotate to the liver for the purpose of treating liver metastases, a substantially reduced absorbed dose to organs at risk could be achieved. The development of such a technique requires the capability of measuring the Lu activity concentration in tissues in vivo. The aim of this study was to evaluate different performance parameters of two commercially available intraoperative gamma detectors in order to investigate whether intraoperative gamma detector measurements could be used to determine Lu activity concentration in vivo.
Measurements were made using different sources containing Lu. Response linearity, sensitivity, spatial resolution and its depth dependence, organ thickness dependence of the measured count rate and tumour detectability were assessed for two intraoperative gamma detectors. The two detectors (a scintillation and a semiconductor detector) showed differences in technical performance. For example, the sensitivity was higher for the scintillation detector, while the spatial resolution was better for the semiconductor detector. Regarding organ thickness dependence and tumour detectability, similar results were obtained for both detectors, and even relatively small simulated tumours of low tumour-to-background activity concentration ratios could be detected.
Acceptable results were obtained for both detectors, although the semiconductor detector proved more advantageous for our purpose. The measurements demonstrated factors that must be corrected for, such as organ thickness or dead-time effects. Altogether, intraoperative gamma detector measurements could be used to determine Lu activity concentration in vivo.
表达生长抑素受体的神经内分泌肿瘤患者可接受静脉注射¹⁷⁷Lu-奥曲肽治疗。由于目前对肾脏等正常危险器官的剂量限制，采用当前方案治愈的患者较少。通过将¹⁷⁷Lu-奥曲肽局部注入肝脏以治疗肝转移，可显著降低危险器官的吸收剂量。开发这样一种技术需要具备在体内测量组织中¹⁷⁷Lu活度浓度的能力。本研究的目的是评估两种市售术中γ探测器的不同性能参数，以研究术中γ探测器测量是否可用于确定体内¹⁷⁷Lu活度浓度。
使用含有¹⁷⁷Lu的不同源进行测量。对两种术中γ探测器评估了响应线性、灵敏度、空间分辨率及其深度依赖性、测量计数率的器官厚度依赖性和肿瘤可探测性。这两种探测器（一种闪烁探测器和一种半导体探测器）在技术性能上存在差异。例如，闪烁探测器的灵敏度较高，而半导体探测器的空间分辨率较好。关于器官厚度依赖性和肿瘤可探测性，两种探测器获得了相似的结果，甚至相对较小的、肿瘤与本底活度浓度比值较低的模拟肿瘤也能被检测到。
两种探测器均获得了可接受的结果，尽管半导体探测器在我们的研究目的方面证明更具优势。测量结果表明了一些必须校正的因素，如器官厚度或死时间效应。总体而言，术中γ探测器测量可用于确定体内¹⁷⁷Lu活度浓度。
