Zeimpekis Konstantinos G, Sari Hasan, Gözlügöl Nasir, Achangwa Ngwe Rawlings, Shi Kuangyu, Schindewolf Marc, Afshar-Oromieh Ali, Rominger Axel, Seifert Robert
Department of Nuclear Medicine, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse 18, Bern, 3010, Switzerland.
Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.
Eur J Nucl Med Mol Imaging. 2025 Mar;52(4):1460-1471. doi: 10.1007/s00259-024-07034-9. Epub 2024 Dec 28.
Long axial field-of-view (LAFOV) positron emission tomography/computed tomography (PET/CT) scanners enable high sensitivity and wide anatomical coverage. Therefore, they seem ideal to perform post-selective internal radiation therapy (SIRT) Y scans, which are needed, to confirm that the dose is delivered to the tumors and that healthy organs are spared. However, it is unclear to what extent the use of LAFOV PET is feasible and which dosimetry approaches results in accurate measurements.
In this retrospective analysis, a total number of 32 patients was included (median age 71, IQR 14), which had hepatocellular carcinoma, cholangiocarcinoma, or liver metastases. All patients underwent SIRT, and the post-therapy scan was acquired on a single photon emission computed tomography/computed tomography (SPECT/CT) and a LAFOV Biograph Quadra PET/CT with a 20-minute acquisition time. Post-treatment dosimetry, regarding the tumor, whole-liver and lung (LMD) absorbed dose was done using an organ-wise (Simplicit90Y) and a voxel-wise approach (HERMIA Dosimetry) which used a semi-Monte Carlo algorithm. The lung shunt fraction (LSF) was also measured using the voxel-wise approach and compared to the planned.
The planning, post-treatment SPECT and PET (SPECT, SPECT, PET) median tumor doses based on the organ-wise dosimetry were 276.0 Gy (200.0-330.0 Gy), 232.0 Gy (158.5-303.5 Gy) and 267.5 Gy (182.5-370.8 Gy). In contrast, the median voxel-wise PET dose was significantly smaller than the planned SPECT (152.5 Gy (94.8-223.8 Gy); p < 0.00001). Moreover, the median tumor absorbed dose at 90% (D90) of the tumor volume was significantly higher in SPECT compared with PET (123.5 Gy; 81.5-180.0 vs. 30.5 Gy; 11.3-106.3; p < 0.00001). The PET measured LSF was significantly lower compared to the planned SPECT (0.89%; 0.4-1.3% vs. 2.3%; 1.5-3.6%; p < 0.0001). Similarly, the measured PET median LMD was considerably lower to the planned SPECT (1.2 Gy; 0.6-2.3 vs. 2.5 Gy; 1.4-4.7; p < 0.0001).
LAFOV PET enabled the direct measurement of post therapy lung dose and tumor doses that correlated well with the planned treatment doses. However, current voxel-wise-based tumor dosimetry seems to be inaccurate for LAFOV PET. In addition, dose volume histogram-based metrics also significantly underestimate the delivered dose. Therefore, improved dosimetry tools are needed for reliable voxel-wise Y dosimetry to leverage the sensitivity and spatial resolution of LAFOV PET scanners.
长轴视野（LAFOV）正电子发射断层扫描/计算机断层扫描（PET/CT）扫描仪具有高灵敏度和广泛的解剖覆盖范围。因此，它们似乎非常适合进行选择性内放射治疗（SIRT）后的Y扫描，这对于确认剂量是否输送到肿瘤以及健康器官是否得到保护是必要的。然而，目前尚不清楚LAFOV PET的使用在多大程度上可行，以及哪种剂量测定方法能得出准确的测量结果。
在这项回顾性分析中，共纳入了32例患者（中位年龄71岁，四分位距14），他们患有肝细胞癌、胆管癌或肝转移瘤。所有患者均接受了SIRT治疗，并在单光子发射计算机断层扫描/计算机断层扫描（SPECT/CT）和LAFOV Biograph Quadra PET/CT上进行了治疗后扫描，采集时间为20分钟。使用器官层面（Simplicit90Y）和体素层面方法（HERMIA剂量测定法）进行治疗后剂量测定，后者使用了半蒙特卡罗算法，测定肿瘤、全肝和肺（LMD）的吸收剂量。还使用体素层面方法测量了肺分流分数（LSF），并与计划值进行比较。
基于器官层面剂量测定法的计划、治疗后SPECT和PET（SPECT、SPECT、PET）的中位肿瘤剂量分别为276.0 Gy（200.0 - 330.0 Gy）、232.0 Gy（158.5 - 303.5 Gy）和267.5 Gy（182.5 - 370.8 Gy）。相比之下，体素层面PET剂量的中位数明显低于计划的SPECT（152.5 Gy（94.8 - 223.8 Gy）；p < 0.00001）。此外，肿瘤体积90%（D90）处的肿瘤吸收剂量中位数在SPECT中显著高于PET（123.5 Gy；81.5 - 180.0对比30.5 Gy；11.3 - 1
