Dilaver Akar Ayşe, Yeyin Nami, Akyol Sinem, Demir Özge, Gülce Çoker Eylem, Demir Mustafa
İstanbul Aydın University, Graduate Education Institute, Health Physics Program, İstanbul, Türkiye.
İstanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Department of Nuclear Medicine, İstanbul, Türkiye.
Mol Imaging Radionucl Ther. 2025 Aug 13. doi: 10.4274/mirt.galenos.2025.77200.
Yttrium-90 (Y) radioembolization has become increasingly important in the treatment of liver tumors. This study aims to experimentally determine the extent to which small liver tumors are affected by the partial volume effect (PVE) in single photon emission computed tomography/computed tomography (SPECT/CT) scintigraphy using technetium-99m-macroaggregated albumin (Tc-99m-MAA), and to investigate the impact of PVE on tumor dosimetry and image quality.
In this experimental study, a custom-designed liver phantom containing four tumor mimics with diameters of 1 cm, 2 cm, 3 cm, and 5 cm was used. The tumor and liver parenchyma volumes were filled with Tc-99m at a ratio of 4.86: 1. The phantom was imaged in a water tank using SPECT/CT according to standard clinical protocols. Volumetric regions of interest were drawn for each lesion and tumor volumes, contrast values (C), contrast to noise ratios (CNR), and absorbed tumor doses were calculated from the counts obtained. Since this study does not involve live subjects and was conducted solely on a phantom model, ethical approval, informed consent, and consent forms are not required for this study.
Tumor diameters measured on SPECT/CT images matched those obtained from both CT images and the actual dimensions. The contrast values calculated from the SPECT/CT images for lesions with diameters of 2 cm and 5 cm were 2.03 and 3.89, respectively. Similarly, the corresponding CNR values were 8.64 and 21.07. Tumor-to-normal tissue ratios were 2.03 and 3.89 for the 2 cm and 5 cm lesions, respectively. For the 2 cm lesion, the actual and SPECT/CT-derived absorbed doses were 15.3 Gy and 7.87 Gy, respectively. For the 5 cm lesion, these values were 15.4 Gy and 13.38 Gy, respectively. the absorbed tumor doses significantly decreased as tumor diameter decreased due to the influence of PVE.
Tumors smaller than 2 cm in diameter were markedly affected by the PVE. Considering the influence of PVE, or applying appropriate corrections in dosimetric calculations, is of critical importance for improving the accuracy of dosimetry results.
钇 - 90（Y）放射性栓塞在肝肿瘤治疗中变得越来越重要。本研究旨在通过实验确定在使用锝 - 99m - 大颗粒白蛋白（Tc - 99m - MAA）的单光子发射计算机断层扫描/计算机断层扫描（SPECT/CT）闪烁显像中，小肝肿瘤受部分容积效应（PVE）影响的程度，并研究PVE对肿瘤剂量测定和图像质量的影响。
在本实验研究中，使用了一个定制设计的肝脏模型，其中包含四个直径分别为1 cm、2 cm、3 cm和5 cm的肿瘤模拟物。肿瘤和肝实质体积以4.86∶1的比例充满Tc - 99m。根据标准临床方案，在水箱中使用SPECT/CT对模型进行成像。为每个病变绘制感兴趣的体积区域，并根据获得的计数计算肿瘤体积、对比度值（C）、对比噪声比（CNR）和吸收的肿瘤剂量。由于本研究不涉及活体受试者，仅在模型上进行，因此本研究无需伦理批准、知情同意和同意书。
SPECT/CT图像上测量的肿瘤直径与CT图像和实际尺寸获得的直径匹配。直径为2 cm和5 cm病变的SPECT/CT图像计算出的对比度值分别为2.03和3.89。同样，相应的CNR值分别为8.64和21.07。2 cm和5 cm病变的肿瘤与正常组织比值分别为2.03和3.89。对于2 cm病变，实际和SPECT/CT得出的吸收剂量分别为15.3 Gy和7.87 Gy。对于5 cm病变，这些值分别为15.4 Gy和13.38 Gy。由于PVE的影响，吸收的肿瘤剂量随着肿瘤直径的减小而显著降低。
直径小于2 cm的肿瘤受PVE影响明显。考虑PVE的影响或在剂量计算中应用适当的校正对于提高剂量测定结果的准确性至关重要。
