Tjuvajev J G, Macapinlac H A, Daghighian F, Scott A M, Ginos J Z, Finn R D, Kothari P, Desai R, Zhang J, Beattie B
Cotzias Neuro-Oncology Laboratory, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
J Nucl Med. 1994 Sep;35(9):1407-17.
Iodine-131-iododeoxyuridine (IUdR) uptake and retention was imaged with SPECT at 2 and 24 hr after administering a 10-mCi dose to six patients with primary brain tumors. The SPECT images were directly compared to gadolinium contrast-enhanced MR images as well as to [18F]fluorodeoxyglucose (FDG) PET scans and 201Tl SPECT scans.
Localized uptake and retention of IUdR-derived radioactivity was observed in five of six patients. The plasma half-life of [131I]IUdR was short (1.6 min) in comparison to the half-life of total plasma radioactivity (6.4 hr). The pattern of [131I]IUdR-derived radioactivity was markedly different in the 2-hr compared to 24-hr images. Radioactivity was localized along the periphery of the tumor and extended beyond the margin of tumor identified by contrast enhancement on MRI. The estimated levels of tumor radioactivity at 24 hr, based on semiquantitative phantom studies, ranged between < 0.1 and 0.2 microCi/cc (< 0.001% and 0.002% dose/cc); brain levels were not measurable.
Iodine-131-IUdR SPECT imaging of brain tumor proliferation has low (marginal) sensitivity due to low count rates and can detect only the most active regions of tumor growth. Imaging at 24 hr represents a washout strategy to reduce 131I-labeled metabolites contributing to background activity in the tumors, and is more likely to show the pattern of [131I]IUdR-DNA incorporation and thereby increase image specificity. Iodine-123-IUdR SPECT imaging at 12 hr and the use of [124I]IUdR and PET will improve count acquisition and image quality.
对6例原发性脑肿瘤患者给予10毫居里剂量后，于2小时和24小时用单光子发射计算机断层扫描（SPECT）对碘-131-碘脱氧尿苷（IUdR）摄取和滞留情况进行成像。将SPECT图像直接与钆对比增强磁共振成像（MR）图像、[18F]氟脱氧葡萄糖（FDG）正电子发射断层扫描（PET）以及铊-201单光子发射计算机断层扫描（SPECT）进行比较。
6例患者中有5例观察到IUdR衍生放射性的局部摄取和滞留。与总血浆放射性半衰期（6.4小时）相比，[131I]IUdR的血浆半衰期较短（1.6分钟）。与24小时图像相比，2小时时[131I]IUdR衍生放射性的模式明显不同。放射性位于肿瘤周边，并延伸至磁共振成像上通过对比增强确定的肿瘤边缘之外。基于半定量体模研究，24小时时肿瘤放射性估计水平在<0.1至0.2微居里/立方厘米（<0.001%和0.002%剂量/立方厘米）之间；脑内水平无法测量。
由于计数率低，碘-131-IUdR SPECT对脑肿瘤增殖的成像敏感性较低（边缘性），只能检测到肿瘤生长最活跃的区域。24小时成像代表一种洗脱策略，以减少对肿瘤背景活性有贡献的131I标记代谢物，更有可能显示[131I]IUdR-DNA掺入模式，从而提高图像特异性。12小时时进行碘-123-IUdR SPECT成像以及使用[124I]IUdR和PET将改善计数采集和图像质量。
