Henze Marcus, Mohammed Ashour, Schlemmer Heinz, Herfarth Klaus K, Mier Walter, Eisenhut Michael, Debus Jürgen, Haberkorn Uwe
Department of Nuclear Medicine, University of Heidelberg, Germany.
Eur J Nucl Med Mol Imaging. 2002 Nov;29(11):1455-61. doi: 10.1007/s00259-002-0896-0. Epub 2002 Aug 20.
Conventional MRI often fails to distinguish between progressive tumour and radiation injury, because both appear as mass lesions with unspecific Gd-DTPA enhancement. Furthermore, the sensitivity of FDG PET for the evaluation of malignant lesions in the brain is limited owing to high cortical uptake. The aim of this study was to assess the potential of alternative SPET tracers in the same group of patients. 35.2+/-20.1 months after stereotactic radiotherapy (59.3+/-4.2 Gy) of low-grade astrocytomas (median WHO II), 16 patients, presenting 25 Gd-DTPA-enhancing lesions on MRI, were examined by SPET. Lesions were classified as progressive tumour (PT, n=17) or non-PT (nPT, n=8) based on prospective follow-up (clinical examination, MRI, proton-MR spectroscopy) for 25.6+/-6.7 months after SPET. SPET scans were performed 15 and 60 min after injection of 694+/-67 MBq hexakis(2-methoxyisobutylisonitrile)(99m)Tc(I) (MIBI). 3-[(123)I]iodo-alpha-methyl- L-tyrosine (IMT) SPET was acquired 15 min after injection of 291+/-58 MBq IMT. Lesion-to-normal tissue ratios (l/n) for IMT (l/n(IMT)) and MIBI (l/n(MIBI)) were calculated using a reference region mirrored to the contralateral hemisphere. Using IMT, significantly higher ratios ( P<0.001) were found in PT (1.7+/-0.4) than in nPT (1.1+/-0.1). For MIBI, there was no statistically significant difference ( P=0.206) between PT (3.7+/-2.8) and nPT (1.8+/-1.8). Sensitivities for MIBI and IMT were 53% and 94%, and specificities 75% and 100%, respectively. Positive predictive values for MIBI and IMT respectively reached 80% and 100%, and negative predictive values were 46% and 90%. In conclusion, in contrast to MIBI, IMT showed almost no overlap between the PT and the nPT group. The sensitivity, specificity and predictive values of IMT SPET were obviously higher than those of MIBI SPET. IMT is considered to be a useful tracer for differentiating PT from nPT in the follow-up of irradiated low-grade astrocytomas.
传统的磁共振成像（MRI）常常难以区分进行性肿瘤和放射性损伤，因为二者均表现为具有非特异性钆-二乙三胺五乙酸（Gd-DTPA）强化的肿块病变。此外，由于大脑皮质对氟代脱氧葡萄糖（FDG）摄取量高，FDG正电子发射断层显像（PET）评估脑内恶性病变的敏感性受到限制。本研究的目的是评估同一组患者使用其他单光子发射断层显像（SPET）示踪剂的潜力。在对低级别星形细胞瘤（世界卫生组织（WHO）分级中值为Ⅱ级）进行立体定向放射治疗（59.3±4.2 Gy）后35.2±20.1个月，16例患者因MRI上出现25个Gd-DTPA强化病变而接受SPET检查。根据SPET后25.6±6.7个月的前瞻性随访（临床检查、MRI、质子磁共振波谱），将病变分为进行性肿瘤（PT，n = 17）或非进行性肿瘤（nPT，n = 8）。在注射694±67兆贝可六（2-甲氧基异丁基异腈）（99m）锝（I）（MIBI）后15分钟和60分钟进行SPET扫描。在注射291±58兆贝可3-[(123)I]碘-α-甲基-L-酪氨酸（IMT）后15分钟进行IMT SPET采集。使用与对侧半球镜像的参考区域计算IMT（l/n(IMT)）和MIBI（l/n(MIBI)）病变与正常组织的比值。使用IMT时，PT组（1.7±0.4）的比值显著高于nPT组（1.1±0.1）（P<0.001）。对于MIBI，PT组（3.7±2.8）和nPT组（1.8±1.8）之间无统计学显著差异（P = 0.206）。MIBI和IMT的敏感性分别为53%和94%，特异性分别为75%和100%。MIBI和IMT的阳性预测值分别达到80%和100%，阴性预测值分别为46%和90%。总之，与MIBI不同，IMT显示PT组和nPT组之间几乎没有重叠。IMT SPET的敏感性、特异性和预测值明显高于MIBI SPET。IMT被认为是在接受放疗的低级别星形细胞瘤随访中区分PT和nPT的有用示踪剂。
