In the adrenocortex, one of the key enzymes playing a major role in the biosynthesis, is the 11β-hydroxylase (CYP11B1; P45011β), forming cortisol and aldosterone from the corresponding deoxysteroids. This enzyme can be overexpressed in incidentalomas of the adrenal cortex and was described as a relative excellent target enzyme for adrenocortical imaging. 11C-(R) -1-(1-phenylethyl) -1H-imidazole-5-carboxylic acid methylester (R) -[O-methyl-11 C] metomidate, 11C-MTO, an analogue of etomidate,well known as a narcotic drug,works as a substrate for this enzyme and therefore was introduced for adrenocortical imaging. After years of hard working of researching, the radiosynthesis and quality control methods of the radiopharmaceutical have relatively matured. The automatic radiosynthesis methods of 11C-MTO have been proved to be reliable and suitable for routine clinical PET imaging of the adrenal cortex and its tumors. The results of PET imaging show that significantly higher uptake of 11C-MTO is seen in adrenocortex and cortical lesions. Moderate tracer accumulation is shown in liver, and low tracer accumulation is shown in other organs in the abdomen and noncortical lesions. The studies indicate that PET with 11C-MTO has a promising potential to be used clinically for characterization of adrenal masses and that it positively identifies lesions of adrenocortical origin.%在肾上腺皮质,11β-羟化酶在将相应去氧类固醇产生皮质醇和醛固酮的过程中发挥主要作用.这种酶在肾上腺髓质偶发瘤中过度表达并被描述为在肾上腺皮质显像过程中表现相对出色的靶点酶.美托咪酯作为一种常见的麻醉药物可以充当11β-羟化酶的替代物,因此被应用于肾上腺皮质显像.放射化学工作者经过多年探索,在示踪剂的放射化学合成及质量控制方面,已经摸索出了比较成熟的方法,可以稳定地合成出符合肾上腺皮质临床正电子发射断层显像要求的示踪剂.临床显像研究结果显示肾上腺皮质及肾上腺皮质来源的肿瘤可特异性高摄取11C-美托咪酯,肝脏中度程度摄取,而腹部其他脏器及非肾上腺皮质来源肿瘤低摄取.因此,利用该方法可进行肾上腺皮质来源性肿瘤的早期诊断及特异性鉴别诊断.
展开▼
