Laverman Peter, Boerman Otto C, Corstens Frans H M, Oyen Wim J G
Department of Nuclear Medicine, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Eur J Nucl Med Mol Imaging. 2002 May;29(5):681-90. doi: 10.1007/s00259-001-0716-y. Epub 2002 Jan 11.
The currently preferred radiopharmaceutical for positron emission tomography (PET) in oncology is 2-[(18)F]fluoro-deoxyglucose (FDG). Increased accumulation of this deoxyglucose analogue in tumour cells is based on elevated glucose metabolism by tumour cells and subsequent trapping in the cells. In the search for new PET tracers, amino acids have been widely studied. A new amino acid tracer should preferably have similar high uptake in tumour cells but low non-specific uptake in normal tissues and any pathology other than tumour. In recent years, several amino acids have been labelled with either gamma radiation-emitting radionuclides or positron-emitting radionuclides, the most commonly used being carbon-11. However, the longer half-life of fluorine-18 matches better with the relatively slow process of protein synthesis and also facilitates shipping of the radiolabelled amino acids to hospitals without an on-site cyclotron or dedicated radiochemistry laboratory. The number of fluorinated amino acids under investigation is increasing, and one of the major points of discussion is the underlying mechanism of the tumour visualisation. While it has been shown that some amino acids can be used to measure the protein synthesis rate, others are used with the sole aim of measuring the rate of uptake into the cell. The differences between measuring amino acid transport (rate) and protein synthesis rate with (18)F-labelled amino acids are discussed.
目前在肿瘤学正电子发射断层扫描（PET）中首选的放射性药物是2-[(18)F]氟脱氧葡萄糖（FDG）。这种脱氧葡萄糖类似物在肿瘤细胞中积累增加，是基于肿瘤细胞葡萄糖代谢升高以及随后在细胞内的滞留。在寻找新的PET示踪剂的过程中，氨基酸已得到广泛研究。一种新的氨基酸示踪剂最好在肿瘤细胞中有类似的高摄取，但在正常组织和除肿瘤外的任何病变中具有低非特异性摄取。近年来，几种氨基酸已用发射γ射线的放射性核素或发射正电子的放射性核素进行标记，最常用的是碳-11。然而，氟-18较长的半衰期与相对缓慢的蛋白质合成过程更匹配，也便于将放射性标记的氨基酸运送到没有现场回旋加速器或专门放射化学实验室的医院。正在研究的氟化氨基酸数量在增加，主要讨论点之一是肿瘤可视化的潜在机制。虽然已经表明一些氨基酸可用于测量蛋白质合成速率，但其他氨基酸仅用于测量进入细胞的摄取速率。本文讨论了用(18)F标记的氨基酸测量氨基酸转运（速率）和蛋白质合成速率之间的差异。
