[11C]蛋氨酸 PET 研究的优化：合适的扫描时间和血浆氨基酸浓度对 SUV 的影响。
Optimization of [11C]methionine PET study: appropriate scan timing and effect of plasma amino acid concentrations on the SUV.
机构信息
Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita City, Osaka 565-0871, Japan.
出版信息
EJNMMI Res. 2013 Apr 15;3(1):27. doi: 10.1186/2191-219X-3-27.
BACKGROUND
[11C]methionine (MET) has been used to monitor amino acid metabolism in tumors, the pancreas, liver, and myocardium. The aim of the present study was to standardize [11C]MET positron emission tomography (PET) by optimizing the timing of initiation of the scan and applying correction to the plasma concentrations of neutral amino acids (NAAs), where necessary.
METHODS
Sequential whole-body MET PET/computed tomography (CT) was performed in 11 normal adults after they had fasted for at least 4 h. After whole-body CT for attenuation correction and intravenous bolus injection of MET, the subjects were scanned from the parietal to the groin. The scanning was repeated six to seven times. Decay of radioactivity during the PET scan was corrected to the time of initiation of the first scan. The standardized uptake values (SUVs) were evaluated in various organs by setting regions of interest on the tomographic images. Plasma concentrations of NAAs were examined in relation to the SUV values.
RESULTS
The SUVs in the pancreas reached their plateau from 6.5 to 11 min after the MET injection, and in the brain, lung, and myocardium, they reached their plateau from 19.6 to 24.1 min. The MET uptake in the spleen and kidney peaked early after the injection and steadily decreased thereafter. The SUVs in the liver and stomach wall rapidly increased during the first 0 to 4.5 min and gradually elevated thereafter during the scan period. Urinary radioactivity in the bladder reached its plateau from 26.1 to 30.6 min after the MET injection. There were no correlations between the plasma concentrations of NAAs and the maximal SUV in any organs.
CONCLUSIONS
The present study revealed the times taken to reach the plateau of MET uptake in various important organs, and little effects of the plasma neutral amino acid concentrations on the SUVs in PET studies conducted after the patients had fasted for at least 4 h. In the MET PET study, 4 h fasting period before MET administration and the scan initiation 20 min after MET administration provide the SUV values independent of scan initiation time and the plasma neutral amino acid concentrations.
背景
[11C]蛋氨酸（MET）已被用于监测肿瘤、胰腺、肝脏和心肌中的氨基酸代谢。本研究的目的是通过优化扫描开始时间和必要时对血浆中性氨基酸（NAAs）浓度进行校正来标准化[11C]MET 正电子发射断层扫描（PET）。
方法
11 名正常成年人在禁食至少 4 小时后进行了连续全身 MET PET/计算机断层扫描（CT）。全身 CT 用于衰减校正和静脉推注 MET 后，受检者从顶骨到腹股沟进行扫描。扫描重复六到七次。在 PET 扫描期间，放射性衰减校正为第一次扫描的开始时间。通过在断层图像上设置感兴趣区域来评估各器官的标准化摄取值（SUV）。检查了与 SUV 值相关的血浆 NAAs 浓度。
结果
胰腺 SUV 从注射 MET 后 6.5 到 11 分钟达到平台期，脑、肺和心肌 SUV 从注射 MET 后 19.6 到 24.1 分钟达到平台期。注射后脾脏和肾脏的 MET 摄取迅速达到峰值，此后逐渐下降。肝和胃壁 SUV 迅速增加，在扫描期间从 0 到 4.5 分钟逐渐升高。膀胱内的尿液放射性从注射 MET 后 26.1 到 30.6 分钟达到平台期。在禁食至少 4 小时后进行的 PET 研究中，任何器官的血浆 NAAs 浓度与最大 SUV 之间均无相关性。
结论
本研究揭示了各种重要器官达到 MET 摄取平台期所需的时间，以及患者禁食至少 4 小时后进行的 MET PET 研究中血浆中性氨基酸浓度对 SUV 值的影响很小。在 MET PET 研究中，MET 给药前 4 小时禁食期和 MET 给药后 20 分钟开始扫描提供了与扫描开始时间和血浆中性氨基酸浓度无关的 SUV 值。
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