Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ, Groningen, The Netherlands.
Mol Imaging Biol. 2019 Apr;21(2):240-248. doi: 10.1007/s11307-018-1245-4.
An important issue in rodent imaging is the question whether a mixed population of male and female animals can be used rather than animals of a single sex. For this reason, the present study examined the test-retest stability of positron emission tomography (PET) with 2-deoxy-2-[F]fluoro-D-glucose ([F]FDG) in male rats and female rats at different phases of the estrous cycle.
Long-Evans rats (age 1 year) were divided into three groups: (1) males (n = 6), (2) females in metestrous (low estrogen levels, n = 9), and (3) females in proestrous (high estrogen levels, n = 7). Two standard [F]FDG scans with rapid arterial blood sampling were made at an interval of 10 days in subjects anesthetized with isoflurane and oxygen. Body temperature, heart rate, and blood oxygenation were continuously monitored. Regional cerebral metabolic rates of glucose were calculated using a Patlak plot with plasma radioactivity as input function.
Regional metabolic rate of glucose (rCMR) in male and female rats, or [F]FDG uptake in females at proestrous and metestrous, was not significantly different, but females showed significantly higher standardized uptake values (SUVs) and Patlak flux than males, particularly in the initial scan. The relative difference between the scans and the test-retest variability (TRV) were greater in females than in males. Intra-class correlation coefficients (ICCs) of rCMR, SUV, normalized SUV, and glucose flux were good to excellent in males but poor to moderate in females.
Based on these data for [F]FDG, the mixing of sexes in imaging studies of the rodent brain will result in an impaired test-retest stability of PET data and a need for larger group sizes to maintain statistical power in group comparisons. The observed differences between males and females do not indicate any specific gender difference in cerebral metabolism but are related to different levels of non-radioactive glucose in blood plasma during isoflurane anesthesia.
啮齿动物成像中的一个重要问题是，是否可以使用混合性别的雄性和雌性动物群体，而不是单一性别的动物。出于这个原因，本研究在不同动情周期阶段的雄性和雌性大鼠中检查了正电子发射断层扫描（PET）与 2-脱氧-2-[F]氟-D-葡萄糖（[F]FDG）的测试-重测稳定性。
长爪沙鼠（年龄 1 岁）分为三组：（1）雄性（n=6），（2）动情前期（低雌激素水平，n=9）和（3）动情前期（高雌激素水平，n=7）的雌性。在异氟烷和氧气麻醉下，在 10 天的间隔内对受试者进行两次标准的[F]FDG 扫描和快速动脉采血。连续监测体温、心率和血氧饱和度。使用 Patlak 图和血浆放射性作为输入函数计算局部脑葡萄糖代谢率。
雄性和雌性大鼠的局部葡萄糖代谢率（rCMR）或动情前期和动情前期雌性的[F]FDG 摄取没有显著差异，但雌性的标准化摄取值（SUV）和 Patlak 通量明显高于雄性，特别是在初始扫描中。两次扫描之间的相对差异和测试-重测变异性（TRV）在雌性中大于雄性。雄性的 rCMR、SUV、归一化 SUV 和葡萄糖通量的组内相关系数（ICC）良好至优秀，而雌性的 ICC 则较差至中等。
基于这些[F]FDG 数据，啮齿动物大脑成像研究中混合性别会导致 PET 数据的测试-重测稳定性受损，并且需要更大的组大小来维持组间比较的统计效力。雄性和雌性之间观察到的差异并不表示大脑代谢存在任何特定的性别差异，而是与异氟烷麻醉期间血浆中非放射性葡萄糖的不同水平有关。
