Department of Nuclear Medicine, Ludwig-Maximilians University, Munich, Germany.
J Nucl Med. 2010 Oct;51(10):1576-83. doi: 10.2967/jnumed.110.078451. Epub 2010 Sep 16.
Data collection in preclinical small-animal PET studies has been hindered by the small number of recordings typically obtained for a single radiosynthesis. Therefore, we tested procedures for obtaining 8 simultaneous small-animal PET recordings from the brains of 8 mice using an acrylic anesthesia distributor (the Octamouse), with the dopamine D(2/3) ligand (18)F-fallypride serving as a test substance for brain receptor imaging.
The effect of scatter correction on the small-animal PET recordings was first evaluated in phantom studies in which sources of different radioactivity concentration were placed within the chambers of the Octamouse. Next, potential effects of mass on the (18)F-fallypride binding potential (BP(ND)) in the striatum were tested in groups of mice receiving (18)F-fallypride at 2 different specific activities (140 and 50 GBq/μmol), with and without scatter correction. Finally, the relationship between BP(ND) and injected dose of (18)F-fallypride (3.5-17 MBq/mouse) was tested.
Scatter correction improved the contrast between sources and air space within the Octamouse phantom. The magnitude of (18)F-fallypride BP(ND) in mouse striatum was invariant across the tested range of specific activities, and scatter correction increased BP(ND) by a mean of 6%; covariances of the inter- and intraoperator variability of BP(ND) were 10%. There was a positive correlation between radiochemical dose and BP(ND) with (R(2) = 0.53) and without (R(2) = 0.63) scatter correction, which was driven by increasing area under the percentage injected dose curve in the striatum.
The quantitation of emission sources placed within the Octamouse is linear over a wide range of source activities. In the striatum of living mice, the magnitude of (18)F-fallypride BP(ND) was highly reproducible between operators and was constant over a 3-fold range of specific activities, indicating a lack of significant occupancy. Scatter correction improved quantitation but did not entirely correct for the dependence of BP(ND) on injected dose, which was deemed to arise because of effects propagating from detector dead time when the total radiochemical dose in the field of view exceeded 50 MBq. Given this consideration, we were still able to quantify (18)F-fallypride BP(ND) in 16 mice from a single radiosynthesis, an economy that should be generalizable to brain studies of diverse radioligands.
使用丙烯酸麻醉分配器（Octamouse）从 8 只小鼠的大脑中同时获得 8 个小动物 PET 记录，测试这种方法在获取单个放射性合成物的单个记录方面是否可行，多巴胺 D2/3 配体（18）F-氟比拉嗪可用作脑受体成像的示踪剂。
在 Octamouse 腔室内放置不同放射性浓度源的体模研究中，首先评估散射校正对小动物 PET 记录的影响。接下来，在接受不同比活度（140 和 50GBq/μmol）（18）F-氟比拉嗪的小鼠组中测试质量对纹状体中（18）F-氟比拉嗪结合潜能（BP（ND））的潜在影响，是否进行散射校正。最后，测试（18）F-氟比拉嗪剂量（3.5-17MBq/只）与 BP（ND）之间的关系。
散射校正提高了 Octamouse 体模中源与空气空间之间的对比度。在所测试的比活度范围内，小鼠纹状体中（18）F-氟比拉嗪 BP（ND）的幅度保持不变，散射校正平均增加了 6%；BP（ND）的操作者间和操作者内变异性的协方差为 10%。放射性化学剂量与 BP（ND）之间存在正相关（R2=0.53），与无散射校正（R2=0.63）相比，该相关关系是由纹状体中注入剂量百分比曲线下面积的增加驱动的。
在广泛的源活性范围内，放置在 Octamouse 中的发射源的定量是线性的。在活鼠的纹状体中，（18）F-氟比拉嗪 BP（ND）的幅度在操作者之间具有高度可重复性，在比活度的 3 倍范围内保持不变，表明没有明显的占有率。散射校正提高了定量，但并未完全纠正 BP（ND）与注入剂量的依赖性，这被认为是由于视场中的总放射性化学剂量超过 50MBq 时探测器死时间的影响所致。考虑到这一点，我们仍然能够从单个放射性合成物中对 16 只小鼠的（18）F-氟比拉嗪 BP（ND）进行定量，这种经济方法应该适用于各种放射性配体的脑研究。
