Hildebrandt Isabel J, Su Helen, Weber Wolfgang A
Department of Molecular and Medical Pharmacology at the David Geffen School of Medicine at the University of California, Los Angeles, CA 90095-6942, USA.
ILAR J. 2008;49(1):17-26. doi: 10.1093/ilar.49.1.17.
The use of small animal imaging is increasing in biomedical research thanks to its ability to localize altered biochemical and physiological processes in the living animal and to follow these processes longitudinally and noninvasively. In contrast to human studies, however, imaging of small animals generally requires anesthesia, and anesthetic agents can have unintended effects on animal physiology that may confound the results of the imaging studies. In addition, repeated anesthesia, animal preparation for imaging, exposure to ionizing radiation, and the administration of contrast agents may affect the processes under study. We discuss this interplay of factors for small animal imaging in the context of four common imaging modalities for small animals: positron emission tomography (PET) and single photon emission computed tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and optical imaging. We discuss animal preparation for imaging, including choice of animal strain and gender, the role of fasting and diet, and the circadian cycle. We review common anesthesias used in small animal imaging, such as pentobarbital, ketamine/xylazine, and isoflurane, and describe techniques for monitoring the respiration and circulation of anesthetized animals that are being imaged as well as developments for imaging conscious animals. We present current imaging literature exemplifying how anesthesia and animal handling can influence the biodistribution of PET tracers. Finally, we discuss how longitudinal imaging studies may affect animals due to repeated injections of radioactivity or other substrates and the general effect of stress on the animals. In conclusion, there are many animal handling issues to consider when designing an imaging experiment. Reproducible experimental conditions require clear, consistent reporting, in the study design and throughout the experiment, of the animal strain and gender, fasting, anesthesia, and how often individual animals were imaged.
由于小动物成像能够在活体动物中定位改变的生化和生理过程，并能纵向和非侵入性地跟踪这些过程，其在生物医学研究中的应用正在增加。然而，与人体研究不同的是，小动物成像通常需要麻醉，而麻醉剂可能会对动物生理产生意想不到的影响，这可能会混淆成像研究的结果。此外，重复麻醉、动物成像准备、暴露于电离辐射以及使用造影剂可能会影响正在研究的过程。我们在小动物的四种常见成像模式的背景下讨论这些影响小动物成像的因素之间的相互作用：正电子发射断层扫描（PET）和单光子发射计算机断层扫描（SPECT）、计算机断层扫描（CT）、磁共振成像（MRI）和光学成像。我们讨论成像的动物准备工作，包括动物品系和性别的选择、禁食和饮食的作用以及昼夜节律。我们回顾了小动物成像中常用的麻醉方法，如戊巴比妥、氯胺酮/赛拉嗪和异氟烷，并描述了监测正在成像的麻醉动物的呼吸和循环的技术以及清醒动物成像的进展。我们展示了当前的成像文献，举例说明了麻醉和动物处理如何影响PET示踪剂的生物分布。最后，我们讨论了纵向成像研究可能如何因放射性或其他底物的重复注射以及应激对动物的总体影响而对动物产生影响。总之，在设计成像实验时，有许多动物处理问题需要考虑。可重复的实验条件要求在研究设计和整个实验过程中清晰、一致地报告动物品系和性别、禁食、麻醉以及对单个动物成像的频率。
