The usefulness and limitations of MRI for diagnosis of brain disease in small animals

1. 采用永磁体磁共振成像机（日立，MRP-ARIS, 0.3T）对小动物最佳成像技术进行评价。然后，我们决定使用3张自旋回波图像（T1称重，T2称重和FLAIR成像）作为常规MRI方案。场衰减反转恢复（FLAIR）图像是诊断各种疾病。由于T1图像的增强能力低于人体图像，因此采用高剂量（0.3 m mol/kg）的钆进行对比增强。本文对157例自发性脑障碍犬、猫的MRI诊断进行了研究。磁共振成像有助于区分功能性癫痫与症状性癫痫、脑肿瘤、脑炎、脑积水等疾病。在犬中，由于侧脑室的大小在个体和品种之间变化很大，因此诊断脑积水非常困难。因此，我们通过磁共振图像评估了许多犬种的心室容积。测量结果显示，大狗侧脑室通常较小且一致，而偏爱脑积水的小狗侧脑室相对较大且大小不一。许多犬类病例怀疑为慢性犬瘟热脑炎，但该类型脑炎的MRI特征不一致，且并非犬瘟热脑炎特异性。部分患者诊断为坏死性脑炎（巴哥犬脑炎），并对其临床病程进行随访。此外，活着的患者通过MRI和CSF分析诊断为肉芽肿性脑膜脊髓炎。MRI图像可以帮助识别某些特定的颅内肿瘤类型，如脑膜瘤。核磁共振成像的体积数据对确定手术程序非常有用。

1. Evaluation of magnetic resonance imaging technique for small animals Optimum imaging techniques for small animals were evaluated using permanent magnet type MR machine (Hitachi , MRP-ARIS, 0.3T). Then, we decided to use 3 spin echo images (T1 weighed, T2 weighed, and FLAIR imaging) for the routine MRI protocol. Field attenuated inversion recovery (FLAIR) images were diagnostic in various disorders. Higher dose of gadolinium (0.3 m mol/kg) was used for the contrast enhancement of the T1 images because its enhancing ability was lower than that in human images.2. MRI diagnosis of spontaneous brain disorders in dogs and cats One hundred and fifty seven cases with brain disorders were studied. MR imaging was useful to differentiate functional epilepsy from symptomatic epilepsy, brain tumor, encephalitis, hydrocephalus and other disorders. In dogs, diagnosis of hydrocephalus was very difficult because the size of the lateral ventricle was highly variable between individuals and breeds. So, we assessed ventricular volume in many dog breeds on MR images. Measurements revealed that in common, large dogs have small and consistent lateral ventricle, and small dogs that had predilection to hydrocephalus have comparatively large and variable sized one. Chronic canine distemper encephalitis was suspected in many dog cases, but MRI features of this type of encephalitis was inconsistent and not specific to canine distemper encephalitis. Necrotizing encephalitis (Pug dog encephalitis) was diagnosed in some patients and followed up their clinical courses. Moreover, granulomatous meningoencephalomyelitis was diagnosed in live patients by MRI and CSF analysis. MRI images may help to identify some specific intracranial tumor types, e.g. meningioma. The volume data of the MRI was very useful to determine surgical procedures.