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

1.小动物磁共振成像技术的评价使用永磁型MR机（Hitachi，MRP-ARIS，0.3T）评价小动物的最佳成像技术。然后，我们决定使用3个自旋回波图像（T1加权，T2加权和FLAIR成像）进行常规MRI方案。场衰减反转恢复（FLAIR）图像诊断各种疾病。T1图像增强能力低于人体图像，故采用较高剂量的钆（0.3mmol/kg）进行增强.犬、猫自发性脑病变的MRI诊断本文对157例脑病变进行了研究。MRI有助于功能性癫痫与症状性癫痫、脑肿瘤、脑炎、脑积水等疾病的鉴别诊断。在犬中，脑积水的诊断非常困难，因为侧脑室的大小在个体和品种之间差异很大。因此，我们在MR图像上评估了许多犬种的心室容积。测量结果显示，在共同的，大型犬有小和一致的侧脑室，和小型犬，有脑积水的偏好，有相对较大的和可变大小的一个。慢性犬瘟热脑炎怀疑在许多狗的情况下，但这种类型的脑炎的MRI特征是不一致的，而不是特定的犬瘟热脑炎。部分患者诊断为坏死性脑炎（哈巴狗脑炎），并随访其临床病程。此外，肉芽肿性脑膜脑脊髓炎的诊断，在活的病人的MRI和CSF分析。MRI图像可能有助于识别某些特定的颅内肿瘤类型，例如脑膜瘤。MRI的体积数据对确定外科手术非常有用。

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.