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27To evaluate the localization of functional deficit area in epileptogenic zones of the 28 brain in seven refractory and seven non-refractory epilepsy dogs using technetium 99m 29 labeled with ethyl cysteinate dimer and interictal Single Photon Emission Computed 30 Tomography [ 99m Tc-ECD SPECT] co-registration with Magnetic Resonance Imaging (MRI). 31Regions showing perfusion deficits in the SPECT images were analyzed by using the standard 32 semiquantitative evaluation method to compare the level of cortical perfusion to the 33 maximum number of counts within the cerebellum (max C), considered the area of reference. 34This study showed that SPECT imaging revealed abnormalities in several regions of the brain 35 in both epilepsy groups. The refractory epilepsy dogs showed more frequency area of 36 hypoperfusion in temporal lobe than non-refractory group with not statistically significance 37 (p=0.28). The result suggests the lesion in temporal might be relevance with refractory 38 epilepsy in canine patients. 39 40 KEY WORDS: dogs, drug-resistant epilepsy, ethyl cysteinate dimer, single photon 41 emission computed tomography 42 43 44 45 46 47 48 52

Background Quantitative magnetic resonance imaging (MRI) is used to study the anatomy of the brain in dogs with idiopathic epilepsy. Purpose To quantitate MRI images in terms of volumetric ratios and histogram analyses of the following regions of interest (ROI) in dogs with idiopathic epilepsy: frontal; parietal; temporal; piriform; thalamic; and hippocampal regions. Material and Methods Nine dogs with epilepsy and four healthy controls were evaluated. We examined the volumetric ratios and histogram analyses of six ROIs in all dogs. Results MR images, in T1-weighted, T2-weighted, FLAIR, diffusion-weighted imaging, and apparent diffusion coefficient sequences detected changes in 4/9 (44%) epileptic dogs found in 5/6 regions: frontal; parietal; temporal; piriform; and hippocampal regions. However, no such changes were observed in the thalamic region. Interestingly, the frontal and piriform volumetric ratios of epileptic dogs were significantly lower than those of control dogs. The histogram analyses in 4/6 regions were significantly increased in epileptic dogs. Conclusion Our results demonstrated MRI finding abnormalities in several regions of the brain in several sequences including T1-weighted, T2-weighted, FLAIR, diffusion-weighted imaging, and apparent diffusion coefficient in epileptic dogs. In several regions of the brain, atrophy may exist, and hyperintensity may be present on MR images in epileptic dogs. These findings suggest that the diagnostic yield of MRI, which is an advanced neuroimaging technique, is high in epileptic dogs and has good reliability and sensitivity in detecting abnormal areas in patients.