Investigated regional apparent diffusion coefficient values of the morphologically normal feline brain

Abstract

Objectives Diffusion-weighted imaging (DWI) MRI is increasingly available in veterinary medicine for investigation of the brain. However, apparent diffusion coefficient (ADC) values have only been reported in a small number of cats or in research settings. The aim of this study was to investigate the ADC values of different anatomical regions of the morphologically normal brain in a feline patient population. Additionally, we aimed to assess the possible influence on the ADC values of different patient-related factors, such as sex, body weight, age, imaging of the left and right side of the cerebral hemispheres and white vs grey matter regions. Methods This retrospective study included cats undergoing an MRI (3T) examination with DWI sequences of the head at the Vetsuisse Faculty of the University Zurich between 2015 and 2021. Only cats with morphologically normal brains were included. On the ADC maps, 10 regions of interest (ROIs) were manually drawn on the following anatomical regions: caudate nucleus; internal capsule (two locations); piriform lobe; thalamus; hippocampus; cortex cerebri (two locations); cerebellar hemisphere; and one ROI in the centre of the cerebellar vermis. Except for the ROI at the cerebellar vermis, each ROI was drawn in the left and right hemisphere. The ADC values were calculated by the software and recorded. Results A total of 129 cats were included in this study. The ADC varied in the different ROIs, with the highest mean ADC value in the hippocampus and the lowest in the cerebellar hemisphere. ADC was significantly lower in the white cerebral matter compared with the grey matter. ADC values were not influenced by age, with the exception of the hippocampus and the cingulate gyrus. Conclusion and relevance ADC values of different anatomical regions of the morphologically normal feline brain in a patient population of 129 cats in a clinical setting are reported for the first time.

Regional ADC values of the morphologically normal canine brain

“…Similarly, to our results, no difference in ADC values depending on the sex has been found in cats (3). Studies in canines and humans showed an effect of age on diffusivity in the brain.…”

“…Other studies report the highest ADC values in the hippocampus followed by the piriform lobe (4); in the cortex of the frontal and parietal lobes followed by the occipital lobe and hippocampus (5). The lowest ADC value was found in the cerebellar white matter, similar to findings in cats (3). As shown in Table 4, ADC values of the present study were substantially similar as reported ( 5), except for the gray matter of the cerebellum.…”

“…Moreover, myelinated axons are responsible for a directional diffusion pattern, parallel to the axonal pathways, called anisotropy (5,42). This finding is reproducible in dogs and humans (4, 5, 23, 43) and has been recently described also in cats (3).…”

“…Hence, DWI provides information about integrity and to some extent functionality of tissue, and consequently potential pathology (3)(4)(5). Based on DWI sequences, apparent diffusion coefficient (ADC) maps can be generated, and the ADC quantified (in mm 2 /s) in specific regions of interest (ROIs).…”