Contrast research on accurate measurement of hippocampal volume in normal rats based on the gray scale difference method by 7.0 T and 3.0 T magnetic resonance

Objective To evaluate the ability of 7.0 T MRI in detecting volume of hippocampaus and hippocampal subregions in normal Wistar rats. Methods Forty normal Wistar rats were scanned with T2WI sequence by 7.0 T MR, images were imported into IMAGE J. Based on gray scale difference method which was used to identify the anatomical points of hippocampus and subareas, the volume of, hippocampaus and hippocampal subregions was calculated. Subsequently, the measured results were compared with data of 3.0 T MRI. Results In 7.0 T magnetic resonance images, the identification rate of lateral ventricle and cisterna ambiens was 100%(40/40); the identification rate of ventral hippocampal fissure and subiculum was 95%(38/40); the identification rate of nuclei lateralis thalami and dorsal lateral geniculate nucleus was 90%(36/40). 3.0 T images could only clearly identify the bilateral lateral ventricles and cisterna, but could not identify the hippocampal subregions in normal Wistar rats. Compared with the floor areas [left: (2.81±0.86) mm2, right: (2.77±0.80) mm2)] and volume of hippocampus [(left: (56.36±5.98) mm3, right: (55.61±6.03) mm3)] measured by 3.0 T magnetic resonance, the layer areas [left: (3.25±0.92) mm2, right: (3.14±0.81) mm2)] and hippocampal volume [(left: (64.29±7.13) mm3, right: (65.34±7.74) mm3)] measured by 7.0 T MRI were increased, the difference was significant (all P values<0.05). The layer areas of hippocampal CA1 measured by 7.0 T were left: (2.81±0.98) mm2, right: (2.88±0.92) mm2 , the volume was left: (27.02±4.62) mm3, right: (27.64±4.13) mm3. The layer areas of hippocampal CA3-DG measured by 7.0 T were left: (4.21±1.21) mm2, right: (4.19±1.40) mm2, the volume was left: (38.73±4.17) mm3, right: (38.11±5.09) mm3. Conclusions Using gray scale difference method, the boundary markers of hippocampus and hippocampal subregions can be accurately detected on 7.0 T magnetic resonance images, and the relevant data could be referenced for such related researches. Key words: Hippocampus; Rat; Volume; Gray scale difference method; Magnetic resonance imaging