Abstract: Objective To evaluate the measurement of the gastrocnemius voulme by MRI detection in Cynomolgus monkeys. Methods Right lower limbs of two Cynomolgus monkeys were fixed with fiber polymer bandages (from knee to ankle) for 15 weeks. By performing MRI examinations on the gastrocnemiuses of both legs at week 11, 13 and 15Ł¬257 images were obtained. After measuring the coronal area of the gastrocnemius for 3 times by the same person and different persons, the volume of gastrocnemius was determined. Areas in all images detected by the same person at different time and areas in all images detected by different persons were compared, respectively. Result The gastrocnemiuses were all clearly detected in the MRI images. The measurement error of the area of the gastrocnemius in all images by the same person was 0 ~3.47 cm². The percentage of the mean difference in the total area of one leg was 0.8%, and the CV was 1.34%. The measurement error by different persons was 0 ~3.47 cm². The percentage of the mean difference in the total area of one leg was 1.7%, and the CV was 1.08%. The measurement error by different persons at the same period was 0 ~1.5 cm³. The percentage of the mean difference in one leg volume was 5.8%, and the CV was 6.5%. Conclusion MRI examination may be used as a valuable method in evaluating the muscle atrophy model in Cynomolgus monkeys with comparatively higher accuracy and lower error by combining the manual operation and software control.

Key words: Magnetic Resonance Imaging (MRI), Cynomolgus Monkeys, Gastrocnemius, Volume