Objective:To investigate MRI characteristics of normal rhesus uterus.Methods:Sixteen female rhesus were inspected in their breeding season and non-breeding season using MRI

in order to observe the shape and the MR signal characteristics of their uteri and to measure the size of the uteri;and the size of uteri was measured in 3 animals after laparotomy procedures in breeding season and non-breeding season

respectively.Results:On MRI

the shape of the uterus was elliptic in axial view and dumbbell shape in sagittal view in different season (breeding season and non-breeding season).The signal-intensity of the uterine body was similar to the pelvic muscle in T 1WI.In T 2WI

the signal-intensity of the uterine body muscle layer was higher than the uterine neck

and 2～3 different signal-intensity strips were observed in uterine body.On enhanced MRI

uterine cavity showed slightly low-signal-intensity

and uterine muscle layer and inner membrane showed homogeneous enhancement.The average size of the uteri was 4.9cm×2.6cm×1.9cm in breeding season

and 3.0cm×1.76cm×1.32cm in non-breeding season.There were significant differences between the average diameters and average sizes of the uteri in breeding season and that in non-breeding season ( P <0.05)

and there was no significant difference between the diameters and sizes determined by MRI and that measured under gross inspection( P >0.05).Conclusion:MRI could clearly display the shape and size and signal-intensity characteristics of the uterus

so it is an appropriate approach to guide and follow up HIFU (high intensity focused ultrasound) study.