Accuracy of follicle count and ovulation confirmation using magnetic resonance imaging in microminipigs with normal estrus cycles

Magnetic resonance imaging (MRI) is suggested to be useful for counting follicles and confirming ovulation in microminipigs. However, its accuracy is unknown. We have compared the number of follicles counted by MRI to that of corpus hemorrhagicum confirmed directly by visual inspection. The follicles of 17 microminipigs were counted by using ovarian MRI on a 0.4 Tesla MRI System every 24 hr after estrus until follicle images disappeared. Then, we performed laparotomy to count their corpus hemorrhagicum. Significant correlation was observed between follicle counts obtained using MRI (5.18 ± 1.78 per head) and the numbers of corpus hemorrhagicum (5.47 ± 1.74 per head). In conclusion, follicle counts using 0.4-T MRI were reliable, and confirmed microminipig ovulation.