Changes of the normal ovary during menstrual cycle in reproductive age on the diffusion-weighted image

Objective: The objective of this study was to investigate changes in magnetic resonance findings of the normal ovary during menstrual cycle on diffusion-weighted image (DWI). Methods: Magnetic resonance imaging was performed in 9 healthy females at the menstrual, periovulatory, and luteal phases using a 1.5-T unit. Signal intensity (SI) of the ovary on DWI with a b value of 1000 s/mm² was visually scored. The ovary-to-muscle contrast ratios on DWI and apparent diffusion coefficient (ADC) values were also evaluated. Results: All the ovaries were identified, and higher SI than the nerve root was identified in 70% (38/54) of the ovaries, although visual scores did not show significant difference among menstrual phases. The mean ADC values (10^-3 mm²/s) were 1.71 (SD, 0.27), 1.71 (SD, 0.22), and 1.67 (SD, 0.19) in menstrual, periovulatory, and luteal phases, respectively. No phase-dependent change was observed in contrast ratios and ADC values. Conclusion: The normal ovary in fertile period shows high SI enough to be identified on DWI, and observed values are independent of the menstrual cycle.