Variations of ADC of normal uterine zones in postmenopausal and reproductive women

Purpose : The aim was to establish normal values and to compare the apparent diffusion coefficient (ADC) of the uterine zones in postmenopausal and reproductive age women in the three phases of the menstrual cycle.  Materials and Methods: This retrospective study included 194 women. All magnetic resonance imaging (MRI) examinations were performed on a 1.5 T scanner. Diffusion-weighted imaging (DWI) was performed using a single shot, multislice spin-echo diffusion planar sequence and b-values of 0 and 800 s/mm 2 . ADC of normal endometrium/myometrium was classified into four groups according to menstrual status: menopause, menstrual, proliferative and secretory phase. Analysis of Variance followed by the Least Significant Difference (LSD) test was used for statistical analysis.  Results: The mean and SD (standard deviation) of ADC (×10 −3 mm 2 /s) of the endometrium was: menopause: 1.36 ± 0.18; menstrual phase: 1.24 ± 0.22; proliferative phase: 1.38 ± 0.20; and secretory phase: 1.50 ± 0.18 (F: 12.317, P <0.001). The LSD test showed differences between menopause and menstrual phase (P: 0.020) and between menopause and secretory phase (P: 0.001), but not between menopause and proliferative phase (P: 0.643). The mean and SD (standard deviation) of ADC (×10 −3 mm 2 /s) of the myometrium was: menopause: 1.60 ± 0.15; menstrual phase: 1.92 ± 0.28; proliferative phase: 1.72 ± 0.24; and secretory phase: 1.86 ± 0.27 (F: 16.034, P <0.001). Significant difference was observed between all phases (P < 0.05). Conclusion: A wide variation of ADC of normal endometrium/myometrium was found between postmenopausal and reproductive age women. A standard reference of ADC of normal uterine zones is helpful, serving as a baseline when interpreting uterine diseases.