Apparent diffusion coefficient values of the normal uterus: Interindividual variations during menstrual cycle.

Objectives: To assess the apparent diffusion coefficient (ADC) changes of the normal uterine zones among reproductive women during the menstrual cycle.

Methods: The study included 101 women of reproductive age, each with regular cycle and normal endometrium/myometrium, as proved on histopathology or MR imaging examination. Diffusion-weighted (DW) imaging was performed along the axial plane, using a single shot, multi-slice spin-echo planar diffusion pulse sequence and b-values of 0 and 800s/mm(2). The mean and standard deviation of the ADC values of normal endometrium/myometrium were calculated for menstrual, proliferative and secretory phase. Analysis of variance followed by the least significant difference test was used for statistical analysis.

Results: The ADC values of the endometrium were different in the three phases of the menstrual cycle (menstrual phase: 1.25±0.27; proliferative phase: 1.39±0.20; secretory phase: 1.50±0.18) (F: 9.64, p: 0.00). Statistical significant difference was observed among all groups (p<0.05). The ADC values of the normal myometrium were different in the three phases of the menstrual cycle (menstrual phase: 1.91±0.35; proliferative phase: 1.72±0.27; secretory phase: 1.87±0.28) (F: 3.60, p: 0.03). Statistical significant difference was observed between menstrual and proliferative phase and between proliferative and secretory phase (p<0.05). No significant difference was noted between menstrual and secretory phase (p>0.05).

Conclusions: A wide variation of ADC values of normal endometrium and myometrium is observed during different phases of the menstrual cycle.