Variation of amide proton transfer signal intensity and apparent diffusion coefficient values among phases of the menstrual cycle in the normal uterus: A preliminary study

To explore changes in the amide proton transfer (APT) signal intensity (SI) among different phases of the menstrual cycle in healthy young women and to determine whether the APT SI correlates with the apparent diffusion coefficient (ADC).Twenty healthy women of childbearing age received regular pelvic magnetic resonance imaging (MRI) examinations and APT scans during the menstrual, proliferative and secretory phases of their menstrual cycle. Then, the APT SI and ADC values of the endometrium, myometrium and junctional zone were measured and analyzed to explore the changes during different phases of the menstrual cycle. The Pearson correlation coefficients between the APT SI and ADC were calculated.Besides the APT SI in the secretory phase, the APT SI and ADC in each menstrual phase were higher in the myometrium and endometrium than in the junctional zone, the APT Si did not differ significantly between the endometrium and myometrium during any phase. In each uterine structure, both the SI and ADC were highest in the secretory phase, second highest in the proliferative phase and lowest in the menstrual phase, but the APT SI did not differ significantly between the menstrual phase proliferative phases. Interindividual variation in APT SI and ADC for a given zone or phase ranged from 1.86% to 2.75% and from 0.37 × 10-3 mm2/s to 0.85 × 10-3 mm2/s, respectively. The Pearson correlation coefficient between APT SI and ADC was 0.481 (P < 0.01).When the APT SI or ADC values are used to analyze uterine lesions, their changes during the menstrual cycle in childbearing aged women should be considered.