Water mass exchange across the edges of continental shelves is one of the key problems in coastal physical oceanography. There are often great differences in temperature, salinity, and nutrient level between the waters on the shelves and in the neighboring slope seas. Exchange across the shelf-edge water-mass boundary can thus result in substantial cross-shelf fluxes of physical and biogeochemical materials, which affects the heat, salt, nutrient and carbon budgets of the continental shelves. Cross-shelf exchange is generally limited by the tendency of geostrophic flows following the isobath, which causes the cross-shelf volume transport being smaller in magnitude than the along-shelf transport. However, the impact of water mass exchange across a shelf edge on the shelf and slope water properties may be far greater than its relatively small magnitude (Brink, 2016

PURPOSE This study aimed to compare the variability of the uterus during the menses phase (MP), follicular phase (FP), and luteal phase (LP) of the menstrual cycle using intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI). METHODS This prospective study was conducted at the Guangdong Provincial Hospital of Traditional Chinese Medicine between January 2022 and January 2023. Women of childbearing age (18–45 years) with appropriate progesterone levels were included in this study. Conventional magnetic resonance imaging and IVIM-DWI scans were performed during the MP, FP, and LP. The differences in IVIM-DWI-derived parameters between these phases were then compared, and the overlap was quantitatively described. RESULTS The apparent diffusion coefficient (ADC) and pure molecular diffusion coefficient ( D ) values from the endometrium, uterine junctional zone (UJZ), and myometrium indicated statistical differences between the MP and FP and the MP and LP (ADC: endometrium, both P < 0.001; UJZ, P = 0.008 and P < 0.001, respectively; myometrium, P = 0.033 and P = 0.006, respectively; D: endometrium, both P < 0.001; UJZ, P = 0.008 and P = 0.006, respectively; myometrium, P = 0.041 and P = 0.045, respectively). The perfusion-related diffusion coefficient ( D* ) values from the myometrium indicated statistical differences between the FP and MP and the FP and LP ( D* : myometrium, P = 0.049 and P = 0.009, respectively). The overlapping endometrium ratios between the MP and FP or LP were lower than 50% in the ADC and D values (ADC: overlapping of MP and FP: 33.33%, overlapping of MP and LP: 23.33%; D : overlapping of MP and FP: 40.00%, overlapping of MP and LP: 43.33%). CONCLUSION The ADC and IVIM-derived parameters indicated differences in the uterus in diverse phases of the menstrual cycle, especially in the endometrium in relation to ADC and D values.