Diving deep into uterine layers: ADC and IVIM at 0.55-T MRI

OBJECTIVE: To investigate and analyze the microstructure of uterine layers and to evaluate the feasibility and physiological variability of uterine diffusion metrics at 0.55-T MRI in healthy volunteers and participants with adenomyosis. MATERIALS AND METHODS: In this prospective study, 106 women, including healthy controls without (n = 47) and with hormonal contraception (n = 37), and patients diagnosed with adenomyosis (n = 22), underwent uterine diffusion MRI at 0.55 T. Apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) were modeled using nine b-values in the myometrium, junctional zone, and endometrium. Quantitative intergroup differences, intragroup comparisons, and anterior-posterior wall analyses were performed. Evaluation of scan repetitions, intra-annotator and inter-annotator variability, and IVIM fit quality assessments were performed in subcohorts. RESULTS: The intergroup analysis was performed on 106 women aged 27.2 ± 5.9 years (mean ± standard deviation) without bowel preparation or antispasmodics. A reduced median myometrium ADC (p = 0.024), reduced endometrial mean diffusivity (p = 0.017), and increased perfusion fraction (p = 0.014) were observed in the cohort with adenomyosis compared to healthy volunteers. Interindividual and intra-individual analysis of healthy volunteers demonstrated increased diffusivity in the endometrium during the luteal phase (p = 0.024). Additionally, differences in diffusion and IVIM parameters were observed in adenomyosis participants undergoing hormonal therapy. Repeat measurements, intra-annotator and inter-annotator agreement, and IVIM metric stability demonstrated good consistency. CONCLUSION: This study provides early evidence that uterine diffusion and IVIM at 0.55 T enable robust, non-invasive characterization of uterine microstructure sensitive to menstrual phase, hormonal status, and adenomyosis, providing insight into uterine physiology and pathology. KEY POINTS: Question Can 0.55-T MRI characterize functional changes associated with adenomyosis compared with healthy uteri? Findings 0.55-T uterine diffusion MRI without bowel preparation quantified uterine microstructure, with layer-specific ADC and IVIM distinguishing adenomyosis, hormonal effects, menstrual phase, and anterior-posterior differences. Relevance statement Quantitative diffusion and IVIM metrics at 0.55-T distinguish adenomyosis from healthy tissue through reduced myometrial ADC, endometrial diffusivity, and increased perfusion fraction. These biomarkers hold promise in clarifying diagnosis and supporting future studies assessing hormonal therapy response and treatment monitoring.