Abstract
BACKGROUND: Preoperative differentiation of atypical from conventional uterine leiomyomas remains challenging on routine MRI due to overlapping morphological characteristics and signal heterogeneity related to degeneration or necrosis. PURPOSE: To evaluate whether time-dependent diffusion MRI (t(d)-dMRI) derived from oscillating and pulsed gradient spin-echo (OGSE/PGSE) sequences improves differentiation between atypical and conventional uterine leiomyomas compared with routine MRI (T1WI, T2WI and DWI). MATERIALS AND METHODS: In this prospective study, 119 patients with pathologically confirmed uterine leiomyomas (78 conventional, 41 atypical) underwent both routine MRI and t(d)-dMRI examinations. Relative signal intensity of lesion to gluteus muscle, and apparent diffusion coefficients (ADCs) were derived from routine MRI protocols, while microstructural parameters including intracellular fraction ( fin ), cell diameter, extracellular diffusivity ( Dex ), and cellularity, and ADCs at different diffusion times were estimated from t(d)-dMRI modelling. Group differences were assessed using independent-sample tests, and diagnostic performances were evaluated with generalized linear models (GLMs) and receiver operating characteristic (ROC) analyses. RESULTS: Atypical leiomyomas demonstrated significantly lower fin (0.39 ± 0.10 vs. 0.49 ± 0.10, P < 0.001) and cellularity (4.12 ± 4.33 vs. 5.50 ± 4.34, P = 0.002), but higher Dex (2.71 ± 0.64 vs. 2.09 ± 0.96 µm²/msec, P = 0.001) and ADCs at all diffusion times (all P < 0.001) compared with conventional leiomyomas. The t(d)-dMRI-base(d) GLM achieved an area under the ROC curve (AUC) of 0.84 (95% CI, 0.77-0.92), significantly higher than that of routine MRI characteristics (AUC 0.76, 95% CI 0.66-0.85; P = 0.037). The model combining both t(d)-dMRI an(d) routine MRI characteristics yielded additional improvement to that of routine MRI (AUC 0.86, 95% CI 0.79-0.93; P = 0.0075). CONCLUSION: t(d)-dMRI provides quantitative microstructural information that enables superior differentiation of atypical from conventional uterine leiomyomas compared with routine MRI. t(d)-dMRI may serve as a promising adjunct for preoperative characterization and treatment planning of uterine leiomyomas.