Diffusion MRI of uterine and ovarian masses: identifying the benign lesions.

PURPOSE: The purpose of the study was to assess the diagnostic performance of qualitative and quantitative diffusion-weighted imaging (DWI) in differentiating benign from malignant ovarian and uterine masses.

MATERIALS AND METHODS: Institutional review board approval was obtained for this HIPAA-compliant retrospective study, with waiver of informed consent. DWI MRIs of 222 women acquired over 1.5 years were evaluated. Reference standard was pathology or follow-up imaging. For qualitative assessment, two radiologists independently reviewed DWI and apparent diffusion coefficient (ADC) images for diffusion restriction. Differences were resolved by consensus. For quantitative assessment, a single reader measured ADC values. Readers were blinded to the reference standard.

RESULTS: 222 lesions, 121 ovarian (99 benign and 22 malignant) and 101 uterine (54 benign and 47 malignant), were included. Final diagnosis was established with pathology in 129 (58%) or with imaging follow-up in 93 (42%). Mean (range) follow-up interval was 27 (13-48) months. Qualitative assessment yielded sensitivity (ratio, 95% CI), specificity, PPV and NPV of 100% (22/22, 85-100), 68% (68/99, 58-76), 41% (22/54, 27-54), and 100% (68/68, 94-100) for ovarian and 94% (44/47, 83-98), 91% (49/54, 80-96), 90% (44/49, 78-95) and 94% (49/52, 84-98) for uterine malignancies. ADC (mean ± SD) between benign ovarian [(1.11 ± 0.76) × 10-3  mm2 /s] vs. malignant [(0.71 ± 0.26) × 10-3  mm2 /s] lesions was significantly different (p < 0.001). ADC cutoff value of 1.55 × 10-3  mm2 /s for ovarian lesions resulted in 99.9% confidence for the absence of malignancy. ADC (mean ± SD) of benign uterine [(0.64 ± 0.38) × 10-3  mm2 /s] vs. malignant [(0.68 ± 0.19) × 10-3 mm2 /s] lesions was not significantly different (P < 0.54).

CONCLUSION: Quantitative and qualitative DWI assessment can be used to confidently characterize a subset of ovarian lesions as benign. With uterine lesions, although DWI is useful in differentiating benign from malignant lesions, the technique does not allow for definitive quantitative characterization.