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 mm/s] vs. malignant [(0.71 ± 0.26) × 10 mm/s] lesions was significantly different (p < 0.001). ADC cutoff value of 1.55 × 10 mm/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 mm/s] vs. malignant [(0.68 ± 0.19) × 10 mm/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.