Ovarian masses: Evaluation with diffusion weighted MR imaging

Purpose: to prospectively evaluate the diagnostic capabilities of diffusion weighted Magnetic Resonance Imaging (DWMRI) in characterizing ovarian masses. Materials and methods: 40 consecutive patients with ultrasound evidence of 46 ovarian masses underwent pelvic MRI examination using a 1.5 Tesla MR unit. MRI protocol included conventional T1 and T2-weighted FSE sequences and single shot echo-planar diffusion weighted sequence with five different b values: b=0, 200, 300, 500, 1000 sec/mm². Apparent diffusion coefficient (ADC) maps were reconstructed. The ADC value of the ovarian masses was calculated and correlated with the histopathological examination available in all patients and considered as reference standard. Results: the mean ADC value of malignant lesions was 1.65±0.14 x 10-3 mm²/sec, benign masses was 1.53±0.57 x 10-3 mm²/sec and inflammatory masses was 1.21±0.28 x 10-3 mm²/sec. There was statistically significant difference in the mean ADC values between malignant and inflammatory ovarian masses (p<0.001) and within benign masses (p<0.006). There was insignificant difference in ADC values between malignant and benign lesions (p=0.094) and within malignant masses (p=0.624). Conclusion: diffusion weighted MRI is a non-invasive imaging tool that can be useful for differentiating malignant from inflammatory ovarian masses. Its role in the differential diagnosis between malignant and benign lesions is still unclear.