The diagnostic value of Diffusion-Weighted MRI in differentiating benign and malignant ovarian masses

Abstract

Examining DW MRI images of different lesions has shown that measuring ADC values can indicate the degree of cellularity of the lesion. In the last few years, there have been studies on the usefulness of DW MRI sequences for the evaluation of ovarian masses, which have had conflicting results. The purpose of this study is to investigate the diagnostic value of DWI MRI and determine the quantitative cut-off value of ADC by determining the diagnostic accuracy, sensitivity, and specificity for differentiating between benign and malignant ovarian lesions. Methods and materials: In this study, which was conducted for one year at the imaging center of Imam Reza and Al-Zahra Hospital, 64 patients (with 75 ovarian lesions) who underwent pelvic MRI (with dynamic contrast administration and containing DWI/ADC sequence) and then underwent surgery were included. Then the post-op histopathologic results were compared with pre-op DW MRI findings. Quantitative analysis of ADC values was performed using two ROI measurement methods (round method and free hand method) on the solid enhancing components of ovarian lesions. Also, the radiologic characteristics of the masses were evaluated in the conventional MRI and each lesion was scored separately according to ORADS MRI Score. An enhancement diagram over time of suspicious lesions was also drawn with the help of DCE-MRI and their time-intensity curve (TIC) type was determined. Finally, two series of quantitative findings with Round and Freehand methods of min, mean, and max ADC values of the lesions were compared with each other, and then the relationship between the mean quantitative ADC of the ovarian lesions with the postoperative pathology of the lesions, ORADS score, and their TIC was investigated. Finally, ADC quantitative cut-offs were determined by measuring sensitivity, specificity, and diagnostic accuracy for each of the mentioned methods (round and free hand) to differentiate benign lesions from malignant and borderline lesions from malignant ones. Results: In total, the cut-off values determined by min-freehand ADC value had higher diagnostic accuracy, sensitivity and specificity than the cut offs determined by other ADC values for differentiation of ovarian lesions from each other. Min-freehand ADC value of less than 0.823× 10−3 mm2/s with a sensitivity of about 71%, specificity of 75% and diagnostic accuracy of about 70% is able to differentiate malignant from benign lesions and was significantly in favor of malignant ovarian mass. Min-Freehand ADC value of less than 0.709 with a sensitivity of 92%, specificity of 50% and diagnostic accuracy of 71 % was significant for distinguishing malignant lesions from histologically borderline ovarian lesions. ADC value measurements with both methods were not significant in differentiating borderline lesions from benign ones. Lesions with higher ORADS scores had significantly lower Min-Freehand ADC values than lesions with lower ORADS scores. The Max-Freehand ADC value of lesions with TIC type 3 was significantly higher than lesions with TIC type 2.