MRI perfusion in evaluating ovarian masses: diagnostic performance of wash out rate

Preoperative Imaging evaluation of an ovarian lesion enables the surgeon to anticipate malignant lesions before the operation and plan an adequate operative procedure. In this study we assessed the role of semiquantitative MR perfusion parameters including wash-out rate in differentiating benign from malignant ovarian masses.

A prospective study of 82 indeterminate adnexal lesions on ultrasound basis. According to the inclusion criteria 29 patients with 32 adnexal lesions underwent conventional MRI sequences followed by MR perfusion technique based on a Dynamic Contrast Enhanced (DCE) 3D GE T1 high resolution isotropic volumetric examination (THRIVE). The conventional sequences were used to evaluate the lesion's morphological criteria by two independent readers. Then tumor semi-quantitative enhancement parameters were calculated by computer software including Wash in Rate (WIR), wash out Rate (WOR), Maximum absolute enhancement (SI max), Maximum Relative Enhancement (SI rel), and Time to Peak (TTP). Morphological findings and calculated parameters were correlated with the histopathological results.

A significant correlation was found between pathological diagnosis and T2 signal intensity, ascites and peritoneal deposits where predicative features of malignancy were isointense signal on T2 (p value0.028), presence of ascites (p value 0.008), and peritoneal deposits (p value 0.022). For the correlation between the Semi quantitative perfusion MRI parameter and the pathological diagnosis the WOR in the study group ranged from 0.06 to 68.84 with mean value of 12.6 ± 17.46. Both SI max and WOR were able to significantly differentiate benign and malignant lesions (P = 0.017*&0.028* respectively). Applying cutoff value of WOR >6.03 provided accuracy of 86.2% with 82.4% sensitivity, 90% specificity, 93.3% Positive Predictive value (PPV) and 75% Negative Predictive value (NPV). While applying a cutoff value of SI max >1391.07 provided accuracy of 73.2% with 76.5 sensitivity, 70% specificity,81.2% PPV and 63.6% NPV.

The addition of DCE MR Sequence to the conventional MRI has improved its diagnostic accuracy. we can depend upon WIR in depicting malignant masses and correct our diagnosis by applying the cutoff of WOR to exclude the false positive cases and avoid unnecessary radical surgery especially in women aiming at preserving fertility.