Proton MR spectroscopy and the detection of malignancy in ovarian masses

Objective: To assess the impact of MR spectroscopy (MRS) on the detection of malignancy in ovarian masses. Methods: This prospective work included 230 females that had 245 adnexal/ovarian masses. Tumours were spotted by preliminary pelvic ultrasound. Masses assessed by MRI, multi- or single-voxel spectroscopy. Patients’ spectra were assessed for peaks of lactate (Lac, 1.31 ppm), lipid (Lip, 1.33 ppm), N-acetyl aspartate (2.0 ppm), acetone (A, 2.05 ppm), choline (Cho, 3.23 ppm) and creatinine (Cr, 3.4 ppm) and the mean values of the (Cho/Cr) ratios were performed by a semi-quantitative approach. The operative pathology served as the standard of reference. Results: Cho peak twofold higher than the average noise level was detected in 72% of the malignant and only 5.4% of the benign masses with an accuracy of 83%. Adding lactate to the choline enhanced the accuracy to 93%. The mean Cho/Cr ratios of the malignant ovarian masses (2.8) were significantly higher than that of the benign ones (1.2) . We used a receiver operating characteristic curve to determine the best cut-off value (1.7) for the mean Cho/Cr ratio to discriminate malignancy with sensitivity: 81.2%, specificity: 93.3 %, positive-predictive value: 92.9 %, negative-predictive value: 82.4% and accuracy: 87.1%. Conclusion: The simultaneous presence of choline and lactate peaks in MRS examination of the ovarian masses minimizes the overlap between benign and malignant categories. N-acetyl aspartate and acetone are the metabolites for diagnosing complex cystic masses as benign teratoma, endomterioma and tubo- ovarian abscess. Advances in knowledge: MRS is a non-contrast based and fast MR sequence that gives an idea about tissue components could be used to improve the sensitivity and the accuracy of detecting malignancy in ovarian masses.