Diagnostic value of MR imaging in comparison to CT in the detection and differential diagnosis of renal masses: ROC analysis.

The aim of this work was to compare MR imaging and CT in the detection of renal masses and in the differential diagnosis between benign and malignant lesions. In 33 patients with 54 renal lesions CT and MR images were evaluated by four readers with regard to tumor detection and characterization using a receiver-operating-characteristics (ROC) analysis. The MRI protocol consisted of a T1-weighted spin-echo (SE) sequence (TR/TE: 300/10 ms) before and after contrast administration and a heavily T2-weighted turbo-SE (TSE) sequence (TR/TE: 5500/150 ms). Az values for the area under the ROC curves for lesion detection were 0.92 +/- 0.04 for CT and 0.91 +/- 0.05 for MRI, respectively, which was not statistically different. The MRI technique was slightly, but not significantly, better than CT in the overall characterization (accuracy in differentiation between benign and malignant) of renal lesions with an Az value of 0.90 +/- 0.05 compared with 0.88 +/- 0.06 for CT. The MRI technique proved to be statistically superior to CT (p < 0.01) in the correct characterization of benign renal lesions. MRI equals CT in the overall detection and differential diagnosis of renal masses. MRI is very helpful for further differential diagnosis of lesions which are equivocal on CT especially in the differentiation between complicated cysts and cystic or hypovascular renal cell carcinoma.