Role of MRI diffusion in evaluation of renal masses

Abstract

Renal masses are being discovered more frequently in the last years due to advances in cross sectional imaging. US remains the first and initial imaging modality for detection of renal masses and tumors, then CT and MR are used for better detection, characterization and staging of these masses. Accurate characterization of renal masses is essential to ensure appropriate case management and to assist in staging and prognosis and to differentiate surgical lesions from nonsurgical lesions. Diffusion-weighted Imaging (DWI) is a new functional imaging technique that derives image contrast from differences in water molecule diffusion within tissues. Cellular tissues as tumors that exhibit the greatest degree of restricted diffusion are seen as areas of retained (bright) signal on high b-value images and show low signal intensity on the corresponding ADC map with low ADC value. DW MRI does not rely on intravenous contrast, so patients with renal failure who are at risk for nephrogenic systemic fibrosis or nephrotoxicity may particularly benefit from this technique in the evaluation for renal and upper urinary tract cancer in a noninvasive manner. Because there is wide range and overlap between the ADC values of benign and malignant lesions, the use of ADC value alone may lead to inaccurate assessment of renal lesions. The combination of conventional MRI and ADC value in the diagnosis of renal lesions can increase the diagnostic accuracy. We recommend that DWI with low and high b value (b 0-800) and quantitative ADC measurements to be added to a routine renal MR imaging protocol as it is rather an accurate method for renal lesion characterization & can be useful in the differentiation of benign and malignant renal lesions.