Value of the Diffusion-Weighted MRI in the Differential Diagnostics of Malignant and Benign Kidney Neoplasms – Our Clinical Experience

BACKGROUND Diffusion-weighted imaging (DWI) is an MRI modality using strong bipolar gradients to create a sensitivity of the signal to the thermally-induced Brownian motions of water molecules and in vivo measurement of molecular diffusion. The apparent diffusion coefficient (ADC) is a quantitative parameter calculated from DWI images which is used as a measure of diffusion. DWI allows to obtain comprehensive information on morphological and functional state of the kidney during a single examination without contrast medium administration. The purpose of the study was to evaluate the value of DWI in differentiating benign and malignant solid kidney tumors based on the initial stage of the study. MATERIAL/METHODS The study included 19 adult patients with pathologically verified renal tumors: 9 patients with clear cell subtype of the renal cell carcinoma, 5 patients with oncocytoma and 5 patients with angiomyolipoma (AML). In addition, 5 healthy volunteers with completely normal findings according to kidney ultrasound were included into this study and set as reference. All patients underwent renal MR imaging which included DWI with subsequent ADC measurement. MR imaging was performed with a 1.5 T body scanner using an eight-channel phased-array body coil. RESULTS The mean ADC value of ccRCC was significantly lower than that of normal renal parenchyma (2.11±0.25×10(-3) mm(2)/s vs. 3.36±0.41×10(-3) mm(2)/s, p<0.01). There was a significant difference in ADC between the malignant and benign renal lesions: in patients with angiomyolipoma the ADC value was 2.36±0.32×10(-3) mm(2)/s vs. 2.11±0.25×10(-3) mm(2)/s; p<0.05 and in patients with oncocytoma - 2.75±0.27×10(-3) mm(2)/s vs. 2.11±0.25×10(-3) mm(2)/s; p<0.05. The difference in ADC values in patients with high and low ccRCC grades was observed. CONCLUSIONS DWI can be used to characterize renal lesions; the ADC of a renal lesion can be potentially used as an additional parameter to help determine the appropriate clinical management.