Investigation of renal lesions by diffusion-weighted magnetic resonance imaging applying intravoxel incoherent motion-derived parameters-Initial experience

Purpose: Usefulness of biexponentially fitted signal attenuation at different b-values for differentiating the histological characteristics of renal tumors. Materials and methods: A total of 26 patients with 28 renal masses (histologically proven: 20 clear cell renal cell carcinomas [ccRCC], three transitional cell carcinomas, two oncocytomas, and one papillary RCC) and 30 volunteers with healthy kidneys were examined at 1.5 Tesla using an echo-planar DWI sequence. Using the IVIM model, we calculated the perfusion fraction f and the diffusion coefficient D. Furthermore, the ADC was obtained. These tumor parameters were compared to healthy renal tissue nonparametrically, and a receiver operating characteristic (ROC) analysis was performed. Results: Healthy renal parenchyma showed higher ADC and D values (p < 0.001) than ccRCC (ADC 1.95 +/- 0.10 [SD] mu m(2)/ms, f 18.32 +/- 2.52%, and D 1.88 +/- 0.11 mu m(2)/ms versus ADC 1.45 +/- 0.38 mu m(2)/ms, f 18.59 +/- 6.16%, and D 1.34 +/- 0.38 mu m(2)/ms). When detecting malignancies the area under the curve for D was higher than for ADC. The f values for ccRCC were higher (p < 0.001) than for non-ccRCC (ADC 1.52 +/- 0.47 mu m(2)/ms, f 8.44 +/- 1.24%, and D 1.30 +/- 0.18 mu m(2)/ms). Both f and D correlated with ccRCC grading. Conclusion: IVIM imaging is able to provide reliable diffusion values in the human kidney and may enhance the accuracy of tumor diagnosis. The D value was the best parameter to distinguish renal tumors from healthy renal tissue. The f value is promising for determining the histological subgroups. (C) 2011 Elsevier Ireland Ltd. All rights reserved.