Catherine Roy MD, Presenter: Nothing to Disclose

Francesco Agnello, Abstract Co-Author: Nothing to Disclose

Gauthier Bazille, Abstract Co-Author: Nothing to Disclose

Jeanne Flesch, Abstract Co-Author: Nothing to Disclose

Thomas Charles, Abstract Co-Author: Nothing to Disclose

Herve Lang, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to describe the appearance of small solid renal masses (< 3cm) on DW- MR (DWI) images and to determine if ADC measurements may help to differentiate benign from malignant lesions.

We retrospectively evaluated 70 patients with 94 small renal masses (46 malignant, 48 benign) who underwent between April 2008 and July 2011 MR examination on a 3T (Achieva, Philips Medical System) including a DWI (b value 1000 mm2/sec -TR/TE 7000/55, matrix 288×288 interpolated to 512, FOV 120 x100 mm, 5 mm, EPI and ETL : 53, 3 excitations) to our conventional protocol.. Qualitative and quantitative analysis of DWI were performed. Correlations were done with pathological data obtained either by US guided biopsy or surgical removal of the masses (82 masses) or follow up (12 masses). Mann-Whitney test and Student –t test were performed to determine the efficiency of ADC value to predict malignant or benign lesion.

All masses were hyperintense to kidney on high b-value. The mean ADC value of CC RCCs was higher than that of AMLs, NCC RCCs and metastases, and was lower than that of oncocytomas. The mean ADC of the lesions was lower than that of kidney [1.22± 0.3 versus 1.85± 0.12 mm2/sec)] (p< 0.005; Mann-Whitney test). The mean ADC was different between Renal Cell Carcinomas (RCCs) [1.2± 0.01 mm2 /sec (0.76-1.73)], metastases [1.25± 0.04 mm2/sec], angiomyolipomas (AMLs) [1.07 ± 0.3 mm2 /sec (0.85-1.28)], and oncocytomas [1.56± 0.08 mm2 /sec] (p< 0.05, Kruskal-Wallis test). The mean ADC value of Clear Cell (CC) RCCs was higher than that of Not Clear Cell (NCC) RCCs [1.38± 0.34 versus 0.83 ± 0.34 mm2 /sec]. The best cut-off ADC value for differentiating CC RCCs from NCC RCCs, AMLs and oncocytomas were 1.2 mm2/sec (sensitivity, 100%; specificity 100%); 1.12 mm2/sec (sensitivity,88%; specificity 69%) and 1.73 mm2/sec (sensitivity, 100%; specificity 60%), respectively. The best cut-off ADC value for differentiating AMLs from oncocytomas was 1.21 mm2/sec (sensitivity 86%; specificity 88%).

Small solid renal masses with different tissue composition have different ADC values. Our results suggests that DWI may be used as a non invasive procedure to characterize small solid renal masses.

MR - DWI is feasible for characterizing small solid renal tumors. ADC value calculation can discriminate between benign and malignant lesion. It must be included in routine MR protocol to study kidney

Roy, C, Agnello, F, Bazille, G, Flesch, J, Charles, T, Lang, H, Small Solid Renal Masses: Characterization by Diffusion Weighted Magnetic Resonance Imaging at 3.0 Tesla: Retrospective Study.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12022098.html