[Image analysis in the differential diagnosis of renal parenchyma lesions]

Abstract

Purpose: Visual analysis of echo intensity is of importance for the differential diagnosis of focal renal lesions. Quantification of the echo intensity and of other parameters might help with differential diagnosis.

Materials and methods: In 145 patients with focal renal lesions, digitized images were evaluated (40 angiomyolipomas [group A], 70 renal cell carcinomas [group B], 20 pseudo-tumors [group C] and 15 other focal lesions in group D). With Photoshop®, the average grayscale values of the lesion (defined as echo intensity focal, EF) and its variance s2 (as expression of the inhomogeneity focal, IF) were measured. These measurements were compared to the renal cortex (echo intensity renal cortex=ER, inhomogeneity renal renal cortex=I R). Other calculated parameters: Echo intensity quotient, echo intensity index, inhomogeneity quotient and inhomogeneity index.

Results: Angiomyolipomas had a higher echo intensity quotient EQ and echo intensity index EI than renal cell carcinomas, pseudo-tumors and other lesions (p<0.001). Pseudo-tumors had a lower inhomogeneity quotient than angiomyolipomas (p<0.001), renal cell carcinomas (p<0.05). Echo intensity quotient EQ≥2.0 and echo intensity index EI≥0.5 were typical for angiomyolipomas with a sensitivity of 96.4 % and a specificity of 97.3 % for tumors<3 cm.

Conclusion: Quantitative echo intensity measurements enhance the differential diagnosis of focal renal lesions. The differentiation of typical angiomyolipomas to other lesions could be improved.