Purpose: To evaluate the diagnostic value of measuring relative echogenecity of mass to renal sinus and cortex in differentiating small renal cell carcinomas from angiomyolipomas on PACS system.
Materials and Methods: 37 RCCs and 39 AMLS less than 3cm belonged to this study. AMLs were diveded into fatty and nonfatty AMLs according to CT findings. RCCs were devided into clear cell and nonclear cell subtypes. The relative echogenesity (RE) of tumor was calculated by setting the echogenecity of the renal parenchyma as 0% and that of renal sinus fat as 100%. The echogenecity was measured by the value of ROIs on PACS system. The diagnostic power of measuring RE in differentiating AML and RCC was determined by using receiver operating characteristic (ROC) analysis.
Results: The average RE of AMLs (117.8% ± 48.2) was significantly higher than that of RCCs (47.9%± 50.9) (P < .01). The area under the ROC curve (AUC) was as high as 0.885 with using RE larger than 60.9% as an optimal cutoff value(P<.01). The sensitivity and specificity of optimal cutoff value were 0.974 and 0.703. There were also significant difference between RE of nonfatty AMLs and RE of all RCCs (p<.01). The AUC was as high as 0.855 with the optimal RE value of 78.5% and the sensitivity and specificity on this optimal value were 0.917 and 0.811.
Conclusion: The measurement of relative echogenecity by ROIs on PACS system could be helpful in differentiating AML and RCC, especially in terms of convenience and simplicity.