1Department of Radiology, Seoul National University Hospital, Korea. radjycho@radiol.snu.ac.kr 2Institute of Radiation Medicine, Seoul National University Medical Research Center, Korea. 3Kidney Research Institute, Seoul National University Medical Research Center, Korea.
Published online: June 1, 2010.
ABSTRACT
PURPOSE: To retrospectively evaluate the diagnostic value of ultrasonographic differentiation of small angiomyolipomas (AMLs) from renal cell carcinomas (RCCs) by measuring relative echogenicity (RE) on PACS. MATERIALS AND METHODS: Thirty-six cases of < 3 cm, pathologically-proven RCCs and 42 cases of size-matched AMLs were enrolled. We measured the grayscale representing echogenicity of the mass, the renal cortex, and the sinus fat on PACS using a ROI cursor. The RE of the tumor was calculated by setting the grayscale of the renal cortex and sinus fat as 0% and 100%, respectively. We compared REs of AMLs and RCCs, including subgroups of each tumor. ROC analyses between RCCs and AMLs or non-fatty AMLs were performed for obtaining diagnostic performance (Az value) of RE measurement and for extracting sensitivities of RE with fixed specificities of 90% and 95%. RESULTS: The RE of AMLs was higher than RCCs (p < 0.05). The RE of non-fatty AMLs was significantly lower than fatty AMLs, and higher than any subgroups of RCCs (p < 0.05). RE measurement provided good diagnostic performance (Az > or = 0.840, p < 0.05) with competitive sensitivity/specificity for differentiating AMLs from RCCs regardless of AML subgroups. CONCLUSIONS: RE measurement on PACS can be helpful in the differential diagnosis of small AMLs and RCCs with the intrinsic merits of ultrasonography.
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