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| The value of tumor to cortex index in MDCT in the differentiation ofangiomyolipoma with minimal fat from renal clear cell carcinoma |
| XU Hua-zhi, ZHENG Xiang-wu, CAO Guo-quan, YE Cai-er, ZHU Ji-ying |
| Department of Radiology, the First Affiliated Hospital of Wenzhou Medical College, Wenzhou Zhejiang 325000, China |
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Abstract Objective: To compare renal angiomyolipoma(RAML) with minimal fat with those of size-matched renal clear cell carcinoma(ccRCC) with three-phase tumor-to-cortex index in multiple-detectors computed tomography(MDCT). Materials and Methods: Twenty-one patients of RAML with minimal fat(confirmed by surgery and pathology) and 52 cases of RCC were evaluated. The data came from the First Affiliated Hospital of Wenzhou Medical College from July 2006 to July 2009. The attenuation of ROI(region-of-interest measurements within tumor and uninvolved renal cortex pre- and post-enhancement) was measured. The tumor to normal renal cortex enhancement index R[R=tumor(CTpost-CTpre)/cortex(CTpost-CTpre), in which CTpost was the CT value of ROI post-enhancement, CTpre was the CT value of ROI before enhancement] was calculated. χ2 test was performed for comparing patient sex. Two dependent t test was done for patient age, CT value pre- and post-enhancement, and the tumor-to-cortex enhancement index R between the two groups. The diagnostic performance of R value analysis in differentiating RAML with minimal fat from ccRCC was determined by using receiver operating characteristic(ROC) analysis. Results: The statistics differences between the RAML with mini-fat group and the RCC group in patient sex, age, and unenhanced tumor attenuation were significant(P<0.05). There was no difference between the two groups in tumor attenuation after contrast(including corticomedullary, nephrographic and excretory phase). The R value of ccRCC group was higher than that of RAML group on all three phases(P<0.01). The area under the ROC curve of corticomedullary, nephrographic and excretory phase was 0.719, 0.767, 0.748, respectively. Tumor-to-cortex enhancement index R on corticomedullary phase was the most effective parameter for distinguishing RAML from ccRCC with threshold value of 0.4649, 71.2% sensitivity and 81% specificity. Conclusion: Three-phase enhancement MDCT scan may be useful in differentiating RAML with minimal fat from ccRCC.
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Received: 24 March 2010
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2010, Vol. 21 
