3.0T MR Imaging Differentiation Of Renal Cell Carcinoma Subtypes

Partâ… Dynamic Contrast-Enhanced MR Imaging for Differentiation of Renal Cell Carcinoma SubtypesPurpose:To evaluate whether the enhancement patterns of pathologically proved clear cell,papillary,and chromophobe renal cell carcinomas(RCCs) measured on clinical dynamic contrast agent-enhanced magnetic resonance(MR) images permit accurate diagnosis of RCC subtype.Material and Method.This study was Institutional Review Board approved and HIPAA compliant;informed consent was waived.Eight-three(54 men,29 women;age range,23-75 years;mean age, 49.4 years) underwent MR imaging of 85 renal masses(mean diameter,4.7 cm) with pathologic diagnoses of clear cell(n =49),papillary(n=22),or chromophobe (n=14) RCC.A 3.0-T clinical MR protocol was used before and after(cortical, medullar and delayed phases) intravenous administration of contrast agent. Region-of-interest measurements within tumor and uninvolved renal cortex were used to calculate percentage signal intensity change and tumor-to-cortex enhancement index.Subtype groups were compared by using one-way ANOVA method.Receiver operating characteristic(ROC) curve analysis was performed for the comparison of clear cell and non-clear cell RCCs.Results:On the cortical, medullary and delayed phase images,clear cell RCCs showed greater signal intensity change(245.9%,286.4%and 257.1%,respectively) than did papillary RCCs(63.8%,136%and 126%,respectively)(P＜0.01).Chromophobe RCCs showed intermediate change(122.5%,239.4%and 198.6%,respectively).The tumor-to-cortex enhancement indexes at the cortical,medullar and delayed phases were largest for clear cell RCCs(1.1,0.8 and 0.8,respectively),smallest for papillary RCCs(0.2,0.4 and 0.4,respectively),and intermediate for chromophobe RCCs(0.5,0.7 and 0.6,respectively).Signal intensity changes on cortical phase images were the most effective parameter for distinguishing clear cell and non-clear cell RCC(area under ROC curve,0.981);a threshold value of 180.1% permitted distinction with 91.8%sensitivity and 97.2%specificity.Conclusion: Clear cell,papillary,and chromophobe RCCs demonstrate different patterns of enhancement on three-time point clinical dynamic contrast-enhanced MR images, allowing their differentiation with high sensitivity and specificity.Partâ…¡Diffusion-Weighted MR Imaging for Differentiation of Renal Cell Carcinoma SubtypesPurpose:To assess the usefulness of apparent diffusion coefficients(ADCs) for characterizing renal cell carcinoma subtypes.Material and Method:The institutional review board waived the requirement for informed consent for this retrospective HIPAA-compliant study.The data of 83 patients(54 men,29 women; age range,23-75 years;mean age,49.4 years) who underwent diffusion-weighted MR imaging of 85 renal masses(mean diameter,4.7 cm) with pathologic diagnoses of clear cell(n =49),papillary(n=22),or chromophobe(n=14) RCC. Precontrast single-shot spin-echo echo-planar diffusion-weighted images were obtained with b values of 0,500,800 and 1000 sec/mm² at 3.0 T.Regions of interest were placed on renal lesions to measure the ADC of the area of most marked visible enhancement.One-way ANOVA was used to compare the ADC value of the various subtypes of RCC.The difference of ADC value between RCC and uninvolved renal cortex was tested using Paired-Samples T Test.Receiver operating characteristic(ROC) curve analysis was performed for the comparison of clear cell and non-clear cell RCCs.Results:With b value of 500 sec/mm²,clear cell RCCs showed significantly higher ADC value(1.849×10^-3mm²/sec) than did papillary RCCs(1.087×10^-3mm²/sec) and chromophobe RCCs(1.307×10^-3mm²/sec)(P＜0.01).However,the difference between papillary RCCs and chromophobe RCCs showed no statistical significance(p=0.068).With b value of 800 and 1000 sec/mm².clear cell RCCs showed the largest ADC value(1.698×10^-3mm²/sec and 1.560×10^-3mm²/sec,respectively) in three subtypes and the difference between each pair of subtypes demonstrated remarked statistical significance(p＜0.01).ADC values with b of value of 800 sec/mm² were the most effective parameter for distinguishing clear cell and non-clear cell RCC(area under ROC curve,0.973);a threshold value of 1.281×10^-3mm²/sec permitted distinction with 95.9%%sensitivity,94.4%specificity and Youden's Index 0.903.Conclusion:Clear cell,papillary,and chromophobe RCCs demonstrate different ADC values with high b value on diffusion-weighted MR images,allowing their differentiation with high sensitivity and specificity.