Evaluation Of Diffusion Tensor Imaging In Clear Cell RCC And Angioleiomyolipoma: A Preliminary Study

PartⅠ Diffusion tensor imaging in normal human kidneyObjective: To investigate the feasibility of diffusion tensor imaging of thenormal kidney and to provide comparative data for further studies on renal lesions.Materials and methods:20healthy volunteers （male10, female10） underwentMR diffusion tensor imaging at b values of0and600s/mm2. Apparent diffusioncoefficient （ADC） and fractional anisotropy （FA） in the upper, middle and lower partsof renal cortex and medulla were calculated and analyzed, respectively. Thenmodularly fiber tractography was conducted.Results: There were no statistical differences among the ADC and FA values inupper, middle and lower parts of kidneys（P＞0.05）.The ADC values in cortex weresignificantly higher than those of renal medulla（2.355±0.143vs2.100±0.155）×10－3mm2/s （P <0.001）, while the FA values in cortex were significantly lower than thoseof medulla（0.163±0.032vs0.404±0.063）（P <0.001）. Medulla fiber tractographyshowed that fibers were orientated in a radial architecture from medulla to cortex.Conclusion: DTI is a useful technique to study the ultra-microstructure ofkidney. Measurement in different parts of kidneys shows no significant differences.High anisotropy was found in medulla, while lower anisotropy was in cortex. Part Ⅱ Application of magnetic resonance diffusion tensor imagingin clear cell carcinoma and angioleiomyolipomaObjective: The objective of our study was to assess the value of diffusion tensorimaging in clear cell carcinoma and angioleiomyolipomaMaterials and methods: Conventional magnetic resonance imaging anddiffusion tensor magnetic resonance imaging at b values of0and600s/mm2were performed on20healthy subjects and50patients with solid renal lesions（30renalcarcinoma，20angioleiomyolipoma）．The ADC and FA values of the renal lesions andnormal kidneys were measured in ADC and FA maps, respectively．Statistical analysisbased on AVOVA was applied to the ADC and FA values for the normal renal cortexgroup, normal medullary group, clear-cell RCC group and angioleiomyolipoma group.Fiber tractography was carried out in the lesion group.Results:30cases clear-cell RCC showed low signal and necrosis part showedhigh signal on ADC map.20cases renal angioleiomyolipoma showed mixed signalson ADC，and fat content showed low signal. There were significant differencesamong the ADC value in renal cortex, medulla, clear-cell RCC and renalangioleiomyolipoma. There were significant differences between the FA values inrenal medulla and those of clear-cell RCC（P＜0.05）,and no significant differenceswere observed among clear-cell RCC, renal cortex and renal angioleiomyolipoma.For the FA value of angioleiomyolipoma, significant difference was found in renalcortex and medulla （P<0.001）, but not for the clear cell carcinoma （P=0.214）. Thearea under the ROC curve for identifying ccRCC was0.878,Selection of1.369×10－3mm2/s as a cutoff point of ADC value to predict ccRCC revealed sensitivity of76.7%, and specificity of95%.Conclusion: The study of ADC and FA value in DTI reveals the structure ofrenal tumors, which can be applied in the diagnosis and prognosis of clear-cell RCCand angiomyolipoma. Part Ⅲ Application of diffusion tensor imaging in theevaluation of nuclear grade of clear cell RCCObjective: The purpose of our study was to assess the utility of the DTI indistinguishing low-grade and high-grade clear cell renal cell carcinoma （ccRCC）.Materials and methods: The study cohort consisted of30patients whounderwent MRI （with diffusion tensor imaging at b values of0and600s/mm2）andwere found to have30pathologically-proven clear cell RCCs. There were25low grade （grades I and II） and5high grade tumors （grades III and IV）. ADC and FAvalues were measured for solid portions of ccRCC. ADC and FA values werecompared between different grades.Results: The ADC values was decreased with the increase of the nuclear gradeand the ADC of high grade RCC was significantly lower than that of the low grade（1.247±0.225vs1.607±0.238）×10^－3mm²/s（P=0.004）. The area under the ROCcurve for identifying low-grade ccRCC was87.2%,Selection of1.270×10^－3mm²/s asa cutoff point of ADC value to predict low-grade revealed sensitivity of92%, andspecificity of80%. However, no significant difference was observed for FA valuesbetween low grade of clear-cell RCC and high clear-cell carcinoma（0.184±0.072vs0.207±0.070）（P=0.513）.Conclusion: ADC values provide a non-invasive means to predict the nucleargrade of clear cell RCC.