Functional Magnetic Resonance Imaging In Characterization Of Lipid-poor Adrenal Lesions At3.0T MR

Objective The purpose of our study was to evaluate the value of dynamic contrast-enhanced MRI,chemical shift imaging (CSI) and diffusion weighted imaging (DWI) at3.0T MRI in adrenal lipid-poor lesions.Methods Fifty-seven lipid-poor adrenal lesions in44patients were evaluated. Time-SI enhancement rate curve type, signal intensity index (SII), adrenal to spleen ratio (ASR) and apparent diffusion coefficient (ADC) were used as quantitative analysis parameters.Results Time-SI enhancement rate curve types were:benign pheochromocytomas95%(21/22) was type Ⅱ; lipid-poor adenomas100%(18/18) was type Ⅰ; malignant tumors70%(7/10) was type Ⅲ and30%(3/10) was type II. The mean SII, ASR and ADC values were:benign pheochromocytomas (n=22),7.17%;0.96,1.10×10-3mm2/s; lipid-poor adenomas (n=18),27.74%,0.74,1.10×10-3mm2/s; malignant tumors(n=10),9.83%;0.96;0.96×10-3mm2/s. The optimal diagnostic threshold point of SII for lipid-poor adenomas was11.96%, the sensitivity and specificity were83.3%and78.9%. The optimal diagnostic threshold point of ASR for benign pheochromocytomas was0.84, the sensitivity and specificity were94.7%and75%. There were significant differences between lipid-poor adenomas and benign pheochromocytomas SⅡ values (P=0.002). The optimal diagnostic threshold point was11.96%(AUC=0.829,95%CI,0.668to 0.990; p=0.002) in ROC curve analysis (fig5a). Using SⅡ of11.96%as a threshold value for diagnosing lipid-poor adenomas, the sensitivity was83.3%, specificity was78.9%. However, no statistic difference was found between benign pheochromocytomas and malignant tumors. There were also significant difference between the lipid-poor adenomas and the ganglioneuromas, as well as between the malignant tumors and the ganglioneuromas (P=0.043, P=0.034, respectively).There were significant differences between the lipid-poor adenomas and the benign pheochromocytomas for ASR (P=0.002). The optimal diagnosis threshold point was0.84(AUC=0.842,95%CI,0.671to1.013; p=0.002) in ROC curve analysis. Using ASR of0.84as a threshold for diagnosing the benign pheochromocytomas, the sensitivity was94.7%and the specificity was75%. There was also significant difference between the benign pheochromocytomas and ganglioneuromas, lipid-poor adenomas and ganglioneuromas, lipid-poor adenomas and malignant tumors (P=0.04,P=0.021, and P=0.039, respectively). The mean value of adrenal cysts was2.61×10-3mm2/s, which is higher than the other lesions ADC value. There was a significant difference between the ganglioneuromas and benign pheochromocytomas, lipid-poor adenomas, malignant tumors (P=0.025, P=0.009, and P=0.034, respectively). There was also significant difference between the adrenal cysts, benign phaeochromocytomas and lipid-poor adenomas (P=0.023, P=0.028, respectively). However, no statistic difference was found between the benign pheochromocytomas, lipid-poor adenomas and malignant tumors for ADC values.Conclusion Conventional MRI and quantitative analysis of chemical shift MRI can help characterize the lipid-poor adrenal lesions, especially in differentiating adenomas and benign pheochromocytomas. There were significant differences between lipid-poor adenomas and non adenomas for time-SI enhancement rate curve type. There were significant differences between lipid-poor adenomas and benign pheochromocytomas for SII and ASR time-SI enhancement rate curve type, while there were no significant differences for ADC values.