Study Of Mutiple B Values In Adadrenal Tumors With MR Diffusion Weighted Imaging

Objective To study the manifestations of MR diffusion weighted imaging (DWI) and to compare the difference of apprenal diffusion coefficient (ADC) values of adrenal tumor in different b factors,so as to investigate the section of optimal b factors as well as the range of threahold of ADC values of benigen and malignant adrenal Tumors with the optimal b factors.Methods A total of 23 patients with pathologically or clinically proven adrenal tumor underwent pain and DWI scanning. Various b factor were set as 0,400,800 and 1000 s/mm².The signal difference of various tumors were studied.The ADC values of adrenal tumors among different b factors were measured respectively and analyzed statistically.Results (1) The signal intensities of tumors on T₂WI were in consistent with that of DWI when b value is 0 s/mm². With b value increased to 400,800,1000 s/mm²,the DWI signal of adrenal cortical adenoma and leiomyoma substance declined in order,however there was no significant chang for malignant tumor and phaeochromocytoma as b values increased. (2)Of the 3 groups of adrenal tumors with different b values,the means ADC value is the largest in the low b values group.Yet reduced following the increase of b value with significant statistical difference(F=13.543, P <0.05).(3)There was no ststistical difference between the ADC values of benign and malignant adrenal tumors with b value= 400-0 s/mm² (t=-2.033,P=0.054).Yet the ADC value of the b values =800-0 s/mm² group showed statistical difference when compared with that of 1000s/mm² (t=-2.700, P=0.013; t=-3.529,P=0.002) . (4) Used the ADC values with the b=800-0 s/mm² for ROC curve analysis.The diagnosis threshold point was 0.986×10^-3mm²/s by ROC analysis. The sensitivity in differentiating benign or malignant adrenal tumor was 80%,the specificity was 78%.Conclusion 800-0 s/mm² are the optimal b factors for DWI of adrenal tumor. In the mean time. The mean ADC value of benign tumor is (1.138±0.180)×10^-3 mm^2/s the mean ADC value of malignant tumor is (0.916±0.218)×10^-3 mm²/s. DWI is valuable for differentiating adrenal tumors and is a useful supplement for conventional MRI.