The Basic Rearch On Gd-EOB-DTPA Enhanced MR Imaging On Rabbits

Part I:Optimal Flip Angle for Gd-EOB-DTPA Enhanced Hepatic MR Imaging of RabbitsOBJECTIVE:Gd-EOB-DTPA is a newly developed hepatocyte-specific magnetic resonance (MR) imaging contrast agent. In Gd-EOB-DTPA enhanced imaging, selection of flip angle has a great influence on presenting images with high quality. The study aimed at finding the optimal flip angle for Gd-EOB-DTPA enhanced hepatic MR imaging of healthy New Zealand rabbits by taking statistical tests of MR imaging quality including SNR(signal-to-noise ratio) of liver and CNR(contrast-to-noise ratio) of liver versus muscle during hepatobiliary phase。MATERIALS AND METHODS:Nine adult New Zealand white rabbits were performed with3-T MR system. T1-weighted imaging, with Flip Angle ranges from2to44°, at interval of2°, were carried out30minutes after the administration of intravenous Gd-EOB-DTPA (2seconds for each Flip Angle scanning time, so the total scanning time44seconds). SNR and CNR, as the evaluating indicators of image quality, were calculated for different angles and tested by statistical ways.RESULT:As flip angle broadened, SNR and CNR showed an increasing to decreasing trend with a platform between the two. The peaking value of SNR and CNR was both at22°. Neither SNR values of angle14-36°nor CNR values of18-36°had statistical significance in comparison with22°.CONCLUSION:In order to gain optimal SNR and CNR values, the best flip angles recommended for Gd-EOB-DTPA hepatic MR imaging would be angle14-36°and18-36°, respectively. Part Ⅱ:Variations of Apparent Diffusion Coefficient Values of Diffusion-weight Imagings before and after Gd-EOB-DTPA Magnetic Resonance Imaging in Normal Rabbit LiverPurpose:To investigate changes on diffusion-weighted images (DWIs) of the liver before and after contrast injection in gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) enhanced magnetic resonance imaging.Materials and Methods:Ten normal rabbits were examined. DWI sequences was performed before and at5,10,15,20,25,30, and35min after Gd-EOB-DTPA administration at the b value of0/500mm/s. Apparent diffusion coefficient (ADC) values of the DWIs of liver pre-and post-contrast enhancement were measured. Repeated Measures were used to testify the statistical significance of ADC values recorded at different time points before or after the injection of the contrast agent. Afterward, multiple comparison was carried out in the way of Bonferroni, seeing whether the difference between ADC values recorded before contrast enhanced and every time point after the injection of the contrast agent had statistical significance, respectively. Statistical significance level was set at0.05.Results:The ADC values of the liver showed no difference among all time points after Gd-EOB-DTPA administration.Though decline of ADC value was observed after the contrast agent injection, no significant differences were found before and every time points after the contrast was used,respectively.Conclusion:DWI sequence can be done at any time point before or after Gd-EOB-DTPA administration for healthy rabbits.