经动脉磁共振门静脉成像的实验研究

目的在犬模型上评价不同的造影动脉、对比剂剂量及血管扩张剂应用与否对经动脉磁共振门静脉成像(MR imaging during arterial portography,MRAP)图像的影响,总结出MRAP的最佳技术参数,为下一步的临床应用做准备.方法健康成犬16条,通过随机化分组表法分配到造影动脉、对比剂剂量及有无血管扩张剂3个研究组中.每条犬行腹腔麻醉后,在X线监视下经股动脉穿刺插管至肠系膜上动脉或脾动脉,行MRAP检查.计算增强前后肝实质信号强度的相对增强值,比较各因素不同水平间的相对增强值之间差异有无统计学意义.分析时间-增强曲线,总结MRAP的最佳技术参数.结果在16条犬上均获得了较为理想的MRAP图像.肠系膜上动脉组肝实质相对增强峰值为29.3%～106.0%,脾动脉组为29.5%～105.0%,肠系膜上动脉组达到肝实质相对增强峰值的时间为24～27 s,而脾动脉组为24～28 s,两组间差异无显著性意义(F=0.03,P>0.05).0.025 mmol/kg组的相对增强峰值为29.3%～30.9%,与0.050 mmol/kg组的95.5%～98.8%,0.100 mmol/kg组的102.0%～106.0%和0.200 mmol/kg组的104.0%～105.0%比较,除后两组之间差异无显著性意义(P>0.05)外,其他各组间差异均有非常显著性意义(P<0.01).有血管扩张剂组达到肝实质相对增强峰值的时间为21～27 s,早于无血管扩张剂组的24～28 s(P<0.05),但两组肝实质相对增强峰值差异无显著性意义(P>0.05).结论 (1)MRAP是一项新的安全可行的肝脏影像学检查技术,20 ml 钆喷替酸葡甲胺(Gd-DTPA)混合液(0.050～0.100 mmol/kg)以1 ml/s注射速度经造影动脉注入,在注射开始后21～28 s即可获得实验动物肝实质的最佳门静脉增强MRAP图像.(2)肠系膜上动脉或脾动脉作为造影动脉,在MRAP影像和时间-增强曲线上无差别.(3)0.050～0.100 mmol/kg的Gd-DTPA剂量完全可以引起肝实质足够的增强(95.5%～106.0%).(4)血管扩张剂的应用并不影响MRAP图像肝实质增强峰值达到的时间和峰值的大小.

MR imaging during arterial portography: an experimental study

Objective To evaluate the optimization of perfusing artery and contrast agent dose, and to determine the effect of precontrast injection of papaverine into the perfusing artery or not on the degree of contrast enhancement of the hepatic parenchyma during MRAP in dog models. Methods Sixteen dogs were included in this study and distributed to three study groups (perfusing artery, dose of Gd-DTPA and use of papaverine or not). Animals were anesthetized with Thiopental Sodium. After placement of a 5F end hole angiography catheter with no metal parts into the perfusing artery, the dogs were transferred immediately to the MR imaging unit. Unenhanced GRE MR and MRAP images were performed with a 2.0 T superconducting magnet. Signal intensity of liver parenchyma was measured with 6 different regions of interest. Relative value (%) of liver parenchymal enhancement was measured and compared. Time-enhancement curves were created and compared. Results MRAP images with good quality were obtained in all 16 dogs. The peak relative value of liver parenchymal enhancement and the time to the peak enhancement was similar in the superior mesenteric artery (SMA) group and in the splenic artery (SA) group. The peak relative value of liver parenchymal enhancement was the lowest in the 0.025 mmol/kg group among all groups. There was no statistical difference in the time to relative peak liver enhancement across the four groups. The time to relative peak liver enhancement in the group with papaverine injection was statistically earlier than that in the group without papaverine injection. Conclusion MRAP is a new and feasible imaging technique to detect hepatic masses before operation. When a 20 ml mixed solution of Gd-DTPA(0.050 -0.100 mmol/kg)was injected into perfusing artery at the rate of 1 ml/s, MRAP image of best liver parenchymal enhancement in dogs could be obtained at 21-28 s after the start of injection of Gd-DTPA. We can place catheters in SMA or SA and there was no statistical difference on MRAP images and time-enhancement curves. The dose of 0.050-0.100 mmol/kg Gd-DTPA was sufficient for MRAP. Application of papaverine precontrast advanced the time to peak liver enhancement, but the peak value of liver enhancement was not affected.