MR Angiography of Collateral Arteries in a Hind Limb Ischemia Model: Comparison between Blood Pool Agent Gadomer and Small Contrast Agent Gd-DTPA

The objective of this study was to compare the blood pool agent Gadomer with a small contrast agent for the visualization of ultra-small, collateral arteries (diameter3) was performed on a 3 Tesla clinical system after administration of either Gadomer (dose: 0.10 mmol/kg) or a small contrast agent (gadopentetate dimeglumine (Gd-DTPA), dose: 0.20 mmol/kg). All animals received both contrast agents on separate days. Selective intra-arterial x-ray angiograms (XRAs) were obtained in the ligated limb as a reference. The number of collaterals was counted by two independent observers. Image quality was evaluated with the contrast-to-noise ratio (CNR) in the femoral artery and collateral arteries. CNR for Gadomer was higher in both the femoral artery (Gadomer: 73±5 (mean ± SE); Gd-DTPA: 40±3; pp = 0.04). Neither day of acquisition nor contrast agent used influenced the number of identified collateral arteries (p = 0.30 and p = 0.14, respectively). An average of 4.5±1.0 (day 14, mean ± SD) and 5.3±1.2 (day 21) collaterals was found, which was comparable to XRA (5.6±1.7, averaged over days 14 and 21; p>0.10). Inter-observer variation was 24% and 18% for Gadomer and Gd-DTPA, respectively. In conclusion, blood pool agent Gadomer improved vessel conspicuity compared to Gd-DTPA. Steady-state MRA can be considered as an excellent non-invasive alternative to intra-arterial XRA for the visualization of ultra-small collateral arteries.

本研究旨在对比血池造影剂Gadomer与小分子量造影剂，用于可视化超小侧支动脉（直径3）。实验于3特斯拉临床磁共振系统上开展，所有实验动物均在两个独立日期分别接受两种造影剂给药扫描：其一为Gadomer（剂量：0.10 mmol/kg），其二为钆喷酸葡胺（gadopentetate dimeglumine, Gd-DTPA，剂量：0.20 mmol/kg）。
以结扎肢体的选择性动脉内X线血管造影（X-ray angiograms, XRA）作为参考标准。由两名独立观察者计数侧支动脉数量，并通过股动脉与侧支动脉的对比信噪比（contrast-to-noise ratio, CNR）评估图像质量。结果显示，Gadomer组的对比信噪比在股动脉（Gadomer组：73±5，均值±标准误（standard error, SE）；Gd-DTPA组：40±3；p=0.04）及侧支动脉中均显著更高。
扫描日期与所用造影剂类型均未对检出的侧支动脉数量产生显著影响（分别对应p=0.30与p=0.14）。实验分别于第14天与第21天检出平均4.5±1.0（均值±标准差（standard deviation, SD））与5.3±1.2侧支动脉，该结果与XRA参考标准（第14、21天均值为5.6±1.7；p>0.10）无统计学差异。Gadomer组与Gd-DTPA组的观察者间变异率分别为24%与18%。
综上，相较于Gd-DTPA，血池造影剂Gadomer可提升血管显影清晰度。稳态磁共振血管造影（steady-state MRA）可作为可视化超小侧支动脉的优秀无创替代方案，替代有创的动脉内X线血管造影。