Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland.
Invest Radiol. 2012 Feb;47(2):121-7. doi: 10.1097/RLI.0b013e3182300603.
To evaluate the effect of the contrast medium (CM) concentration and the saline chaser volume and injection rate on first-pass aortic enhancement characteristics in contrast-enhanced magnetic resonance angiography using a physiologic flow phantom.
Imaging was performed on a 3.0-T magnetic resonance system (MAGNETOM Trio, Siemens Healthcare Solutions, Inc, Erlangen, Germany) using a 2-dimensional fast low angle shot T1-weighted sequence (repetition time, 500 milliseconds; echo time, 1.23 milliseconds; flip angle, 8 degrees; 1 frame/s × 60 seconds). The following CM concentrations injected at 2 mL/s were used with 3 different contrast agents (gadolinium [Gd]-BOPTA, Gd-HP-DO3A, Gd-DTPA): 20 mL of undiluted CM (100%) and 80%, 40%, 20%, 10%, 5%, and 2.5% of the full amount, all diluted in saline to a volume of 20 mL to ensure equal bolus volume. The CM was followed by saline chasers of 20 to 60 mL injected at 2 mL/s and 6 mL/s. Aortic signal intensity (SI) was measured, and normalized SI versus time (SI/Tn) curves were generated. The maximal SI (SI(max)), bolus length, and areas under the SI/Tn curve were calculated.
Decreasing the CM concentration from 100% to 40% resulted in a decrease of SI(max) to 86.1% (mean). Further decreasing the CM concentration to 2.5% decreased SI(max) to 5.1% (mean). Altering the saline chaser volume had no significant effect on SI(max). Increasing the saline chaser injection rate had little effect (mean increase, 2.2%) on SI(max) when using ≥40% of CM. There was a larger effect (mean increase, 19.6%) when ≤20% of CM were used. Bolus time length was significantly shorter (P < 0.001), and area under the SI/T(n) curve was significantly smaller (P < 0.01) for the CM protocols followed by a saline chaser injected at 6 mL/s compared with a saline chaser injected at 2 mL/s.
With 40% of CM and a fast saline chaser, SImax close to that with undiluted CM can be achieved. An increased saline chaser injection rate has a more pronounced effect on aortic enhancement characteristics at lower CM concentrations than at higher CM concentrations.
使用生理流控体模评估对比剂（CM）浓度、盐水冲注量和注射率对对比增强磁共振血管造影中初次通过主动脉增强特征的影响。
在 3.0T 磁共振系统（Siemens Healthcare Solutions，Inc.的 MAGNETOM Trio）上进行成像，使用二维快速低角度发射 T1 加权序列（重复时间 500 毫秒；回波时间 1.23 毫秒；翻转角 8 度；1 帧/秒×60 秒）。使用 3 种不同的造影剂（钆-BOPTA、钆-HP-DO3A、钆-DTPA）以 2ml/s 的速度注射以下 CM 浓度：20ml 未稀释 CM（100%）和 80%、40%、20%、10%、5%和全量的 2.5%，均用盐水稀释至 20ml 以确保等量的射流体积。CM 后以 2ml/s 和 6ml/s 注射 20-60ml 的盐水冲注。测量主动脉信号强度（SI），并生成 SI/Tn 时间曲线。计算最大 SI（SI(max)）、射流长度和 SI/Tn 曲线下面积。
将 CM 浓度从 100%降低至 40%会导致 SI(max)降低至 86.1%（平均值）。进一步将 CM 浓度降低至 2.5%会使 SI(max)降低至 5.1%（平均值）。改变盐水冲注量对 SI(max)无显著影响。当使用≥40%CM 时，增加盐水冲注速度对 SI(max)的影响较小（平均增加 2.2%）。当使用≤20%CM 时，影响较大（平均增加 19.6%）。与以 2ml/s 注射的盐水冲注相比，以 6ml/s 注射的 CM 方案的射流时间长度明显缩短（P<0.001），SI/Tn 曲线下面积明显减小（P<0.01）。
以 40%CM 和快速盐水冲注，可实现接近未稀释 CM 的 SI(max)。在较低的 CM 浓度下，增加盐水冲注速度对主动脉增强特征的影响比在较高的 CM 浓度下更为明显。
