Measurement of coronary blood flow using MRI for the course observation after stent placement

我们开发了一个模拟血管血流的模型，用于MRI单元。它有三个组成部分：旋转泵、流量测量单元和封闭的长回路。电路内充满膨胀造影剂（钆）。将电路中膨胀造影剂的T1值调整为1200 msec，模拟1.5特斯拉的血液。测量单元被放置在磁铁孔中，连接到泵的长软管被放置在MR单元的外面，并通过部分打开的门。该系统能够通过手动操作和电磁阀产生脉动流。脉冲流量的模式和周期由三个定时器t1-t3控制，分别调节周期：1)周期开始与阀门开启时间之间，2)阀门开启时间之间，3)阀门关闭时间与周期结束时间之间。该系统运行成功，产生了脉动流。虽然本实验的目的是观察通过狭窄病变的血流模式和速度的变化，但当管道被压缩以模拟血管狭窄时，泵的流出量减少。此外，长回路中的气泡对MRI测量流量和速度也有一定的障碍。由于支架的易感性，流量测量不适用。距离支架末端1厘米的距离是磁共振成像测量血流的必要条件。

We developed a model simulating blood flow in the vessel for the usage in MRI units. It has three components of a rotary pomp, flow-measurement unit and closed long circuit. The circuit was filled with dilated contrast material (Gadolinium). T1 value of the dilated contrast material in the circuit was adjusted to 1200 msec to simulate the blood at 1.5 Tesla. The measurement unit was placed in the magnet bore and the long hose connected to the pump was placed outside of the MR unite and through partly opened door. The system was able to generate the pulsatile flow, using manually operated and electromagnetic valves. The pattern and cycle of the pulsatile flow were controlled using three timers t1-t3, regulating the periods, 1) between the start of the cycle and the time when valve opened, 2) during the valve opened and 3) between the time when the valve closed and the end of the cycle. The system was successfully operated to generate the pulsatile flow.Although the aim of this experiment was to observe the change of flow pattern and speed through stenotic lesion though, the outflow of the pump decreased when the pipe was compressed to simulate the stenosis of the vessel. In addition, the air bubble in the long circuit was obstacle to measure flow rate and speed with MRI.Flow measurement was not applicable in the stent due to susceptibility. The distance of one centimeter from the end of stent was necessary to enable the flow measurement with MRI.