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

我们开发了一个模型，模拟血管中的血液流动，用于MRI单元。它由旋转泵、流量测量装置和闭合长回路三部分组成。用扩张的造影剂（钆）填充回路。将回路中扩张造影剂的T1值调整为1200 msec，以模拟1.5 T下的血液。将测量装置放置在磁体孔中，将连接到泵的长软管放置在MR装置外部并穿过部分打开的门。该系统能够产生脉动流，使用手动操作和电磁阀。使用三个定时器t1-t3控制脉动流的模式和周期，调节周期：1）周期开始和阀门打开时间之间，2）阀门打开期间，3）阀门关闭和周期结束时间之间。本实验的目的是观察通过狭窄病变的流态和速度的变化，但当管道被压缩以模拟血管狭窄时，泵的流出量减少。此外，长回路中的气泡是使用MRI测量流速和速度的障碍。由于敏感性，流量测量不适用于支架。距离支架末端1 cm的距离是必要的，以便能够使用MRI进行流量测量。

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.