Magnetic Resonance Imaging of Fleeting Signals

磁共振成像是众所周知的诊断临床工具。不太为人所知的是，MR图像可用于测量扩散和流速。我们的研究集中在流体运动的MRI测量的进展，在气体和液体中，在湍流，气泡流，甚至在火焰中。在NSERC的支持下，我们开发了一种新的MRI方法，该方法能够比以前更快地成像更多的湍流（具有短暂的MRI信号）。该提案资助的研究将这些测量扩展到接近马赫数1的气流和能源工业中至关重要的多相流。首先，我们正在改进现有MRI方法的运动敏感性，以用于产生短暂（短暂）反应的材料。我们正在发展加速度、速度相关性和湍流动能的测量，这些都是描述湍流的关键参数。在第二个方面，我们正在开发新的方法，通过使用射频激励的成形脉冲来对具有短暂MRI响应的样本进行成像。这些新的MRI工具最终也将是运动敏感的，以增加可以理解复杂流体运动的技术范围。

Magnetic resonance imaging is well-known as a diagnostic clinical tool. Less well-known is the fact that MR images can be used to measure diffusion and flow velocities. Our research is focused on advances in the MRI measurement of fluid movements, in gases and in liquids, in turbulent flows, bubbly flows, and even in flames. With NSERC support, we have developed a new MRI method which is capable of imaging much faster and more turbulent flows (which have short-lived MRI signals) than previously possible. The research funded in this proposal extends those measurements to gas flows approaching Mach 1 and to multi-phase flows which are critical in the energy industry.The research has two thrusts. In the first, we are improving the motion sensitization of existing MRI methods for materials which give rise to short-lived (fleeting) responses. We are developing measurement of acceleration, of velocity correlations and of turbulence kinetic energy, which are all critical parameters in describing turbulent flows. In the second thrust, we are developing new ways to image samples with fleeting MRI responses, by using shaped pulses of radiofrequency excitation. These new MRI tools will eventually also be motion sensitized, to add to the range of techniques with which complicated fluid motion can be understood.