NMR Based Diffusion Pore Imaging: A novel imaging concept

弥散加权成像是医学成像中应用广泛的磁共振成像技术，常规应用于急性卒中的诊断。这是一种经常用于检测阻碍扩散运动的细胞结构的技术，特别是用于检测白质束的方向。例如，主要的白质束可以以令人印象深刻的方式重建。20世纪90年代初，保罗·卡拉汉可能表明，核磁共振扩散实验可以获得关于细胞结构的更多信息。特别是，他可以证明，可以使用短扩散梯度来测量孔隙空间函数的等级谱。这个实验可以解释为一个散射实验。不幸的是，就像在X射线结晶学中一样，位相信息丢失了，无法进行逆傅立叶变换。最近，我们可以从理论上说明如何通过修改扩散加权磁场梯度的时间分布来明确地测量孔的形状。这确实是一种新的成像方法，因为可以获得孔的相控谱，并且可以执行逆傅立叶变换，类似于磁共振层析成像。该方案的目的是对已有的理论结果进行实验验证。因此，计划对孔洞成像技术进行深入分析，以便适当地选择模体、序列参数等-使用超极化氙气作为肺泡的模型进行孔洞成像-使用充满水的毛细血管作为轴突的模型进行孔洞成像除了孔洞成像方法外，拟议的扩散加权梯度的修改产生了一种新的磁共振成像对比度：扩散加权相。因此，计划分析这种新的对比度的特性，并在此基础上进行磁共振成像。

Diffusion weighted imaging is a widely applied magnetic resonance technique in medical imaging, that is applied routinely in diagnostics of acute stroke. It is a technique that is often used to detect cellular structures hindering the diffusive motion, and in particular to detect the orientation of white matter tracts. For example, main white matter tracts can be reconstructed in an impressive manner. In the early 1990s, Paul Callaghan could show that nuclear magnetic resonance diffusion experiments can yield further information about the cellular structure. In particular, he could show that the magnitude spectrum of the pore space function can be measured using short diffusion gradients. The experiment can be interpreted as a scattering experiment. Unfortunately - as in x-ray crystallography - the phase information is lost, and an inverse Fourier transform cannot be performed. Thus the cell shape cannot be detected unambiguously.Recently, we could show theoretically how the shape of the pore can be measured unambiguously by modifying the temporal profile of the diffusion weighting magnetic field gradients. This is indeed a new imaging method, since the phased spectrum of the pore can be acquired, and since the inverse Fourier transform can be performed, similarly as in magnetic resonance tomography. The aim of this proposal is the experimental verification of the existing theoretical results. Therefore it is planned to- perform an in-depth analysis of the pore imaging technique in order to chose phantoms, sequence parameters etc. appropriately- perform pore imaging using hyperpolarized xenon as model for lung alveoli - perform pore imaging using water-filled capillaries as model for axonsBesides the pore imaging approach, the proposed modification of the diffusion weighting gradients yields a new magnetic resonance imaging contrast: The diffusion-weighted phase. Therefore, it is planned to analyze the properties of this new contrast, and perform magnetic resonance imaging based on it.