NMR Based Diffusion Pore Imaging: A novel imaging concept

扩散加权成像是一种广泛应用的磁共振技术在医学成像，这是常规应用于诊断急性中风。这是一种经常用于检测阻碍扩散运动的细胞结构的技术，特别是用于检测白色物质束的方向。例如，可以以令人印象深刻的方式重建主要的白色物质束。在20世纪90年代早期，保罗·卡拉汉（Paul Callaghan）可以证明核磁共振扩散实验可以产生关于细胞结构的进一步信息。特别是，他可以表明，可以使用短扩散梯度测量孔隙空间函数的幅度谱。该实验可以解释为散射实验。不幸的是-如在X射线晶体学中-相位信息丢失，并且不能执行逆傅里叶变换。最近，我们可以从理论上证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，因为可以获取孔隙的相位谱，并且因为可以执行逆傅立叶变换，类似于磁共振断层摄影。本建议的目的是现有的理论结果的实验验证。因此，计划-对孔隙成像技术进行深入分析，以便适当地选择体模、序列参数等-使用超极化氙作为肺泡模型进行孔隙成像-使用充水毛细管作为轴突模型进行孔隙成像。除了孔隙成像方法之外，所提出的扩散加权梯度的修改产生了新的磁共振成像对比度：扩散加权阶段。因此，计划分析这种新造影剂的特性，并基于其进行磁共振成像。

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.