Optimized noise filters for improved contrast in MRI

我们建议开发和实施磁共振成像（MRI）实验，调制核自旋和它们的环境之间的相互作用，使所得图像的信息内容最大化的优化实验方案。根据具体的诊断要求，可以优化它以（i）最佳地抑制活组织的结构化介质特性中的去相干（噪声）效应;（ii）最佳地测量和分析噪声频谱，并从噪声中提取诊断信息。对于这两个目标，最佳调制方案必须对临床环境中通常遇到的实验缺陷具有鲁棒性，并将SAR值保持在可接受的水平。我们期望这种最佳设计的场调制方案将导致信噪比的实质性改善和/或产生提供更直接信息的图像，例如关于组织中的分子扩散过程的图像。这些序列将在最优控制理论的帮助下进行设计，并建立在多特蒙德集团以及我们在以色列的合作伙伴Gershon Kurizki集团的大量专业知识基础上。初步实验将在高分辨率NMR光谱仪上进行。这允许更多的测量时间，避免了与临床扫描仪相关的许多并发症，并允许理论和实验之间的最直接的比较。当初步检查完成后，我们将把实验转移到一个显微成像系统，该系统允许对需要空间分辨率的所有方面进行良好控制的测试。为了测试特定于全身成像系统的方面，我们将在Erwin Hahn研究所的7特斯拉MRI扫描仪上进行实验。作为最终的结果，我们预计临床MRI将有新的工具可供使用，大大扩展了MRI的诊断工具集。

We propose to develop and implement optimized experimental schemes for magnetic resonance imaging (MRI) experiments that modulate the interaction between the nuclear spins and their environment such that the information content of the resulting images is maximized. Depending on the specific diagnostic requirements, it can be optimized to either (i) optimally suppress decoherence (noise) effects in structured media characteristic of living tissue; (ii) optimally measure and analyze the noise spectra, and extract diagnostic information from the noise. For both goals, the optimal modulation scheme must be robust against experimental imperfections that are typically encountered in a clinical environment and keep the SAR values at acceptable levels. We expect that such optimally designed field modulation schemes will result in substantial improvements in signal-to-noise ratios and / or generate images that provide more direct information, e.g. on molecular diffusion processes in the tissues. The sequences will be designed with the help of optimal control theory, building on a substantial amount of expertise in the group in Dortmund as well as in the group of Gershon Kurizki, our cooperation partner in Israel. Initial experiments will be performed on a high-resolution NMR spectrometer. This allows for more measurement time, avoids many of the complications associated with clinical scanners and allows the most direct comparison between theory and experiment. When the initial checks are completed, we will move the experiment to a microimaging system that allows well-controlled tests of all aspects that require spatial resolution. To test aspects that are specific to whole-body imaging systems, we will implement the experiments on the 7 Tesla MRI scanner of the Erwin Hahn Institute. As the ultimate result, we expect that clinical MRI will have new tools at its disposal that significantly extend the diagnostic toolset of MRI.