Separation of 23Na Compartments and Semi-Quantitative Determination of the Intracellular Sodium Concentration Using Ultra High Field Magnetic Resonance Imaging

本项目的目的是在体内无创分离不同的钠室和半定量测定细胞内钠浓度。将开发和评价用于超高场磁共振成像（MRI）（7特斯拉）的不同序列。首先，将开发一种新序列，该序列允许更短的采集时间和双指数加权钠信号的SNR和SAR有效检测。为了分离不同的钠室，弛豫时间的确切知识是不可避免的。因此，三重量子滤波（TQF）的单体素光谱（SVS）序列将被实施，允许快速测量的本地（如在肿瘤组织）的双指数弛豫时间。除了校正静磁场（B 0）的不均匀性和射频线圈（B1）的灵敏度曲线外，1H-MRI的高分辨率信息将用于更好地量化23 Na-MRI信号。在人体内，钠溶于水。因此，应将组织钠浓度标准化为局部含水量。因此，将采用一种水资源定量绘图技术。在肌肉疾病脂肪浸润往往存在。这些结构的尺寸通常小于23 Na-MRI的空间分辨率。因此，肌肉脂肪含量的定量测定和脂肪浸润的高分辨率可视化对于部分容积效应的校正是必要的。此外，将纳入来自1H-MRI数据的先验知识（例如，骨组织没有23 Na信号），以实现关于SNR和空间分辨率的更好的23 Na-MR图像质量。基于新开发的技术和序列，可从以前的工作，模型，允许半定量测定细胞内钠浓度将被开发。在成功检查开发的方法测量非常适合的体模后，将在健康受试者中进行体内评价。将为脑和肌肉组织提供细胞内钠浓度的半定量测定模型。最后，将对具有明确定义的肌肉通道病的患者进行检查，作为模型疾病。 在这些疾病中，刺激（冷却和肌肉运动）导致细胞内钠浓度增加。这种增加可以以高再现性激发。将在肌肉组织激发前后进行测量，以评价使用开发的方法可视化细胞内钠含量增加的潜力。

The aim of the current project is the non-invasive separation of different sodium compartments in vivo and the semi-quantitative determination of the intracellular sodium concentration. Different sequences for ultra-high field magnetic resonance imaging (MRI) (7 Tesla) will be developed and evaluated.First, a new sequence that allows for shorter acquisition time and SNR- and SAR-efficient detection of the bi-exponential weighted sodium signal will be developed. To separate different sodium compartments the exact knowledge of the relaxation times is inevitable. Thus, a triple-quantum-filtered (TQF) single voxel spectroscopy (SVS) sequence will be implemented that allows for a rapid measurement of the local (e.g. in tumor tissue) bi-exponential relaxation times.To provide sufficient accuracy and reproducibility for the determination of signal intensities of the different 23Na-MRI techniques, several corrections have to be performed. In addition to the correction of inhomogeneities of the static magnetic field (B0) and the sensitivity profiles of the radiofrequency coils (B1), high resolution information from 1H-MRI will be used to enable a better quantification of the 23Na-MRI signals. In the human body sodium is dissolved in water. Therefore, the tissue sodium concentration should be normalized to the local water content. Thus, a technique for quantitative water mapping will be implemented. In muscular diseases fatty infiltration are often present. The sizes of these structures are often smaller than the spatial resolution of 23Na-MRI. Therefore, a quantitative determination of the muscular fat content and a highly resolved visualization of the fat infiltrations is necessary the correct for partial volume effects. Furthermore, prior knowledge from 1H-MRI data (e.g. bone tissue gives no 23Na-signal) will be incorporated to enable a better 23Na-MR image quality regarding SNR and spatial resolution. Based upon the newly developed techniques and the sequences that are available from prior work, models that allow for a semi-quantitative determination of the intracellular sodium concentration will be developed. After a successful check of the developed method in measurements of well suited phantoms, in vivo evaluation in healthy subjects will be performed. Models for the semi-quantitative determination of the intracellular sodium concentration will be provided for brain and muscle tissue.Finally, examinations of patients with well-defined muscular channelopathies as model diseases will be performed. In these diseases provocation (cooling and muscle exercise) leads to an increase of the intracellular sodium concentration. This increase can be provoked with high reproducibility. Measurements before and after provocation of the muscle tissue will be performed to evaluate the potential to visualize an increase of the intracellular sodium content with the developed methods.