Technical Advances for Sodium Magnetic Resonance Imaging

磁共振成像（MRI）是一项核心的现代医疗保健技术，它提供了无与伦比的非侵入性人体图像，反映了各种器官的潜在结构、功能和代谢。在过去的35年里，基于大学的硬件、软件和成像物理的工程进步大大提高了MRI的质量和能力。常规临床MRI从我们主要组成的水分子中的两个氢核（1H）获取信号。然而，水磁共振并不能检测到所有的异常。我们的解决方案是从其他对正常细胞功能和健康很重要的化学元素（如钠（23Na））中获取MRI图像。值得注意的是，23Na的MRI物理比1H的复杂得多。在过去的20年里，我们一直致力于开发钠核磁共振成像，重点关注大脑（用于中风和多发性硬化症）和软骨（用于骨关节炎）。拟议的NSERC发现拨款是为了推进核磁共振成像技术，以成像皮肤中的钠。饮食中的盐（或钠）在健康中起着关键作用，特别是因为它与“无声杀手”高血压（即高血压）有关，高血压在加拿大和世界范围内太普遍了。虽然人们可以测量血液样本中的钠含量，但这并不能显示出钠在全身各组织中积累了多少。事实上，最近发现皮肤（身体最大的器官）是过量钠的主要储存库。国际上使用钠核磁共振成像（通常是人类小腿）进行的非侵入性研究表明，男性、衰老、高血压、肥胖和糖尿病、心力衰竭和肾脏疾病等临床疾病的皮肤钠含量升高。尽管这些结果显示了钠核磁共振成像的应用前景，但这些研究中使用的成像方法只是简单地借鉴了1H核磁共振成像，其低分辨率图像在钠水平估计中产生了很大的误差。我们的主要研究目标是通过专门为皮肤的钠核磁共振量身定制的新颖工程开发来实现准确的钠浓度，这是具有挑战性的，因为它很薄（只有1-2毫米厚）。高分辨率图像（如4K电视屏幕）是必要的，但这需要设计和建造更敏感的MRI硬件（天线），以及发明和优化新的钠特异性图像采集软件。这些技术的进步将以计算机模拟和实验测量为指导。这些最佳的钠核磁共振成像方法将用于测量广泛年龄范围（儿童到老年人）的健康个体皮肤（小牛）中的钠浓度，包括男性和女性。这将为今后与患病人群的比较建立一个新的“规范”基础。我们的钠核磁共振进展也将公开和免费提供给世界各地的团体使用，以改进他们的研究。

Magnetic Resonance Imaging (MRI) is a core modern health care technology that provides unparalleled non-invasive images of the human body reflecting underlying structure, function, and metabolism in various organs. Over the last 35 years, university-based engineering advances in hardware, software and imaging physics have greatly increased the quality and capability of MRI. Routine clinical MRI acquires signal from the two hydrogen nuclei (1H) in the water molecule, of which we are primarily composed. However, water MRI cannot not detect all abnormalities. Our solution is to enable MRI image acquisition from other chemical elements important for proper cell functioning and health, like sodium (23Na). Note that the MRI physics of 23Na is considerably more complicated than that of 1H. Over the last 20 years, we have been developing sodium MRI with a focus on the brain (for stroke and multiple sclerosis) and cartilage (for osteoarthritis). The proposed NSERC Discovery grant is to advance MRI technology to image sodium in the skin. Salt (or sodium) in diet plays a key role in health, particularly as it relates to the "silent killer" hyper-tension (i.e. high blood pressure), which is far too prevalent in Canada and world-wide. Although one can measure sodium levels in a blood sample, this does not show how much sodium is accumulated in various tissues throughout the body. In fact, it has recently been discovered that skin (the largest organ of the body) is a major reservoir for excess sodium. International non-invasive studies with sodium MRI (usually of the human calf) has shown that skin sodium is elevated in men, aging, hypertension, obesity and clinical conditions such as diabetes, heart failure, and kidney disease. Although these results demonstrate promising utility for sodium MRI, the imaging methods used in these studies were simply borrowed from 1H MRI, and their low resolution images yield large errors in sodium level estimation. Our primary research goal is to enable accurate sodium concentration through novel engineering development specifically tailored for sodium MRI of the skin, which is challenging given how thin it is (only 1-2 mm thick). High-resolution images (like 4K television screens) are necessary, but this requires the design and construction of more sensitive MRI hardware (antennas), as well as inventing and optimizing new sodium-specific image acquisition software. These technology advancements will be guided by both computer simulation and experimental measurements. These optimal sodium MRI methods will be used to measure sodium concentrations in the skin (calf) of healthy individuals over a wide age range (children to the elderly), both males and females. This will establish a new `normative' basis for future comparisons to people with disease. Our sodium MRI advancements will also be made publicly and freely available for use by groups world-wide to improve their studies.