Development and evaluation of cardiac sodium (23Na) MR imaging to quantify myocardial sodium accumulation in vivo in humans

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Cardiovascular diseases are the leading cause of death worldwide. Increased salt (NaCl) intake is a significant risk factor for the development of cardiovascular diseases. Recent studies using sodium (23Na) magnetic resonance imaging (MRI) have shown pathophysiologically relevant sodium accumulation in skin and muscle tissue in vivo in humans, which was linked to the development of hypertension. This occurred in at-risk cardiovascular patients such as diabetics and dialysis patients. In patients with chronic kidney disease (CKD), increased tissue sodium concentrations were also identified as the most important factor for left ventricular hypertrophy, an independent risk factor for cardiac morbidity and mortality. Whether increased tissue sodium concentrations also occur directly in the heart is not yet known.In order to quantify the cardiac tissue sodium concentration for the first time in CKD patients, cardiac 23Na MRI will be implemented in close interdisciplinary cooperation between MR physicists and physicians, and optimized for clinical application. The first step is to develop new efficient measurement techniques for cardiac 23Na MRI at 7 Tesla, which allow reproducible quantification of tissue sodium concentration in the myocardium within clinically acceptable measuring time (< 15 min). In addition, acquisition techniques will be developed that provide information about the physiological environment of sodium ions in the myocardium. Moreover, robust correction methods for cardiac and respiratory motion, as well as for correcting partial volume effects, will be developed and implemented. By using double-resonant coils, data for 23Na and 1H MRI will be acquired in a time-interleaved manner. The almost simultaneous recording of this data is intended to enable shorter measurement times on the one hand and an improved correction of motion artifacts on the other. Data from all respiratory phases should be used to increase the temporal efficiency of cardiac 23Na MRI. For this purpose, so-called "motion vector fields" are to be calculated, which allow a deformable registration. These will be integrated directly into the image reconstruction so that motion-corrected 23Na MRI data can be generated. In the second step, the new acquisition techniques will be used in the first clinical trials. We plan to examine dialysis patients before and after hemodialysis treatment using cardiac 23Na-MRI. We assume that these patients accumulate sodium in the myocardium and that this excess sodium is associated with cardiac structural disorder and thus end organ damage. In the future, the methods developed could be used to specifically identify patients with chronic myocardial sodium overload and to provide personalized therapy, e.g. by adjusting dialysis prescription.