NMR-Based Rapid Fluid Assessment: Device Design and Signal Processing PROJECT SUMMARY Our goal is to develop a portable, non-invasive, measurement of volume status to improve quality of life and reduce morbidity and mortality among hospitalized patients. Maintenance of euvolemic status and proper fluid balance are critical for health and improved outcomes for renal, cardiovascular, and many other disease types as well as in healthy populations prone to dehydration such as athletes and soldiers. Our laboratory has previously constructed a portable single sided magnetic resonance (MR) sensors that is capable of resolving individual fluid compartments (subcutaneous, intramuscular, etc.) within tissue. This sensor was used in a pilot clinical trial with end stage kidney disease patients. Quantitative MRI results on these patients demonstrated that the first sign of fluid overload among hemodialysis patients is an expanded skeletal muscle extracellular fluid (ECF) space. The early stage nature of the technology was evident in that study as the portable sensor could not unambiguously differentiate skeletal muscle tissue from subcutaneous tissue. The proposed research includes the design of a new portable low-field MR sensor and improved signal processing that will allow it to capture the same quantitative assessment of volume status currently achievable with quantitative MRI (qMRI). We measure local fluid distribution in the target in vivo tissue compartment. In the case of fluid volume status, our hypothesis is that a localized skeletal muscle measurement is representative of systemic fluid distribution based on results from a prior study1. The optimized sensor will have the sensitive region of the magnetic field designed to target the skeletal muscle. The existing and newly designed portable MR sensors will be used to measure intramuscular fluid distribution in end stage kidney disease patients undergoing dialysis treatment as well as in healthy athletes experiencing exercise induced fluid loss. The sensor measurement will allow for quantification of volume overload (hypervolemia) or depletion (hypovolemia) and allow for its use in clinical decision making. Dialysis patients and athletes are the target population for the following proposal. The rapid reduction in fluid volume during a dialysis session and exercise respectively provides the ideal clinical context for performing repeated fluid status measurements.