This device is a portable magnetic resonance sensor that identifies changes in intramuscular fluid distribution by performing a non-invasive scan of skeletal muscle in the lower leg of human patients. To determine muscle hydration status, a RF excitation signal is emitted from the device. This RF excitation frequency can be tuned to acquire measurements at various tissue depths to enable spatial selection, with shorter RF excitation frequencies localizing measurements to deeper tissues. This sensor measures the multicomponent T2 decay signal produced from the targeted tissue and detects changes in hydration status through fluctuations in amplitude of multicomponent T2-based signal. The presence of subcutaneous fat can confound signals produced by muscle; however, the inventors have developed a diffusion-weighting algorithm to estimate the relative contribution of muscle and fat tissue to the hybrid signal. Thus, the multicomponent T2-based signal corresponding to muscle can be isolated. The magnetic resonance signal produced by muscle changes as a function of hydration status. Therefore, measurements of muscle can be collected over time to detect shifts in tissue fluid distribution with high sensitivity to improve patient outcomes in medical procedures that require removal of excess fluid.