Described herein are systems and methods for quantitatively measuring manganese ion efflux in a subject. In general, the systems and methods compare imaging data from a subject taken over specific periods of time to pharmacokinetic models in order to measure manganese ion efflux rates from an organ in a subject. By understanding the specific location and rate of manganese ion efflux and influx from the organ, it is possible to more accurately correlate calcium ion activity. Calcium ion efflux is associated with a number of biological mechanisms in the subject, and the methods and systems described herein can be used as a diagnostic tool not only for monitoring calcium efflux in the subject but also aid in the treatment of diseases associated with changes in calcium ion efflux.