Heart transplantation is a great procedure for selected patients with end-stage heart failure, but graft rejection remains a major factor limiting long-term survival despite continued advancement in the scientific skill of immunosuppression. The only reliable method used today to detect rejection is doing repeated biopsy of the heart. This is expensive, invasive, inconvenient to the patient, and associated with a significant risk of serious complications, as a piece directly from the inner surface of the patients heart is needed. The magnetocardiograph (MCG) device is an invention that may provide new means to assess changes in the heart tissue, as it may detect small changes that happen in the heart cells when they are undergoing rejection.