How does this relate to physics?

http://www.cedars-sinai.edu/Patients/Programs-and-Services/Heart-Institute/Research-and-Outcomes/Cardiac-Imaging-Research-Team-CIRT/CIRT-Core-Laboratory.aspx


The physics of the heart is a bit simple at first glance - the heart exerts a force that causes the blood to flow through blood vessels and causes a measurable pressure (blood pressure) on them. Blood pressure changes with volume, when the blood vessels dilate (more volume) blood pressure goes does; when blood vessels constrict (less volume) blood pressure goes up.

Physics is used in nuclear cardiology to help pinpoint the cause of a patient's chest pain without having to do more invasive procedures. Using nuclear imaging one can see the blood flow to the heart non invasively. Looking at the change in volume allows us to figure out the change in pressure and see if something more invasive needs to be done in order to remedy the lack of blood flow.