1. A method of detecting partial occlusion of a coronary circulation system in a patient having a bloodstream, comprising: injecting the bloodstream with a bolus comprising a radioactive tracer; obtaining measurements related to a time variation in concentration of the radioactive tracer for a plurality of adjacent regions in the patient that encompass an area greater than a left ventricle region; determining a subset of the plurality of regions that correspond to the left ventricle region; and assessing whether the coronary circulation system is partially occluded based at least in part on those of the measurements that correspond to the left ventricle region.