Methods, systems, devices and computer program products monitor in vivo detected radiation in a target localized site within a subject, over a selected time period, to do one or more of: (a) quantify a radiation dose received at a local site; (b) assess bioreceptiveness to a particular treatment time or type; (c) evaluate the pharmacokinetics of a radiolabeled analyte corresponding to a non-radiolabeled analyte; (d) monitor or evaluate metabolic activity; or (e) evaluate a tumor prior to or after a therapeutic treatment.