This invention relates to a system for determining a biodistribution of radioactive agents in a subject. According to the invention, a detector system comprising two or more detectors arranged to be attached to the subject at localized areas is used for detecting the radiation emitted from the imaging agents at localized tissues within the subject. The measuring results in separate radiation data sets associated to the tissues. The detectors are further being arranged to adapt the measuring rate to the pharmacokinetic behavior of the tissues in order to capture all relevant data points. A processor then uses the data sets for determining the radioactivity within each respective tissue and based thereon the biodistribution within the subject.