Abstract: A method and system for non-invasive quantitative assessment of radionuclide tracer levels in the blood stream. The method relies on the finding that the gamma-radiation signal acquired using a gamma scintillation probe, is the resultant from a wave-component with changing amplitude, resulting from the radiotracer in the bloodstream and a non-wave background component resulting from radiotracer distributed throughout the tissue surrounding the arterial vessel. The method involves phase-sensitive conversion of the ‘input signal’, extracting there from an output signal representing the signal component originating from the bloodstream, using the changes in arterial blood volume as the reference wave-form. A particular aspect of the invention concerns methods of quantitative PET or SPECT imaging wherein the concentration of radionuclides in the blood stream as a function of time after injection is assessed using the method of the invention.

Abstract: Described are methods and devices for determining a concentration of oxygen in a compartment comprising exciting protoporphyrin IX.

Abstract: Described are methods for determining a concentration of a substance in a compartment comprising exciting an endogenous compound, or a functional part, derivative, analogue or precursor thereof, measuring the lifetime of the luminescence and/or transient absorption exhibited by the compound, functional part, derivative, analogue and/or precursor, and correlating the lifetime with the concentration of the substance.