Positron emission tomography systems based on ionization-activated organic fluor molecules, planar pixelated photodetectors, or both

A method for imaging a sample using a positron emission tomography system comprising:

• a plurality of imaging modules, the imaging modules comprising:
• a scintillator compartment containing a low atomic number scintillating medium comprising one or more fluors, the scintillator compartment having a front face and a back face;
• a photodetector system comprising:
• one or more photodetectors optically coupled to the scintillator compartment and configured to detect scintillation photons generated in the scintillating medium;
• and
• one or more reflecting surfaces configured to reflect scintillation photons generated in the scintillating medium to the one or more photodetectors;
• an optical imaging system comprising:
• one or more excitation light sources optically coupled to the scintillator compartment and configured to direct excitation light onto the scintillating medium;
• and
• one or more fluorescence detectors optically coupled to the scintillator compartment and configured to detect fluorescence generated by the fluors in the scintillating medium,
• the method comprising:
• positioning a sample within an imaging volume defined by the plurality of imaging modules, wherein positron-electron annihilation events in the sample generate coincident gamma-ray pairs;
• detecting coincident gamma-ray pairs arriving at a pair of imaging modules using the time-of-flight photodetector system by detecting scintillation photons generated when a first gamma-ray of a coincident gamma-ray pair interacts with the scintillating media in a first imaging module and a second gamma-ray of the coincident gamma-ray pair interacts with the scintillating medium in a second imaging module within a coincidence time window;
• initiating a sequence of steps for the first and second imaging modules of each pair of imaging modules that detects a coincident gamma-ray pair, the sequence of steps comprising:
• triggering a recording of scintillation light by the time-of-flight photodetector system;
• interrogating the scintillating medium by directing excitation light from the one or more excitation light sources onto the scintillating medium, wherein the excitation light excites fluors that have been activated by ionization energy deposited in the scintillating medium by Compton electrons;
• recording fluorescence emitted by the excited fluors to generate images of energy clusters corresponding to Compton scatters of the first gamma ray in the scintillating medium of the first imaging module and images of energy clusters corresponding to Compton scatters of the second gamma-ray in the scintillating medium of the second imaging module;
• identifying the location of a first collision for the first gamma-ray in the scintillating medium of the first imaging module and the location of a first collision for the second gamma-ray in the scintillating medium of the second imaging module;
• and
• forming a line-of-response between the location of the first collision for the first gamma-ray and the location of the first collision for the second gamma-ray;
• and
• generating an image of a spatial distribution of the positron-electron annihilation events within the sample based on the lines-of-response.

A method for detecting gamma-rays using a detection system comprising at least one imaging module having an associated imaging volume, the imaging module comprising:

• a scintillator compartment containing a low-atomic number scintillating medium;
• and
• a planar, pixelated photodetector optically coupled to the scintillator compartment and configured to detect scintillation photons generated in the scintillating medium,
• the method comprising:
• positioning a sample within the imaging volume, wherein the sample generates at least one gamma-ray from a gamma-ray source location, and further wherein the at least one gamma-ray undergoes a first Compton scatter in the scintillating medium of the at least one imaging module to generate a scintillation photon wavefront;
• and
• imaging the scintillation photon wavefront as a time-series of expanding rings of scintillation photons arriving at the planar, pixelated photodetector;
• and
• reconstructing a location and time of the first Compton scatter from the time-series of expanding rings of scintillation photons and the arrival-times of the scintillation photons at the planar, pixelated photodetector.