Method for processing an X-ray or gamma ray spectrum

A method for processing an X-ray or gamma-ray radiation spectrum formed by a spectrometric measuring device, the spectrometric measuring device comprising:

• a detector configured to detect X-ray or gamma-ray photons and, upon each detection, to form a pulse an amplitude of which depends on an energy released by the X-ray or gamma-ray photon that interacted in the detector;
• and
• a spectrometric measuring circuit, configured to form a spectrum, the spectrum corresponding to a number of photons detected in various channels, an amplitude or an energy corresponding to each channel,
• the method comprising:
• a) arranging the device facing an object likely to contain one or more radionuclides emitting X-ray or gamma-ray photons that are incident on the detector, each radionuclide emitting photons at at least one emission energy;
• b) detecting, using the detector, a portion of the incident photons and forming a spectrum of the detected photons, the spectrum containing peaks extending around each emission energy of each radionuclide, each peak resulting from pulses detected in a channel and corresponding to the at least one emission energy;
• c) processing the spectrum so as to obtain a quantity of pulses detected in each peak of the spectrum,
• wherein c) comprises:
• c1) forming a list of radionuclides that are present or likely to be present in the object;
• c2) forming an input vector each term of which containing a quantity of pulses in each peak extracted from the spectrum resulting from b);
• c3) forming a spectral dispersion matrix each term of which being associated with a channel and an emission energy, and corresponding to a probability of an incident photon an energy of which is the emission energy being detected in the channel;
• c4) forming a transfer matrix, using the spectral dispersion matrix;
• c5) forming a direct model, according to which the input vector is obtained by a matrix product of the transfer matrix and an output vector, each term of the output vector corresponding to at least one of:
• an activity of at least one radionuclide;
• a number of photons detected at an energy corresponding to an emission energy of a radionuclide;
• or
• a detection efficiency at an emission energy of a radionuclide;
• and
• c6) inverting the direct model, so as to estimate the output vector.