TOF-PET tomograph and a method of imaging using a TOF-PET tomograph, based on a probability of production and lifetime of a positronium

A method of imaging using a TOF-PET (Time-Of-Flight Positron Emission Tomography) tomograph, the method comprising the steps of:

• introducing into a scintillation chamber of the tomograph an object comprising a radioisotope to emit positrons and deexcitation gamma quanta having a lifetime of a daughter nucleus in an excited state not exceeding 100 ps;
• recording the deexcitation quanta and annihilation quanta in a TOF-PET detection module comprising scintillators having a time resolution less than 100 ps;
• determining detection modules that registered the annihilation gamma quanta and detection modules that registered the deexcitation quanta of a common event registered in at least two detection modules within a predetermined time interval, the common event comprising:
• registering three gamma quanta (μ=3), wherein two of the three gamma quanta meet criteria for identification of quanta from annihilation of electron with positron into two comma quanta and a third gamma quantum meets a criterion for identification of gamma quanta from deexcitation of daughter nucleus having the lifetime of the daughter nucleus in an excited state not exceeding 100 ps,
• or registering four gamma quanta (μ=4), wherein at least one gamma quantum meets a criterion for identification of gamma quanta from deexcitation of a daughter nucleus having a lifetime of the daughter nucleus in an excited state not exceeding 100 ps;
• performing for the common events a reconstruction of the position of annihilation into two gamma quanta (ra) and the time of annihilation into two gamma quanta (ta);
• performing reconstruction of a time difference (Δt) between a time of the positron annihilation ta and an emission time of deexcitation quantum te, where the position of emission of the deexcitation quantum is considered as the position of annihilation of the positron;
• calculating, for every voxel, on the basis of the time difference (Δt) between a time of the positron annihilation ta and an emission time of deexcitation quantum te, an average lifetime of ortho-positronium τo-Ps(x,y,z) and a probability of production of positronium Ppoz(x,y,z).