Study On Threshold Correction Method Of All-Digital SiPM/PET Detector Based On MVT

Positron Emission Tomography(PET)is the only medical imaging equipment which can observe the metabolism in living organisms.It plays a significant role in cancer diagnosis,drug discovery,organ function research and the diagnosis and treatment of various diseases.In recent year,the digital PET detector has attracted the attention and research of many organizations and scholars because of its strong anti-interference capability,good maintainability and information processing with the digital signal processing technology.Firstly,the information of scintillation pulse is not accuracy because of the inconsistent bias voltages of threshold comparators.To estimate the bias voltages of threshold comparators,this thesis proposes a detector-energy-response-based threshold correction algorithm(DERTCA).In the method,we need to firstly acquire the peak voltage spectrum of the scintillation pulse for several radioactive source.Then we can extract the characteristic peak from the peak voltage spectrum according to characteristics of the radioactive source,and obtain some sets of "scintillation pulse peak vs.gamma photon energy",which would be used for curve fitting.According to the energy response model of the all-digital SiPM/PET detector,we will obtain an estimate of the bias voltage.The experimental results show that the DERTCA method is able to effectively estimate the bias voltages of the threshold comparators in the PET detector.In addition,the dissertation also proposes a method of getting the peak voltage spectrum of the scintillation pulse.Firstly the voltage thresholds will be obtained according to the range of the peak voltage.Then we need to count scintillation pulses that cross different voltage thresholds.And the data collection time for different voltage thresholds must be the same.Finally,the peak spectrum of the scintillation pulse can be obtained by taking the difference of adjacent scintillation pulse counts.The method of getting the peak voltage spectrum of the scintillation pulse is feasible,simple and easy to implement.And the peak voltage spectrum obtained by the method is true and reliable.