Design Of Multiplexed Readout PET Detector

Positron emission tomography is an advanced nuclear medicine imaging device.It performs positron nucleation labeling on some substances required for metabolism,and then introduces labeled positron drugs into the organism.Since different concentration distributions of the drugs are produced according to the metabolic needs of various tissues and organs,we can use PET to detect position of the radiotracer and reflect distribution of the drugs,thus evaluating the metabolic level,biochemical reaction and functional activities of various organs in the human body non-invasively,quantitatively and dynamically.At present,PET has been applied to early diagnosis and follow-up treatment of tumor,heart and nervous system diseases.People are also trying to apply it in other fields.High-performance detector is one of the most important part of PET system,and it has always been the research focus of PET.The main content of this thesis is the design of a compact and reliable PET detector based on multiplexing readout method and digital PET technology.At present,most PET detector designs are based on silicon photomultiplier(SiPM).SiPM has a small size,high gains,and low operating voltage,besides it is insensitive to magnetic fields.It can be applied to modal medical devices PET/CT and PET/MR,and used to develop full-length PET with full-length wheelbase and DOI(Depth-Of-Interaction,DOI)PET with information of reaction depth.Some technical and design requirements are proposed along with these applications.One of the most significant problems is that due to the small size of SiPM,the number of readout signal channels is large,and the back-end electronics system is huge and complicated when the system is built.In this thesis,a scalable multiplexing read-out architecture of scintillation pulse signal is designed based on transmission line.The multiplexing output is combined to reduce the number of signals needed to be processed in back-end electronics.At the same time,the corresponding data acquisition module is designed based on Multi-Voltage-Threshold(MVT)method to complete the design of multiplexing read-out PET detector.The multiplexing readout method based on transmission line has achieved 16:2 multiplexing ratio,which means 16 outputs are connected to the same transmission line and are located and recovered by signals at both ends of the transmission line.This method can theoretically multiplex more signal readout channels.The data acquisition module based on MVT method can get very good experimental results.In the coincidence experiment,the MVT board can get the same experimental results as the high-speed oscilloscope at 6.25 G sampling rate with a 200 ps time resolution,and 12% energy resolution.The performance of the multiplexed readout detector module is evaluated.The average energy resolution of the detector module is 11.8% and the normalized time resolution of 9 LORs are 254 ps.Compared with the results of the single readout,the average energy resolution is about 11% and the average time resolution is about 200 ps,the number of output signals is greatly reduced,which can effectively reduce the hardware cost of the back end.At the same time,the slight deterioration of detector performance has little impact on the overall system,which is a very promising design of multiplex readout PET detector.