Development and evaluation of a double-plane detector system for multi-radionuclide imaging

Purpose To develop a multi-radionuclide imaging system with a flexible and compact structure that has a potential for breast and other applications,and to evaluate its performances under both positron emission tomography and single photon emission imaging conditions.Methods The plane detector was composed of 5×6 blocks with an effective detection area of 168.6 mm×202.4 mm.Each block consisted of a 16×16 LYSO array.The pixel size is 1.9 mm×1.9 mm×15 mm.An 8×8 silicon photomultiplier(SiPM)array with SensL’s C-30035 sensors was coupled to the LYSO array,separated by a 1.5-mm-thick glass.To minimize the influence of temperature on the detector,the active part of the front-end electronics was kept away from SiPMs.Self-designed data acquisition system and reconstruction software were utilized to evaluate the performances of the whole system.Results All the blocks had excellent pixels identification.An average energy resolution of 11.39%for 511 keV and 21.37%for 140 keV was obtained.In the PET mode,the best spatial resolution was better than 2 mm and the system sensitivity reached up to 11.05%at 60 mm distance.In the single photon emission imaging mode,a spatial resolution better than 3 mm was obtained.Conclusion The results indicated that the system has a good overall performance and can be used in breast imaging and other general PET applications.It also has the potential to be used for single photon emission imaging.In pursuit of a better spatial resolution of cross-plane,PSF and DOI technology will be developed in the next work.For specific applications,further improvement of the detector system such as performance evaluation with phantoms will be carried out.

Prototype of an array SiPM-based scintillator Compton camera for radioactive materials detection

Purpose The Compton camera,which visualizes the distribution of gamma-ray sources based on the kinematics of Compton scattering,has advantage of wide field of view,broad range of energy and compact structure.Methods In this study,we proposed a prototype of Compton camera,which included array silicon photomultiplier(SiPM)-based position-sensitive detectors,data acquisition(DAQ)system and image reconstruction system.The detectors were composed of Ce-doped Gd_(3)Al_(2)Ga_(3)O_(12) scintillator arrays and pixel Si-PM arrays.In DAQ system,symmetric charge division circuit,impedance bridge circuit and the delay coincidence algorithm were designed to record coincidence events.Simple back-projection algorithm and list-mode maximum likelihood expectation maximization algorithm were adopted for image reconstruction.The coordinate of longitude and latitude was used for image fusion.Results The performance of this Compton camera prototype system was evaluated.The results indicated that this system was able to locate a ^(137)Cs point source within 20 s with the corresponding radiation dose of~1.0μSv/h.The angular resolution of point source was~7°(FWHM),and the total energy resolution of 662 keV was 7.2%.Furthermore,we succeeded in separating two point sources of different energy[^(22)Na(511 keV),^(137)Cs(662 keV)]in laboratory test.Conclusions This prototype of scintillator Compton camera offers capabilities for applications like source term investigation and radioactive materials detection.