Multi-pixel Photon Counter Research Articles

Design and characterization of a hybrid PET detector with DOI capability.

Monolithic or semi-monolithic detectors are attractive for positron emission tomography (PET) scanners with depth-of-interaction (DOI) capability. However, they often require complicated calibrations to determine the interaction positions of gamma photons. We introduce a novel hybrid detector design that combines pixelated and semi-monolithic elements to achieve DOI capability while simplifying the calibrations for positioning. A prototype detector with eight hybrid lutetium-yttrium oxyorthosilicate (LYSO)layers having dimensions of 25.8×12.9×15mm3 was constructed. The energy-weighted and energy-squared weighted averages were used for estimating the x- (pixelated direction) and y-positions (non-pixelated direction). Pseudo-pixels were defined as discrete areas on the flood image based on the crystal look-up table (LUT). The intrinsic spatial resolutions in the pixelated and non-pixelated directions were measured. The ratio of the maximum to the sum of the multipixel photon counter (MPPC) signals was used to estimate the DOI positions. The coincidence timing resolution (CTR) was measured using the average and energy-weighted average of the earliest n time stamps. Two energy windows of 250-700 and 400-600keV were applied for the measurements. The pattern of the flood images showed discrete event clusters, demonstrating that simple calibrations for determining the x- and y-positions of events could be achieved. Under 400-600keV energy window, the average intrinsic spatial resolutions were 1.15 and 1.34mm for the pixelated and non-pixelated directions; the average DOI resolution of the second row of pseudo-pixels was 5.1mm in full width at half maximum (FWHM); when using the energy-weighted average of the earliest four-time stamps, the best CTR of 350ps was achieved. Applying a broader energy window of 250-700keV only slightly degrades the DOI resolution while maintaining the intrinsic resolution; the best CTR degrades to 410ps. The proposed hybrid detector concept was verified, and a prototype detector showed high performance for 3D positioning and timing resolution. The novel detector concept shows promise for preclinical and clinical PET scanners with DOI capability.

First application of scintillator-based photon-counting computed tomography to rock samples: Preliminary results and prospects

Abstract Knowledge of the three-dimensional distribution of minerals in a rock sample is of fundamental importance to deciphering a sample’s properties and history. Attenuation-contrast X-ray computed tomography (X-ray CT) is widely used in the geosciences to determine the three-dimensional distributions of minerals or pores, or both. Photon counting CT (PC-CT) uses a novel energy-resolved X-ray detector that allows X-rays with a continuous energy spectrum to be detected separately within arbitrary energy ranges. Here we report the first results of applying laboratory-build PC-CT combined with multi-pixel photon counter (MPPC) to common minerals such as quartz and calcite. In the low-energy range, PC-CT produced higher contrast images than single-energy X-ray CT. Minerals were successfully identified from the relationships between the mean CT values for each energy window and the mean difference between pairs of energy windows. These results suggest that PC-CT can produce high-contrast images of minerals and may be able to distinguish mineral phases with different attenuation curves, even when their CT values are similar. We obtained CT images of minerals in a natural sedimentary rock sample, composed mainly of quartz and carbonate. Although the spatial resolution of the detector in this study was insufficient for the sample, the main carbonate veins were clearly visible as high carbonate-content areas in the PC-CT images. Given some prior knowledge of mineral phases from other methods, it may be possible to use PC-CT imaging to obtain further information about their chemical compositions.

Real-time gamma-ray energy spectrum / dose monitor with k-α method based on sequential bayesian estimation

Medical applications of radiation have been widely spread until now. However, the exposure of medical staff is sometimes overlooked, because treatment of patients is the first priority. The purpose of this study is to develop a small and light monitor that can measure the energy spectrum and dose of gamma-rays at the same time in real-time for medical applications. Using the monitor, the medical staff could be guided to be more aware ofthe risk of radiation, and finally the exposure to them could be substantially suppressed. So far, a CsI scintillator has been chosen as a detection device of gamma-rays and combined with a Multi-Pixel Photon Counter (MPPC) to develop a prototype monitor. Then we confirmed its basic performance with standard gamma-ray sources. To achieve the real-time measurement, α method (sequential Bayesian estimation) was adopted and improved to propose a new unfolding process, named k-α method, with which the convergence speed could really be accelerated to realize real-time measurement. Also, gamma-ray measurements with a mixed source of 133Ba, 137Cs and 60Co were carried out to confirm the validity of the present monitor. As a result, it was found that gamma-ray energy spectrum could be estimated successfully in several-tens seconds in the field of around 6 μSv/h. For the dose estimation, the correct values could be estimated just after starting measurement.

Balancing Performance and Portability: A Study on CsI(Tl) Crystal Sizes for Real-Time Gamma-Ray Spectrum and Dose Monitoring

Current radiation dosimeters sometimes face accuracy limitations or provide only cumulative doses over long periods. To contribute to this area, we developed a portable monitor that measures the energy spectrum and dose of gamma rays in real time. To achieve this, we used an improved sequential Bayesian estimation algorithm. The dose rate was then derived from the energy spectrum by applying a flux-to-dose conversion coefficient. The monitor consists mainly of a CsI(Tl) scintillator and a multi-pixel photon counter (MPPC). In developing this device, we focused on striking a balance between measurement accuracy, ease of use, and portability. As an essential aspect of the research, we investigated the influence of the CsI(Tl) crystal size on the performance of the monitor to determine an optimal size. This was accomplished by calculating the detection efficiency and energy resolution through experimental measurements using standard gamma-ray sources and simulations using MCNP5. Within the scope of the research, detector response functions were created for each crystal size for an energy range of 10 keV to 3 MeV. Considering an optimal balance of detection efficiency and energy resolution alongside a compact size suitable for portable applications, the crystal measuring 2.6 × 2.6 × 1.3 cm3 was deemed preferable.

Electron density estimation using MPPC-based photon-counting CT for radiation therapy planning

Photon-counting computed tomography (PCCT) has been attracting attention recently, as a potential alternative to the conventional computed tomography (CT). With PCCT, the photon energy can be obtained, and the amount of exposure can be reduced compared with the conventional CT. We developed a detector system composed of a scintillator and multi-pixel photon counter (MPPC). This makes the system simple and inexpensive compared with the semiconductor-based PCCT, like CdTe and CZT. In this study, we propose estimating electron density for radiation therapy planning using a six-threshold MPPC-based photon-counting detector. Electron density is an essential information for determining beam energy in radiation therapy planning. Therefore, accurate electron density estimation is required. The estimation method used in this study is based on the method proposed by Saito et al. (2012) PCCT images of electron-density-known phantoms were acquired, and information of the two out of the six energy bands was used for estimation. As a result, we succeeded in estimating the electron density with an accuracy of 4.59% root-mean-square error. However, the lung phantoms, which had a relatively low electron density, still had a large deviation from the true value. In addition, dual-energy CT and PCCT estimation results were compared. PCCT results has not yet surpassed the accuracy of dual-energy CT (DECT) results; however, the high electron density materials were obtained almost at the same level of accuracy. In future, we will continue to work on more accurate electron density estimation using multiple energy band information.

Optical crosstalk of protective cover on MPPC array for TOF PET detector

Objective. Time-of-flight (TOF) is an important factor that directly affects the image quality of PET systems, and various attempts have been made to improve the coincidence resolving time (CRT) of PET detectors. For independent readout detectors, the timing is acquired for each silicon photomultiplier (SiPM), so they are less sensitive to diffused scintillation light, resulting in a better CRT. Further improvement can be expected if the light can be focused on a single SiPM. However, existing SiPM arrays have a thin protective cover on the SiPM and the gap between the SiPMs is filled with either air or the protective cover, so the light must diffuse through the cover. In this work, we investigated optical crosstalk in the protective cover to improve the CRT. Approach. We used 3.1 × 3.1 × 20 mm3 fast LGSO crystals and 3 mm square 8 × 8 multi pixel photon counter (MPPC) arrays. Pitch of the MPPCs was 3.2 mm and thickness of the protective cover on them was 150 μm. To reduce diffusion of scintillation light in the protective cover, the part of the inactive areas on the MPPC array were optically separated using reflective material. Specifically, 50, 100, 150, and 350 μm deep grid-shaped slits were made along the inactive area of the MPPCs and they were filled with BaSO4 powder as the reflective material. Main results. Coincidence counts were measured with a pair of TOF detectors, and the CRT was shorter with a deeper slit depth. The CRT before improvement was 235 ps, and using the cover having the 350 μm deep slits filled with reflective material lowered the CRT to 211 ps. Significance. Up to 10% of the scintillation light was diffused to other MPPCs by the protective cover, and the CRT was degraded by 10% due to optical crosstalk of the cover. The proposed method promises to improve the CRT of the TOF detector.

Plastic scintillator fiber detectors for heavy ion trajectory reconstruction for the Super-FRS at FAIR

At the FAIR facility, currently under construction at GSI (Darmstadt), a 1.5 AGeV uranium beam with intensities up to 2.5 × 1011 238U/spill will impinge on a graphite target at the entrance of the Super-FRS for the production of a wide range of rare isotopes by projectile fission and fragmentation. The next generation in-flight magnetic separator Super-FRS, operated up to a magnetic rigidity of 20 Tm with a large angular acceptance (Δθ = ± 40 mrad, Δϕ = ± 20 mrad) and momentum acceptance (Δ p/p = ± 2.5%), requires a new generation of tracking detectors with a position resolution of 0.2 mm (σx ) over large detector areas reaching up to 570 cm2. Besides gas detectors, planar detectors made of scintillating fibers are an option worth investigating not only because of the comparable material budget but especially for the fast response and high-rate capability. A one-dimensional prototype consisting of 128 fibers with active area of 25.6 × 100 mm2 coupled to Multi-Pixel-Photon Counters (MPPCs) and readout by FPGA TDC is described together with some recent 197Au beam test results.

Quantitative analysis of silicon photomultipliers for thermoluminescence measurement

The employment of silicon photomultipliers (SiPMs) in photon detection systems facilitates the reduction of detection module size, enhances portability and ruggedness, and lowers product costs. This study investigated the potential of SiPM in thermoluminescence (TL) measurements, focusing on its detection limits, temperature dependency, and dose responses. A 3 × 3 mm2 multi-pixel photon counter (MPPC, Hamamatsu MPPC) composed of 50 μm single-photon avalanche diodes (SPADs) was utilized in single-photon counting mode as the detector. This experimental setup was compared with a conventional photomultiplier tube (PMT) in TL readout case. To ensure comparable light exposure between the two detectors, a 3-mm diameter pinhole was positioned in front of the PMT. By using a thermoelectric (TE) cooling module to maintain the sensor temperature at −20 °C, signal reproducibility was achieved with a fluctuation of less than 1.2%, and a detection limit ranging from 30 to 300 μGy was assessed for four dosimeters: LiF:Mg,Ti, LiF:Mg,Cu,P, LiF:Mg,Cu,Si, and Al2O3:C. The dose response of the system was limited by significant signal saturation due to pile-up effects. We introduced a correction model with a 50 ns paralyzable deadtime, which enhanced the signal response by more than 20-fold. Furthermore, this model also correlated well with the observed count rates under high dark count rate (DCR) conditions up to 1.67 MHz. The findings from this study further contributes to the discussion regarding the perspective of SiPM as TL detectors.

Phenomena observed in electron EBRT using a pulse-by-pulse radioluminescence dosimetry system with cloud-based analytics

The pulse-by-pulse characteristics of electron beams from a clinical linear accelerator (linac) at high dose rates are crucial for ensuring precise dose delivery in radiation therapy. In this research, we employ a radioluminescence scintillator made from Ge-doped silica optical fiber to analyse electron beams at standard therapy dose rates 600 cGy/min with energy of 15 MeV. The scintillator is combined with a photomultiplier tube (PMT) and a photon-counting setup to achieve microsecond (μs) gating times, providing high temporal resolution. For sub-microsecond (sub-μs) temporal resolution, we utilize a multi-pixel photon counter and a rapid digital oscilloscope. Our study examines the peak time and the time it takes for pulses to return to baseline, uncovering the effects of afterglow at elevated dose rates and its potential implications for dosimetry precision. Our results indicate that monitor chambers, which have lower temporal resolution than the radioluminescence system outlined in this study, may struggle to accurately track high-rate dose delivery, emphasizing the necessity for advanced monitoring methods in FLASH radiotherapy. The dosimetric data was further analysed for deeper analytics on a cloud-based system. The dosimetric data underwent advanced analysis on a cloud-based platform, employing a prototype analytics software system comprised of Dosi-Client and Dosi-Cloud Backend components for real-time data acquisition and processing. This innovative approach revealed significant insights into radiation dosimetry, including the detection of anomalies through a reconstruction convolutional autoencoder, enhancing the precision and reliability of dosimetric measurements.

A compact start time counter using plastic scintillators readout with MPPC arrays for the WASA-FRS HypHI experiment

We have developed a compact detector for measuring beam particles using plastic scintillators readout through Multi-Pixel Photon Counters, which is employed for hypernuclear measurements in the WASA-FRS experiment at GSI. The Time-of-Flight resolution of the newly-developed detector has been investigated in relation to the overvoltage with respect to the breakdown voltage, a maximum counting rate of approximately 3×106/s per segment, and a maximum beam charge of Z = 6. The evaluated Time-of-Flight resolutions between the neighboring segments of the detector range from 44.6±1.3 ps to 100.3±3.6 ps (σ) depending on the segment, overvoltage values, and beam intensity. It is also observed that the Time-of-Flight resolution is inversely correlated to the beam atomic charge (Z).

Multi-energy in-vivo imaging of multiple contrast agents in a mouse using MPPC-based photon-counting CT

Contrast-enhanced computed tomography (CT) is an indispensable technique in modern diagnostic medicine because it not only allows non-destructive, three-dimensional observation of the inside of the body but also provides images that highlight lesions. Recent developments in photon-counting (PC) CT systems have enabled contrast-enhanced CT scanning and quantitative evaluations, such as material discrimination and concentration estimation of contrast agents, using X-ray energy information. We established a PC-CT system that combines fast scintillators and multipixel photon counters (MPPCs) and demonstrated its performance. In this paper, we report the imaging performance of a PC-CT system using a mixture of contrast agents containing gadolinium and iodine. We performed CT imaging of a static phantom containing a mixture of the two contrast agents. The concentration of each contrast agent from the CT images in multiple energy bands were estimated. We succeeded in obtaining the concentration distributions for each contrast agent and verified the possibility of discriminating between two substances with different atomic numbers. In addition, the same procedures and analytical methods used for the static phantom were applied to the in vivo imaging of a mouse, in which gadolinium- and iodine-containing contrast agents were injected at different time intervals. We also succeeded in discriminating between the two contrast agents in vivo, making it possible to provide new imaging diagnostics such as the determination of necrotic tissues and normal blood vessels. Furthermore, we succeeded in creating three-dimensional concentration maps of gadolinium and iodine in a mouse, demonstrating the great potential of MPPC-based PC-CT for future clinical applications.

Validation of the design of a high-sensitivity and high-resolution PET system for a preclinical PET/EPR hybrid scanner

We report the development of a high-sensitivity and high-resolution PET subsystem for a next-generation preclinical PET/EPR hybrid scanner for investigating and improving hypoxia imaging with PET. The PET subsystem consists of 14 detector modules (DM) installed within a cylindrical supporting frame whose outer and inner diameters are 115 mm and 60 mm, respectively. Each DM contains eight detector units (DU) in a row and each DU is made of a 12 × 12 array of 1 × 1 × 10mm3 LYSO crystals (with a 1.05 mm pitch) coupled to a 4 × 4 silicon photomultiplier (SiPM) array that has a 3.2 mm pitch (Hamamatsu multi-pixel photon counter (MPPC) array 14161-3050HS-04). The PET subsystem has a 104 mm axial field-of-view (AFOV) that is sufficient for full-body mouse imaging, therefore enabling temporal and spatial correlation studies of tumor hypoxia between PET and EPR. It employs 1mm-width crystals to support sub-millimeter image resolution that is desired for mouse imaging. Although a DM contains 1,152 LYSO crystals, by use of a newly devised signal readout method only six outputs are produced. Recently a partial prototype of this subsystem consisting of four DMs is built. In this paper, we present performance measurement results obtained for the developed DMs and initial imaging results obtained by the prototype. The developed DMs show uniformly superior performance in identifying the hit crystal and detector unit, in energy resolution, and in coincidence time resolution. The images obtained for a 22Na point source and a 18F-filled U-shaped tube source show an image resolution of about 1.1 mm and 1.2 mm FWHM in the transverse and axial directions respectively, and demonstrate successful imaging over the entire 104 mm AFOV of the prototype. This estimated image resolution however includes the contribution by the source size.

A study for gamma attenuation behavior of polyimide (PI) film by MPPC

Although lead is a very good radiation shielding material, its toxicity has led researchers to find alternative materials instead of it. Moreover, as the use of Kapton polyimide (PI) film in nuclear power plants and space exploration increases, the need to reveal the radiation degradation properties of this material has come along. In this regard, in the present study, it is aimed to determine the mass and linear attenuation coefficients, half value layer, tenth value layer, mean free path and radiation protection efficiency attenuation parameters for this material, experimentally and theoretically, by using the gammas of the 133Ba radioisotope. Experimental gamma attenuation measurements were made by a spectrometer using a Hamamatsu multi pixel photon counter device with a silicon photomultiplier sensor. The constant fraction discrimination timing method was used to reduce the electronic noise of the spectrometer. The attenuation parameters determined experimentally by following two ways were compared with the theoretical ones obtained from the XCOM program.

A multi-resolution TOF-DOI detector for human brain dedicated PET scanner

Objective. We propose a single-ended readout, multi-resolution detector design that can achieve high spatial, depth-of-interaction (DOI), and time-of-flight (TOF) resolutions, as well as high sensitivity for human brain-dedicated positron emission tomography (PET) scanners. Approach. The detector comprised two layers of LYSO crystal arrays and a lightguide in between. The top (gamma ray entrance) layer consisted of a 16 × 16 array of 1.53 × 1.53 × 6 mm3 LYSO crystals for providing high spatial resolution. The bottom layer consisted of an 8 × 8 array of 3.0 × 3.0 × 15 mm3 LYSO crystals that were one-to-one coupled to an 8 × 8 multipixel photon counter (MPPC) array for providing high TOF resolution. The 2 mm thick lightguide introduces inter-crystal light sharing that causes variations of the light distribution patterns for high DOI resolution. The detector was read out by a PETsys TOFPET2 application-specific integrated circuit. Main result. The top and bottom layers were distinguished by a convolutional neural network with 97% accuracy. All crystals in the top and bottom layers were resolved. The inter-crystal scatter (ICS) events in the bottom layer were identified, and the measured average DOI resolution of the bottom layer was 4.1 mm. The coincidence time resolution (CTR) for the top–top, top-bottom, and bottom–bottom coincidences was 476 ps, 405 ps, and 298 ps, respectively. When ICS events were excluded from the bottom layer, the CTR of the bottom–bottom coincidence was 277 ps. Significance. The top layer of the proposed two-layer detector achieved a high spatial resolution and the bottom layer achieved a high TOF resolution. Together with its high DOI resolution and detection efficiency, the proposed detector is well suited for next-generation high-performance brain-dedicated PET scanners.

Development Research of an ADT-24 Multichannel Real-time Fluorescence PCR Detection System

This study describes a fluorescence detection system for purified ADT-24 nucleic acids and a PCR detection-integrated machine. The application background and structure of the fluorescence scanning system are described. We designed a confocal 4-channel fluorescence detection scanning head with monochromatic LEDs as the excitation light source, a multipixel photon counter (MPPC) as the optical path detection terminal, and a narrow-band filter and dichroic mirror as the main optical components. This paper discusses in detail the principle of the working system, including optical path selection and standards, optical component selection, channel spectral characteristic analysis, detector selection, performance evaluation, optical path simulation, and sensitivity verification. The design and use of this optical system are also summarized. Finally, a 4-fold dilution of mix reagent was used to test the detection effect of the fluorescence scanning head, and a scheme to control “temperature drift” and optimize performance was proposed. According to the verification results and subsequent live debugging, the debugged results achieved the expected design objectives.

Modality for estimating NMR relaxation time using perturbed angular correlation in double-photon emission nuclides

T2 relaxation time in magnetic resonance imaging (MRI), which is determined by magnetic dipole interactions, has been employed as a parameter for tumor detection. However, owing to the lack of MRI detection sensitivity, nuclear medicine imaging is currently the basic option for tracking low concentrations of chemical probes. Previous studies utilizing cascade radionuclides have focused on the relaxation due to electric quadrupole interactions. However, magnetic dipole interactions, which are crucial in MRI, remains to be elucidated. In this study, we determined the magnetic relaxation rate by using 111In, a cascade radionuclide used in clinical single-photon emission computed tomography (SPECT) scans. As the angle between the gamma rays from the nuclei is affected by the electrical and magnetic interactions acting on the nuclei, we measured the angular correlation ratio by using eight gadolinium gallium garnet (GAGG) multi-pixel photon counter (MPPC) 8 × 8 array detectors and extracted the magnetic relaxation rate. Consequently, we obtained a rate that increased with the Fe concentration, similar to the T2 relaxation rate, although it was influenced by the inhomogeneity of the external magnetic field. This study utilized low concentrations of the liquid-state radionuclide, which is commonly used in clinical nuclear medicine imaging scans and is expected to provide much higher sensitivity and more selective detection of tumors than conventional MRI.

Enhanced performance of an indoor non-line-of-sight VLC system utilizing a multi-pixel photon counter and interleaved single-carrier FDM scheme

A non-line-of-sight (NLOS) visible light communication (VLC) system, utilizing a multi-pixel photon counter (MPPC) as the detector and interleaved single-carrier frequency division multiplexing (I-SC-FDM) scheme, was first proposed and experimentally investigated in this work. Specifically, the I-SC-FDM scheme exhibits a significantly lower peak-to-average power ratio (PAPR) than the original orthogonal frequency division multiplexing (OFDM) and widely used discrete Fourier transform spread (DFTs)-OFDM schemes, thereby necessitating a much lower power gain, which is greatly beneficial for indoor power-sensitive VLC systems. Meanwhile, the implementation of an MPPC with high sensitivity enables the detection of faintly scattered light and thus facilitates the possibility of omnidirectional optical transmission based on indoor NLOS links. Following this, an MPPC-based omnidirectional VLC system was developed and successfully achieved a net data rate up to 18 Mbps in a 3.6 m × 3 m × 3 m room, with a joint deployment of the I-SC-FDM scheme and hybrid time-frequency domain equalization (TFD-EQ) strategy. Such results can be viewed as an expansion of indoor VLC systems beyond line-of-sight (LOS) links and serve as a reference for the practical application of Light-Fidelity (LiFi) in future optical wireless access.

RAAD: LIGHT-1 CubeSat's payload for the detection of terrestrial gamma-ray flashes

The Rapid Acquisition Atmospheric Detector (RAAD), onboard the LIGHT-1 3U CubeSat, detects photons between hard X-rays and soft gamma-rays, in order to identify and characterize Terrestrial Gamma Ray Flashes (TGFs). Three detector configurations are tested, making use of Cerium Bromide and Lanthanum BromoChloride scintillating crystals coupled to photomultiplier tubes or Multi-Pixel Photon Counters, in order to identify the optimal combination for TGF detection. High timing resolution, a short trigger window, and the short decay time of its electronics allow RAAD to perform accurate measurements of prompt, transient events. Here, we describe the overview of the detection concept, the development of the front-end acquisition electronics, as well as the ground testing and simulation that the payload underwent prior to its launch on December 21st, 2021. We further present an analysis of the detector's in-orbit system behavior and some preliminary results.

Time and Energy Resolving Time-over-Threshold ASIC for MPPC module in TOF-PET system (ToT-ASIC2)

ToT-ASIC2 is a new custom front-end application specific integrated circuit (ASIC) to readout silicon photomultiplier (SiPM) and multi-pixel photon counter (MPPC) for time-of-flight positron emission tomography (ToF-PET). ToT-ASIC2 is a 64-channel ASIC fabricated using a commercial 0.25 μm CMOS process. Each channel has an input-current buffer that sends signals to the SLOW and FAST paths, which are used for incident radiation energy and timing information, respectively. Time-over-Threshold (ToT) signals from these paths are combined into one ToT signal to be output outside the ASIC. The power consumption is approximately 2.9 mW per channel.This study developed a detection system comprising an MPPC with coupled GAGG pixelated scintillators, a front-end board with ToT-ASIC2 and ToT-DAQ. Consequently, energy and timing measurement experiments were performed using this system to confirm the ToT-ASIC2 energy- and timing-resolving capability. Prototype positron emission tomography experiments with 22Na indicated an energy resolution of 6.7% for 511 keV with the coincidence timing resolution being 215 ps.

Compton Camera Arrangement With a Monolithic LaBr3(Ce) Scintillator and Pixelated GAGG Detector for Medical Imaging

The results presented in this manuscript are divided in two main parts. The aim of the presented work is to conduct feasibility tests on a Compton camera setup to be later scaled up and used for PET and triple coincidence γ-PET purposes. The first part is focused on laboratory characterization of a monolithic LaBr3(Ce) scintillator coupled to a 64-channel multi-anode photomultiplier (H8500C PMT from Hamamatsu) in combination with a well-established algorithm allowing to determine the interaction’s position resolution. The second part of the article is dedicated to the evaluation of a Compton camera detector arrangement in which the monolithic scintillator acts as an absorber, while a pixelated GAGG scintillator array, read out by a SiPM multi-pixel photon counter (MPPC), is used as a scatterer component. The accuracy achievable with this system for detecting γ rays from laboratory point sources is investigated. The Compton camera system has been tested with radioactive 137Cs and 60Co point sources. The signal readout and data acquisition system is based on individual spectroscopy electronics modules (NIM and VME), for the absorber and a customized electronics based on Anger logic for the GAGG scatter array. The raw data were analyzed to serve as input for the image reconstruction, performed using the MEGAlib toolkit software. With a spatial resolution of 1 mm for the scatterer and less than 3 mm for the absorber component, respectively, shifts of 2 mm of both radioactive sources (137Cs and 60Co) could be resolved with the whole Compton camera system.