Enhancing timing performance of heterostructures with double-sided readout.

Heterostructured scintillators offer a promising solution to balance the sensitivity and timing in TOF-PET detectors. These scintillators utilize alternating layers of materials with complementary properties to optimize performance. However, the layering compromises time resolution due to light transport issues.

Tetris-inspired detector with neural network for radiation mapping.

Radiation mapping has attracted widespread research attention and increased public concerns on environmental monitoring. Regarding materials and their configurations, radiation detectors have been developed to identify the position and strength of the radioactive sources. However, due to the complex mechanisms of radiation-matter interaction and data limitation, high-performance and low-cost radiation mapping is still challenging.

Scintillation and cherenkov photon counting detectors with analog silicon photomultipliers for TOF-PET.

Standard signal processing approaches for scintillation detectors in positron emission tomography (PET) derive accurate estimates for 511 keV photon time of interaction and energy imparted to the detection media from aggregate characteristics of electronic pulse shapes. The ultimate realization of a scintillation detector for PET is one that provides a unique timestamp and position for each detected scintillation photon. Detectors with these capabilities enable advanced concepts for three-dimensional (3D) position and time of interaction estimation with methods that exploit the spatiotemporal arrival time kinetics of individual scintillation photons.

Investigation of Electronic Signal Processing Chains for a Prototype TOF-PET System With 100-ps Coincidence Time Resolution.

We have evaluated CTR performance of four different mixed-signal front-end electronic readout configurations with the goal to achieve 100 picoseconds (ps) coincidence time resolution (CTR). The proposed TOF-PET detector elements are based on two 3 × 3 × 10 mm "fast LGSO" crystal segments, side-coupled to linear arrays of 3 × 3 mm silicon photomultipliers (SiPMs), to form a total crystal length of 20 mm. We studied multiple configurations and components for the front-end readout: 1) high speed radio frequency (RF) amplifiers; 2) an ASIC-based discriminator; 3) combination of RF amplifier, balun transformer, and discriminator ASIC; and 4) combination of balun transformer, and discriminator ASIC.

Low power implementation of high frequency SiPM readout for Cherenkov and scintillation detectors in TOF-PET.

State-of-the-art (SoA) electronic readout for silicon photomultiplier (SiPM)-based scintillation detectors that demonstrate experimental limits in achievable coincidence time resolution (CTR) leverage low noise, high frequency signal processing to facilitate a single photon time response that is near the limit of the SiPMs architecture. This readout strategy can optimally exploit fast luminescence and prompt photon populations, and promising measurements show detector concepts employing this readout can greatly advance PET detector CTR, relative to SoA in clinical systems. However, the technique employs power hungry components which make the electronics chain impractical for channel-dense time-of-flight (TOF)-PET detectors.

Front-End Design for SiPM-Based Monolithic Neutron Double Scatter Imagers.

Neutron double scatter imaging exploits the kinematics of neutron elastic scattering to enable emission imaging of neutron sources. Due to the relatively low coincidence detection efficiency of fast neutrons in organic scintillator arrays, imaging efficiency for double scatter cameras can also be low. One method to realize significant gains in neutron coincidence detection efficiency is to develop neutron double scatter detectors which employ monolithic blocks of organic scintillator, instrumented with photosensor arrays on multiple faces to enable 3D position and multi-interaction time pickoff.

Free-moving Quantitative Gamma-ray Imaging.

The ability to map and estimate the activity of radiological source distributions in unknown three-dimensional environments has applications in the prevention and response to radiological accidents or threats as well as the enforcement and verification of international nuclear non-proliferation agreements. Such a capability requires well-characterized detector response functions, accurate time-dependent detector position and orientation data, a digitized representation of the surrounding 3D environment, and appropriate image reconstruction and uncertainty quantification methods. We have previously demonstrated 3D mapping of gamma-ray emitters with free-moving detector systems on a relative intensity scale using a technique called Scene Data Fusion (SDF).

Study of optical reflectors for a 100ps coincidence time resolution TOF-PET detector design.

Positron Emission Tomography (PET) reconstructed image signal-to-noise ratio (SNR) can be improved by including the 511 keV photon pair coincidence time-of-flight (TOF) information. The degree of SNR improvement from this TOF capability depends on the coincidence time resolution (CTR) of the PET system, which is essentially the variation in photon arrival time differences over all coincident photon pairs detected for a point positron source placed at the system center. The CTR is determined by several factors including the intrinsic properties of the scintillation crystals and photodetectors, crystal-to-photodetector coupling configurations, reflective materials, and the electronic readout configuration scheme.

High-resolution time-of-flight PET detector with 100 ps coincidence time resolution using a side-coupled phoswich configuration.

Photon time-of-flight (TOF) capability in positron emission tomography (PET) enables reconstructed image signal-to-noise ratio (SNR) improvement. With the coincidence time resolution (CTR) of 100 picosecond (ps), a five-fold SNR improvement can be achieved with a 40 cm diameter imaging subject, relative to a system without TOF capability. This 100 ps CTR can be achieved for adetector design (crystal element length ≥20 mm with reasonably high crystal packing fraction) using a side-readout PET detector configuration that enables 511 keV photon interaction depth-independent light collection efficiency and lower variance in scintillation photon transit time to the silicon photomultiplier (SiPM).

Scalable electronic readout design for a 100 ps coincidence time resolution TOF-PET system.

We have developed a scalable detector readout design for a 100 ps coincidence time resolution (CTR) time of flight (TOF) positron emission tomography (PET) detector technology. The basic scintillation detectors studied in this paper are based on 2 × 4 arrays of 3 × 3 × 10 mm'fast-LGSO:Ce' scintillation crystals side-coupled to 6 × 4 arrays of 3 × 3 mmsilicon photomultipliers (SiPMs). We employed a novel mixed-signal front-end electronic configuration and a low timing jitter Field Programming Gate Array-based time to digital converter for data acquisition.

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET.

Depth-of-interaction (DOI) variability of annihilation photons is known to be a source of coincidence time resolution (CTR) degradation for fast time-of-flight-positron emission tomography detectors. An analytical model was recently proposed to explicitly include the DOI time bias separately from variance-related statistical factors, such as scintillation photon emission and photosensor jitter, in the CTR evaluation. In the present work, an experimental validation of this new model is provided.

Electronics method to advance the coincidence time resolution with bismuth germanate.

Exploiting the moderate Cherenkov yield from 511 keV photoelectric interactions in bismuth germanate (BGO) scintillators enables one to achieve a level of coincidence time resolution (CTR) appropriate for time-of-flight positron emission tomography (TOF-PET). For this approach, owing to the low number of promptly emitted light photons, single photon time resolution (SPTR) can have a stronger influence on achievable CTR. We have previously shown readout techniques that reduce effective device capacitance of large area silicon photomultipliers (SiPMs) can yield improvements in single photon response shape that minimize the influence of electronic noise on SPTR.

Advances in Nuclear Radiation Sensing: Enabling 3-D Gamma-Ray Vision.

The enormous advances in sensing and data processing technologies in combination with recent developments in nuclear radiation detection and imaging enable unprecedented and "smarter" ways to detect, map, and visualize nuclear radiation. The recently developed concept of three-dimensional (3-D) Scene-data fusion allows us now to "see" nuclear radiation in three dimensions, in real time, and specific to radionuclides. It is based on a multi-sensor instrument that is able to map a local scene and to fuse the scene data with nuclear radiation data in 3-D while the instrument is freely moving through the scene.

Improved single photon time resolution for analog SiPMs with front end readout that reduces influence of electronic noise.

A key step to improve the coincidence time resolution of positron emission tomography detectors that exploit small populations of promptly emitted photons is improving the single photon time resolution (SPTR) of silicon photomultipliers (SiPMs). The influence of electronic noise has previously been identified as the dominant factor affecting SPTR for large area, analog SiPMs. In this work, we measure the achievable SPTR with front end electronic readout that minimizes the influence of electronic noise.

Evaluation of a clinical TOF-PET detector design that achieves ⩽100 ps coincidence time resolution.

Commercially available clinical positron emission tomography (PET) detectors employ scintillation crystals that are long ([Formula: see text]20 mm length) and narrow (4-5 mm width) optically coupled on their narrow end to a photosensor. The aspect ratio of this traditional crystal rod configuration and 511 keV photon attenuation properties yield significant variances in scintillation light collection efficiency and transit time to the photodetector, due to variations in the 511 keV photon interaction depth in the crystal. These variances contribute significant to coincidence time resolution degradation.

Highly multiplexed signal readout for a time-of-flight positron emission tomography detector based on silicon photomultipliers.

Maintaining excellent timing resolution in the generation of silicon photomultiplier (SiPM)-based time-of-flight positron emission tomography (TOF-PET) systems requires a large number of high-speed, high-bandwidth electronic channels and components. To minimize the cost and complexity of a system's back-end architecture and data acquisition, many analog signals are often multiplexed to fewer channels using techniques that encode timing, energy, and position information. With progress in the development SiPMs having lower dark noise, after pulsing, and cross talk along with higher photodetection efficiency, a coincidence timing resolution (CTR) well below 200 ps FWHM is now easily achievable in single pixel, bench-top setups using 20-mm length, lutetium-based inorganic scintillators.

Time-over-threshold for pulse shape discrimination in a time-of-flight phoswich PET detector.

It is well known that a PET detector capable of measuring both photon time-of-flight (TOF) and depth-of-interaction (DOI) improves the image quality and accuracy. Phoswich designs have been realized in PET detectors to measure DOI for more than a decade. However, PET detectors based on phoswich designs put great demand on the readout circuits, which have to differentiate the pulse shape produced by different crystal layers.

Advances in coincidence time resolution for PET.

Coincidence time resolution (CTR), an important parameter for time-of-flight (TOF) PET performance, is determined mainly by properties of the scintillation crystal and photodetector used. Stable production techniques for LGSO:Ce (Lu1.8Gd0.

Analytical calculation of the lower bound on timing resolution for PET scintillation detectors comprising high-aspect-ratio crystal elements.

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector's timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic.

The lower timing resolution bound for scintillators with non-negligible optical photon transport time in time-of-flight PET.

In this work, a method is presented that can calculate the lower bound of the timing resolution for large scintillation crystals with non-negligible photon transport. Hereby, the timing resolution bound can directly be calculated from Monte Carlo generated arrival times of the scintillation photons. This method extends timing resolution bound calculations based on analytical equations, as crystal geometries can be evaluated that do not have closed form solutions of arrival time distributions.

Benchmarking the Geant4 full system simulation of an associated alpha-particle detector for use in a D-T neutron generator.

The position-sensitive alpha-particle detector used to provide the starting time and initial direction of D-T neutrons in a fast-neutron imaging system was simulated with a Geant4-based Monte Carlo program. The whole detector system, which consists of a YAP:Ce scintillator, a fiber-optic faceplate, a light guide, and a position-sensitive photo-multiplier tube (PSPMT), was modeled, starting with incident D-T alphas. The scintillation photons, whose starting time follows the distribution of a scintillation decay curve, were produced and emitted uniformly into a solid angle of 4π along the track segments of the alpha and its secondaries.