Time-resolved photoluminescence analysis of ceramic Ce:GAGG scintillators.

This paper introduces the characteristics and efficiency of post-treatment methods for enhancing the timing resolution of ceramic Ce:GAGG scintillators. The thermal annealing and surface treatments were included to analyze their impact on time-resolved photoluminescence (TRPL) and thermoluminescence (TL) characteristics. Optical properties were improved by suppressing nonradiative recombination due to the reduced surface defects, while heat-treatment removes traps as confirmed by TL measurements.

Improvement of phoswich detector-based β+/γ-ray discrimination algorithm with deep learning.

Background: Positron probes can accurately localize malignant tumors by directly detecting positrons emitted from positron-emitting radiopharmaceuticals that accumulate in malignant tumors. In the conventional method for direct positron detection, multilayer scintillator detection and pulse shape discrimination techniques are used. However, some γ-rays cannot be distinguished by conventional methods.

Scintillation characteristics of chemically processed Ce:GAGG single crystals.

We investigated the correlation between the surface finish and luminescence properties of chemically polished cerium-doped single-crystal Gd3Al2Ga3O12 scintillators (Ce:GAGG), from the crystallographic perspective. The intrinsic defects in the crystals were identified via photoluminescence spectroscopy followed by scanning electron microscopy and X-ray diffraction to analyze their surface morphologies. Finally, the samples were individually wrapped with an enhanced specular reflector (ESR), coupled with a photomultiplier tube, placed inside a dark box, connected to a digitizer, and irradiated with a 137Cs radioactive source to evaluate the relative light (signal) output and energy resolution of each sample.

2-D Array Design and Fabrication With Pitch-Shifting Interposer at Frequencies From 4 MHz up to 10 MHz.

High element density and strict constraints of the element's size have significantly limited the design and fabrication of 2-D ultrasonic arrays, especially fully sampled 2-D arrays. Recently, 3-D printing technology has been one of the most rapidly developing fields. Along with the great progress of 3-D printing technology, complex and detailed 3-D structures have become readily available with a short iteration cycle, which allows us to reduce the complexity of routing and helps to ameliorate assembly problems in 2-D ultrasound array fabrication.

Performance Comparison of CdTe:Na, CdTe:As, and CdTe:P Single Crystals for Solar Cell Applications.

We compared thermal stability, open-circuit voltage, short-circuit current, and fill factor values of single-crystal Cadmium telluride (CdTe) grown using the vertical Bridgman (VB) technique and doped with group V elements (phosphorus and arsenic), and group Ⅰ element (sodium), followed by an annealing process. The sodium-doped CdTe maintained a hole density of 10 cm or higher; after annealing for a long time, this decreased to 10 cm or less. The arsenic-doped CdTe maintained a hole density of approximately 10 cm even after the annealing process; however its bulk minority carrier lifetime decreased by approximately 10%.

Simultaneous Acquisition of Ultrasound and Gamma Signals with a Single-Channel Readout.

We propose an integrated front-end data acquisition circuit for a hybrid ultrasound (US)-gamma probe. The proposed circuit consists of three main parts: (1) a preamplifier for the gamma probe, (2) a preprocessing analog circuit for the US, and (3) a digitally controlled analog switch. By exploiting the long idle time of the US system, an analog switch can be used to acquire data of both systems using a single output channel simultaneously.

Wavelength discrimination (WLD) TOF-PET detector with DOI information.

Depth-of-interaction (DOI) encoding can contribute to improving spatial resolution uniformity and sensitivity in positron-emission-tomography (PET) scanners. In addition, time-of-flight (TOF) PET scanners with DOI encoding have received considerable interest because of their potential for improving the spatial resolution, sensitivity, and image quality of the overall system. In this study, a new DOI detector configuration utilizing scintillators' emission wavelength is proposed, and experimental results on the energy, timing, and DOI performance of the detector are provided.

Ultrawide-angle optical system design for light-emitting diode-based ophthalmology and dermatology applications.

Background: Compared to laser, light-emitting diodes - non-coherent and divergent light sources requires that the developed optical system support steering and focusing of light on the desired target when acquiring information regarding human tissues.

Objective: A new optical system with an ultrawide angle was designed to cover large areas of the eye, including facial areas near the eye, in order to overcome the limited field of view of optical systems used for ophthalmology and dermatology applications.

Methods: To achieve a compact and handheld optical system for ophthalmology and dermatology applications, a contrast auto-focus (AF) method must be used, and the weight reduction of the AF group is considered during the design process to satisfy the effective focal length (EFL), back focal length (BFL), and front focal length (FFL) in the proposed optical system using Gaussian-bracket method.

Development of a Multiwavelength Visible-Range-Supported Opto⁻Ultrasound Instrument Using a Light-Emitting Diode and Ultrasound Transducer.

A new multiwavelength visible-range-supported opto⁻ultrasound instrument using a light-emitting diode and ultrasound transducer was developed in order to produce multiwavelength visible light with minimized color aberration errors, and detect ultrasound signals emitted from the target. In the instrument, the developed optical systems can provide multiwavelength optical transmission with low optical aberration within 10-cm ranges that are reasonably flat in the modulation transfer function at spatial frequencies of 20 and 40 lp/mm, except at the end of the diagonal edge of the samples. To assess the instrument capability, we performed pulse⁻echo responses with eye samples.

Power MOSFET Linearizer of a High-Voltage Power Amplifier for High-Frequency Pulse-Echo Instrumentation.

A power MOSFET linearizer is proposed for a high-voltage power amplifier (HVPA) used in high-frequency pulse-echo instrumentation. The power MOSFET linearizer is composed of a DC bias-controlled series power MOSFET shunt with parallel inductors and capacitors. The proposed scheme is designed to improve the gain deviation characteristics of the HVPA at higher input powers.

Development of a Double-Gauss Lens Based Setup for Optoacoustic Applications.

In optoacoustic (photoacoustic) systems, different echo signal intensities such as amplitudes, center frequencies, and bandwidths need to be compensated by utilizing variable gain or time-gain compensation amplifiers. However, such electronic components can increase system complexities and signal noise levels. In this paper, we introduce a double-Gauss lens to generate a large field of view with uniform light intensity due to the low chromatic aberrations of the lens, thus obtaining uniform echo signal intensities across the field of view of the optoacoustic system.

Simulation study of a novel target oriented SPECT design using a variable pinhole collimator.

Purpose: In the past decade, demands for organ specific (target oriented) single-photon emission computed tomography (SPECT) is increasing, and several groups have conducted studies on developing clinical dedicated SPECT with pinhole collimator to improve the spatial resolution. However, acceptance angle of the collimator cannot be adjusted to fit the different ROIs of target objects because the shape of pinhole could not be changed, and the magnifying factor cannot be maximized as the collimator-to-detector distance is fixed. Furthermore, those dedicated pinhole SPECTs are typically made for a single purpose and therefore possess a drawback in that it cannot be utilized for any other purpose.

Instrumentation for Time-of-Flight Positron Emission Tomography.

Positron emission tomography (PET) is a molecular imaging modality that provides information at the molecular level. This system is composed of radiation detectors to detect incoming coincident annihilation gamma photons emitted from the radiopharmaceutical injected into a patient's body and uses these data to reconstruct images. A major trend in PET instrumentation is the development of time-of-flight positron emission tomography (ToF-PET).

Electrical delay line multiplexing for pulsed mode radiation detectors.

Medical imaging systems are composed of a large number of position sensitive radiation detectors to provide high resolution imaging. For example, whole-body Positron Emission Tomography (PET) systems are typically composed of thousands of scintillation crystal elements, which are coupled to photosensors. Thus, PET systems greatly benefit from methods to reduce the number of data acquisition channels, in order to reduce the system development cost and complexity.

Side readout of long scintillation crystal elements with digital SiPM for TOF-DOI PET.

Purpose: Side readout of scintillation light from crystal elements in positron emission tomography (PET) is an alternative to conventional end-readout configurations, with the benefit of being able to provide accurate depth-of-interaction (DOI) information and good energy resolution while achieving excellent timing resolution required for time-of-flight PET. This paper explores different readout geometries of scintillation crystal elements with the goal of achieving a detector that simultaneously achieves excellent timing resolution, energy resolution, spatial resolution, and photon sensitivity.

Methods: The performance of discrete LYSO scintillation elements of different lengths read out from the end/side with digital silicon photomultipliers (dSiPMs) has been assessed.

Optimizing timing performance of silicon photomultiplier-based scintillation detectors.

Precise timing resolution is crucial for applications requiring photon time-of-flight (ToF) information such as ToF positron emission tomography (PET). Silicon photomultipliers (SiPM) for PET, with their high output capacitance, are known to require custom preamplifiers to optimize timing performance. In this paper, we describe simple alternative front-end electronics based on a commercial low-noise RF preamplifier and methods that have been implemented to achieve excellent timing resolution.