Proposed Detector Design Research Articles

First experimental demonstration of real-time neutron capture discrimination in helium and carbon ion therapy

This work provides the first experimental proof of an increased neutron capture photon signal following the introduction of boron to a PMMA phantom during helium and carbon ion therapies in Neutron Capture Enhanced Particle Therapy (NCEPT). NCEPT leverages 10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{10}$$\\end{document}B neutron capture, leading to the emission of detectable 478 keV photons. Experiments were performed at the Heavy Ion Medical Accelerator in Chiba, Japan, with two Poly(methyl methacrylate) (PMMA) targets, one bearing a boron insert. The BeNEdiCTE gamma-ray detector measured an increase in the 478 keV signal of 45 ± 7% and 26 ± 2% for carbon and helium ion irradiation, respectively. Our Geant4 Monte Carlo simulation model, developed to investigate photon origins, found less than 30% of detected photons originated from the insert, while boron in the detector’s circuit boards contributed over 65%. Further, the model investigated detector sensitivity, establishing its capability to record a 10% increase in 478 keV photon detection at a target 10\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{10}$$\\end{document}B concentration of 500 ppm using spectral windowing alone, and 25% when combined with temporal windowing. The linear response extended to concentrations up to 20,000 ppm. The increase in the signal in all evaluated cases confirm the potential of the proposed detector design for neutron capture quantification in NCEPT.

Method and stabilization system of position-sensitive spectrometer based on semiconductor strip detector

The paper proposes a method and its realization for stabilizing the characteristics of a multichannel position-sensitive spectrometer. The device uses a new design of the semiconductor strip detector, which allows a simultaneous injection of stable in time electric charges on all strips. This solution enables the electronics to track changes in the conversion characteristics of all electronic channels including detectors strips, and correct them during the spectrometer operation. In addition, the proposed detector design makes it possible to control the signal propagation along the strips, thus providing an on-line check of the integrity of strips metallization and the quality of their connection with the readout electronics.

Design and Performance Evaluation of a BGO + SiPM Detector for High-Energy Prompt Gamma Imaging in Proton Therapy Monitoring

Proton therapy is attracting increasing attention nowadays owing to its accurate dose delivery to the target tumor. However, this advanced treatment modality is subject to proton beam range uncertainty, which could lead to overdose in healthy tissues. In the past decades, prompt gamma imaging (PGI) has gained increasing interest and been proved promising for realtime proton beam monitoring. The detection of 2-8 MeV high energy prompt gamma, however, poses a serious challenge for PGI system design, especially, for the detector design. In this article, we propose a prompt gamma detector design for a PGI system under development in our lab. The detector was composed of a 12 x 12 BGO block coupled to an 8 x 8 SiPM array with a crystal pixel size of 3.5 mm x 3.5 mm x 30 mm. A numerical simulation model was developed to evaluate the SiPM saturation effect caused by the finite number of microcells in each SiPM pixel while a huge number of optical photons might impinge the SiPM pixel under high energy gamma ray irradiation. Experiments under high energy gamma isotopes ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na - 511 keV, 1.275 MeV, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">88</sup> Y - 898 keV, 1.836 MeV, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">232</sup> Th - 2.6 MeV) irradiation were conducted to evaluate positioning performance, energy response linearity, and energy resolution (ER) of the detector. Root mean squared (RMS) metric was defined to assess the detector's positioning performance quantitatively. The numerical simulation results demonstrated that the SiPM saturation effect of the proposed detector design is negligible up to 10-MeV gamma photon detection. In the experimental studies, the obtained energy response linearity was 0.9997±0.0005, indicating almost no SiPM saturation effect for up to 2.6-MeV gamma photon detection with the proposed detector design. ER of 31.96% (511 keV), 26.67% (898 keV), 20.19% (1.275 MeV), 17.38% (1.836 MeV), and 15.88% (2.6 MeV) were achieved. With increased gamma photon energy, the crystal elements in the flood maps became clearer with reduced RMS value of the flood maps, indicating improved positioning performance. Based on the simulation and experimental results, we conclude that the proposed detector design is feasible for the PGI system with good energy and positioning performance as well as excellent anti-saturation capability for high energy gamma ray detection.

Compton PET: a simulation study for a PET module with novel geometry and machine learning for position decoding

This paper describes a simulation study of a positron emission tomography (PET) detector module that can reconstruct the kinematics of Compton scattering within the scintillator. We used a layer structure, with which we could recover the positions and energies for the multiple interactions of a gamma ray in the different layers. Using the Compton scattering formalism, the sequence of interactions can be estimated. The true first interaction position extracted in the Compton scattering will help minimize the degradation of the reconstructed image resolution caused by intercrystal scatter events. Because of the layer structure, this module also has readily available user-defined resolution for the depth of interaction. The semi-monolithic crystals enable high light collection efficiency and an energy resolution of ∼10% has been achieved in the simulation. We used machine learning to decode the gamma ray interaction locations, achieving an average spatial resolution of 0.40 mm. Our proposed detector design provides a pathway to increase the sensitivity of a system without affecting other key performance features.

A method for measuring the energy spectrum of neutrons with energies of 1–15 MeV

The characteristics of the detector prototype for 1–15 MeV neutrons are described. The prototype is a full absorption detector consisting of interlaced plastic scintillators and 6Li doped glasses. A neutron incident on the detector deposits all its energy in the plastic scintillator, is moderated to thermal energies, and detected in the lithium glass. The measured time of complete neutron moderation is ∼60 μs. Recording two signals in this time interval from the first event of neutron scattering in the plastic scintillator and from the neutron absorption by a lithium atom in the glass, it is possible to effectively suppress background thermal neutrons and γ rays and, therefore, detect low-intensity neutron sources. Owing to the proposed detector design, the direction toward the neutron source can be determined.

MO-E-I-609-04: New Detector for Low Dose Cone Beam Computed Tomographic (CT) Mammography Based On Microchannel Plate Image Amplifiers

Purpose: It is becoming recognized that tomosynthesis and/or full cone‐beam CTmammography may provide more diagnostic information than standard two view projection mammography; however, current flat panel digital image receptors have limitations on image quality and low dose due to excessive lag and detectornoise. Maintaining the same or lower total procedure dose can severely restrict the per‐view exposure, or the number of views. A new high‐resolution detector with adjustable high gain is being investigated to overcome these limitations. Method and Materials: A detector design consisting of a CsI x‐ray converter, fiber‐optic taper, microchannel‐plate‐based image amplifier with variable gain of 6 orders of magnitude, and optical coupling to a high resolution rapid sequence, low noise, 10242–20482 matrix pixel CCD camera is being investigated for this application. Results: A detector with a 16 cm diameter FOV can be achieved with the capability for total scan times of a few seconds. Additionally, off‐center magnification modes of full‐field‐corrected truncated cone‐beam CT are possible involving either geometric or optical magnification to improve spatial resolution. Initial tests of a small field‐of‐view prototype detector of the proposed design with 10242 matrix demonstrated linear response (quantum limited performance) for a range of detector entrance exposures from less than 0.2 microR to greater than 1 mR per view for pixels below 35 microns. Conclusion: The proposed detector design has advantages over flat panel detectors of exhibiting virtually no ghosting or lag and of providing more than 10× lower exposure per view capability due to the huge gain dynamic range and low noise available. Further investigations involving optimization of voxel size, number of views, reconstruction algorithm, exposure per view, exposing x‐ray spectrum, equalization filters, scatter reduction, patient positioning, and total scan times are proceeding. (Partial support: NIH grants R01EB002873 and R01NS43924)

Feasibility Study of Compton Scattering Enhanced Multiple Pinhole Imager for Nuclear Medicine.

This paper presents a feasibility study of a Compton scattering enhanced (CSE) multiple pinhole imaging system for gamma rays with energy of 140keV or higher. This system consists of a multiple-pinhole collimator, a position sensitive scintillation detector as used in standard Gamma camera, and a Silicon pad detector array, inserted between the collimator and the scintillation detector. The problem of multiplexing, normally associated with multiple pinhole system, is reduced by using the extra information from the detected Compton scattering events. In order to compensate for the sensitivity loss, due to the low probability of detecting Compton scattered events, the proposed detector is designed to collect both Compton scattering and Non-Compton events. It has been shown that with properly selected pinhole spacing, the proposed detector design leads to an improved image quality.

Feasibility study of Compton scattering enchanced multiple pinhole imager for nuclear medicine

This paper presents a feasibility study of a Compton scattering enhanced (CSE) multiple pinhole imaging system for gamma rays with energy of 140 keV or higher. This system consists of a multiple-pinhole collimator, a position sensitive scintillation detector as used in a standard gamma camera, and a Si pad detector array, inserted between the collimator and the scintillation detector. The problem of multiplexing, normally associated with multiple pinhole system, is reduced by using the extra information from the detected Compton scattering events. In order to compensate for the sensitivity loss, due to the low probability of detecting Compton scattered events, the proposed detector is designed to collect both Compton scattering and non-Compton events. It has been shown that with properly selected pinhole spacing, the proposed detector design leads to an improved image quality.

Parity violation in charged-particle resonance reactions.

Parity nonconservation (PNC) measurements utilizing charged-particle resonance reactions are proposed. PNC observables have been calculated for over 300 resonance pairs (with the same angular momentum and opposite parity) in five {ital s}-{ital d} shell nuclei. Detailed numerical results are presented for the longitudinal analyzing powers in the {sup 31}P({ital p}{searrow},{alpha}{sub 0}) reaction. There is strong dependence on energy, angle, and resonance parameters. A figure of merit that includes both the relative enhancement of the parity violation and the cross section is used to identify the most promising resonances for study. A proposed detector design and experimental procedure are described. These measurements should provide information on the weak spreading width (the effective nucleon-nucleus weak interaction) in light nuclei. {copyright} {ital 1996 The American Physical Society.}