Ray Imaging System Research Articles

Characterization of organic glass scintillator bars and their potential for a hybrid neutron/gamma ray imaging system for proton radiotherapy range verification

For accurate and simultaneous imaging of fast neutrons (FNs) and prompt gamma rays (PGs) produced during proton therapy, the selection of a highly performant detector material is crucial. In this work, a promising candidate material known as organic glass scintillator (OGS) is characterized for this task. To this end, a precisely-timed source of neutrons and Bremsstrahlung radiation produced by the nELBE facility was used to study the light output and neutron/gamma ray pulse shape discrimination (PSD) properties of a 1 × 1 × 20 cm3 OGS bar with double-sided readout. Furthermore, the energy, timing, and depth-of-interaction (DOI) resolutions of 1 × 1 × 10 cm3 and 1 × 1 × 20 cm3 OGS and EJ-200 bars were characterized with radioactive sources. For electron-equivalent energies above 0.5 MeVee, OGS was found to have excellent PSD capabilities (figure-of-merit above 1.27), energy resolution (below 12%), coincident time resolution (below 500 ps), and DOI resolution (below 10 mm). This work establishes the data analysis methods required for hybrid FN/PG imaging using OGS, and demonstrates the materials' excellent performance for this application.

Improvement of double photon emission Compton imaging using angular and polarization correlations in cascade photons

A Compton camera is a gamma ray imaging system that produces images by superposing Compton cones calculated from Compton kinematics. However, the reconstructed images exhibit a high background. In this study, the angular correlation and polarization correlation were used to decrease the background. 111In, which emits 171 keV and 245 keV cascade gamma rays, was imaged using Compton camera modules in the ring structure. The 3D list-mode ordered subset expectation maximization method was used to reconstruct the images. Probability modeling of events reflecting angular and polarization correlations was applied to the image-reconstruction algorithm. The results were compared with those of a typical Compton camera method using only 245 keV Compton cones. The sensitivity of the proposed method was 1.03% of that of the typical method. However, compared to the typical method, the application of angular and polarization correlations improved the signal-to-background ratio. The proposed method is expected to be useful in capturing low-background images wherein a ring-type Compton camera and cascade photon-emitting nuclides can be used.

A cosmic ray imaging system based on plastic scintillator detector with SiPM readout

Cosmic ray muons can be used to detect materials which traditional methods cannot due to its high penetration ability. It's able to image 3-dimension density distribution of target by measuring scattering angle of muon tracks. We designed a muon imaging system aiming at the density reconstruction of various materials by measuring the scattering angle and momentum of cosmic ray muon. In addition, a GEANT4 simulation is developed to evaluate its material reconstruction performance. Detector prototypes composed of plastic scintillators with different geometries and SiPM readout modules are developed and tested. The test results show that 1.7 mm, 3.3 mm and 6.4 mm spatial resolution can be acquired by triangle, square and slab detector geometries respectively.

Development of hand-held coded-aperture gamma ray imaging system based on GAGG(Ce) scintillator coupled with SiPM array

Emerging gamma ray detection applications that utilize neutron-based interrogation result in the prompt emission of high-energy (>2 MeV) gamma-rays. Rapid imaging is enabled by scintillators that possess high density, high atomic number, and excellent energy resolution. In this paper, we evaluate the bright (50,000 photons/MeV) oxide scintillator, cerium-doped Gd2Al2Ga3O12 (GAGG(Ce)). A silicon photomultiplier (SiPM) array is coupled to a GAGG(Ce) scintillator array (12 × 12 pixels) and integrated into a coded-aperture based gamma-ray imaging system. A resistor-based symmetric charge division circuit was used reduce the multiplicity of the analog outputs from 144 to 4. The developed system exhibits 9.1%, 8.3%, and 8.0% FWHM energy resolutions at 511 keV, 662 keV, and 1173.2 keV, respectively. In addition, a pixel-identification resolution of 602 μm FWHM was obtained from the GAGG(Ce) scintillator array.

Evaluation of a new position sensitive detector based on the plastic rod scintillators

In this work, a new gamma ray imaging system was developed. The system consisted of a plastic-based rod detector (BC400) coupled with a PMT at one side and a fan shaped 60Co gamma source having about 1 mCi activities. The experiments were done using metal plates with different thicknesses. It was found that using a suitable deconvolution method, the output gamma spectra of the system can provide useful information about the size and position of the gamma ray exposed objects.

ピクセル検出器を用いたガンマ線イメージングの展開～高分解能ポジトロン断層法検出器を中心に

ピクセル検出器を用いたガンマ線イメージングの展開～高分解能ポジトロン断層法検出器を中心に

FIRST IMAGES FROM THE CRIPT MUON TOMOGRAPHY SYSTEM

The CRIPT Cosmic Ray Imaging and Passive Tomography system began data taking in September 2012. CRIPT is a “proof of principle” muon tomography system originally proposed to inspect cargo in shipping containers and to determine the presence of special nuclear materials. CRIPT uses 4 layers of 2 m x 2 m scintillation counter trackers, each layer measuring two coordinates. Two layers are used to track the incoming muon and two for the outgoing muon allowing the trajectories of the muon to be determined. The target volume is divided into voxels, and a Point of Closest Approach algorithm is used to determine the number of scattering events in each voxel, producing a 3D image. The system has been tested with various targets of depleted uranium, lead bricks, and tungsten rods. Data on the positional resolution has been taken and the intrinsic resolution is unfolded with the help of a simulation using GEANT4. The next steps include incorporation of data from the spectrometer section, which will assist in determining the muon's momentum and improve the determination of the density of the target.

Initial Result of Successive SXR Imaging Measurement in Low-A RFP

A fast successive soft-X ray (SXR) imaging system where SXR camera and high-speed camera for the study of time evolution of magnetic islands has been constructed. A preliminary experimental result in which we observed tangential SXR images from quasi-periodic quasi-single helicity (QSH) state in low-aspect-ratio (low-A) reversed field pinch (RFP) is presented. We successfully obtained time evolution of SXR images from tangential port. By comparison obtained images with simulated images, we may conclude that the evolution of experimental SXR image suggests the rotating QSH RFP configuration. The filamentous configuration tends to be observed in QSH state rather than in multi-helicity (MH) state.

A Phase I/II Clinical Trial of Accelerated Partial Breast Irradiation Using External Beam and Image-Guidance in Early-Stage Breast Cancer Patients Treated with Breast Conservative Surgery.

Abstract Purpose: To evaluate the early therapeutic outcome of accelerated partial breast irradiation(APBI) in low-risk breast cancer patients treated with breast conservative surgery(BCS) in a Chinese population, to analyze the intra-fractional and residual error with image-guidance.Material and methods: Eligible patients were age ≥18 years, unicentric Stage I invasive carcinoma or ductal carcinoma in situ(DCIS), treated with BCS with margin>2mm. Sixteen patients were enrolled between June 2008 and April 2009, with median age 53 ys (46-71). Clinical target volume(CTV) is defined by surgical cavities plus 1.5cm margin, another 1cm is expanded to form the planning target volume(PTV), with edition to no closer than 5 mm to the skin surface and no deeper than the anterior chest wall. Three-dimensional treatment plannings with field in field technique were generated with dose of 38.5Gy/10F, bid with interval≥6 hours. Two online cone beam CTs (CBCT) was acquired for each fraction, using Elekta Synergy, X- Ray Imaging system. One is after setup with skin-markers and the other at the end of fraction. Three different registrations: bony structure, grey and grey with manual adjustment(gmanual) were compared. The clip box included: whole breast, ipsilateral lung and part of the vertebras. The registration results of each fraction were recorded. The mean shifts and standard deviation (SD) were calculated on the CBCT pre and post-treatment.Results: The ratio of APBI PTV/whole breast PTV was 25%-40% (median 29.3%). 6MV photon with median fields of 4(3-6) was used. Grade I skin toxicity was found in all the 16 patients after 15-20(median 17) days of treatment, grade II skin reaction occured in 2 patients.The setup errors detected by the initial CBCT are 7mm in lateral(X), 10mm in longitudinal(Y) and 7mm in vertical directions(Z).Table 1 Setup errors detected by the differences between pre-treatment CBCT with skin marker and planning CT grey gmanual x (cm)y(cm)z(cm)x (cm)y(cm)z(cm)Mean-0.010.14-0.1 0.15-0.13SD0.260.370.290.280.370.28system error0.210.320.230.210.310.23random error0.180.190.180.180.230.2margin0.650.930.700.650.940.72 The bony algorithm showed statistical difference with grey or gmanual algorithms (p<0.05). Shift was applied when the registration result by gmanual was >3mm in any directions. The residual error and intra-fraction error was then analyzed after on-line shift and the post-fraction CBCT, which resulted in 6.9mm(X)l, 6.4mm(Y)and 7.3mm (Y) directions, see Table 2.Table 2 The summary of residual errors and intra-fraction errors after shift alignment x (cm)y (cm)z (cm)mean0.010.00-0.07SD0.260.290.29system error0.210.200.23random error0.230.200.22margin0.690.640.73 Conclusion: APBI with 3-D conformal external beam and image guidance is a feasible technique. Grey registration with manual adjustment is recommended for clinical application. The initial set-up error data confirmed the safety of 1cm margin from CTV to PTV. With online shift of any error above 3mm, the combination of residual error and intra-fraction error is 6.9mm, 6.4mm and 7.3mm in X, Y and Z directions, which might provide potential for margin reduction with image guidance. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4111.

Detection of Sentinel Node by Fluorescence and Infrared Ray Imaging System in Gastric Cancer

Detection of Sentinel Node by Fluorescence and Infrared Ray Imaging System in Gastric Cancer

Monte Carlo modeling of a cosmic ray imaging system for non-destructive evaluation of a reinforced concrete column

A detailed knowledge of the condition of reinforced concrete columns is essential for the planning of maintenance of a large building. We performed a Monte Carlo simulation to examine how well cosmic-ray muon radiography technique works on non-destructive testing of reinforcing concrete and we found that this technique can be an efficient tool for obtaining information such as the size and depth of reinforcing bars beneath concrete. We examined a concrete column with a cross-sectional size of 559×559 mm 2, reinforced with steel bars of 52 mm diameter, in order to estimate the positioning accuracy. Using simulations of 6 million muons/sr, we found that the precision for bar size measurement is 4.1 mm and that for bar location is 2.5 mm. We describe a possible inexpensive imaging system capable of determining the size and depth of an object and discuss the technique and the benefits of cosmic-ray radiography.

The Infrared Ray Imaging (IRI) System May Predict Delayed-Type Bleeding from the Mucosal Defect After EMR Or ESD for the Gastric Tumors

The Infrared Ray Imaging (IRI) System May Predict Delayed-Type Bleeding from the Mucosal Defect After EMR Or ESD for the Gastric Tumors

Design of Soft-X Ray Imaging System for Magnetic Islands of RFP Plasmas

A soft X ray (SXR) imaging system for diagnosing magnetic islands of a reversed field pinch (RFP) plasma is proposed. The SXR imaging system utilizes a microchannel plate (MCP) to record a higher-resolution distribution of two-dimensional (2D) luminosity on a phosphor plate. In order to identify the structure of the magnetic island from the obtained SXR image, we have calculated the 2D image expected from RFP plasmas. It is found that the 2D image reflects the change in the radiation intensity caused by the magnetic island. Also, the magnetic island can be distinguished clearly when the radiation power emitted from the magnetic island is more than about 20 % of that on the magnetic axis of RFP. Regarding with the view angle α of the SXR imaging system, the magnetic island due to a tearing mode on the m = 1/n = 8 rational surface can be detected as far as α > π/10.

SPEIR: A Ge Compton camera

The SPEctroscopic Imager for γ - Rays (SPEIR) is a Compton scatter γ -ray imaging system of high efficiency and spectroscopic resolution with a 4- π field-of-view. The imaging system consists of double-sided segmented (DSSD) planar Ge detectors, an acquisition system instrumenting the detectors, and a set of data analysis methods. The analysis methods employ event reconstruction algorithms that increase the intrinsic position resolution and granularity of the detectors, and provide photon scattering information relevant for Compton imaging.

3-D isotropic imaging of environmental sources using a compact gamma camera

In this work, the three-dimensional (3-D) position information of a radiation source is determined by a compact gamma ray imaging system. Two-dimensional (2-D) gamma ray images were obtained from different positions by the gamma camera and the third dimension, the distance between the detector and the radiation source, was calculated using triangulation. Additionally, a CCD camera is attached to the top of the gamma camera and provides associated 2-D visual information. The inferred distances from the center of the two measurement points and a radiation source had less than a 5% error for sources within 3 m and /spl plusmn/45/spl deg/ FOV. From the measured distances and camera intrinsic efficiencies /spl epsiv/(/spl theta/,/spl phi/) from MCNP simulations, the activity of the source was normally determined within 80% of the true value depending upon source position. The parallax between the two visual images was corrected using the inferred distance between the detector and the radiation source. The radiation image from gamma camera and the visual image from CCD camera are superimposed into one combined image using a maximum-likelihood (ML) algorithm to make the image alignment more precise. Energy dependent response functions were found to be better than a fixed energy response function for ML image processing.

Observation of the adhesion of thin Ta polycrystalline films to Si wafers via in situtopography/radiography

The adhesion of thin polycrystalline metallic Ta films to Si wafer substrates was studied in situ under real–time conditions using white–beam synchrotron Laue transmission diffraction topography with simultaneous radiographic imaging. The observations were carried out using a newly developed experimental apparatus, which consisted of a computer–controlled mini–tensile stage, an 800°C ancillary furnace, and a CCD X–ray imaging system. The stress and imaging data were collected simultaneously via a video recorder and also at selected intervals by frame–grabbing/storage technology on a microcomputer. This allowed direct correlation between the stress, temperature and film–failure processes. The results for sputtered Ta polycrystalline thin films deposited onto Si wafers indicated that induced stresses led to buckling delaminations along well–defined directions. These observations can be readily extended to study a variety of film–adhesion and cycle–failure problems.

An imaging nuclear survey system

A combined video and gamma ray imaging system has been developed which can rapidly determine the location, distribution, and intensity of gamma ray sources. This instrument includes both a conventional video camera and a gamma ray imaging system, which is based upon a position sensitive photomultiplier tube, a scintillator, and a pinhole collimator. The gamma camera records the position and energy of each interaction, determining the energy spectrum and count rate from each direction. We have used a prototype of such an instrument in preliminary field tests to image radioactive sources with gamma ray energies between 120 keV and 2.4 MeV. At 662 keV, this new system achieves an angular resolution of 4/spl deg/ FWHM with an absolute efficiency of 1/spl times/10/sup -6/ at 1 meter, with sensitivity such that a 0.5 mCi /sup 137/Cs source at 5 meters can be located in <60 seconds. Higher efficiency and sensitivity can be achieved at lower spatial resolution.

A combined video and gamma ray imaging system for robots in nuclear environments

An integrated imaging sensor system is being developed to enhance operations of robots and telerobotic systems used in nuclear industry. This system combines a gamma ray image of the distribution of radioactivity with a video image of the area, allowing a rapid and intuitive determination of the source location. The gamma ray imaging system is based upon a position sensitive photomultiplier tube, a segmented scintillator, and a pinhole collimator which provides high quality images in the energy range of 0.1 to 1.5 MeV. The design and measured performance of a prototype of this system will be discussed.

Gamma ray imaging probes 2: Code optimization

The Hotelling trace is used as a figure of merit for optimizing the azimuthal aperture in a coded aperture gamma ray imaging system. We present simulations for a particular aperture size that incorporates the combined effects of signal and background variability, additive nonstationary noise, aperture code choice, and detector integration time. It is shown that crossing points occur wherein different codes are, in principle, optimal for short vs long detector count times. The optimization approach may be generalized to more complex coded aperture imaging systems.

Gamma-Ray Imaging with a Rotating Hexagonal Uniformly Redundant Array

Laboratory experiments have been performed to demonstrate the capabilities of a ?-ray imaging system employing a NaI Anger camera and a rotating coded aperture mask. The mask incorporates in its design a new type of hexagonal uniformly redundant array (HURA) which is essentially antisymmetric under 60° rotation. The image formation techniques are described and results are presented that demonstrate the imaging capability of the system for individual and multiple point sources of ?-ray emission. The results are cornpared to analytical predictions for the imaging and point source localization capabilities of coded aperture systems using continuous detectors.