Young Jun Jung

Super multiview 3D display system using reflective vibrating scanner array

In this paper, we present a primitive system design of a super multi-view (SMV) 3-D display system based on a focused light array (FLA) concept using reflective vibrating scanner array (ViSA). The parallel beam scanning using a vibrating scanner array is performed by moving left and right an array of curvature-compensated mirrors or diamond-ruled reflective grating attached to a vibrating membrane. The parallel laser beam scanner array can replace the polygon mirror scanner which has been used in the SMV 3-D display system based on the focused light array (FLA) concept proposed by Kajiki at TAO (Telecommunications Advancement Organization). The proposed system has great advantages in the sense that it requires neither huge imaging optics nor mechanical scanning parts. Some mathematical analyses and fundamental limitations of the proposed system are presented. The proposed vibrating scanner array, after some modifications and refinements, may replace polygon mirror-based scanners in the near future.

Modeling high energy (I-131) pinhole collimator for small animal gamma ray imaging device by Monte Carlo simulation (GATE 6.0)

We investigated optimized collimator designs for I-131 high energy gamma ray imaging on small animal gamma camera. The simulated structures of the pinhole collimator were evaluated by sensitivity, true, scatter and penetration count rates, and spatial resolution. The parameters, which were pinhole diameter, acceptance angle, and aperture thickness, were determined to improve image resolution with geometric conditions. In this study we showed optimized pinhole design for high energy I-131 imaging to meet the tradeoff between sensitivity and resolution

Development of a Multipurpose Gamma-Ray Imaging Detector Module With Enhanced Expandability

A silicon photomultiplier (SiPM) is considered a next generation photo-sensor for low-light applications. In this study, we propose and develop the general concept of a multipurpose submillimeter gamma-ray (MSG) imaging module that is applicable to most gamma-ray imaging devices. The main features of the MSG module are submillimeter intrinsic resolution, geometrically expandable structure, expandable data acquisition system, multi-energy capability and usability in intense magnetic fields. The elements of the gamma-ray detector are pixelated Ce:GAGG (

Performances of a protector against scattered radiation during intraoperative use of a C-arm fluoroscope

31\times 31

Development of a prototype SPECT system using a variable pinhole collimator

pixels, 0.8 mm pitch), a 1.5-mm acrylic light guide, and one SiPM array (

Diffusion studies on Si-PIN X-ray detectors with guard-rings for single photon counting sensors

8 \times 8

Feasibility study of a lens-coupled charge-coupled device gamma camera

pixels). The readout electronics are composed of a symmetric charge division resistive network, 16 channel preamplifiers, multiplexing amplifiers, and analog-to-digital converter (ADC) circuits. We use a subminiature field-programmable gate array (FPGA) board as a data acquisition system. To make the system more expandable, we apply a 10 GbE-based tree structure using a FPGA-based data acquisition board and switching hub. To verify multipurpose capabilities, the energy spectra and the flood images are obtained using Co-57, Na-22, and Cs-137 isotopes. We measure temperature characteristics of the detector module. A pinhole image is obtained to confirm high resolution property. The maximal data transfer rate that is measured using dummy gamma-ray event packets is 963.143 Mbps. This detector module can be applied to nuclear medicine imaging devices and radiation monitoring systems.

Experimental evaluation of a multi-pinhole collimator for a small organ by using a small-field-of-view gamma camera

The scattered radiation protector for mobile x-ray systems, Creative Valuable Protector-2, has been recently developed. However, there have been no studies investigating the effects of this device. We aim to investigate the effects of the scattered radiation protector on the equivalent doses from scattered radiation delivered to radiosensitive organs while simulating spine surgery using a C-arm fluoroscope. Chest and rando phantoms were used to simulate a patient and a surgeon in this study. The equivalent dose from scattered radiation to radiosensitive organs was measured in four different situations according to the use of the scattered radiation protector and the C-arm configuration. To compare the quality of the images with and without the scattered radiation protector, an acryl step phantom with five steps was used, and the contrast resolution of each step was calculated. The equivalent dose from the scattered radiation to the surgeons eye, thyroid, and gonad decreased significantly by using the scattered radiation protector for both the Posteroanterior (PA) (p  <  0.001) and Anteroposterior (AP) (p  <  0.001) C-arm configurations. The installation of the scattered radiation protector also reduced the direct radiation dose to the chest phantom. A scattered map showed that scattered radiation doses decreased by approximately 50% for the PA configuration and 75% for the AP configuration by using the scattered radiation protector. Before and after installation of the scattered radiation protector, the contrast resolution of each adjacent step area was 0.025-0.404 and 0.216-0.421. The scattered radiation protector was effective in reducing not only the equivalent dose from scattered radiation to the surgeons radiosensitive organs, but also the direct radiation dose to the patient. This was all achieved without decreasing the quality of the C-arm fluoroscopic images.

Corrigendum to “Development of a DAQ system for a plasma display panel-based X-ray detector (PXD)” [Nucl. Instrum. Methods Phys. Res. A 784 (2015) 213–219]

We designed a novel single-photon emission computed tomography (SPECT) system with a variable pinhole (VP) collimator for obtaining high-sensitivity and high-spatial resolution imaging of a region of interest (ROI). Extending the capabilities of conventional SPECT systems, this novel SPECT system with a VP collimator can adjust its driving parameters, such as a collimator diameter, acceptance angle, and distances between the ROI, collimator, and detector at different rotation angles. Previously, we simulated a VP collimator and demonstrated the superiority of the VP SPECT system in terms of its sensitivity and spatial resolution. Based on these previous results, we developed a prototype SPECT system for performance evaluation of a VP collimator. The collimator was made from 99.9% pure tungsten layers, with 16 holes of different diameters. The area of the CsI(Tl) scintillator was 45.7 × 45.7 mm2 (51 × 51 pixels), with pixel dimensions of 0.7 × 0.7 × 5 mm3. The multi-pixel photon counter was tiled into a 2 × 2 configuration with dimensions of 52 × 52 mm2. The collimator, detector, and gantry of this SPECT system were independently controlled. We acquired initial reconstructed images from a point source (Co-57) and an ultra-micro phantom (Tc-99m). The point source and the phantom were clearly resolved, demonstrating satisfactory detector response, signal processing, and imaging processing capabilities. The 1.35mm phantom was also clearly resolved in the ultra-micro phantom.

Development of a DAQ system for a plasma display panel-based X-ray detector (PXD)

PIN diodes for digital X-ray detection as a single photon counting sensors were fabricated with a guard ring structure with p+ doping for reducing the leakage current. The efficiency of the guard ring was verified by significantly reduced leakage current compared to the Si-PIN diodes without guard ring structure and the gap distance between the active area and the guard ring was optimized as the leakage currents showed strong dependency on it. In this paper, secondary ion mass spectroscopy (SIMS) profile was measured and characterized to investigate potential process improvement. Since a large transient enhanced diffusion (TED) as the broadening of 200 nm at the tail is observed in the boron SIMS profile, it is suggested to reduce the annealing process time of RTA or to use spike annealing process. Also, in order to investigate the effect of reduced TED or other possible process to achieve shorter junction depth for improving device performance, it is in progress to fully optimize the process simulation incorporating the transient enhanced diffusion model of boron in Si.