• Journal of the Korean Society of Radiology
• /
• v.13 no.2
• /
• pp.313-318
• /
• 2019

To improve the sensitivity, a detector using a block scintillator was developed. In the pixelated scintillator, a reflector is located between pixels to move the light generated from the scintillator to the photosensor as much as possible, and sensitivity loss occurs in the reflector portion. In order to improve the sensitivity and to have the characteristics of the pixelated scintillator, the block scintillator was processed into a scintillator in pixel form through three-dimensional laser engraving. The energy spectra and energy resolution of each pixel were measured, and sensitivity analysis of block and pixel scintillator was performed through GATE simulation. The measured global energy resolution was 20.7%, and the sensitivity was 18.5% higher than that of the pixel scintillator. When this detector is applied to imaging devices such as gamma camera and positron emission tomography, it will be possible to shorten the imaging time and reduce the dose of patient by using less radiation source.

• Journal of radiological science and technology
• /
• v.35 no.4
• /
• pp.315-319
• /
• 2012

The aim of this study was to develop a signal process circuit for a position sensitive avalanche photodiode detector. The circuit parts consisted of amplification, differential and peak/hold circuit. This research was the baseline to develop highly compact radiation detector. The signal was amplified by an amplification chip and its shape was changed in a differential circuit to minimize the pulse tailing. The peak/hold circuit detect the peak of the signal from the differential circuit and hold the amplitude of the peak for data acquisition. In order to test the intrinsic function of the circuit, the input signal was transmitted from a commercial pulse generator.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2001.11a
• /
• pp.15-15
• /
• 2001

• The Korean Journal of Nuclear Medicine
• /
• v.34 no.1
• /
• pp.82-93
• /
• 2000

Purpose: We characterized the signals obtained from the components of a small gamma camera using Nal(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. Materials and Methods: The small gamma camera system consists of a Nal(Tl) crystal ($60{\times}60{\times}6mm^3$) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y -). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. Results: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately $8{\times}10^3$ counts/sec/${\mu}Ci$. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and $^{99m}Tc$ point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing $2{\sim}7mm$ diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2003.05a
• /
• pp.23-23
• /
• 2003

Cu 단결정과 다결정 Cu 막대(rod)를 시료로 하여 구부린 완전결정(bent perfect crystal, BPC)을 이용한 중성자 단색기의 특성을 평가함으로써 단결정 회절 및 집합조직 측정장치인 4축 단결정 회절장치(FCD)에 BPC 단색기를 적용할 수 있는지 시험하였다. 측정은 한국원자력연구소의 연구용 원자로인 하나로의 571 수평공에 구성된 test station에서 수행하였다. 단색기와 시료 사이의 거리는 3000mm, 시료와 검출기 사이는 600mm, 단색화빔 인출각도(2θ/sub M/)는 44.6°로 고정하여 FCD와 거의 같은 배치를 구현하였다 직사빔의 단면분포와 강도는 저효율 2차원 위치민감형 검출기(2-D PSD)를 이용하여 확인하였다. 이 검출기는 검출면적 90x90㎟, 공간 분해능 1.2mm, 검출효율 약 1%인 저효율 검출기이다. 회절빔은 검출면적 190x190㎟, 검출효율은 1Å에서 60%인 고효율 2-D PSD를 이용하여 측정하였다. Cu 단결정 측정에 사용한 ePC 단색화 결정은 200×40×3.4㎣ 크기의 Si(220) 슬랩이며, 비대칭 기하로 Si(331)면을 사용하여 파장 λ=0.954Å으로 중성자빔을 단색화시켰다. BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행배치일 때 Cu(200), (220), (400), (420)면의 rocking curve를 측정하여 각 조건에서의 분해능과 강도를 평가하였다. BPC 단색기를 집합조직 측정에 적용할 수 있는지 시험하기 위하여 다결정 Cu 막대(직경 4.5mm, 길이 18mm)를 시료로 선택하였다. 207x30x3.0㎣ 크기의 Si 슬랩을 단색화 결정으로 사용하였다. 이 슬랩은 다양한 결정면을 이용한 특별한 기하를 구현할 수 있도록 Si(111)면에서 10° 벗어난 면을 절단한 것이다. 비대칭 기하로 Si(311)면을 사용하여 파장 λ=1.253Å의 단색화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.93-98
• /
• 2010

The aim of this work was to establish the methodology for event positioning by measuring depth of interaction (DOI) information and to evaluate the system sensitivity and spatial resolution of the new detector for I-125 and Tc-99m imaging. For this purpose, a Monte Carlo simulation tool, DETECT2000 and GATE were used to model the energy deposition and light distribution in the detector and to validate this approach. Our proposed detector module consists of a monolithic CsI(Tl) crystal with dimensions of $50.0{\times}50.0{\times}3.0\;mm^3$. The results of simulation demonstrated that the resolution is less than 1.5 mm for both I-125 and Tc-99m. The main advantage of the proposed detector module is that by using 3 mm thick CsI(Tl) with maximum-likelihood position-estimation (MLPE) method, high resolution I-125 imaging and high sensitivity Tc-99m imaging are possible. In this paper, we proved that our new detector to be a reliable design as a detector for a multi-energy SPECT.

• Journal of the Korean Society of Radiology
• /
• v.18 no.2
• /
• pp.65-71
• /
• 2024

To achieve high resolution and sensitivity of positron emission tomography (PET) for small animals, the detector is constructed using very thin and long scintillation pixels. Due to the structure of these scintillation pixels, spatial resolution deterioration occurs outside the system's field of view. To solve this problem, we designed a detector that could improve spatial resolution by measuring the interaction depth and improve sensitivity by using a quasi-block scintillator. A quasi-block scintillator size of 12.6 mm x 12.6 mm x 3 mm was arranged in four layers, and optical sensors were placed on all sides to collect light generated by the interaction between gamma rays and the scintillator. DETECT2000 simulation was performed to evaluate the performance of the designed detector. Flood images were acquired by generating gamma-ray events at 1 mm intervals from 1.3 mm to 11.3 mm within the scintillator of each layer. The spatial resolution and peak-to-peak distance for each location were measured in an 11 x 11 array of flood images. The average measured spatial resolution was 0.25 mm, and the average distance between peaks was 1.0 mm. Through this, it was confirmed that all locations were separated from each other. In addition, because the light signals of all layers were measured separately from each other, the layer of the scintillator that interacted with the gamma rays could be completely separated. When the designed detector is used as a detector in a PET system for small animals, it is considered that excellent spatial resolution and sensitivity can be achieved and image quality can be improved.

• The Journal of the Korea Contents Association
• /
• v.14 no.2
• /
• pp.475-481
• /
• 2014

The aim of this work was to develop the gamma camera system for small animal gamma imaging and environmental radiation monitoring imaging using a parallel hole collimator and pinhole collimator. The small gamma camera system consists of a CsI(Tl) scintillation crystal with 6 mm in thickness and $50{\times}50mm$ in area coupled with a Hamamatsu H8500C PSPMT, are resistive charge divider, pre-amplifiers, charge amplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a computer for control and display. We have developed a radiation monitoring system composed of a combined pinhole gamma camera and a charge-coupled devices (CCD) camera. The results demonstrated that the parallel hole collimator and pinhole collimator gamma camera designed in this study could be utilized to perform small animal imaging and environmental radiation monitoring system. Consequently in this paper, we proved that our gamma detector system is reliable for a gamma camera which can be used as small animal imaging and environmental radiation monitoring system.

• Journal of Advanced Navigation Technology
• /
• v.13 no.4
• /
• pp.482-489
• /
• 2009

This paper proposes a CW(Continuous-Wave) bio-radar applying a new adaptive noise canceller based on ALE(Adaptive Line Enhancer) which can remove the Gaussian noise and system noise. Recently the research works on this CW bio-radar which can be used to detect heartbeat and respiration are advanced by the university and research facility. Although the researches describe CW bio-radar not only is vulnerable for the Gaussian noise but also has a disadvantage of decreasing the heart-rate accuracy due to the noise, the researches do not demonstrate the effective method for removing the noise component in a baseband signal. In this paper, a CW bio-radar applying the new adaptive noise canceller based on ALE which can remove the noise component is proposed. This paper compares and analyzes the performance for increasing the heart-rate accuracy according to removing the Gaussian noise and system noise in the baseband signal through the quadrature receiver which can alleviate the demodulation sensitivity to target position.

• Journal of Biomedical Engineering Research
• /
• v.20 no.1
• /
• pp.107-113
• /
• 1999

The purpose of this study was to develop a miniature imaging gamma probe with high performance that can detect small or residual tumors after surgery. Gamma probe detector system consists of NaI(Tl) scintillator, position sensitive photomultiplier tube (PSPMT), and collimator. PSPMT was optically coupled with 6.5 mm thick, 7.62 cm diameter of NaI(Tl) crystal and supplied with -1000V for high voltage. Parallel hexagonal hole collimator was manufactured for characteristics of 40-mm hole length, 1.3-mm hole diameter, and 0.22 mm septal thickness. Electronics consist of position and trigger signal readout systems. Position signals were obtained with summing, subtracting, and dividing circuit using preamplifer and amplifier. Trigger signals were obtained using summing amplifier, constant fraction discriminator, and gate and delay generator module with preamplifer. Data acquisition and processing were performed by Gamma-PF interface board inserted into pentium PC and PIP software. For imaging studies, flood and slit mask images were acquired using a point source. Two hole phantom images were also acquired with collimator. Intrinsic and system spatial resolutions were measured as 3.97 mm and 5.97 mm, respectively. In conclusion, Miniature gamma probe images based on the PSPMT showed good image quality, we conclude that the miniature imaging gamma probe was successfully developed and good image data were obtained. However, further studies will be required to optimize imaging characteristics.