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RISS 인기검색어
- 검색키워드
- 저자 : ( Jiwoong Choe ) (검색결과 5 건)
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An improved time over threshold method using bipolar signals
Jung, Jiwoong,Choi, Yong,Kim, Kyu bom,Lee, Sangwon,Choe, Hyeok-jun IOP 2018 Physics in medicine & biology Vol.63 No.13
<P>The time over threshold (TOT) method has been recently proposed as a signal processing method used to calculate time and energy information by measuring the pulse arrival time and pulse duration over a preset threshold. Although TOT has been reported as an effective method for front end readout in PET applications, it has several limitations, including its non-linearity, lower dynamic range, and a trade-off between energy resolution and coincidence resolving time (CRT). In this study, we propose a novel design we developed to improve performance with regard to these problems occurring in the conventional TOT by employing a bipolar signal and two comparators. Using a high frequency CR shaping filter, a detected signal was converted into a bipolar signal, and the positive pulse of the converted bipolar signal had a fast rising time, while the negative pulse had a linear slope. The bipolar TOT circuit was composed of a preamplifier, a CR shaping filter, and two comparators. The PET detector was composed of a single LYSO coupled with 4 × 4 SiPM arrays, a bipolar TOT circuit, and an FPGA based TDC. And this was constructed to evaluate the performance of the proposed bipolar TOT method. A 16-ch PET detector module consisting of a 4 × 4 array LYSO coupled to a 4 × 4 SiPM arrays, an Anger logic discretized positioning circuit, and a 4-ch bipolar TOT circuit was also constructed to evaluate the functionality of the bipolar TOT method for PET applications. The pulse height resolution and CRT were measured using both the bipolar TOT method and the conventional TOT method. While the bipolar TOT method provided a similar pulse height resolution (10.4% ± 0.1%), the integral non-linearity (1.4%) and CRT (168 ± 4 ps) measured using the bipolar TOT method were greatly improved compared to those (17.2% and 258 ± 15 ps, respectively) measured with the conventional TOT method. The positions of the crystals were clearly identified, as seen in the flood histogram acquired using the 4-ch bipolar TOT circuit. The measured average pulse height resolution and average CRT for the 16-ch detector module were 11.5% ± 0.2% and 516 ± 24 ps. The results obtained in this study indicate that the bipolar TOT method requiring a relatively small number of electronic components could effectively improve the CRT, linearity and dynamic range. Furthermore, they also demonstrated the extendibility allowing the development of a PET system that consists of a large number of detectors.</P>
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박호병 ( Hobyung Park ),김형진 ( Hyoungjean Kim ),( Jiwoong Choe ) 한국정보처리학회 2007 한국정보처리학회 학술대회논문집 Vol.14 No.1
본 논문에서는 제품 정보를 교환 및 공유하기 위한 국제 표준인 ISO 15926에 근거한 해양 플랜트 기자재의 제품 정보의 온톨로지 모델링을 소개한다. 모델링 방법은 코어 데이터 모델과, 참조 데이터 라이브러리, 템플릿과 객체 정보 모델을 이용한다. 코어 데이터 모델은 보편적인 개념을 정의하고, 참조데이터 라이브러리는 코어 데이터 모델을 확장한 공통 용어 사전이다. 의미를 표현하는 가장 작은 조각으로 템플릿을 사용하고, 객체 정보 모델을 통하여 객체들 사이의 관계를 정의한다. 모델링은 OWL을 이용하여 제품 데이터의 온톨로지를 생성하여 이기종 소프트웨어 간의 제품 정보를 교환하고 공유하도록 한다.
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Lee, Sangwon,Choi, Yong,Jung, Jin Ho,Jung, Jiwoong,Kim, Kyu Bom,Choe, Hyeok-jun,Leem, Hyun Tae,Lee, Hwunjae,Huh, Yong-Min Institute of Physics in association with the Ameri 2019 Physics in medicine & biology Vol.64 No.4
<P>Small animal positron emission tomography (PET) is a noninvasive imaging modality that enables <I>in vivo</I> imaging and quantification of the biological processes of small experimental animals. We have developed a small animal PET that utilizes a high-resolution multiplexed readout and charge signal transmission (CST) method. The small animal PET was composed of six detector blocks consisting of SiPMs and LYSO arrays. Six detector blocks were mounted on a PET gantry having an inner diameter of 76 mm, outer diameter of 112 mm, and axial length of 40.8 mm. The charge signals of SiPM output were transmitted to the input of multiplexed readout using 4 m flexible flat cables. The multiplexed readout was composed of six main boards, each of which included 36 detector boards, to reduce the number of readout channels by a factor of 36, with a multiplexing ratio of 144:4. The performance of the small animal PET was evaluated using NEMA NU 4-2008 standards, and its imaging capability was demonstrated by <I>in vivo</I> mouse imaging studies. The average energy and time resolutions were 13.2% ± 0.3% and 3.8 ns, respectively. The spatial resolution at the center of the transaxial FOV was 1.1 mm, and the peak sensitivity at the center of the axial FOV was 1.5%. The peak noise equivalent count (NEC) rate and scatter fraction were 21.1 kcps at 18.2 MBq and 21%, respectively. The acquired images demonstrated high quality tracer uptake patterns of small experimental animals. The results of performance evaluation and animal imaging indicate that the small animal PET developed in this study can provide high-quality small animal imaging with cost-effectiveness and compactness.</P>
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