의료영상정량화를 위한 KRISS 모듈팬텀 개발

조효민,도일,안봉영 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

의료영상검사법, 의료영상화질의 품질관리체계가 강화되면서 이에 대한 가이드라인이 제정되는 등 품질관리의 중요성이 강조되고 있다. 현재 국내에서 사용되고 있는 의료영상품질 평가방법은 1990년 대 초 미국에서 개발된 ACR팬텀을 이용한 평가방법을 사용하고 있어 급속히 발전하고 있는 장비의 성능에 따른 평가가 어려운 실정이다. 장비의 성능을 맞춤형으로 평가할 수 있는 표준화 및 정량화된 성능평가 기술이 필요하다. 이에 기존에 사용하던 빌트인 타입(Built-in type) 팬텀과 비교해 일관성과 표준화된 다양성을 갖는 모듈단위매핑 방식의 KRISS 모듈팬텀을 개발하였다. 다양한 형태와 크기의 단위 블럭으로 구성되며 내부에 영상품질평가용 모듈을 삽입하거나 영상 모달리티에서 대조도를 유발시킬 수 있는 용액을 주입하여 인체구조를 모사함으로써 기하학적 특성 및 조직 특성의 평가가 가능하다.

Control of Mitochondrial Dynamics by Fas-induced Caspase-8 Activation in Hippocampal Neurons

조효민,선웅 한국뇌신경과학회 2015 Experimental Neurobiology Vol.24 No.3

Cells undergo apoptosis mainly via two pathways—the mitochondrial pathway and the cytosolic pathway. It has been well documented that activation of the mitochondrial pathway promotes mitochondrial fragmentation and inhibition of mitochondrial fragmentation partly represses cell death. However, the mitochondrial events following activation of the cytosolic pathway are less understood. In this study, we treated Fas-activating antibody and found mitochondrial fragmentation without cell death in hippocampal primary neurons and HT-22 cell lines. Fas antibody treatment, in fact, promoted rapid activation of caspase-8, while executioner caspase-3 activation was not observed. Furthermore, blockage of caspase-8 efficiently prevented Fas antibody-induced mitochondrial fragmentation. These results suggest that the cytosolic pathway induced by death receptor activation promotes caspase-8-dependent mitochondrial fission.

Molecular cross talk among the components of the regulatory machinery of mitochondrial structure and quality control

조효민,선웅 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-

Mitochondrial dysfunction critically impairs cellular health and often causes or affects the progression of several diseases, including neurodegenerative diseases and cancer. Thus, cells must have several ways to monitor the condition of mitochondrial quality and maintain mitochondrial health. Accumulating evidence suggests that the molecular machinery responding to spontaneous changes in mitochondrial morphology is associated with the routine mitochondrial quality control system. In this short review, we discuss recent progress made in linking mitochondrial structural dynamics and the quality control system.

Optimization of a Photon Rejecter to Separate Electronic Noise in a Photon-counting Detector

조효민,최유나,이승완,이영진,류현주,김희중 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.11

Photon counting-based x-ray imaging technology provides the capability to count individual photons and characterize photon energies. The cadmium telluride (CdTe)-based photon-counting detector is limited in capability, however, under a high x-ray flux. A photon rejecter composed of aluminum, for example, can reduce this limitation by modulating the incident number of photons. In addition to this function, the optimal photon rejecter can separates electronic noise, which degrades image quality. The aim of this work was to optimize the photon rejecter for high quality image acquisition by removing electronic noise from the actual pulse signal. The images and spectra were acquired using a micro-focus x-ray source with a CdTe-based photon-counting detector. We acquired data with various types of photon rejecter materials composed of aluminum (Al) and iodine at three different tube voltages (50, 70 and 90 kVp). A phantom composed of high atomic number materials was imaged to evaluate the efficiency of the photon rejecter. Photon rejecters composed of 1-mm Al, 10-mm Al, and a combination of 10-mm Al and iodine provided optimum capability at 50, 70 and 90 kVp, respectively. Each optimal combination of photon rejecter material and voltage effectively separated electronic noise from the actual pulse signal and gave highest contrast-to-noise ratio for materials on the image. These optimized types of photon rejecter can effectively discriminate electronic noise and improve image quality according to the different tube voltages.

Evaluation of the Effective Detective Quantum Efficiency for Various Tube Voltages with Digital Radiography for Chest Imaging

조효민,김희중,박혜석,김대홍,이창래,최유나,이승완 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.3

The concept of effective detective quantum efficiency (eDQE) has recently been developed and introduced. The purpose of this study was to use the eDQE to evaluate the effect of tube voltage and grid for chest imaging with a direct flat-panel-based digital radiographic system. The exposure factors that we considered were the tube potential and an anti-scatter moving grid. The incident air kerma was adjusted for each tube potential to yield an effective dose of 34 μSv. The scatter fraction (SF), transmission fraction (TF), effective modulation transfer function (eMTF), and effective normalized noise power spectrum (eNNPS) were measured using a phantom that simulate the attenuation and scatter properties of the human chest. Our results showed that the resolution properties measured by using eMTFs were independent of the tube potential regardless of whether or not a grid was used. The noise properties through the phantom were greater with the use of an anti-scatter grid than without while the eDQE was largest at a lower tube potential, which we tested without a grid. In conclusion, we measured a high efficiency at a low tube potential without an anti-scatter grid for digital radiography (DR) in chest imaging. The eDQE reflected the real exam environment better than the general DQE because it better reflected the effect of the total X-ray system.

이동형 디지털 X선 촬영장치의 구축 및 성능평가

조효민,남소라,이창래,정지영,김희중,Cho, Hyo-Min,Nam, So-Ra,Lee, Chang-Lae,Jung, Ji-Young,Kim, Hee-Joung 한국의학물리학회 2007 의학물리 Vol.18 No.3

최근 국내에서는 원거리에 있는 응급환자에 대한 원격의료서비스를 제공하기 위한 이동형 응급 의료 시스템에 대한 연구가 활발히 진행되고 있다. 본 연구의 목적은 응급구조 차에 탑재 할 수 있는 이동형 디지털 X선 촬영 장치를 구축하고 시스템으로부터 획득한 영상에 대하여 영상 성능평가의 주요인자인 MTF (modulation transfer function), NPS (noise power spectrum) 및 DQE (detective quantum efficiency)를 정량화함으로써 응급상황 시 임상적으로 효용성 있는 영상의 획득 가능성을 평가하는 것이었다. 이동형 X선 장치(Mobix-1000; LISTEM, Wonju, Korea)와 디지털 X선 detector 시스템 (Alpha-R4000; Teleoptic PRA, Kyiv, Ukraine)으로 구축된 영상시스템에 대하여 성능평가를 수행하였다. 측정결과로 10% MTF는 2.4 cycles/mm를 나타내었고, DQE (0)는 조건선량 0.19, 0.5 그리고 1.3 mR에 따라 각각 54%, 55%, 그리고 76%로 측정되었다. 본 연구에서 획득한 영상평가 결과는 연구 중인 이동형 디지털 X선 촬영 장치의 응급 원격 의료에의 사용가치를 확인 할 수 있는 기초자료로서 이용될 수 있을 것으로 판단된다. Current digital radiography systems are rapidly glowing in clinical applications. The purpose of this study was to evaluate the characteristics of a mobile digital radiographic system. The performance of the mobile DR system was evaluated by measuring the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Measurements were made on a LISTEM Mobix-1000 generator and a Teleoptic PRA Alpha-R4000 detector. Imaging characteristics were measured for these two systems using the IEC-61267 defined RQA5 (kVp: 74, additional filtration: 21 mmAl) radiographic condition. The MTF at 10% was measured as 2.4 cycles/mm and the DQE(0) values for radiation exposure 0.19, 0.5, and 1.3 mR were measured as 54%, 55%, and 76%, respectively. The NPS curves gradually decreased at high spatial frequencies. This high DQE at low frequencies, may be useful for low frequency information. The results suggested that mobile DR system could be integrated with emergency ambulance system in teleradiologic imaging applications.

Characteristic Evaluation of a Novel CdTe Photon Counting Detector for X-Ray Imaging

조효민,김희중,류현주,최유나 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.1

The purpose of this paper is to investigate the characteristics of a novel cadmium-telluride (CdTe)photon counting detector optimized for X-ray imaging applications. CdTe was studied as a potential detector material for hard X-ray and gamma-ray detection. In this study, we used a CdTe photon counting detector manufactured by AJAT Ltd. (PID 350, Finland) for the purposes of both Xray and gamma-ray detection. However, it is noted that X-ray detection can be limited by the characteristics of gamma-ray detectors. For the investigation of the characteristics of a detector for X-ray imaging, the detector has been studied in terms of detector calibration, count rate, and pixel sensitivity variation by using a poly-energetic X-ray. The detector calibration was evaluated to determine the effects of offset, gain, and energy. An optimal calibration increases the accuracy of the output energy spectrum. The pixel sensitivity variation was evaluated using profiles of various rows and columns from white (with X-ray) and dark (without X-ray) images. The specific trend of each image was observed around the edges of the hybrids. These pixel variations of the CdTe sensor were corrected. The image quality was improved by using the optimal correction method based on an understanding of the pixel sensitivity variation. The maximum recorded count rate of the detector was measured in all pixels. The count rate was measured by setting the energy windows from just above the noise level to the maximum energy. The average count rate was fairly linear up to 1.6 × 106 cps/8 modules and saturated at about 2.2 × 106 cps/8 modules. In this paper, we present several characteristics of the detector and demonstrate the improved spectrum and image obtained after calibration and correction. These results show that the novel CdTe photon counting detector can be used in conventional X-ray imaging, but exhibits limitations when applied to spectral X-ray imaging.

ROC Analysis of Simulated Chest Lesions for Computed Radiography and Digital Radiography at Various Tube Voltages

조효민,김희중,이창래,정지영,박혜숙,Cho, Hyo-Min,Kim, Hee-Joung,Lee, Chang-Lae,Jung, Ji-Young,Park, Hye-Suk Korean Society of Medical Physics 2008 의학물리 Vol.19 No.4

본 연구에서는 다양한 관전압 사용에 따른 CR, DR 모의병변 흉부 영상을 이용하여 병변 검출 정도를 ROC 평가하였다. 모의 제작된 미세 폐 병변, 초기 침윤성 병변, 작은 혹 모양의 병변은 아크릴 판을 이용하여 인체형 흉부 팬텀과 포개놓고 영상을 획득하였으며 CR과 DR에서 각각 3개의 관전압(70 kV, 90 kV, 120 kV) 조건을 사용하였다. 총 18,000개의 관찰결과를 ROC평가 하였다. CR에서는 모든 병변에 대하여 70 kV로 획득한 영상이 높은 $A_z$값을 나타내었으나 DR에서는 두 개 병변에서만 70 kV로 획득한 영상이 높은 $A_z$값을 나타내었다. 본 연구내용을 바탕으로 검출기 종류와 관심 병변에 따른 최적의 관전압 조건을 사용하기 위하여 실제 환자에서의 임상 연구가 필요할 것으로 사료된다. Current digital radiographic systems are rapidly growing in clinical applications. The purpose of this study was to evaluate the diagnostic performance of computed radiography (CR) and digital radiography (DR) at different tube voltages in the detection of simulated chest lesions. Patterns of simulated interstitial lung disease, incipient infiltration, and nodules were superimposed over an anthropomorphic chest phantom. A simulated chest phantom radiograph was obtained with CR and DR at different tube voltages (70 kV, 90 kV, and 120 kV). A total of 18,000 observations were analyzed using a receiver operating characteristic (ROC) analysis. The detection of all lesions showed higher $A_z$ values at 70 kV than 120 kV with CR. For the DR, mean $A_z$ values at 70 kV were higher than other tube voltages not all lesions but for micro-nodule interstitial lung disease, linear interstitial lung disease, and incipient infiltration. Based on these results, a clinical study should be performed to judge the use of suitable tube voltage according to the type of detector system and lesions.

금융회사 컴플라이언스의 쟁점과 실무

이한경,조효민 서울대학교 금융법센터 2022 BFL Vol.113 No.-

금융소비자보호법상 책임 - 손해배상책임과 징벌적 과징금을 중심으로 -

이한경,조효민 서울대학교 금융법센터 2022 BFL Vol.111 No.-