• Journal of Chest Surgery
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• 제53권5호
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• pp.310-312
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• 2020

Transcatheter leadless pacemaker dislodgment is a rare and potentially fatal complication of leadless device implantation. We present the first case of multidetector computed tomography images of leadless pacemaker migration and embolization in the pulmonary middle lobe artery. The patient was managed by percutaneous retrieval of the dislodged device and re-implantation in the appropriate position.

• Korean Journal of Radiology
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• 제23권9호
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• pp.854-865
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• 2022

Photon-counting detector (PCD) CT is a new CT technology utilizing a direct conversion X-ray detector, where incident X-ray photon energies are directly recorded as electronical signals. The design of the photon-counting detector itself facilitates improvements in spatial resolution (via smaller detector pixel design) and iodine signal (via count weighting) while still permitting multi-energy imaging. PCD-CT can eliminate electronic noise and reduce artifacts due to the use of energy thresholds. Improved dose efficiency is important for low dose CT and pediatric imaging. The ultra-high spatial resolution of PCD-CT design permits lower dose scanning for all body regions and is particularly helpful in identifying important imaging findings in thoracic and musculoskeletal CT. Improved iodine signal may be helpful for low contrast tasks in abdominal imaging. Virtual monoenergetic images and material classification will assist with numerous diagnostic tasks in abdominal, musculoskeletal, and cardiovascular imaging. Dual-source PCD-CT permits multi-energy CT images of the heart and coronary arteries at high temporal resolution. In this special review article, we review the clinical benefits of this technology across a wide variety of radiological subspecialties.

• Journal of Radiation Protection and Research
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• 제49권1호
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• pp.29-39
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• 2024

Background: The gamma emission tomography (GET) device has been reported a reliable technique to inspect partial defects within spent nuclear fuel (SNF) of pin-by-pin level. However, the existing GET devices have low accuracy owing to the high attenuation and scatter probability for SNF inspection condition. The purpose of this study is to design and optimize a Yonsei single-photon emission computed tomography version 2 (YSECT.v.2) for fast inspection of SNF in water storage by acquisition of high-quality tomographic images. Materials and Methods: Using Geant4 (Geant4 Collaboration) and DETECT-2000 (Glenn F. Knoll et al.) Monte Carlo simulation, the geometrical structure of the proposed device was determined and its performance was evaluated for the ¹³⁷Cs source in water. In a Geant4-based assessment, proposed device was compared with the International Atomic Energy Agency (IAEA)-authenticated device for the quality of tomographic images obtained for 12 fuel sources in a 14 × 14 Westinghouse-type fuel assembly. Results and Discussion: According to the results, the length, slit width, and septal width of the collimator were determined to be 65, 2.1, and 1.5 mm, respectively, and the material and length of the trapezoidal-shaped scintillator were determined to be gadolinium aluminum gallium garnet and 45 mm, respectively. Based on the results of performance comparison between the YSECT.v.2 and IAEA's device, the proposed device showed 200 times higher performance in gamma-detection sensitivity and similar source discrimination probability. Conclusion: In this study, we optimally designed the GET device for improving the SNF inspection accuracy and evaluated its performance. Our results show that the YSECT.v.2 device could be employed for SNF inspection.

• Imaging Science in Dentistry
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• 제40권2호
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• pp.63-68
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• 2010

Purpose : To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each. Materials and Methods : Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, $\rho$ ($g/cm^3$), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images. Results : CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were $\rho$=0.001H+1.07 with $R^2$ value of 0.999 for Somatom Emotion, $\rho$=0.002H+1.09 with $R^2$ value of 0.991 for Alphard VEGA, $\rho$=0.001H+1.43 with $R^2$ value of 0.980 for i-CAT and $\rho$=0.001H+1.30 with $R^2$ value of 0.975 for Implagraphy. Conclusion: CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.

• 대한영상의학회지
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• 제84권5호
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• pp.1047-1065
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• 2023

다중검출기컴퓨터단층촬영(multi-detector CT; 이하 MDCT)은 높은 정확도를 가진 진단도구로서 충수염과 그 합병증을 평가하기 위해 보편적으로 사용된다. MDCT 소견에 근거한 충수염의 진단은 영상 소견이 전형적인 모습과 일치하지 않을 때 어려울 수 있다. 비전형적인 충수염에는 충수 및 맹장의 위치이상을 동반하는 경우, 합병증이 나타난 경우 그리고 충수염을 모방하거나 유발하는 병리학적 소견을 동반한 경우 등 다양한 스펙트럼의 질환이 포함된다. 본 임상화보는 비전형적이고 복잡한 충수염 및 충수염과 유사한 상태의 다양한 스펙트럼을 위치이상, 드문 합병증 및 종양, 반응성 충수염, 충수게실염, IgG4 연관 질환을 포함한 병리학적 이상의 관점에서 설명했다. 본 임상화보를 통해 독자들은 다양한 스펙트럼의 비전형적 충수염 MDCT 소견에 더 익숙해질 수 있다.

• 한국의학물리학회지:의학물리
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• 제21권2호
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• pp.137-144
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• 2010

64 multi-detector computed tomography (MDCT)에서 두개부의 과도한 선량이 문제가 되어 고정관류기법과 관전류 자동노출조절(automatic exposure control, AEC) 기법을 이용하여 선량 감소 정도를 비교 평가하고자 한다. 연구에 사용한 장비는 Siemens사의 SOMATOM Definition 64 multi-detector CT를 이용했으며, Whole body phantom (KUPBU-50, Kyoto Kagaku CO. Ltd)의 두개부를 사용했다. 실험 protocol은 helical scan 방식을 적용하여 120 kVp, rotation time은 1 sec, slice thickness와 increment는 각각 5 mm, FOV는 250 mm, matrix size는 $512{\times}512$, collimation은 $64{\times}0.625\;mm$, pitch는 1로 조사하였다. 선량감소효과의 측정방법은 관전류를 350 mAs로 고정한 방법과 AEC 기법을 적용한 방법으로 나누어 평가하였으며, 영상품질은 CT number의 표준편차를 이용하여 영상의 잡음을 측정하였다. 이 때 두개부(craniofacial bone)는 머리덮개뼈(calvaria) 끝부분에서 눈썹활(superciliary ridge)까지를 1구역, 논썹활 아래부터 코가시점(acanthion)까지를 2구역, 그리고 코가시점 아래부터 턱(mentum)끝까지를 3구역으로 정의하여 측정하였다. 고정관류기법에서 구역별로 CTDIvol은 57.7 mGy였으며, DLP는 $640.2\;mGy{\cdot}cm$로 동일하였다. AEC 기법을 적용한 1구역은 CTDIvol: 30.7 mGy, DLP: $340.7\;mGy{\cdot}cm$, 2구역은 CTDIvol: 46.5 mGy, DLP: $515.0\;mGy{\cdot}cm$, 그리고 3구역은 CTDIvol: 30.3 mGy, DLP: $337.0\;mGy{\cdot}cm$으로 나타났다. 영상품질을 나타내는 CT number의 표준편차는 1구역에서 고정 관류기법은 2.6, AEC 기법은 3.0, 2구역에서 고정 관류기법은 3.1, AEC 기법은 3.4, 3구역에서 고정 관류기법은 2.7, AEC 기법은 3.2으로 측정되었다. 64 MDCT에서의 AEC 기법은 기존의 고정관류법에 비해 안구, 이하선 그리고 갑상선 부위에 대해 큰 선량 감소효과가 나타났으며, 두개부의 방사선량을 감소시키는데 매우 유용한 기법으로 사료된다.

• 한국방사선학회논문지
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• 제10권1호
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• pp.45-51
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• 2016

본 연구에서는 비등방성 2차원 확산 기반 필터를 이용하여 전산화단층영상(computed tomography, CT)의 노이즈 제거와 공간분해능을 향상하고자 하였다. 실험은 4-채널 다중검출기 전산화단층영상기기(4-channel multi-detector computed tomography, MDCT)를 이용하였으며, CT 영상품질 평가를 위해 미국 의학물리학자협의회(american association of physicists in medicine, AAPM) CT 성능 평가용 팬톰을 사용하였다. X-선 조사 조건은 120 kVp, 100 mAs로 고정한 후 ultra-high resolution으로 10 mm 축 방향 스캔 하였다. 본 연구에서 제안한 비등방성 2차원 확산 기반 필터는 원 영상에 각 픽셀에 가중치 1.2를 곱하고 0.4% 히스토그램 스트레칭을 통해 영상의 대조도를 증가시킨 후 비등방성 2차원 확산 필터를 적용하였다. 그 결과, 공간분해능은 원 영상에서 0.75 mm까지 구분되었지만 제안한 비등방성 2차원 확산 기반 필터 영상에서는 0.40 mm까지 구분되었다. 원 영상의 노이즈는 46.0, 제안한 비등방성 2차원 확산 기반 필터 영상의 노이즈는 33.5로 27.2%가 감소하였다. 우리가 제안한 비등방성 2차원 확산 기반 필터는 CT의 노이즈 제거와 공간분해능을 향상시킬 수 있었다.

• Korean Journal of Radiology
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• 제24권10호
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• pp.1006-1016
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• 2023

Objective: Computed tomography (CT) is an established method for the diagnosis, staging, and treatment of multiple myeloma. Here, we investigated the potential of photon-counting detector computed tomography (PCD-CT) in terms of image quality, diagnostic confidence, and radiation dose compared with energy-integrating detector CT (EID-CT). Materials and Methods: In this prospective study, patients with known multiple myeloma underwent clinically indicated whole-body PCD-CT. The image quality of PCD-CT was assessed qualitatively by three independent radiologists for overall image quality, edge sharpness, image noise, lesion conspicuity, and diagnostic confidence using a 5-point Likert scale (5 = excellent), and quantitatively for signal homogeneity using the coefficient of variation (CV) of Hounsfield Units (HU) values and modulation transfer function (MTF) via the full width at half maximum (FWHM) in the frequency space. The results were compared with those of the current clinical standard EID-CT protocols as controls. Additionally, the radiation dose (CTDIvol) was determined. Results: We enrolled 35 patients with multiple myeloma (mean age 69.8 ± 9.1 years; 18 [51%] males). Qualitative image analysis revealed superior scores (median [interquartile range]) for PCD-CT regarding overall image quality (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), edge sharpness (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), image noise (4.0 [4.0-4.0] vs. 3.0 [3.0-4.0]), lesion conspicuity (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]), and diagnostic confidence (4.0 [4.0-5.0] vs. 4.0 [3.0-4.0]) compared with EID-CT (P ≤ 0.004). In quantitative image analyses, PCD-CT compared with EID-CT revealed a substantially lower FWHM (2.89 vs. 25.68 cy/pixel) and a significantly more homogeneous signal (mean CV ± standard deviation [SD], 0.99 ± 0.65 vs. 1.66 ± 0.5; P < 0.001) at a significantly lower radiation dose (mean CTDIvol ± SD, 3.33 ± 0.82 vs. 7.19 ± 3.57 mGy; P < 0.001). Conclusion: Whole-body PCD-CT provides significantly higher subjective and objective image quality at significantly reduced radiation doses than the current clinical standard EID-CT protocols, along with readily available multi-spectral data, facilitating the potential for further advanced post-processing.

• Korean Journal of Radiology
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• 제21권8호
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• pp.1018-1023
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• 2020

The coronavirus disease (COVID-19) outbreak has reached global pandemic status as announced by the World Health Organization, which currently recommends reverse transcription polymerase chain reaction (RT-PCR) as the standard diagnostic tool. However, although the RT-PCR test results may be found negative, there are cases that are found positive for COVID-19 pneumonia on computed tomography (CT) scan. CT is also useful in assessing the severity of COVID-19 pneumonia. When clinicians desire a CT scan of a patient with COVID-19 to monitor treatment response, a safe method for patient transport is necessary. To address the engagement of medical resources necessary to transport a patient with COVID-19, our institution has implemented the use of mobile CT. Therefore, we report two cases of COVID-19 pneumonia evaluated by using mobile cone-beam CT. Although mobile cone-beam CT had some limitations regarding its image quality such as scatter noise, motion and streak artifacts, and limited field of view compared with conventional multi-detector CT, both cases had acceptable image quality to establish the diagnosis of COVID-19 pneumonia. We report the usefulness of mobile cone-beam CT in patients with COVID-19 pneumonia.

• 대한방사선기술학회지:방사선기술과학
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• 제27권2호
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• pp.21-27
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• 2004

본 연구에서는 현재 국내에서 사용되고 있는 여러 기종의 CT장치를 대상으로 하여 CT검사로 인한 방사선피폭 정도를 실험을 통하여 알아보고, 외국의 사례와 비교함으로써 CT장치의 성능관리의 하나인 피폭선량 기준 설정에 필요한 기초 데이터를 제시하고자 서울시 및 경기도에 위치한 병의원 및 종합병원에서 가동 중인 32대의 CT장치를 대상으로 CTDI값을 측정한 결과 다음과 같았다. 1) Head phantom의 100 mAs 당 $CTDI_W$값은 $8.1{\sim}19.1\;mGy$ 범위였고, 평균 $13.5{\pm}3.2\;mGy$였다. 그리고 body phantom의 $CTDI_W$값은 $3.7{\sim}10.9\;mGy$ 범위였고, 평균 $7.1{\pm}2.0\;mGy$였다. 2) Single detector CT와 multi detector CT의 $CTDI_W$값을 비교해 보면, multi detector CT가 single detector CT에 비해 head phantom에서는 평균 3.2 mGy(약 1.26배), body phantom에서는 평균 2.1 mGy(약 1.34배) 높았다. 3) Channel 수에 따른 $CTDI_W$값 비교에서는 head pahantom에서는 4 channel CT가 가장 높았으며, 8 channel CT, 16 channel CT, single detector CT순이었으며, body phantom에서는 역시 4 channel CT와 8 channel CT, 16 channel CT, single detector CT순이었다.