• 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.

• 소성∙가공
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• 제18권5호
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• pp.422-427
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• 2009

Computed tomography(CT) has been applied to measure micro-defects in the aluminum knuckle parts manufactured by the thixoforming process. 6061 aluminum alloys were used to form knuckle samples in the semi-solid temperature after the SIMA processing of billets. Tensile specimens were cut from the different locations in a thixoformed knuckle. The size and the distribution of forming defects in tensile specimens were analyzed using CT scanning and image analysis technology before tensile tests. It has been qualitatively shown that the stress-strain curves were significantly affected by the size and the distribution of forming defects although the defect sizes lie in the range of micro-meters.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.464-467
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• 2002

We propose the use of visible scintillation light for monitoring the X-ray CT in the gantry of a diagnostic CT for its performance test and maintenance works. We placed a disk of bare plastic scintillator disk in the gantry opening area of a helical X-ray CT. When we operated the CT, we could observe the emission of blue scintillation light from the scintillator in a dark room. Visible light was identified under all scanning conditions of diagnostic uses. As a result, we observed the direction and the spread of the incident X-ray in the scintillator. We also observed the change of the part of the scintillator where visible light was generated, and the move that took place associating with the rotation of the X-ray tube during one CT scan. On the basis of the observation, we examined the usefulness of the visible scintillation light as a convenient performance-evaluating tool as well as a maintenance tool of the CT.

• Journal of Korean Neurosurgical Society
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• 제47권2호
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• pp.89-94
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• 2010

Objective : To evaluate the role of cranial sonography and computed tomography in the diagnosis of neonatal intracranial hemorrhage and hypoxic-ischemic injury in an Indian set-up. Methods : The study included 100 neonates who underwent cranial sonography and computed tomography (CT) in the first month of life for suspected intracranial ischemia and hemorrhage. Two observers rated the images for possible intracranial lesions and a kappa statistic for interobserver agreement was calculated. Results : There was no significant difference in the kappa values of CT and ultrasonography (USG) for the diagnosis of germinal matrix hemorrhage/intraventricular hemorrhage (GMH/IVH) and periventricular leucomalacia (PVL) and both showed good interobserver agreement. USG, however detected more cases of GMH/IVH (24 cases) and PVL (19) cases than CT (22 cases and 16 cases of IVH and PVL, respectively). CT had significantly better interobserver agreement for the diagnosis of hypoxic ischemic injury (HII) in term infants and also detected more cases (33) as compared to USG (18). CT also detected 6 cases of extraaxial hemorrhages as compared to 1 detected by USG. Conclusion : USG is better modality for imaging preterm neonates with suspected IVH or PVL. However, USG is unreliable in the imaging of term newborns with suspected HII where CT or magnetic resonance image scan is a better modality.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.271-272
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• 1998

Contrast-enhanced CT has an important role in the assessment of liver lesions. However, the optimal protocol to get most effective result is not clear. The main principle for deciding injection protocol is to optimize lesion detectability by rapid scanning when lesion-to-liver contrast is maximum. For this purpose, we developed a physiological model of contrast medium enhancement based on the compartment modeling and pharmacokinetics. Blood supply to liver was modeled in two paths. This dual supply character distinguishes the CT enhancement of liver from that of the other organs. The first path is by hepatic artery and the second is by portal vein. It is assumed that only hepatic artery can supply blood to hepatocellular carcinoma (HCC) compartment. It is known that this causes the difference of contrast enhancement between normal liver tissue and hepatic tumor. By solving differential equations for each compartment simultaneously using computer program Matlab, CT contrast-enhancement curves were simulated. Simulated enhancement curves for aortic, hepatic, portal vein, and HCC compartments were compared with mean enhancement curves from 24 patients exposed to the same protocols as simulation. These enhancement curves were in a good agreement. Furthermore, we simulated lesion-to-liver curves for various injection protocols, and analyzed the effects. These may help to optimize the scanning protocols for good diagnosis.

• Journal of Trauma and Injury
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• 제23권2호
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• pp.142-150
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• 2010

Purpose: In this study, patients in whom two computed tomography (CT) scans had been obtained within 24 hours of injury were analyzed to determine the incidence, risk factors and clinical significance of a progressive intracerebral hematoma (PIH). Methods: Participants were 182 patients with a traumatic intracerebral hematoma and contusion who underwent a repeat CT scan within 24 hours of injury. Univarite and multivariate statistics were used to define growth (volume increase) and to examine the relationship between the risk factors and hemorrhage expansion. Results: Fifty-four percent of the patients experienced progression in the size of the lesion in the initial 24 hours postinjury. A PIH was independently associated with worsened Glasgow coma scale (GCS) score (2.99, 1.04~8.60), the presence of subarachnoid hemorrhage (6.29, 2.48~16.00), the presence of a subdural hematoma (6.18, 2.13~17.98), the presence of an epidural hematoma (5.73, 1.18~27.76), and the presence of a basal cistern effacement (10.93, 1.19~99.57). Conclusion: For patients undergoing scanning within 2 hours of injury, the rate of PIH approaches 61%. Early repeated CT scanning is indicated in patients with a nonsurgically-treated hemorrhage revealed on the first CT scan. Worsened GCS score, significant hematoma growth and effacement of the basal cisterns on the initial CT scan are powerful predictors of which patients will require surgery. These findings should be important factors in understanding and managing of PIH.

• 대한기계학회논문집A
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• 제35권12호
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• pp.1563-1571
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• 2011

본 연구에서는 인간중이의 소리전달특성 계산을 위한 유한요소모델을 개발하였다. 이소골의 형상을 얻기 위하여 한국인 사체에서 추출한 측두골을 마이크로 CT 촬영하여 3 차원 입체모델로 변환하였다. 유한요소모델은 이소골, 고막, 인대와 근육 등을 포함하여 구성하였다. 유한요소모델을 이용하여 고막에서 등골족판까지의 응답함수를 계산한 후 측정값을 갖는 선행연구와 비교하였고 그 결과 10 kHz 주파수 대역까지 소리전달특성을 잘 표현하고 있음을 보였다. 또한 유한요소 모델을 구성하는 주요 물성인자의 변화에 대한 소리전달특성의 변화를 살피고 침등골관절의 강성값이 중이의 소리전달특성에 큰 영향을 미침을 보였다.

• Tuberculosis and Respiratory Diseases
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• 제83권4호
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• pp.283-288
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• 2020

Background: Latent tuberculosis (TB) infection among TB contacts is diagnosed using plain chest radiography and interferon-gamma release assays (IGRAs). However, plain chest radiographs often miss active TB, and the results of IGRA could fluctuate over time. The purpose of this study was to elucidate changes in the results of the serial IGRAs and in the findings of the serial submillisievert chest computed tomography (CT) scans among the close contacts of active pulmonary TB patients. Methods: Patients age 20 or older with active pulmonary TB and their close contacts were invited to participate in this study. Two types of IGRA (QuantiFERON-TB Gold In-Tube assay [QFT-GIT] and the T-SPOT.TB test [T-SPOT]) and submillisievert chest CT scanning were performed at baseline and at 3 and 12 months after enrollment. Results: In total, 19 close contacts participated in this study. One was diagnosed with active pulmonary TB and was excluded from further analysis. At baseline, four of 18 contacts (22.2%) showed positive results for QFT-GIT and T-SPOT; there were no discordant results. During the follow-up, transient and permanent positive or negative conversions and discordant results between the two types of IGRAs were observed in some patients. Among the 17 contacts who underwent submillisievert chest CT scanning, calcified nodules were identified in seven (41.2%), noncalcified nodules in 14 (82.4%), and bronchiectasis in four (23.5%). Some nodules disappeared over time. Conclusion: The results of the QFT-GIT and T-SPOT assays and the CT images may change during 1 year of observation of close contacts of the active TB patients.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.160-166
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• 2019

This study examined the clinical use of two newly installed computed tomography (CT) simulators in the Department of Radiation Oncology. The accreditation procedure was performed by the Korean Institute for Accreditation of Medical Imaging. An Xi R/F dosimeter was used to measure the CT dose index for each plug of the CT dose index phantom. Image qualities such as the Hounsfield unit (HU) value of water, noise level, homogeneity, existence of artifacts, spatial resolution, contrast, and slice thickness were evaluated by scanning a CT performance phantom. All test items were evaluated as to whether they were within the required tolerance level. CT calibration curves-the relationship between CT number and relative electron density-were obtained for dose calculations in the treatment planning system. The positional accuracy of the lasers was also evaluated. The volume CT dose indices for the head phantom were 22.26 mGy and 23.70 mGy, and those for body phantom were 12.30 mGy and 12.99 mGy for the first and second CT simulators, respectively. HU accuracy, noise, and homogeneity for the first CT simulator were -0.2 HU, 4.9 HU, and 0.69 HU, respectively, while those for second CT simulator were 1.9 HU, 4.9 HU, and 0.70 HU, respectively. Five air-filled holes with a diameter of 1.00 mm were used for assessment of spatial resolution and a low contrast object with a diameter of 6.4 mm was clearly discernible by both CT scanners. Both CT simulators exhibited comparable performance and are acceptable for clinical use.

• 한국지반환경공학회 논문집
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• 제18권1호
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• pp.31-35
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• 2017

Chae et al.(2015)에 따르면 동결 사질토의 역학적 거동은 동결온도와 세립분 함유량에 따라 크게 영향을 받는 것으로 나타났다. 이러한 원인으로 동결온도에 따른 부동수분의 차이일 것이라는 의견과 세립분 함유량 및 간극 내 얼음에 의해 사질토 입자들 이격거리 차이에 의한 것이라는 의견이 제시되었다. 제시된 두 가지 의견 중 사질토 입자들 이격거리의 확인을 위해 micro X-ray CT 촬영을 수행하였다. X-ray CT 촬영에 의한 비파괴 검사는 최근 지반공학 분야에서 진행되고 있는 다양한 융복합 연구 중 하나로 CT 촬영을 통하여 지반재료의 내부 구조를 마이크로미터 단위의 높은 해상도를 통해 평가할 수 있는 방법이다. 본 연구에서는 -5, -10, $-15^{\circ}C$의 동결온도에서 성형된 5, 10, 15%의 세립분을 포함하고 있는 동결 사질토 공시체에 대하여 micro X-ray CT 촬영을 수행하고 기존의 개발된 이미지 해석 기법을 적용하여 동결 사질토 내의 조립질 입자들의 최단거리 및 평균거리를 통하여 세립분 함유량 및 동결온도가 조립질 입자간의 거리에 미치는 영향을 파악하고자 하였다. X-ray CT 촬영 결과, 동결온도 및 세립분 함유량은 동결 사질토 내 입자간 거리에는 큰 영향을 미치지 않는 것으로 나타났다.