• 한국인공지능학회지
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• 제9권2호
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• pp.1-5
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• 2021

Although CT has an advantage in describing the three-dimensional anatomical structure of the human body, it also has a disadvantage in that high doses are exposed to the patient. Recently, a deep learning-based image reconstruction method has been used to reduce patient dose. The purpose of this study is to analyze the dose reduction and image quality improvement of deep learning-based reconstruction (DLR) on the adult's chest CT examination. Adult lung phantom was used for image acquisition and analysis. Lung phantom was scanned at ultra-low-dose (ULD), low-dose (LD), and standard dose (SD) modes, and images were reconstructed using FBP (Filtered back projection), IR (Iterative reconstruction), DLR (Deep learning reconstruction) algorithms. Image quality variations with respect to varying imaging doses were evaluated using noise and SNR. At ULD mode, the noise of the DLR image was reduced by 62.42% compared to the FBP image, and at SD mode, the SNR of the DLR image was increased by 159.60% compared to the SNR of the FBP image. Based on this study, it is anticipated that the DLR will not only substantially reduce the chest CT dose but also drastic improvement of the image quality.

• Journal of Radiation Protection and Research
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• 제47권3호
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• pp.134-142
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• 2022

Background: This study investigated the characteristics of optically stimulated luminescence dosimeters (OSLDs) with fully filled deep electron/hole traps in the kV energy ranges. Materials and Methods: The experimental group consisted of InLight nanoDots, whose deep electron/hole traps were fully filled with 5 kGy pre-irradiation (OSLD_exp), whereas the non-pre-irradiated OSLDs were arranged as a control group (OSLD_cont). Absorbed doses for 75, 80, 85, 90, 95, 100, and 105 kVp with 200 mA and 40 ms were measured and defined as the unit doses for each energy value. A bleaching device equipped with a 520-nm long-pass filter was used, and the strong beam mode was used to read out signal counts. The characteristics were investigated in terms of fading, dose sensitivities according to the accumulated doses, and dose linearity. Results and Discussion: In OSLD_exp, the average normalized counts (sensitivities) were 12.7%, 14.0%, 15.0%, 10.2%, 18.0%, 17.9%, and 17.3% higher compared with those in OSLD_cont for 75, 80, 90, 95, 100, and 105 kVp, respectively. The dose accumulation and bleaching time did not significantly alter the sensitivity, regardless of the filling of deep traps for all radiation qualities. Both OSLD_exp and OSLD_cont exhibited good linearity, by showing coefficients determination (R²) > 0.99. The OSL sensitivities can be increased by filling of deep electron/hole traps in the energy ranges between 75 and 105 kVp, and they exhibited no significant variations according to the bleaching time.

• 한국방사선학회논문지
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• 제12권4호
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• pp.443-450
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• 2018

Geant4 코드는 직선 가속기의 헤드 구조를 사용하여 이전에 구현된 BEAMnrC 데이터를 기반으로 선형가속기 (VARIAN CLINAC.)를 시뮬레이션하였다, 10MV 광자 선속에서 물팬텀의 심부선량백분율과 측면선량의 측정값과 Geant4를 비교 평가하였다. 선량 계산을 인체부위에 적용하기 위해 실제 환자의 Lung 부위를 5mm 간격으로 스캔하였다. Water phantom의 조사야($5{\times}5cm^2$), SAD 100cm에서 10MV 광자를 조사하여 Geant4 선량분포를 구하였다. 이 결과는 실제 환자의 폐(lung)에 흡수되는 선량을 측정하기는 어렵다 그래서 치료계획 시스템에 의한 선량을 비교하였다. 물 팬텀에서 측정된 심부선량 곡선과 Geant4에 의해 계산된 심부선량 곡선은 build-up 영역을 제외한 대부분의 깊이에서 ${\pm}3%$ 이내로 잘 일치하였다. 그러나 5cm와 20cm 지점에서 2.95%와 2.87%로 Geant4를 사용한 선량 계산에서 다소 높은 값을 보이고 있다. 이 두 지점은 Genat4의 geometry 파일을 통해 확인할 수 있었으며, 흉추와 흉골이 위치되어 선량이 증가된 것으로 알 수 있었다. 또한, cone beam CT를 적용한 결과에서 폐(lung)의 선량분포 오차는 3% 이내로 유사한 값을 얻었다. 따라서 Geant4를 이용하여 선량을 계산할 때 DICOM 파일에 직접 선량의 contour map이 표현될 수 있다면 Geant4의 임상적 적용이 다양하게 사용될 것이다.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2187-2193
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• 2002

We present a novel method for 3D microfabrication with LIGA process that utilizes a deep X-ray mask in which a micro-actuator is integrated. The integrated micro-actuator oscillates the X-ray absorber, which is formed on the shuttle mass of the micro-actuator, during X-ray exposures to modify the absorbed dose profile in X-ray resist, typically PMMA. 3D PMMA microstructures according to the modulated dose contour are revealed after GG development. An X-ray mask with integrated comb drive actuator is fabricated using deep reactive ion etching, absorber electroplating, and bulk micromachining with silicon-on-insulator (SOI) wafer. 1mm $\times$ 1 mm, 20 $\mu$m thick silicon shuttle mass as a mask blank is supported by four 1 mm long suspension beams and is driven by the comb electrodes. A 10 $\mu$m thick, 50 $\mu$m line and spaced gold absorber pattern is electroplated on the shuttle mass before the release step. The fundamental frequency and amplitude are around 3.6 kHz and 20 $\mu$m, respectively, for a do bias of 100 V and an ac bias of 20 $V_{p-p}$ (peak-peak). Fabricated PMMA microstructure shows 15.4 $\mu$m deep, S-shaped cross section in the case of 1.6 kJ $cm^{-3}$ surface dose and GG development at 35$^{\circ}C$ for 40 minutes.

• Radiation Oncology Journal
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• 제36권1호
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• pp.79-84
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• 2018

Deep inspiration breathing hold (DIBH) compared to free-breathing (FB) during radiotherapy (RT) has significantly decreased radiation dose to heart and has been one of the techniques adopted for patients with breast cancer. However, patients who are unable to make suitable deep inspiration breath may not be eligible for DIBH, yet still need to spare the heart and lung during breast cancer RT (left-sided RT in particular). Continuous positive airway pressure (CPAP) is a positive airway pressure ventilator, which keeps the airways continuously open and subsequently inflates the thorax resembling thoracic changes from DIBH. In this report, authors applied CPAP instead of FB during left-sided breast cancer RT including internal mammary node in a patient who was unable to tolerate DIBH, and substantially decreased radiation dose the heart and lung with CPAP compared to FB.

• Journal of Dental Anesthesia and Pain Medicine
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• 제19권3호
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• pp.151-158
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• 2019

Background: This study aimed to examine whether the combination of low-dose ketamine and propofol in deep sedation is clinically useful in controlling the behavior in intellectually disabled patients who are typically extremely noncooperative during dental procedures. Methods: A total of 107 extremely noncooperative intellectually disabled adult patients were analyzed. In all patients, deep sedation was performed using either propofol alone (group P) or using a combination of propofol and 0.2 mg/kg or 0.4 mg/kg ketamine (groups PK0.2 and PK0.4, respectively). The procedures were performed in the order of insertion of nasal cannula into the nostril, attachment of mouth gag, and mouth cleaning and scaling. The frequency of patient movement during the procedures, mean arterial pressure, heart rate, peripheral oxygen saturation, recovery time, discharge time, and postoperative nausea and vomiting were examined. Results: The three groups were significantly different only in the frequency of patient movement upon stimulation during single intravenous injection of propofol and scaling. Conclusion: For propofol deep sedation, in contrast to intravenous injection of propofol alone, prior intravenous injection of low-dose ketamine (0.4 mg/kg) is clinically useful because it neither affects recovery, nor causes side effects and can suppress patient movement and vascular pain during procedures.

• Journal of Applied Biological Chemistry
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• 제59권3호
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• pp.227-231
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• 2016

Deep sea water (DSW) is located 100 to 500 m below the sea surface. DSW is widely used in various fields, and is an important source of minerals that can be used to treat mineral deficiency. In the present study, the oral toxicity of DSW-mineral extracts was determined using single-dose and 14-day repeated dose oral toxicity tests in ICR mice. For the single-dose oral toxicity tests, mineral extracts of magnesium (Mg) and calcium (Ca) at doses of 0, 6, 270, 810, and 1,350 mg/kg, respectively, were orally administered to mice once at the beginning of the experiment, and the mice were observed for 14 days. For the 14-day repeated dose oral toxicity tests, Mg and Ca mineral extracts at doses of 0, 3, 135, 405, 675 mg/kg, respectively, were orally administered to mice daily, and the mice were observed for 14 days. Various tests were performed including visual observation; analysis of relative organ weight, food intake, and organ weight; biochemical analysis, and histopathology. The results indicated that mortality and changes in appearance were not observed among differentially administered groups of male and female ICR mice during the experimental period. Differences in body weight gain, food intake, organ weight, and histopathology parameters were not significant between the control and mineral-administered groups. Some results of the biochemical analyses were significantly different, but showed no specific tendencies. Overall, no evidence of toxicity was observed from the oral administration of DSW extracts of Ca and Mg in ICR mice.

• Korean Journal of Radiology
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• 제23권4호
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• pp.402-412
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• 2022

Objective: To evaluate the image quality and lesion detectability of lower-dose CT (LDCT) of the abdomen and pelvis obtained using a deep learning image reconstruction (DLIR) algorithm compared with those of standard-dose CT (SDCT) images. Materials and Methods: This retrospective study included 123 patients (mean age ± standard deviation, 63 ± 11 years; male:female, 70:53) who underwent contrast-enhanced abdominopelvic LDCT between May and August 2020 and had prior SDCT obtained using the same CT scanner within a year. LDCT images were reconstructed with hybrid iterative reconstruction (h-IR) and DLIR at medium and high strengths (DLIR-M and DLIR-H), while SDCT images were reconstructed with h-IR. For quantitative image quality analysis, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured in the liver, muscle, and aorta. Among the three different LDCT reconstruction algorithms, the one showing the smallest difference in quantitative parameters from those of SDCT images was selected for qualitative image quality analysis and lesion detectability evaluation. For qualitative analysis, overall image quality, image noise, image sharpness, image texture, and lesion conspicuity were graded using a 5-point scale by two radiologists. Observer performance in focal liver lesion detection was evaluated by comparing the jackknife free-response receiver operating characteristic figures-of-merit (FOM). Results: LDCT (35.1% dose reduction compared with SDCT) images obtained using DLIR-M showed similar quantitative measures to those of SDCT with h-IR images. All qualitative parameters of LDCT with DLIR-M images but image texture were similar to or significantly better than those of SDCT with h-IR images. The lesion detectability on LDCT with DLIR-M images was not significantly different from that of SDCT with h-IR images (reader-averaged FOM, 0.887 vs. 0.874, respectively; p = 0.581). Conclusion: Overall image quality and detectability of focal liver lesions is preserved in contrast-enhanced abdominopelvic LDCT obtained with DLIR-M relative to those in SDCT with h-IR.

• 한국방사선학회논문지
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• 제17권2호
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• pp.249-255
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• 2023

본 연구는 방사선작업종사자, 방사선관계종사자 그룹의 방사선사들과 수시출입자로 분류된 예비 방사선사인 재학생의 임상실습 과정에서의 피폭선량을 측정하였다. 2021년 1월부터 1년 동안 인천소재의 C 대학병원의 방사선구역에서 근무하였던 방사선사들과 동 의료기관에서 7월 1일부터 8월 31일까지 임상실습을 이수한 121명의 학생들을 연구대상으로 하였다. 방사선 피폭선량으로 인하여 손상위험장기인 폐의 피폭선량으로 인한 부작용 발생확률을 평가하기 위하여 ICRP 103^[12]에 의거한 명목위험계수(Nominal Risk Factor)를 사용하였다. 임상실습기간 중 수시출입자로 분류된 방사선(학)과 학생들의 표층선량은 0.98 ± 0.14 mSv, 심부선량은 0.93 ± 0.14 mSv였다. 즉, 표층선량은 1,000,000당 6.7명, 심부선량은 6.4명이 폐의 피폭선량으로 인한 부작용 발생률이 있음이 나타났다. 이는 1년 피폭선량의 환산 값으로 방사선(학)과 교육과정이 3년 혹은 4년임을 고려하였을 때, 임상실습을 나가는 예비 방사선종사자들에 대한 체계적인 관리와 관심이 필요하며, 방사선의 확률적 영향과 관련하여 방사선 안전관리를 위한 기초자료로 활용될 것으로 사료된다.

• 전자공학회논문지D
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• 제35D권9호
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• pp.54-61
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• 1998

Deep submicron급 CMOS디바이스에서 래치업 면역특성을 향상시키기 위한 새로운 Triple well구조를 제안하였다. Triple well에서 이온주입 에너지와 도즈량 변화에 따른 최적인 래치업 면역을 위한 공정조건을 확립하고 이것을 기존의 Twin well구조와 비교분석하였다. 공정은 공정시뮬레이터인 ATHENA로 소자를 제작하여 도핑프로파일과 구조를 해석하고 래치업 특성은 소자시뮬레이터인 ATLAS를 사용하였다. Triple well과 Twin well의 구조에서 공정상의 차이가 도핑프로파일에 미치는 영향과 프로파일 형태가 래치업 특성에 미치는 영향을 규명하였다. Triple well구조에서 p-well이온주입에너지 2.5MeV, 도즈량 1×10/sup 14/[cm/sup -2/]일 때 트리거 전류가 2.5[mA/${\mu}{m}$]로 매우 큰 래치업 면역특성을 얻었다.