• 한국치위생학회지
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• 제20권3호
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• pp.269-279
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• 2020

Objectives: Previous studies have reported inconsistent findings in the association between dental diagnostic X-ray exposure and thyroid cancer. This study was a meta-analysis of case-control studies evaluating the association between exposure to dental radiation and the thyroid cancer risk. Methods: We searched the PubMed and EMBASE databases to identify studies on dental radiation and thyroid cancer risks that were published up to September 2018. Quality of studies was assessed using the Newcastle-Ottawa scale. A fixed-effects model was used to estimate pooled odds ratios (ORs) and 95% confidence intervals (CIs) using STATA 14.0. Potential publication biases were evaluated using Egger's test and Begg's funnel plot. Results: From the literature search, we included six case-control studies in this meta-analysis. The meta-analysis using the fixed-effects model found that dental X-ray exposure was associated with 2.34 times increased risk for thyroid cancer (OR=2.34, 95% CI=1.79-3.21). There was no heterogeneity in the data (p=0.662, I² =0%). Egger's test showed that there was no publication bias (p=0.532). Conclusions: This meta-analysis confirmed the association of dental X-ray exposure and thyroid cancer risk. The current results underscore the importance of applying safety regulations at dental clinics to protect thyroid glands during dental radiography examinations.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.418-421
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• 2002

Fundamental study on quasi-monochromatic parallel radiography using a polycapillary plate and a plane-focus x-ray tube is described. The x-ray generator consists of a negative high-voltage power supply, a filament (hot cathode) power supply, and an x-ray tube. The negative high-voltage is applied to the cathode electrode, and the transmission type target (anode) is connected to the ground potential. The maximum voltage and current of the power supply were -100 kV (peak value) and 3.0 mA, respectively. In this experiment, the tube voltage was regulated from 20 to 25 kV, and the tube current was regulated by the filament temperature and ranged from 1.0 to 3.0 mA. The exposure time is controlled in order to obtain optimum film density, and the focal spot diameter was about 10 mm. The polycapillary plate is J5022-21 made by Hamamatsu Photonics Inc., and the outside and effective diameters are 87 and 77 mm, respectively. The thickness and the hole diameter of the polycapillary are 1.0 mm and 25 ${\mu}$m, respectively. The x-rays from the tube are formed into parallel beam by the polycapillary, and the radiogram is taken using an industrial x-ray film of Fuji IX 100 without using a screen. In the measurement of image resolution, we employed three brass spacers of 2, 30, and 60 mm in height. By the test chart, the resolution fell according to increases in the spacer height without using a polycapillary. In contrast, the resolution slightly fell with corresponding increases in the height by the polycapillary. In angiography, fine blood vessels of about 100 ${\mu}$m are clearly visible.

• 보존과학회지
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• 제37권3호
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• pp.220-231
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• 2021

문화재 방사선 비파괴 투과 조사 방식은 이미지플레이트(Image Plate, IP)를 사용하는 디지털 방사선영상시스템(Computed Radiography, CR)이 도입되면서 필름방식의 아날로그 이미지에서 점차 디지털 이미지로 교체되고 있다. 방사선 비파괴 투과 조사의 이미지 품질은 촬영 조건(관전압, 관전류, 노출시간), 영상 획득 매체, 촬영 거리, 유물의 두께 등이 영향을 미친다. 이 논문에서는 목재 문화재에 주로 사용되는 수종(소나무, 밤나무, 은행나무, 상수리나무)에 X선 선원의 투과 특성을 GE사(社)의 CR 영상 시스템을 통해 획득된 이미지의 그레이 스케일(Gray Scale)을 분석한 후 신호 대 잡음비(signal to noise ratio) 및 대조도를 평가하고, 이중-선 상질계(Duplex-wire image quality indicator), 구형파 차트(line-pair gauges), 선형 식별계(Image Quality Indicator)를 이용하여 이미지를 분석하였다.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1377-1384
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• 2018

Accurate measurement of the absorbed dose and the effective dose is required in dental panoramic radiography involving relatively low energy with a rotational X-ray tube system using long exposures. To determine the effectiveness of measuring the irradiation by using passive dosimetry, we compared the entrance skin doses by using a radiophotoluminescent glass dosimeter (RPL) and an optically stimulated luminescence detector (OSL) in a phantom model consisting of nine and 31 transverse sections. The parameters of the panoramic device were set to 80 kV, 4 mA, and 12 s in the standard program mode. The X-ray spectrum was applied in the same manner as the panoramic dose by using the SpekCalc Software. The results indicated a mass attenuation coefficient of $0.008226cm^2/g$, and an effective energy of 34 keV. The equivalent dose between the RPL and the OSL was calculated based on a product of the absorbed doses. The density of the aluminum attenuators was $2.699g/cm^3$. During the panoramic examination, tissue absorption doses with regard to the RPL were a surface dose of $75.33{\mu}Gy$ and a depth dose of $71.77{\mu}Gy$, those with regard to the OSL were surface dose of $9.2{\mu}Gy$ a depth dose of $70.39{\mu}Gy$ and a mean dose of $74.79{\mu}Gy$. The effective dose based on the International Commission on Radiological Protection Publication 103 tissue weighting factor for the RPL were $0.742{\mu}Sv$, $8.9{\mu}Sv$, $2.96{\mu}Sv$ and those for the OSL were $0.754{\mu}Sv$, $9.05{\mu}Sv$, and $3.018{\mu}Sv$ in the parotid and sublingual glands, orbit, and thyroid gland, respectively. The RPL was more effective than the OSL for measuring the absorbed radiation dose in low-energy systems with a rotational X-ray tube.

• 대한방사선기술학회지:방사선기술과학
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• 제2권1호
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• pp.85-88
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• 1979

When X-radiation passes through the human body; some is transmitted some is truly absorbed, and some is scattered. In diagnostic radiography, scattered radiation can reach the film if no protective measures are taken. This scattered ray increased density which not necessary for image formation. We studied about absorbtion, scattered ray and the way of get rid of scatter ray according to the x-ray tube kilovoltage and obtained results as follow; 1. Absorbtion ray increased proportion to KVP. 2. Scattered ray increased at high KVP and thick object. 3. Secondary radiation of the primary increased at high KVP and thick object. 4. Remove .ate of scattered ray decreased at thick object and increase at low KVP make use of 6:1 grid ratio

• 대한방사선기술학회지:방사선기술과학
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• 제28권4호
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• pp.273-277
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• 2005

디지털 의료 영상의 빠른 발전은 새로운 기술-비정질 평판형 측정기-에 대한 최적의 기술이 동행되지 못했다. 이번 실험으로 비정질 평판형 측정기를 사용한 흉부 방사선 영상의 대한 환자선량과 영상의 화질에 대하여 비교하였다. 모든 실험은 비정질 평판형 측정기를 사용하였다. 흉부 팬텀을 사용한 흉부 방사선영상은 관전압 $60{\sim}150\;kVp$에서 획득하였다. 이번 실험을 통하여 획득된 비정질 평판형 측정기를 사용한 X-선 에너지에 대한 영상의 질과 환자선량에 관련된 정보들을 보고한다. 이 정보는 비정질 평판형 측정기를 사용한 시스템에서 최적의 관전압의 선정에 효과적인 정보를 제공하며, 특히 일반적인 흉부 검사에 적용될 수 있을 것이다.

• 한국방사선학회논문지
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• 제6권1호
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• pp.39-45
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• 2012

기존 구내 치근단 촬영용 장치는 환자 피폭선량, 촬영시 고통 등의 문제점을 지니고 있다. 본 연구에서는 이러한 문제점을 해결하기 위한 신개념의 삽입형 초소형 X선 시스템의 가능성을 검증하였다. 먼저 초소형 X선 튜브에 사용될 콜리메이터와 필터를 설계하기 위하여 Geant4를 이용하여 최적의 콜리메이터 두께와 필터 두께를 결정하였으며 CdTe 검출기와 PX4 모듈을 이용하여 결정된 두께에서의 X선 스펙트럼을 확인하였다. 또한 기존 상용화된 치근단 촬영장치와 XOFT사의 초소형 X선 튜브를 이용하여 제작된 치아 팬텀에 대한 영상을 획득하였다. 그 결과 제안된 신개념의 삽입형 초소형 X선 시스템은 기존 시스템과 유사한 영상의 질을 나타내었다. 이는 향후 치근단 촬영용 장치를 비롯하여 다양한 응용부위에 활용할 수 있음을 나타낸다.

• 대한의용생체공학회:의공학회지
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• 제12권1호
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• pp.35-42
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• 1991

In this paper, the information capacity, the intergrate performance measure of digital radiography system has been quantitatively analyzed. The effect of various factors affecting the information capacity of the digital radiography system in multistage detection processes has been considered and analyzed In detail. The results show that the more information capacity can be obtained with the smaller detector cell area, despite of the reduced signal to noise ratio due to the reduced number of X ray photons per detector cell. Considering the limit of human visual acuity, however. the sufficient resolution will be obtained when the detector cell size in $0.2{\times}0.2\textrm{mm}^2$ with 8 bit quantizaion. And also the results indicates that the information capacity may be severely reduced by the mixture of electric noise in final read-out stage.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2017년도 제55차 동계학술대회논문집 25권1호
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• pp.235-238
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• 2017

This study was to develop a portable digital radiography (PDR) system with a function measuring the X-ray source-with-detector angle (SDA) and to evaluate the imaging performance for the diagnosis of chest imaging. The SDA device consisted of an Arduino, an accelerometer and gyro sensor, and a Bluetooth module. According to different angle degrees, five anatomical landmarks on chest images were assessed using a 5-point scale. Mean signal-to-noise ratio and contrast-to-noise ratio were 182.47 and 141.43. Spatial resolution (10% MTF) and entrance surface dose were 3.17 lp/mm ($157{\mu}m$) and 0.266mGy. The angle values of SDA device were not significant difference as compared to those of the digital angle meter. In chest imaging, SNR and CNR values were not significantly different according to different angle degrees (repeated-measures ANOVA, p>0.05). The visibility scores of the border of heart, 5th rib and scapula showed significant differences according to different angles (rmANOVA, p<0.05), whereas the scores of the clavicle and 1st rib were not significant. It is noticeable that the increase in SDA degree was consistent with the increase of visibility score. Our PDR with SDA device would be useful to be applicable to clinical radiography setting according to the standard radiography guideline at various fields.

• Imaging Science in Dentistry
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• 제35권4호
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• pp.203-205
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• 2005

Purpose: This study was aimed to compare skin entrance dose of digital radiography with that of film radiography and to show the dose reduction achievement with digital systems at 11 dental schools in Korea. Materials and Methods: Forty six intraoral radiographic systems in 11 dental schools were included in this study. Digital sensors were used in 33 systems and film was used in 13 systems. Researchers and the volunteer visited 11 dental schools in Korea. Researchers asked the radiologic technician (s) at each school to set the exposure parameters and aiming the x-ray tube for the periapical view of the mandibular molar of the volunteer. The skin entrance doses were measured at the same exposure parameters and distance by the technician for each system with a dosimeter (Multi-O-Meter : Unfors instruments, Billdal, Sweden). Results: The median dose was $491.2{\mu}Gy$ for digital radiography and $1,205.0{\mu}Gy$ for film radiography. The skin entrance dose in digital radiography was significantly lower than that of film radiography (p<0.05). Conclusion: Fifty-nine percent skin entrance dose reduction with digital periapical radiography was achieved over the film radiography in Korean dental schools.