• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.404-406
• /
• 2002

We have investigated the contribution of the scattered x rays to the signal imaging in the radiographs acquired with anti-scatter grids of several grid ratios by separating the line spread functions (LSFs) derived from the signal edge image into the primary and the scatter components. By using a 1.0-mm lead plate in the scattering material, the blurred signal edge images were acquired by use of an imaging plate at a tube voltage of 80 kV with the anti-scatter grids of grid ratios for 5:1, 6:1, 8:1, 10:1 and 12:1. The edge profiles of the signal images were scanned and those in relative exposure were differentiated to obtain the LSFs. To investigate the contribution of the scattered x rays to the signal imaging, we proposed a method for separating the LSFs derived from the signal images into the primary and the scatter components, where the scatter component was approximated with exponential function. Our basic approach is to separate the area of the LSFs by ratios of the scattered x-ray exposure to the primary x-ray exposure, which were obtained for the grid ratios by use of a lead disk method. The LSFs and the two components were Fourier transformed to obtain the modulation transfer functions (MTFs) and their two components. As the result, we found that, by using the anti-scatter grids, the scattered x rays were reduced, but the shape of the LSFs of the scatter component hardly changed. The contributions of the scatter component to the MTFs were not negligible (more than 10 %) for spatial frequencies lower than about 1.0 mm$\^$-l/ and that was greater as the grid ratio decreasing. On the other hand, for higher frequencies, the primary component was dominant compared with the scatter component.

• 한국콘텐츠학회논문지
• /
• 제12권7호
• /
• pp.255-260
• /
• 2012

흉부 X-선 촬영 시 피사체의 유무, 촬영실내 X선관과 수광계 (image receptor), 환자 보기창 앞, 환자대기실 출입문 외측, 출입문 개폐여부, 방사선 관계 종사자 출입문 외측, 방사선 관계 종사자 출입문 개폐여부 등으로 구분하여 공간산란선발생을 알아보기 위한 연구로 공간산란선발생에 대한 연구 결과 피사체가 있을 때 수광계 (image receptor) 위치; Chest PA: $663{\pm}3.4$ mR/h, Chest Lateral: $2,067{\pm}3.7$ mR/h, X선관 위치; Chest PA: $293{\pm}2.1$ mR/h, Chest Lateral: $927{\pm}1.9$ mR/h, 환자대기실 출입문 외측 열고; Chest PA: $17{\pm}1.6$ mR/h, Chest Lateral: $88{\pm}2.6$ mR/h, 방사선 관계 종사자 촐입문 외측 열고; Chest PA: $3{\pm}1.6$ mR/h, Chest Lateral: $19{\pm}1.6$ mR/h), 피사체의 두께가 두꺼울수록 각 각의 측정지점에서 산란선 발생이 많았고, 출입문을 닫고 측정한 경우 산란선이 더 적었다. 그러므로 방사선 관계종사자는 촬영실내 산란선 분포에 대한 정확한 정보를 인지하여 불필요한 방사선 피폭을 줄일 수 있도록 노력해야 한다.

• Journal of Radiation Protection and Research
• /
• 제42권4호
• /
• pp.197-204
• /
• 2017

Background: X-ray imaging detectors for the nondestructive cargo container inspection using MeV-energy X-rays should accurately portray the internal structure of the irradiated container. Internal and external factors can cause noise, affecting image quality, and scattered radiation is the greatest source of noise. To obtain a high-performance transmission image, the influence of scattered radiation must be minimized, and this can be accomplished through several methods. The scatter rejection method using an anti-scatter grid is the preferred method to reduce the impact of scattered radiation. In this paper, we present an evaluation the characteristics of the signal and noise according to physical and material changes in the anti-scatter grid of the imaging detector used in cargo container scanners. Materials and Methods: We evaluated the characteristics of the signal and noise according to changes in the grid ratio and the material of the anti-scatter grid in an X-ray image detector using MCNP6. The grid was composed of iron, lead, or tungsten, and the grid ratio was set to 2.5, 12.5, 25, or 37.5. X-ray spectrum sources for simulation were generated by 6- and 9-MeV electron impacts on the tungsten target using MCNP6. The object in the simulation was designed using metallic material of various thicknesses inside the steel container. Using the results of the computational simulation, we calculated the change in the scatter-to-primary ratio and the signal-to-noise ratio improvement factor according to the grid ratio and the grid material, respectively. Results and Discussion: Changing the grid ratios of the anti-scatter grid and the grid material decreased the scatter linearly, affecting the signal-to-noise ratio. Conclusion: The grid ratio and material of the anti-scatter grid affected the response characteristics of a container scanner using high-energy X-rays, but to a minimal extent; thus, it may not be practically effective to incorporate anti-scatter grids into container scanners.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
• /
• pp.6-7
• /
• 2009

We proposed the two-dimensional (2D) / three-dimensional (3D) convertible modified integral imaging system using functional polarizing film named $imazer^{TM}$, which transfer or scatter the incident light ray according to the polarizing direction of ray. When the incident light rays transfer to $imazer^{TM}$, the rays generate 3D image through the process of the modified integral imaging system. However, the scattered light rays generate 2D image through the simple backlight scheme when the incident rays are scattered by the film. The proposed method can be implemented the partial 3D display system without any mechanical movements. In this paper, we propose and verify our system using some basic experiments and its results.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 1999년도 Japanese Journal of Medical Physics
• /
• pp.278-281
• /
• 1999

The purpose of this study is to investigate the effect of the scattered x-rays on the subject contrast and image sharpness for various tube voltages. For the purpose, we measured the scatter-to-primary ratio(SPR) for the tube voltages f 50 to 100kV and obtained the tube voltage dependence of the subject contrast of an aluminum plate in a polymethyl methacrylate(PMMA) phantom. Furthermore, the overall modulation transfer functions(MTFs), which consist of MTFs of a screen-film system and scatter FTMs, were obtained for tube voltages of 50 to 100 kV. The subject contrast decreased with the tube voltage due to that the SPR increased with the tube voltage and that the difference in effective linear attenuation coefficients between the object and its surroundings decreased with the tube voltage. The maximum frequency of the overall MTF decreased from about 2 mm$\^$-1/ to 1 mm$\^$-1/ with the tube voltage increasing from 50 to 100 kV.

• 대한방사선기술학회지:방사선기술과학
• /
• 제23권2호
• /
• pp.69-73
• /
• 2000

This paper studied a C-arm's exposure condition and measured scatter rays by thickness and distance. This study reached the following conclusion. 1. Approrimately exposure dose for a patient using fluoroscopy is as follows : 2. Mostly, an operating room was not shielding by lead and operator put on only apron without thyroid and facial part protection. 3. 0.5 mmPb equivalent's apron shielded about 99% of scattered rays at 60 cm from x-ray tube. 4. Scattered rays are depended on distance and thickness so operators are should be careful when using fluoroscopy by C-arm and if possible use high frequency equipment that has a large output.

• 한국방사선학회논문지
• /
• 제8권2호
• /
• pp.65-74
• /
• 2014

본 연구에서는 에너지 변화에 의하여 발생하는 콤프턴 산란이 화질에 영향을 미친다는 것을 증명하기 위하여 웨이브릿 변환으로 신호의 특성을 추출하였다. 추출된 데이터를 분석하여 에너지의 변화에 따른 산란선의 화질영향 정도를 평가하고자 하였다. 이를 위하여 공학용 도구인 MatLab Tool을 이용하여 프로그램을 작성하였고, 작성된 프로그램을 이용하여 관전압 증가에 따른 산란선의 변화를 평가하였다. 평가결과 CR과 DR 모두 관전압 변화에 따라서 고주파영역의 주파수 변화가 있는 것으로 보아 콤프턴 산란선의 영향이 있는 것으로 나타났다. 급격한 주파수의 변화가 나타나는 관전압 영역이 CR은 80 kVp, DR은 90 kVp로 나타난 것으로 보아 DR의 검출기는 에너지에 대한 민감도가 낮은 것으로 알 수 있다. 결론적으로 본 연구의 결과로 보아 CR보다는 DR이 에너지가 높은 방사선에 민감한 것으로 나타났다. 본 연구의 결과는 공학용 도구인 MatLab Tool을 이용한 영상의 화질평가 방법이 공식적인 화질평가의 방법으로 인정되어 유용하게 적용될 것을 기대한다.

• 대한방사선기술학회지:방사선기술과학
• /
• 제40권1호
• /
• pp.71-78
• /
• 2017

디지털 방사선영상 시스템에서 산란선은 피검사체와 엑스선의 반응에 의해 발생하는 근원적인 현상이다. 방사선 투사영상은 일차선에 의해 형성되는 감쇠정보를 영상화 하므로 산란선은 투사영상에서 노이즈로써 작용한다. 본 연구에서는 다양한 검사조건에서 발생하는 산란선을 빔 저지체(beam stopper)를 이용하여 정량화하고 동시에 반 산란 격자의 효과를 확인하였다. 또한 산란선이 영상의 품질에 미치는 영향을 확인하기 위해 산란선에 의해 저하되는 대조도 대 잡음비를 측정하였다. 본 연구를 통해 산란선은 피검사체의 두께 및 공기층(air gap)에 지배적인 경향을 가짐을 확인하였다. 또한 산란선은 영상의 대조도를 현격히 저하시킴을 정량적으로 측정하였다. 산란선을 저감하기 위해 격자를 장착함으로써 상당량의 산란선을 저감할 수 있었으나 여전히 두꺼운 피검사체에 대해 많은 양의 산란선이 남아 있음을 확인하였다. 본 연구에서는 산란선을 정량화 하는 방법론을 제시하였으며, 향후 시스템의 최적화에 중요한 역할을 할 수 있을 것으로 기대된다.

• 대한방사선기술학회지:방사선기술과학
• /
• 제43권4호
• /
• pp.259-264
• /
• 2020

Radiation causes radiation hazards in the human body. In Korea, a case of radiation necrosis occurred in 2014. In this study, the scatter and shielding efficiency according to lead shielding were classified into epidermis and dermis for 0.511 MeV used in nuclear medicine. In this study, experiments were conducted using the slab phantom that represents calibration and the dose of human trunk. Experimental results showed that the shielding rate of 0.25 mmPb was 180% in the epidermis and 96% in the dermis. Shielding at 0.5mmPb showed shielding rates of 158%in the epidermis and 82% in the dermis. As a result of measuring the absorbed dose by subdividing the thickness of the dermis into 0.5 mm intervals, when the shielding was carried out at 0.25 mmPb, the dose appeared to be about 120% at 0.5 mm of the dermis surface, and the dose was decreased at the subsequent depth. Shielding at 0.5 mmPb, the dose appeared to be about 101% at the surface 0.5 mm, and the dose was measured to decrease at the subsequent depth. This result suggests that when lead aprons are actually used, the scattering rays would be sufficiently removed due to the spaces generated by the clothes and air, Therefore, the scattered ray generated from lead will not reach the human body. The ICRU defines the epidermis (0.07), in which the radiation-induced damage of the skin occurs, as the dose equivalent. If the radiation dose of the dermis is considered in addition, it will be helpful for the evaluation of the prognosis for radiation hazard of the skin.

• 핵의학기술
• /
• 제22권1호
• /
• pp.46-50
• /
• 2018

검출기 외부에 강한 선원은 collimator와 상호 작용으로 산란선이 만들어지게 되는데, 그 산란선이 영상에 얼마나 영향을 주는지 평가하고자 한다. SKY LITE를 사용하여, phantom study의 경우, $^{99m}Tc$ 1.11 GBq를 점선원으로 만들어 검출기 주변을 $10^{\circ}$ 간격으로 돌아가면서 측정하여 각 각도에서의 산란선의 정도를 계수율과 스펙트럼으로 분석을 하였다. Patient study의 경우, 3-phase bone scan을 하는 환자를 대상으로, blood flow와 blood pool 영상을 획득하면서 산란선의 양과 스펙트럼을 분석하였다. 추가로 blood pool 검사 시, 환자의 손위에 납가운을 올려놓고 영상을 획득하였고, 환자의 몸에 납가운을 입히고 영상을 획득하여 각 영상에서의 산란선과 스펙트럼을 비교, 평가하였다. 그 결과, phantom study의 경우, 후방에서는 산란선의 없었지만, 측면부터 전방 $50^{\circ}$ 까지는 산란선이 많이 검출 되었다. patient study의 경우 blood flow 영상과 blood pool 영상에서 환자 몸에서 나온 감마선으로 인해 생긴 산란선이 입사됨을 알 수 있었다. 그리고 납가운은 손 위를 차폐하는것 보다, 환자 몸을 차폐 하는 것이 산란선이 많이 줄었다. 그러므로 외부에 강한 선원이 존재하고, hand blood flow, blood pool 검사처럼 계수 자체가 낮을 검사를 할 경우, 몸에서 나오는 선원 자체를 차폐하는 것이 산란선을 줄이는데 보다 효과가 있으며, 영상에서도 배후 방사선을 줄이는데 효과가 있음을 알 수 있었다.