• Journal of Radiation Protection and Research
• /
• 제41권2호
• /
• pp.111-115
• /
• 2016

Background: The scattered photons cause reduction of the contrast of radiographic image and it results in the degradation of the quality of the image. In order to acquire better quality image, an anti-scattering x-ray gird should be equipped in radiography system. Materials and Methods: The X-ray anti-scattering grid of the inclined type based on the hybrid concept for that of parallel and focused type was tested by MCNP code. The MCNPX 2.7.0 was used for the simulation based test. The geometry for the test was based on the IEC 60627 which was an international standard for diagnostic X-ray imaging equipment-Characteristics of general purpose and mammographic anti-scatter grids. Results and Discussion: The performance of grids with four inclined shielding material types was compared with that of the parallel type. The grid with completely tapered type the best performance where there were little performance difference according to the degree of inclination. Conclusion: It was shown that the grid of inclined type had better performance than that of parallel one.

• 대한방사선치료학회지
• /
• 제21권1호
• /
• pp.9-15
• /
• 2009

목 적: 음경암(carcinoma of the penis)의 방사선치료 시 발생되는 산란선으로부터 고환(testis)을 보호하고, 치료 자세 재현성을 유지하기 위한 device를 제작하여 유용성을 평가하였다. 대상 및 방법: 팬텀(Phantom)고환은 바셀린 거즈로 제작하였으며, device는 두께 5 mm 아크릴과 4 mm 납으로 제작하였다. 조사야는 $3{\times}3\;cm^2$, $4{\times}4\;cm^2$, $5{\times}5\;cm^2$, $6{\times}6\;cm^2$, $7{\times}7\;cm^2$ 그리고 조사야 경계면에서부터 고환의 거리는 4~10 cm까지 1 cm 간격으로 이격(離隔)하였으며, 팬텀고환 부위의 산란선량을 차폐 전과 후 각각 10회 측정하였다. 6 MV X선을 이용하여 200 cGy를 조사하였다. 결 과: 미차폐 시 거리(4~10 cm)에 따라 14.8~4.7 cGy ($3{\times}3\;cm^2$), 15.7~5.2 cGy ($4{\times}4\;cm^2$), 17.6~5.5 cGy ($5{\times}5\;cm^2$), 19.9~6.6 cGy ($6{\times}6\;cm^2$), 22.2~7.6 cGy (7x7 cm2)의 산란선량이 측정 되었고, 차폐 시에는 7.1~2.6 cGy ($3{\times}3\;cm^2$), 8.9~3.6 cGy ($4{\times}4\;cm^2$), 12.3~4.8 cGy (5x5 cm2), 14.6~5.0 cGy ($6{\times}6\;cm^2$), 21.1~6.4 cGy ($7{\times}7\;cm^2$)로 감소하였으며, 차폐 전과 후 감소폭은 조사야 크기($3{\times}3~7{\times}7\;cm^2$)에 따라 7.8∼1.1 cGy (4 cm), 5.1~1.2 cGy (5 cm), 3.8~1.1 cGy (6 cm), 3.4~1.7 cGy (7cm), 2.8~1.7 cGy (8 cm), 2.4~2.5 cGy (9 cm), 2.1~1.8 cGy (10 cm) 거리에(4∼10 cm)에 따른 감소폭은 7.8~2.1 cGy ($3{\times}3\;cm^2$), 6.9~1.6 cGy ($4{\times}4\;cm^2$), 5.3~0.8 cGy ($5{\times}5\;cm^2$), 5.3~1.5 cGy ($6{\times}6\;cm^2$), 1.1~1.8 cGy ($7{\times}7\;cm^2$) 측정되었다. 결 론: 음경암의 방사선치료 시 자체 제작한 device를 사용하여 팬텀고환 주변의 산란선 측정결과 device 사용 시 거리를 이격과 팬텀고환 주위를 차폐함으로 불필요한 피폭을 줄 일수 있었다.

• 한국방사선학회논문지
• /
• 제13권4호
• /
• pp.589-596
• /
• 2019

진단방사선 영상을 획득하기 위해 이용되는 X-ray는 연속적인 에너지 분포를 가지지만 저에너지 광자의 경우에는 영상 형성 보다는 환자피폭에 더 많은 기여를 하는 것으로 알려져 있다. 이러한 저에너지 광자를 제거하기 위해 임상에서는 알루미늄 필터를 적용하고 있으나 이는 빔 경화 현상으로 인한 영상 품질에 악영향을 미칠 가능성이 있다. 이에 본 연구에서는 알루미늄 필터에 의한 산란 선량이 의료 영상의 품질에 미치는 영향에 대하여 고찰하고자 하였다. 또한, 영상의 대조도 저하를 정량적으로 표현하기 위해 상대 표준 편차 및 산란 열화 인자를 평가 지표로서 활용하였다. 연구 결과, 70 kVp 이상의 전압에서 진단 영상을 확보 시 NCRP에 의해 권장되는 2.5 mmAl를 기준에서 전방산란율 분석 결과 0.69 %, 산란 열화 인자 분석 결과는 0.005, NNPS 분석 결과 3.59 mm2의 변화가 나타났다. 이러한 연구 결과를 바탕으로 알루미늄 필터의 두께가 증가함에 따라 발생하는 산란 선량이 의료 영상의 품질을 저하시키는 것을 정량적으로 검증하였다.

• Applied Microscopy
• /
• 제33권2호
• /
• pp.117-130
• /
• 2003

본 연구는 6 MeV LINAC에서 발생한 X-선을 생쥐 생체에 조사한 후, 방사선 조사선량에 따른 난소 조직의 미세구조적 변화를 광학 및 전자현미경으로 관찰하였다. X-선을 200 cGy의 선량을 조사한 후 적출한 난소조직에서 성장난포의 과립층세포는 핵이 응축되어 나타났고, 난자를 둘러싸고 있는 투명층은 정상 대조군에서보다 경계가 불규칙하게 관찰되었다. 400 cGy로 조사된 난소조직에서 과립층세포는 대부분 응축된 핵을 가지고 있었으며, 피폭된 과립층세포의 사멸에 의한 세포질의 단백질 변성이 확인되었다. 600 cGy의 선량을 조사한 난소의 조직표본에서 성장난포는 위축되어 있었으며, 난포동에는 백혈구가 침윤되어 있었고, 난포액은 정상난포와 달리 불균질한 물질로 채워져 있었다. 투과전자현미경으로 관찰한 결과, 200 cGy의 방사선을 조사한 성장난포에서 과립층세포는 정상난포와는 달리 불규칙한 모양을 하고 있었다. 과립세포 사이의 난포동에는 많은 세포성분의 부스러기가 산재하여 있었으며, 이들 주변에 호중구와 대식세포가 관찰되어, 이 시기에 이미 방사선 피폭에 의한 세포사의 기작이 진행되고 있음이 확인되었다. X-선을 600 cGy로 조사한 난소조직의 과립층세포는 세포의 형태나 핵의 변형이 현저하여, 일부 세포는 핵의 분절화가 진행되는 등, apoptosis의 전형적인 특징이 관찰되었다. 특히 성장난포의 난포동에서는 염증반응에 관여하는 호중구가 잘 관찰되었으며, 주변에 산재된 세포 파쇄물 및 apoptotic body와 함께 대식세포의 출현도 확인되었다.

• 한국응용과학기술학회지
• /
• 제15권4호
• /
• pp.11-20
• /
• 1998

The propagation of light radiation in a turbid medium is an important problem that confronts dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. Scattered light is measured as a function of the position(distance r, depth z) between the axis of the incident beam and the detection spot. Turbid sample yields a very forward-directed scattering pattern at short range of position from source to detector, whereas the thicker samples greatly attenuated the on-axis intensity at long range of position. The portions of scattered light reflected from or transmitted throughphantom depend upon internal reflectance and absorption properties of the phantom. Monte Carlo simulation method for modelling light transport in tissue is applied. It uses the photon is moved a distance where it may be scattered, absorbed, propagated, internally reflected, or transmitted out of tissue. The photon is repeatedly moved until it either escape from or is absorbed by the phantom. In order to obtain an optimum therapeutic ratio in phantom material, optimum control the light energy fluence rate is essential. This study is to discuss the physical mechanisms determining the actual light dose in phantom. Permitting a qualitative understanding of the measurements. It may also aid in designing the best model for laser medicine and application of medical engineering.

• 천문학회보
• /
• 제41권2호
• /
• pp.33.2-34
• /
• 2016

The unification model of active galactic nuclei invokes the presence of a thick molecular torus that hides the broad emission line region from a line of sight toward observers with low latitude. It is expected that the illuminated side of the molecular torus may be photodissociated by strong far UV radiation from the central AGN, forming an H I region with a high neutral column density. We propose that the Rayleigh scattering optical depth of this HI region can be significant for most broad $Ly{\alpha}$ line photons with the Doppler factor not exceeding 104 km s-1. Rayleigh scattered $Ly{\alpha}$ photons can be characterized by strong linear polarization depending on their scattering optical depth. We performed Monte Carlo simulations of polarized radiative transfer of $Ly{\alpha}$ adopting simple scattering geometries relevant to the unification model of AGN. We find that for a low torus the Rayleigh scattered $Ly{\alpha}$ is polarized in the direction parallel to the symmetry axis with the polarization degree dependent on wavelength. In the case of a high torus, the core part of $Ly{\alpha}$ is polarized in the direction perpendicular to the symmetry axis whereas the wing part is parallelly polarized. We conclude that careful spectropolarimetry around $Ly{\alpha}$ can be useful in testing the AGN unification model.

• 대한방사선기술학회지:방사선기술과학
• /
• 제23권2호
• /
• pp.63-67
• /
• 2000

The purpose of this study is to survey the present status of portable radiography and the result of free space scattered dose rate when taking a radiography at the general hospital or the university hospital in Taejon city. The results were as follows; 1. The number of cases using portable radiography for three years increased to averages 16.2%, 7.7% per year from January 1st in 1996 to December 31st in 1998. 2. The average of distance of adjacent patients was 219.1 cm at the ward. 3. For portable chest radiography, the free space scattered dose rate was 10.5 mSv/hr at 50 cm distance, 1.8 mSv/hr at 100 cm distance, and 0.2 mSv/hr at 200 cm distance. Therefore, in case of portable chest radiography at the ward, the average of distance of adjacent patients is 219.1 cm, so it does not have influence on the adjacent patients. But during the portable radiography, a guardian who is close to the patient, doctor, nurse and radiologic technologists has to set up the shield to prevent from the unnecessary radiation or the distance should be as great as possible from the mobile X-ray equipment.

• 한국임상수의학회지
• /
• 제40권6호
• /
• pp.429-437
• /
• 2023

In veterinary medicine, most radiographic images are obtained by restraining patients, inevitably exposing the restrainer to secondary scattered radiation. Radiation exposure can result in stochastic reactions such as cancer and genetic effects, as well as deterministic reactions such as skin burns, cataracts, and bone marrow suppression. Radiation-shielding equipment, including aprons, thyroid shields, eyewear, and gloves, can reduce radiation exposure. However, the risk of radiation exposure to the upper arms, face, and back remains, and lead aprons and thyroid shields are heavy, restricting movement. We designed a new radiation-shielding system and compared its shielding ability with those of conventional radiation-shielding systems. We hypothesized that the new shielding system would have a wider radiation-shielding range and similar shielding ability. The radiation exposure dose differed significantly between the conventional and new shielding systems in the forehead, chin, and bilateral upper arm areas (p < 0.001). When both systems were used together, the radiation-shielding ability was better than when only one system was used at all anatomical locations (p < 0.01). This study suggests that the new radiation-shielding system is essential and convenient for veterinary radiation workers because it is a step closer to radiation safety in veterinary radiography.

• 한국해양공학회지
• /
• 제30권3호
• /
• pp.151-160
• /
• 2016

The diffraction and radiation of linear waves by an array of truncated floating multiple buoys are solved using the interaction theory based on a matched eigenfunction expansion method (MEEM). The interaction processes between multiple buoys are very complex and numerous, because the scattered and radiated waves from each buoy affect the others in the array. Our primary aim is therefore to construct the rigorous wave exciting forces and hydrodynamic forces to deal with the problem of multiple interactions. This present method is applied to a square array of four buoys with two incidence angles, and the results are given for the wave excitation forces on each buoy, heave RAO for each buoy heaving independently, and wave elevations around the buoys and wave run-up. The analytical solutions are in good agreement with the numerical solutions obtained from commercial code (WAMIT).

• 정보저장시스템학회논문집
• /
• 제10권2호
• /
• pp.45-49
• /
• 2014

This study deals with obtaining the optimal shape of a patch antenna via the topology optimization method in order to enhance its radiation efficiency. The genetic algorithm scheme is proposed for the optimization process to satisfy the design objective. As a result, the optimal patch shape through the proposed process shows highly improved radiation efficiency and reduced scattered effects. Commercial package COMSOL and Matlab programming are employed for the entire optimization and analysis processes.