• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.272-274
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• 2002

The contribution of light in high-energy film dosimetry was examined using six commercially available solid water substitute phantoms. As six commercially available phantoms; RMI-451, Mix-DP, WE211, WE211-Black, PMMA and PMMA Black were evaluated in this study. It is difficult to evaluate the contribution of Cerenkov radiation and the optical permeability to the relative and/or absolute dosimetry using unpacked film in these phantoms. Therefore the contribution of Cerenkov radiation was estimated by the comparison between film densities in the shielded side (shutting off the light) and unshielded sides on a phantom. The effect of optical permeability was measured under ambient light by the time scale method. The results suggest that the use of black colored phantoms may improve the accuracy of dose measurement in film dosimetry.

• 대한의용생체공학회:의공학회지
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• 제20권2호
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• pp.199-204
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• 1999

생체조직내의 정확한 광선량 측정이 PDT 치료의 효과에 중요한 영향을 주므로 본 연구에서는 광선량 측정을 위해서 Monte Carlo 시뮬레이션을 이용하였다. 실험에 사용한 계수는 실제 생체조직의 광학계수이고 위상함수는 Henyey-Greenstein 위상함수를 사용하였다. 결과는 깊이에 따른 Fluency rate의 변화로 나타내었으며 기존 이론과의 차이는 0.35%에 지나지 않았다. 실험에 사용한 생체조직은 인체조직, 돼지조직, 쥐간조직, 토기근육조직이다. 대부분의 생체조직은 가시광선영역에서 큰 산란계수를 가지고 있으며 이것은 투과도에 큰 영향을 미치는 것으로 밝혀졌다. 가시광선 영역에서 인체조직의 투과 깊이는 1.5~2cm이었다. Monte Carlo 시뮬레이션을 이용하여 생체조직내의 광전파(light propagation), 광선량(light dosimetry), 에너지율(fluence rate), 투과깊이(penetration depth)를 효과적으로 측정할 수 있음을 보여주었다.

• Journal of Radiation Protection and Research
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• 제43권4호
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• pp.160-169
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• 2018

Background: This study aims to develop an integrated optical system that can simultaneously or selectively measure the signals obtained from radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL), which are luminescence phenomena of materials stimulated by radioactivity, heat, and light, respectively. The luminescence mechanism of various materials could be investigated using the glow curves of the luminescence materials. Materials and Methods: RL/TL/OSL integrated measuring system was equipped with a X-ray tube (50 kV, $200{\mu}A$) as an ionizing radiation source to irradiate the sample. The sample substrate was used as a heating source and was also designed to optically stimulate the sample material using various light sources, such as high luminous blue light emitting diode (LED) or laser. The system measured the luminescence intensity versus the amount of irradiation/stimulation on the sample for the purpose of measuring RL, TL and OSL sequentially or by selectively combining them. Optical filters were combined to minimize the interference of the stimulation light in the OSL signal. A long-pass filter (420 nm) was used for 470 nm LED, an ultraviolet-pass filter (260-390 nm) was used for detecting the luminescence of the sample by PM tube. Results and Discussion: The reliability of the system was evaluated using the RL/OSL characteristics of $Al_2O_3:C$ and the RL/TL characteristics of LiF:Mg,Cu,Si, which were used as dosimetry materials. The RL/OSL characteristics of $Al_2O_3:C$ showed relatively linear dose-response characteristics. The glow curve of LiF:Mg,Cu,Si also showed typical RL/OSL characteristics. Conclusion: The reliability of the proposed system was verified by sequentially measuring the RL characteristics of radiation as well as the TL and OSL characteristics by concurrent thermal and optical stimulations. In this study, we developed an integrated measurement system that measures the glow curves of RL/TL/OSL using universal USB-DAQs and the control program.

• Radiation Oncology Journal
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• 제17권3호
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• pp.249-255
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• 1999

목적 : 본 연구의 목적은 섬광판을 사용하는 전자조사문영상장치의 기본적인 선량반응성을 연구하는 것이다. 대상 및 방법 : 팬텀의 두께와 구성 및 팬텀과 영상장치와의 거리를 변화시킴으로 영상장치에 입사하는 방사선질을 변화시켜가면서 조사면평면에서 신호를 읽었다. 또한 섬광에 의한 신호가 전체신호에 기여하는 상대적인 정도를 모사하였다. 결과 : 본 연구는 조사면평면상에서 선량분포가 팬텀과의 거리 및 팬텀의 두께의 함수임을 보였다. 팬텀의 구성에 따라 조사면영상장치에 의한 선량의 오차는 크게는 $7\%$ 에 달하는 것을 발견했다. 영상장치 내부에서 발생하는 섬광의 산란이 오차의 중요한 원인이 됨을 또한 발견했다. 결론 : 본 연구에서 우리는 조사면영상장치의 선량반응성의 기본적인 특성을 알았다. 또한 섬광판을 기초로 한 영상장치는 정확한 선량측정시스템이 되지 못함을 보았다.

• 한국응용과학기술학회지
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• 제15권4호
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• pp.11-20
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• 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.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.169-173
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• 2007

During laser irradiation, mechanically deformed cartilage undergoes a temperature dependent phase transformation resulting in accelerated stress relaxation. Clinically, laser-assisted cartilage reshaping may be used to recreate the underlying cartilaginous framework in structures such as ear, larynx, trachea, and nose. Therefore, research and identification of the biophysical transformations in cartilage accompanying laser heating are valuable to identify critical laser dosimetry and phase transformation of cartilage for many clinical applications. quasi-elastic light scattering was investigated using Ho : YAG laser $(\lambda=2.12{\mu}m\;;\;t_p\sim450{\mu}s)$ and Nd:YAG Laser $(\lambda=1.32{\mu}m\;;\;t_p\sim700{\mu}s)$ for heating sources and He : Ne $(\lambda=632.8nm)$ laser, high-power diode pumped laser $(\lambda=532nm)$, and Ti : $Al_2O_3$ femtosecond laser $(\lambda=850nm)$ for light scattering sources. A spectrometer and infrared radiometric sensor were used to monitor the backscattered light spectrum and transient temperature changes from cartilage following laser irradiation. Analysis of the optical, thermal, and quasi-elastic light scattering properties may indicate internal dynamics of proteoglycan movement within the cartilage framework during laser irradiation.

• 한국응용과학기술학회지
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• 제28권1호
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• pp.102-108
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• 2011

The study of wave propagation and scattering in biological media has become increasingly important in recent years. The propagation of light within tissues is an important problem that confronts the dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. In the clinical application of photodynamic therapy(PDT) and in photobiology, the photon deposition within a tissue determines the spatial distribution of photochemical reactions. Scattered light is measured as a function of the distance (r) between the axis of the incident beam and the detection spot. Consequently, knowledge of the photosensitizer(Chlorophyll-a) function that characterizes a phantom is measured. To obtain the results of scattering coefficients(${\mu}s$) of a turbid material from diffusion described by experimental approach. It was measured the energy fluency of photon radiation at the position of penetration depth. From fluorescence experimental method obtained the analytical expression for the scattered light as the values of $(I/I_o)_{wavelength}$ vs the distance between the center of the incident beam and optical fiber in terms of the condition of "in situ spectroscopy(optically thick)" and real time by fluorometric measurements. The result was compromised with transport of intensities though a random distribution of scatters.

• 대한방사선치료학회지
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• 제16권2호
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• pp.43-61
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• 2004

목적 : 환자의 치료에 있어서 정확한 장비의 설치와 성능 평가는 치료의 질을 향상시키는데 중요한 요소라고 할 수 있으며 사용자가 장비의 특성과 사용 방법을 숙달하고 업무를 수행하는 것이 매우 중요하다고 생각한다. 그러므로 방사선 치료기를 설치하고 방사선 치료를 하기 전에 사용자가 직접 장비의 설치와 성능 평가에 참여하고 특성을 파악하여 이해하는 것이 필요하다. 본 연구에서는 CAP의 과정과 성능 평가결과를 소개하고자 한다. 대상 및 방법 : 선형가속기 21EX(varian, USA)를 대상으로 설치 시부터 성능 검사까지 전 과정을 평가하였고 성능평가는 크게 radiation survey, mechanical test, radiation isocenter test, beam performance, dosimetry, enhanced dynamic wedge로 구분하여 X-omat film(kodark), 선량 측정 장비(multidata, densitometer, electrometa)를 이용하여 실시하였다. 또한 선형가속기에 부착된 MLC(millenium, 120leaf)와 EPID(portal vision)의 성능 평가는 별도로 실시하였다. 결과 : Survey meter를 이용하여 측정한 leakage는 허용 범위 이하의 선량이 검출되었고 mechanical test에서 collimator, gantey, couch rotation은 1mm 이하였고 육안으로 평가한 angle은 digital이 ${\pm}1^{\circ}$이내에 mechanical은 ${\pm}5^{\circ}$이내였다. 또한 light field와 cross-hair의 직선성 검사도 1mm이내로 평가되었다. (A)symmetrical jaw field는 upper/lower 모두 ${\pm}0.5mm$이내였다. X-omat film을 이용한 radiation isocenter test는 1mm 이하였고 light field와 radiation field 의 일치성 검사는 ${\pm}1mm$ 이내였으며 선량 측정 장비를 이용하여 측정한 $\%DD$는 photon energy는 모두 ${\pm}1\%$ 이내로 electron energy는 $90\%,\;80\%,\;50\%,\;30\%$를 측정한 결과 허용 범위 내에서 평가되었다. photon 과 electron energy의 flateness는 각각 $2.3\%$(기준 $3\%$)이내, $3\%$(기준 $4.5\%$)이내이고 symmetry는 $0.45\%$(기준 $2\%$), $0.3\%$(기준 $2\%$)이내에서 평가 할 수 있었다. 그리고 dosimetry test는 sort term, MU setting, rep rate, dose rate accuracy를 photon과 electron energy 별로 MU와 gantry angle을 바꿔가면서 측정한 결과 허용범위 오차이내에 포함되는 것을 확인 할 수 있었다. EPID(portal vision)의 Exact-Arm의 기계적인 검사는 vertical, lateral, longitudinal은 허용범위 내에서 동작했으며 명암과 해상도 검사도 05.mm의 니크롬선이 선명하게 나타났으며 phantom의 음영도 뚜렷하게 나타났다. Multileaf collimator(MLC)검사는 leaf이 isocenter의 중심에 정확하게 배열되었으며 재현성 검사도 정상적으로 동작하였다. 결론 : Clinac 21EX 장치의 customer acceptance를 통해서 향후의 환자의 치료를 하는데 있어 장치의 안정성을 확인 할 수 있었으며 치료 전의 선형가속기와 주변장치의 특성을 파악 할 수 있어서 장비 사용에 있어서 어려움을 감소시킬 수 있으리라고 생각된다. 또한 사용자가 적극적으로 참여함으로써 앞으로 환자를 치료하는데 있어서도 많은 도움이 되리라 생각한다.

• 대한방사선치료학회지
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• 제11권1호
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• pp.16-21
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• 1999

Purpose : The aim of this study is to conform the possibility of the liquid type EPID as a QC tools to clinical indication and of replacement of the film dosimetry. Aditional aim is to describe a procedure for the use of a EPID as a physics calibration tool in the measurements of radiation beam parameters which are typically carried out with film. Method & Materials : In this study we used the Clinac 2100c/d with EPID. This system contains 65536 liquid-filled ion chambers arranged in a $256{\times}256$ matrix and the imaging area is $32.5{\times}32.5cm$ with liquid layer thickness of 1mm. The EPID was tested for different field sizes under typical clinical conditions and pixel values were calibrated against dose by producing images using various thickness of lead attenuators(lead step wedge) using 6 & 10MV x-ray. We placed various thickness of lead on the table of linear accelerator and set the portal vision an SDD of 100cm. To acquire portal image we change the field size and energy, and we recorded the average pixel value in a $3{\times}3$ pixel region of interest(ROI) at field center was recorded. The pixel values were also measured for different field sizes in order to evaluate the dependence of pixel value on x-ray energy spectrum and various scatter components. Result : The EPID, as a whole, was useful as a QA tool and dosimetry device. In mechanical check, cross-hair centering was well matched and the error was less than ?2mm and light/radiation field coincidence was less than 1mm also. In portal dosimetry the wider the field size the the higher the pixel value and as the lead thickness increase, the pixel value was exponentially decreased. Conclusions : The EPID was very suitable for QA tools and it can be used to measure exit dose during patients treatment with reasonable accuracy. But when indicate the EPID to clincal study deep consideration required

• 한국응용과학기술학회지
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• 제22권2호
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• pp.182-190
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• 2005

The propagation of light radiation within tissues is an important problem that confronts the dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. In the clinical application of photodynamic therapy(PDT) and in photobiology, the photon deposition within a tissue determines the spatial distribution of photochemical reactions. Scattered light is measured as a function of the distance (r) between the axis of the incident beam and the detection spot. Consequently, knowledge of the photosensitizer(Chlorophyll-a) function that characterizes a phantom is important. To obtain the results of scattering coefficients(${\mu}s$) of a turbid material from diffusion described by experimental approach. It was measured the energy fluency of photon radiation at the position of penetration depth. From fluorescence experimental method obtained the analytical expression for the scattered light as the values of $(I\;/I_o)_{wavelength}$ vs the distance between the center of the incident beam and optical fiber in terms of the condition of "in situ spectroscopy(optically thick)" and real time by fluorometric measurements.