• 한국의학물리학회지:의학물리
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• 제11권2호
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• pp.147-155
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• 2000

Patient dose verification is one of the most important parts in quality assurance of the treatment delivery for radiation therapy. The dose distributions may be meaningfully improved by modulating two dimensional intensity profile of the individual high energy radiation beams In this study, a new method is presented for the pre-treatment dosimetric verification of these two dimensional distributions of beam intensity by means of a charge coupled device video camera-based fluoroscopic device (henceforth called as CCD-VCFD) as a radiation detecter with a custom-made software for dose calculation from fluorescence signals. This system of dosimeter (CCD-VCFD) could reproduce three dimensional (3D) relative dose distribution from the digitized fluoroscopic signals for small (1.0$\times$1.0 cm$^2$ square, ø 1.0 cm circular ) and large (30$\times$30cm$^2$) field sizes used in intensity modulated radiation therapy (IMRT). For the small beam sizes of photon and electron, the calculations are performed In absolute beam fluence profiles which are usually used for calculation of the patient dose distribution. The good linearity with respect to the absorbed dose, independence of dose rate, and three dimensional profiles of small beams using the CCD-VCFD were demonstrated by relative measurements in high energy Photon (15 MV) and electron (9 MeV) beams. These measurements of beam profiles with CCD-VCFD show good agreement with those with other dosimeters such as utramicro-cylindrical (UC) ionization chamber and radiographic film. The study of the radiation dosimetric technique using CCD-VCFD may provide a fast and accurate pre-treatment verification tool for the small beam used in stereotactic radiosurgery (SRS) and can be used for verification of dose distribution from dynamic multi-leaf collimation system (DMLC).

• 대한디지털의료영상학회논문지
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• 제11권1호
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• pp.5-13
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• 2009

There are several reasons to take X-ray in case of inpatients. Some of them who cannot ambulate or have any risk if move are taken portable X-ray at their wards. Usually, in this case, many other people-patients unneeded X-ray test, family, hospital workers etc-are indirectly exposed to X-ray by scatter ray. For that reason I try to be aware of free space scatter dose accurately and make the point at issue of portable X-ray better in this study. kVp dose meter is used for efficiency management of portable X-ray equipment. Mobile X-ray equipment, ionization chamber, electrometer, solid water phantom are used for measuring of free space scatter dose. First of all the same surroundings condition is made as taken real portable X-ray, inquired amount of X-ray both chest AP and abdomen AP most frequently examined and measured scatter ray distribution of two tests individually changing distance. In the result of measuring horizontal distribution with condition of chest AP it is found that the mAs is decreased as law of distance reverse square but no showed mAs change according to direction. Vertical distribution showed the mAs slightly higher than horizontal distribution but it isnt found out statistical characteristic. In abdomen AP, compare with chest AP, free space scatter dose is as higher as five-hundred times and horizontal, vertical distribution are quite similar to chest AP in result. In portable X-ray test, in order to reduce the secondary exposure by free space scatter dose first, cut down unnecessary portable order the second, set up the specific area at individual ward for the test the third, when moving to a ward for the X-ray test prepare a portable shielding screen. The last, expose about 2m apart from patients if unable to do above three ways.

• 대한방사선치료학회지
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• 제8권1호
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• pp.75-81
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed . This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement, of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and $20.6\%$ for the CO-60, 4MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions the larger beam reductions occur. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.

• 대한방사선치료학회지
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• 제9권1호
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• pp.87-93
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• 1997

The using of compensator is required to adjust the irregular dose distribution due to irregular thickness of the body in Total Body Irradiation. Aluminuim, copper or lead is generally used as compensator. In our study, we would like to introduce a result of the attenuation and compensation effect of radiation use compensator made by duralumin and its clinical use. The thickness of compensator was calculated by the attenustion of radiation, which was measured by polystyrene phantom and ionization chamber(farmer). The compensation effect of radiation was measured by diode detector. All of conditions were set as in real treatment, and the distanc from source to detector was 446 cm. We also made fixation of device to easily attach the compensator to LINAC. Beam spoiler was menufactured and placed on the patient to irradiate sufficient dose to the skin. diode detector were placed on head, neck, chest, umbilicus. pelvis and knee with each their entranced exit points, and datas of dose distribution were evaluated and compared in each points for eleven patients(Feb. 96-Feb. 97). The attenuation rate of irradiation by duralumin compensator was measured as $1.4\%$ in 2mm thickness. The mean attenuation rate was $1.3\%$ per 2mm as increasing the thickness gradually to 50 mm. By using duralunim compensator, dose distribution in each points of body was measured with ${\pm}2.8\%$ by diode detectior. We could easily calculate the thickness of compensator by measuring the attenuation rate of radiation, remarkably reduce the irragularity of dose distribution duo to the thickness of body and magnify the effect of radiation therapy.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.241-243
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• 2002

New types of protocols have been recently in development, all based on an absorbed dose-to-water with the aim of improving the accuracy of measurements of absorbed dose to water. IAEA TRS-277, the air-kerma standard-based present protocol, and IAEA TRS-398 and AAPM TG-51, the absorbed dose-to-water standard-based new one, were studied and compared theoretically and experimentally for photon beams of 6, 10, and 15 MV. NE 2571 and 3 Farmer types of ionization chambers in widely commercial use were used to determine an absorbed dose to water at the reference depth in water. Two different kinds of calibration factors were given respectively for every chamber calibrated in $\^$60/CO gamma ray beams from a Korean Secondary Standard Dosimetry Laboratory (KFDA). This work shows that there is around 1 % of difference of absorbed doses measured between two different types of calibration systems owing to different physical parameters and reference conditions used. We hope this work to help form the basis on development of new type of protocol in Korea.

• 대한치과의사협회지
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• 제58권7호
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• pp.388-397
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• 2020

Objective: The purpose of the study was to calculate the effective and absorbed organ doses of cone-beam computed tomography (CBCT) in pediatric patient using personal computer-based Monte Carlo (PCXMC) software and to compare them with those measured using thermoluminescent dosimeters (TLDs) and anthropomorphic phantom. Materials and Methods: Alphard VEGA CBCT scanner was used for this study. A large field of view (FOV) (20.0 cm × 17.9 cm) was selected because it is a commonly used FOV for orthodontic analyses in pediatric patients. Ionization chamber of dose-area product (DAP) meter was located at the tube side of CBCT scanner. With the clinical exposure settings for a 10-year-old patient, DAP value was measured at the scout and main projection of CBCT. Effective and absorbed organ doses of CBCT at scout and main projection were calculated using PCXMC and PCXMCRotation software respectively. Effective dose and absorbed organ doses were compared with those obtained by TLDs and a 10-year-old child anthropomorphic phantom at the same exposure settings. Results: The effective dose of CBCT calculated by PCXMC software was 292.6 μSv, and that measured using TLD and anthropomorphic phantom was 292.5 μSv. The absorbed doses at the organs largely contributing to effective dose showed the small differences between two methods within the range from -18% to 20%. Conclusion: PCXMC software might be used as an alternative to the TLD measurement method for the effective and absorbed organ dose estimation in CBCT of large FOV in pediatric patients.

• Journal of Yeungnam Medical Science
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• 제8권2호
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• pp.114-120
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• 1991

영남대학병원 치료방사선과에 설치되어 있는 NELAC-1018의 작은 치료 면적에 대한 전자선출력 특성을 측정하여 다음과 같은 결과를 얻었다. 1. $6{\times}6cm$ applicator에서는 콜리메타가 $6{\times}6cm$일때 0.60에서 콜리메타 완전 열림일때 1.39을 나타내었으며, $20{\times}20cm$ applicator에서는 콜리메타 $20{\times}20cm$ 에서 0.89를, 콜리메타 완전 열림일때는 1.15을 나타내어 작은 면적에서는 콜리메타의 열림 정도에 따른 출력특성이 크게 변하였다. 2. 작은 면적에 대한 출력특성은 6MeV에서 $10{\times}10cm$을 기준으로 하여 $2{\times}3cm$ 일때 0.618, $6{\times}6cm$일때 0.826을 나타내었으며, 15MeV에서 $2{\times}3cm$일때 0.887, $6{\times}6cm$ 0.982을 나타내어 에너지가 클수록 치료 면적의 크기에 따른 출력변화가 적음을 나타내었다. 위와 같은 측정결과는 작은 치료면적을 갖는 전자선 치료의 임상적이용에 있어서 콜리메타의 열림 정도의 결정과 에너지 선택이 매우 중요함을 시사하고 있다.

• 한국산업보건학회지
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• 제26권3호
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• pp.301-306
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• 2016

Objectives: Direct-reading instrument(Photoionization detectors, PID) and quantitative analysis using active type air sampling (Gas chromatography-flame ionization detector, GC-FID) were tested to evaluate their ability to detect volatile organic compounds(VOCs) in a semiconductor manufacturing plant. Methods: The organic compounds used were acetone and ethanol which are normally used as cleaning solutions in the semiconductor manufacturing. The evaluation was based on the preparation of test solutions of known acetone and ethanol concentration in a chamber($600{\times}600{\times}1150mm$). Samples were prepared that would be equivalent to 5~100 ppm for acetone and 10~ 200 ppm ethanol. GC-FID and PID were evaluated simultaneously. Quantitative analysis was performed after sampling and the direct-reading instrument was checked using real-time data logging. Results: Positive correlations between PID and GC-FID were found for acetone and ethanol at 0.04~2.4% for acetone(TLV: 500 ppm) and 0.1~8.3% for ethanol(TLV: 1000 ppm). When the sampling time was 15 min, concentration of test solution was the most similar between measurement methods. However, the longer the sampling time, the less similar the results. PID and GC-FID had similar exposure patterns. Conclusions: The results indicate that PID and GC-FID have similar exposure pattern and positive correlation for detection of acetone and ethanol. Therefore, PID can be used for exposure monitoring for VOCs in the semiconductor manufacturing industry. This study has significance in that it validates measuring occupational exposure using a portable device.

• 대한방사선기술학회지:방사선기술과학
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• 제33권2호
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• pp.133-141
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• 2010

선형가속기의 동적쐐기(enhanced dynamic wedge: EDW)의 품질보증을 위하여 다양한 방법으로 동적쐐기의 특성을 평가하였다. 본 연구에서는 6 MV와 15 MV 엑스선에 대하여 각각 7종(10, 15, 20, 25, 30, 45, 60도)의 EDW를 평가하였다. EDW 작동에 필요한 STT(segmented treatment table)를 계산으로 구하고 로그파일을 통하여 기계적 작동을 평가하였으며, 이차원배열형검출기와 전리함을 사용하여 팬텀속 선량분포를 측정하고 치료계획시스템(RTP)과 비교하였다. EDW의 기계적 작동은 예상과 잘 일치하였으며, 빔측면도를 포함한 이차원선량분포는 근사적으로 RTP 계산과 일치하였다. 선형가속기 조사량 100 MU에 대한 출력선량은 RTP 계산과 2.9% 이내로 일치하였으며, 측정된 쐐기인자는 RTP 계산과 최대 2.6%를 보였다. 이 결과들은 본 선형가속기에 장착된 EDW의 임상적 적용에 문제가 없음을 의미한다.

• 대한방사선기술학회지:방사선기술과학
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• 제39권3호
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• pp.323-328
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• 2016

두경부 질환의 인터벤션 시술 시 시술자가 받는 피폭선량의 평가 및 감소연구를 위한 선행 연구로써, 이온 전리함을 이용하여 인터벤션 시술 시 시술자의 위치하는 공간선량 분포를 측정하였다. Bi-plane 인터벤션 시술 장비를 대상으로 4개 구역(45, 135, 225 그리고 315도)으로 나누어 가상의 시술자가 있다는 가정아래에 시술자의 결정장기위치에서 거리(80, 100, 120, 그리고 140 cm)에 따라 조사선량을 측정하였으며, 방사선발생장치의 위치를 변화시켜 선량변화를 분석하였다. 시술자의 대부분이 위치하는 225도의 구역의 조사선량은 가장 가까운 거리인 80 cm에서 시술자 눈의 높이에서 114.5 mR/h, 가슴의 높이는 143.1 mR/h, 그리고 생식기위치는 147 mR/h이었다. 그리고 방사선 발생장치의 위치를 시술자 가까이로 변화시켰을 경우, 평균적으로 $18.1{\pm}10.5%$의 선량이 증가하였다. 본 연구에서 인터벤션 시술 동안 시술자가 위치할 수 있는 곳의 공간선량분포를 확인하였으며, 본 연구 결과를 통하여 시술자의 방사선 방어에 대하여 구체적인 계획을 수립할 수 있을 것이라 사료된다.