• Journal of Radiation Protection and Research
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• v.30 no.4
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• pp.231-236
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• 2005

Dosimeters are manufactured from same process in the manufacturer but the deviation of TL raw counts exists among the dosimeters. TL raw counts are also gradually degrade due to multiple readings and physical abuse. ECF (Element Correction Factor) correct the degradation and deviation of TL raw counts to the average TL raw counts of reference dosimeters. Procedures for producing ECF of thermoluminescent dosimeters were described In detail. ECFs of 319 reference, control and field dosimeters were measured three times and average of three ECF values was calculated. Also, % CV(Coefficient of Variation) of three ECF values was calculated to verify ECF. ECF & % CV distributions for the field and control dosimeters are presented. TL raw counts of field dosimeters, being used about 6 times for the past 3 years, were almost unchanged, but those of control dosimeters being used more frequently, were degraded about 4.7 %.

• The Journal of Korean Society for Radiation Therapy
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• v.8 no.1
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• pp.109-114
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• 1996

PURPOSE : To investigate the effect of asymmetric jaws for delivering a uniform accurate dose of radiation to the junctions. METHODS & MATERIALS : A linear accelerator with a set of asymmetric jaws(varian 600C, 2100C, 2100CD with 4mev, 10mev, 10mev). Dose disribution was measured at the junctions with films in phantom. Total $10{\times}20cm^2$ with each $10{\times}10cm^2$ in deviation of ${\pm}1mm$ jaws. RESULTS : Film dosimetry showed the accuracy of asymmetric jaws depending on the machine. CONCLUSION : Understanding the mechanical characteristics of the use of half-beam at the junctions, without hot or cold regions.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.637-643
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• 2019

To verify internal movements of the body, a DICOM file obtained from CT and a Geant4 code were used to simulate lung cancer patients. In addition, the method is applied to measure the movement of tumor when the movement of t he tumor is located inhale and exhale by creating a virtual tumor in the self-produced moving phantom, and to check the distribution of dose in the treatment plan and the accuracy of tumor in PTV for respiratory and lung cancer patients. It was confirmed that 97% or more respiratory control radiation therapy was effective even if the moving area was more than 3cm, in the 40% to 70% range. Dose distribution with respiratory radiation therapy applied to moving targets, measured by film in the actuation phantom, was shown to be within a 3mm margin of error for dose distribution containing 90%. It was confirmed that for actual patient breathing curves, the treatment time may be shorter than that due to the longer expiratory time.

• Progress in Medical Physics
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• v.16 no.2
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• pp.82-88
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• 2005

In this study, the physical compensator made with the high density material, Cerrobend, and the electronic compensator realized by the movement of a dynamic multileaf collimator were analyzed in order to verify the properness of a design function in the commercial RTP (radiation treatment planning) system, Eclipse. The CT images of a phantom composed of the regions of five different thickness were acquired and the proper compensator which can make homogeneous dose distribution at the reference depth was designed in the RTP. The frame for the casting of Cerrobend compensator was made with a computerized automatic styrofoam cutting device and the Millennium MLC-120 was used for the electronic compensator. All the dose values and isodose distributions were measured with a radiographic EDR2 film. The deviation of a dose distribution was $\pm0.99 cGy\;and\;\pm1.82cGy$ in each case of a Cerrobend compensator and a electronic compensator compared with a $\pm13.93 cGy$ deviation in an open beam condition. Which showed the proper function of the designed compensators in the view point of a homogeneous dose distribution. When the absolute dose value was analyzed, the Cerrobend compensator showed a $+3.83\%$ error and the electronic compensator showed a $-4.37\%$ error in comparison with a dose value which was calculated in the RTP. These errors can be admtted as an reasonable results that approve the accuracy of the compensator design in the RTP considering the error in the process of the manufacturing of the Cerrobend compensator and the limitation of a film in the absolute dosimetry.

• Progress in Medical Physics
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• v.26 no.4
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• pp.201-207
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• 2015

The new function of 3DVH software for dose calculation inside the patient undergoing TomoTherapy treatment by applying the measured data obtained by ArcCHECK was recently released. In this study, the dosimetric accuracy of 3DVH for the TomoTherapy DQA process was evaluated by the comparison of measured dose distribution with the dose calculated using 3DVH. The 2D diode detector array MapCHECK phantom was used for the TomoTherapy planning of virtual patient and for the measurement of the compared dose. The average pass rate of gamma evaluation between the measured dose in the MapCHECK phantom and the recalculated dose in 3DVH was $92.6{\pm}3.5%$, and the error was greater than the average pass rate, $99.0{\pm}1.2%$, in the gamma evaluation results with the dose calculated in TomoTherapy planning system. The error was also greater than that in the gamma evaluation results in the RapidArc analysis, which showed the average pass rate of $99.3{\pm}0.9%$. The evaluated accuracy of 3DVH software for TomoTherapy DQA process in this study seemed to have some uncertainty for the clinical use. It is recommended to perform a proper analysis before using the 3DVH software for dose recalculation of the patient in the TomoTherapy DQA process considering the initial application stage in clinical use.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.78-80
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• 2004

본 연구에서는 쐐기형태의 선량분포를 구현할 수 있도록 고안된 미국 Varian사 동적쐐기(EDW ; Enhanced Dynamic Wedge)의 표면선량(surface dose)과 주변선량(peripheral dose) 특성을 분석하였다. 쐐기각도 15${\circ}$, 30${\circ}$, 45${\circ}$, 50${\circ}$를 대상으로 금속쐐기를 사용했을 경우와 동적쐐기를 사용했을 경우에 대해 해당 선량특성을 비교, 분석하였다. 표면선량 측정 결과, 동적쐐기가 금속쐐기보다 더 높은 선량 분포를 보였으며, 주변선량의 경우, 금속쐐기가 동적쐐기보다 더 높은 선량분포를 보였다. 이는 금속쐐기의 빔 필터링에 의한 빔 경화(hardening) 현상과 광자선과의 산란 현상에 기인한 결과로 방사선치료 계획 시 동적쐐기의 적용에 있어 고려해야 할 주요 특성이라 사료된다.

• Journal of radiological science and technology
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• v.38 no.3
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• pp.237-244
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• 2015

Health professionals in nuclear medicine were known that they get high radiation exposure. To reduce radiation exposure, using shielding materials is needed. In this study, we analyzed the shielding effect about apron during 18F-FDG treatment by using simulation based on Monte Carlo techniques and actual measurement. As a result, absorbed dose distribution of organ varies with handling position of the source. Dose reduction ratio by lead thickness of apron tended to decease, when handling position of the source come close to organ and away from radiation source for simulation. In the case of actual measurement with the dosimetry device, It showed that mean spatial dose distribution was different due to characteristics of dosimetry device. However, spatial dose rate was exponentially reduced according to distance with increasing lead content.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.899-905
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• 1995

포항방사광가속기(Pohang Llght Sousrc)의 시운전기간동안 저장링건물에서의 방사선발생량을 측정하였다. Ionization Chamber와 Moderated BF$_3$ Counter로 구성된 지역방사선감시기시스템(RMS)외에 Pocket Inonization chamber, 연속기록이 가능한 Surveymeter를 고정 또는 이동시키면서 사용하였다. 시운전기간동안 선형가속기로부터의 입사시기와 저장시기에서의 방사선방출분포 및 선량의 정도가 명확히 구별되었으며 RF Cavity나 Bump Magnet등의 오동작에 의한 방사선 발생경로를 추정해 볼 수 있었다 여기서는 저장링실험지역 등에서의 공간선량분포와 부분차폐에 따른 변화를 측정하였으며 측정결과로부터 차폐계산시 사용된 방법을 통해 역으로 각 지역의 빔손실정도를 추정하고 계산식의 타당성을 검토해 보았다.

• Progress in Medical Physics
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• v.22 no.4
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• pp.198-205
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• 2011

Gamma irradiator is widely used for cell, animal experiment, irradiation for blood, dose measurement, and education. Biobeam8000 gamma irradiator (STS Steuerungstechnik &. Strahlenschutz GmbH, Braunschweig, Germany, Cs137, 81.4 TBq) that KIRAMS (Korea Institute of Radiological and Medical Science) has is a irradiation device that enables to be used in large-capacity of 7.5 L and extensive area. Cs-137 source moves range of 24 cm back-and-forth in a regular cycle in beaker for uniform irradiation and a beaker that puts a specimen like existing radiation irradiator such as Gammacell3000 rotates $360^{\circ}$ during irradiation. Precise dose information according to the location of radiation source would be needed because of the movement of radiation source, whereas radiation could be uniformly irradiated in comparison with existing gamma irradiator. In this study, dose distribution of the inside beaker located in Biomeam8000 gamma irradiator was measured using glass dosimeter, and dose evaluation and distribution regarding dose linearity and dose reproducibility were implemented based on measurement results. This aims to show guideline for efficient use of irradiator based on measurement result when doing experiment or radiation exposure.

• Radiation Oncology Journal
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• v.3 no.2
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• pp.145-151
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• 1985

The peripheral dose distributions of wedge fields of Co-60 $\gamma-ray$ and 1 OMV x-ray were measured by the solid state detector controlled by means of semiautomatic water phentom system. The measurements were made on the principal plane parallel to the cross section of wedge filter (blade and ridge direction). For parallel motion of the detector to the beam axis the distance from the margin of radiation field at suface were 3, 5 and 10cm. For tranverse motion the depth of measurement were dm, 5, 10 and 15cm. The followings were drawn from the measurement. 1. The peripheral dose of the blade side of wedges was generally higher than that of the ridge side at symmetric point about beam axis. 2. In the superficial region phenomena of dose build-up appeared. 3. For Co-60 $\gamma-ray$ field, the peripheral dose did not monotonously decrease with the distance from the field margin but increase in some range, consequently showing a peak dose. 4. The peripheral dose did not only depend on radiation quality and field size, but also on wedge angle and wedge direction.