• Journal of the Korea Safety Management & Science
• /
• v.17 no.1
• /
• pp.125-130
• /
• 2015

Techniques, using physical wedge filter and using dynamic wedge filter and FIF(Field in Field) and ISCT(Irregular Surface Compensating Technique), have been developed according to progress of radiation therapy of breast cancer. Measurement of dose was done to judge the usefulness of technique using three cases, non tissue loss after breast conserving operating and tissue loss after breast conserving operating and mastectomy. Dose indexes of breast tissue, CI (Conformity Index), HI (Homogeneity Index) and QOC (Quality of Coverage), dose index of skin, or dose indexes of lung, volume of 50 percent dose and 20 percent dose were estimated and compared. Using dynamic wedge filter is useful plan at non tissue loss allowing for high dose of lung. FIF and ISCT are useful plan at tissue loss. ISCT is useful plan at mastectomy. Henceforth, we need to apply to valid plan and body type and thorax size.

• Current Optics and Photonics
• /
• v.5 no.3
• /
• pp.220-228
• /
• 2021

To improve the measurement accuracy of a solar-radiation observer instrument, aiming at the problem of multiorder-stray-light interference caused by the diffraction of the flat-field concave grating in the spectroscopic system, straylight suppression methods for different forms of optical traps are studied. According to the grating surface-scattering distribution-function model, the bidirectional scattering distribution function (BSDF) of a dust-polluted surface and the flat-field concave grating's transition area of the spectroscopic system is calculated, and a Lyot stop with blade baffle is designed to suppress this kind of stray light. For diffraction multiorder stray light, based on the theory of light-energy transmission, a design for precise positioning of the trench optical trap is proposed. The superiority of the method is verified through simulation and actual measurement. The simulation results show that in a spectroscopic system approximately 160 mm × 140 mm × 80 mm in size, the energy of the stray light is reduced by one order of magnitude by means of the trench optical trap and Lyot stop, and the number of beams is reduced from 5664 to 1040. The actual measurements show that the stray-light-suppression efficiency is about 69.4%, which is effective reduction of the amount of stray light.

• The Journal of Korean Society for Radiation Therapy
• /
• v.15 no.1
• /
• pp.19-27
• /
• 2003

I. Purpose In special cases of Total Body Irradiation(TBI), Half Body Irradiation(HBI), Non-Hodgkin's lymphoma, E-Wing's sarcoma, lymphosarcoma and neuroblastoma a large field can be used clinically. The dose distribution of a large field can use the measurement result which gets from dose distribution of a small field (standard SSD 100cm, size of field under $40{\times}40cm2$) in the substitution which always measures in practice and it will be able to calibrate. With only the method of simple calculation, it is difficult to know the dose and its uniformity of actual body region by various factor of scatter radiation. II. Method & Materials In this study, using Multidata Water Phantom from standard SSD 100cm according to the size change of field, it measures the basic parameter (PDD,TMR,Output,Sc,Sp) From SSD 180cm (phantom is to the bottom vertically) according to increasing of a field, it measures a basic parameter. From SSD 350cm (phantom is to the surface of a wall, using small water phantom. which includes mylar capable of horizontal beam's measurement) it measured with the same method and compared with each other. III. Results & Conclusion In comparison with the standard dose data, parameter which measures between SSD 180cm and 350cm, it turned out there was little difference. The error range is not up to extent of the experimental error. In order to get the accurate data, it dose measures from anthropomorphous phantom or for this objective the dose measurement which is the possibility of getting the absolute value which uses the unlimited phantom that is devised especially is demanded. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field.

• The Journal of Korean Society for Radiation Therapy
• /
• v.13 no.1
• /
• pp.122-125
• /
• 2001

I. 목적 : Primus의 Multi Leaf Collimator는 X측이 29쌍으로 이루어 져 있으며 그중27쌍의 leaf은 1cm이고 2쌍은 6.5cm의 leaf으로 구성되어있다. 이러한 이유로 Paraaortic node를 포함하는 자궁경부암 치료시 현재는 Y가 27cm 이상인 경우는 차폐블럭을 제작하여 치료를 시행하나 차폐 블럭의 제작에 따른 업무의 지연과 차폐 블럭이 무거워져 치료시 환자에게 떨어질 위험을 제거 하기 위해 Asymmetric Field로 Multi Leaf Collimator를 사용한 결과를 보고하고자 한다. II. 재료 및 방법 : 모의 치료(Ximatron, Varian, USA)시 $Y_1$측을 15cm을 기준으로 하여 $Y_2$측을 변경하면서 Field size를 결정한다. ($Y_2$측은 20cm가 최대, 즉 Y측은 35cm까지 적용) 이러한 방법으로 Multi Leaf Collimator를 사용한 환자와 기존의 차폐블럭을 제작하여 치료한 환자와의 업무 개선사항을 확인하기 위하여 실제 공작실 업무 담당자의 블럭 제작 시간과 Beam Shaper를 이 용해 Multi Leaf Collimator를 입력하는 시간을 상호 비교하여 단축된 시간을 조사하였다. III. 결과 : 차폐블럭을 대신해 Multi Leaf Collimator를 이용함으로써 치료실에서 환자에 대한 위험요소(차폐블럭이 무겁다)를 사전에 제거 할 수 있었고 공작실에서 블럭 제작 시간과 LANTIS를 이용해 MLC를 입력하는 시간을 실측 한 결과업무의 시간이 120분에서 5분으로 단축되는 효과가 있었다. 전산화 계획 실에서 선량 계산시 OAR Factor값을 고려하여야 한다. IV. 결론 : Paraaortic node를 포함한 자궁경부암 환자의 차폐부위는 모양이 거의 일직선이기 때문에 Mu]ti Leaf Collimator를 사용하기에 용이 한 치료 부위이다. 하지만 큰 Field size로 인한 불편함이 있었다. 이러한 제 약성을 Asymmetric Field를 이용해서 Multi Leaf Collimator의 사용을 가능하게 하고 차폐 블록의 제작과정과 치료 시에 발생되는 근무자의 업무의 손실을 줄이고 환자에 대한 위험성 을 해결하였다.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2041-2043
• /
• 1999

In order to investigate the radiation characteristics of unmixed line noise from overhead high voltage AC transmission lines, a gap noise generator was manufactured. Disk size which decides capacitance between the noise generator and earth was selected through preliminary indoor experiments and analysis by charge simulation method. The capacitance is one of principal parameters related to inject a proper noise current into lines. The field experiments were performed with the noise generator installed in Kochang 765 kV full scale test line. As the results, the useful data which can be used to analysis the radiation characteristics of noise from transmission lines was obtained. Those are lateral profiles the directivity of antenna toward lines, frequency spectra and so on.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.8
• /
• pp.443-446
• /
• 2004

In this paper, a multi-band ceramic chip antenna for WLAN(Wireless LAN) applications is designed. The design target is to obtain 0 dBi of coverage gain with omni directional radiation pattern. The antenna is fabricated using Low Temperature Co-fired Ceramic(LTCC) technology. The size of the chip antenna is $2.2{\times}9.65{\times}1.02$mm. The measured antenna gain is 1 dBi at 2.44 GHz and 0.5 dBi at 5.5 GHz. The omni directional radiation pattern for the two operating bands is obtained. The measured bandwidth(S11=-10 dB) are 90 MHz at 2.44 GHz and 1280 MHz at 5.5 GHz respectively

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.64.1-64.1
• /
• 2019

Thermal fracture and cracking near the perihelion are found to be a possible mechanism to produce the dust trail of the near-Earth asteroid, (3200) Phaethon (Jewitt and Li, 2013, ApJ 771, L36). It is, however, not well understood how the debris particles were escalated from the regolith against the asteroid's gravity. Thus, the scenario that these debris particles are responsible for the detected activities (Li and Jewitt, 2013, ApJ, 145, 154), is not complete yet. Here, we hypothesize that the thermal radiation pressure around the perihelion passage would exert substantial force outwards from the regolith on dust grains, and they can be lifted up and contributes the dust tail formation with further help of solar radiation pressure. Our modeling indicates that particles with sizes of roughly ~1-10 micron can be ejected from Phaethon by the mechanism, while a detailed model of gravitational field is required for accurate estimation of the particle size range. Our idea is not necessarily limited to Phaethon case, but is applicable to any atmosphereless bodies.

• Progress in Medical Physics
• /
• v.9 no.4
• /
• pp.201-206
• /
• 1998

IMRT optimization method on multiple slice has been developed by using gradient based algorithm. On about 10-30 CT slices including treatment region of a patient, dose optimization has been performed slice by slice to meet the condition that each organ should be exposed below maximum tolerable doses and that the tumor dose within the range of 100$\pm$5 %. Field size was limited to 8$\times$8 cm$^2$ and in this condition, beam divergence was not taken into account to calculate dose distribution. Total dose distribution was calculated by superposing each beamlet whose dose distribution had been precalculated. In order to investigate beam number dependency, dose optimization was performed for one, three, five, seven, and nine coplanar beams and then each optimization index was evaluated. It is found that optimization time was proportional to number of slices to be optimized, and the most efficient plan was obtained from the case of three-to-seven incident beams with respect to calculation time and optimization index. In conclusion, dose optimization of multiple slice was able to be obtained by repeating dose optimization of single slice under condition that the beam size is not too large to ignore beam divergence. And it turns out that result of dose optimization was so sensitive to the position of isocenter that some method to optimize isocenter position is needed to improve it.

• Journal of the Korean Society of Radiology
• /
• v.16 no.5
• /
• pp.499-504
• /
• 2022

Positron emission tomography (PET) uses a very small scintillator to achieve exellent spatial resolution. Therefore, in this study, a PET system using a scintillator to 0.8 mm size was designed and the performance was evaluated. Anihilation radiation was generated from the center of the field of view (FOV) to the outskirts at intervals of 10 mm, and counted simultaneously. The image was reconstructed using the coincidence data, and the spatial resolution was calculated by acquiring the full width at half maximum through the profile. The spatial resolution at the center of the FOV was 1.02 mm, showing a very good result, and the spatial resolution decreased as it was located at the outer edge. To evaluate the phantom image, the Derenzo phantom was constructed to acquire the image, and the degree of classification between radiation sources was evaluated through profile analysis. The result showed that the distance between the radiation sources was larger than the spatial resolution of the radiation sources at each location, and it was confirmed that the radiation sources were distinguished through this. When the PET system designed in this study is applied to PET for small animals, it is considered that excellent performance can be secured through the characteristic of very good spatial resolution.

• The Journal of Korean Society for Radiation Therapy
• /
• v.10 no.1
• /
• pp.69-77
• /
• 1998

When a high energy photon beam is used to treat lesions located in the upper respiratory air passages or in maxillary sinus, the beams often must traverse an air cavity before it reaches the lesion. Because of this traversal of air, it is not clear that the surface layers of the lesion forming the air-tumor tissue interface will be in a state of near electronic equilibrium; if they are not, underdosing of these layers could result. Although dose corrections at large distances beyond an air cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. This problem has been investigated for 4MV and 10MV X-ray beams which are becoming widely available for radiotherapy with linear accelerator. Markus chamber was used for measurement with variouse air cavity geometries in X-ray beams. Underdosing effects occur at both the distal and proximal air cavity interface. The magnitude depended on geometry, energy, field sizes and distance from the air-tissue interfaces. As the cavity thickness increased, the central axis dose at the distal interface decreased. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Fellowing a $20{\times}2{\times}2\;cm^3$\;air\;cavity,\;4{\times}4\;cm\;field\;there\;was\;an\;11.5\%\;and\;13\%\;underdose\;at\;the\;distal\;interface,\;while\;a\;20{\times}20{\times}2\;cm^3\;air\;cavity\;yielded\;a\;24\%\;and\;29\%$ loss for the 4MV and 10MV beams, respectively. The losses were slightly larger for the 10MV beams. The measurements reported here can be used to guide the development of new calculation models under non-equilibrium conditions. This situation is of clinical concern when lesions such as larynx and maxillary carcinoma beyond air cavities are irradiated.