• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.58-58
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• 2003

목적 : 본 연구에서는 C-arm과 CT에 사용 가능한 자궁경부암용 팬톰을 개발하고 이를 이용하여 기존의 필름 방법에 기반한 위치 확인 방법과 CT 재구성 방법의 정확성을 비교 연구하고자 한다. 정확성이 검증된 후에는 두 방법의 장점을 이용하기 위해 CT로 재구성된 좌표를 필름의 좌표로 변환시켜 현재 사용되고 있는 필름에 기반한 근접 치료 계획 시행에 도움을 주고자 한다. 방법 : 자체 제작한 자궁경부암용 팬톰은 인체 등가 물질인 물과 아크릴을 사용하였고, 크게 localizer 부분과 팬톰 부분으로 구성되어 있다. 또한, 실제 자궁경부암 환자의 임상적인 구조를 모사하여 제작하였다. 자궁경부암 치료시 중요 장기인 방광과 직장을 구와 원기둥으로 설계하였고, 고선량율 applicator는 아크릴 판의 흠으로 고정시켜 제작하였기 때문에 CT 촬영시 applicator를 제거한 영상에서도 applicator의 구조가 정확하게 묘사될 수 있도록 제작하였다. 두 시스템에서 재구성된 좌표를 비교하기 위해 각각의 시스템에서의 얻은 재구성 좌표와 팬톰 자체의 localizer와 재구성 알고리즘을 바탕으로 개발된 프로그램을 이용하여 얻은 좌표로 두 재구성 좌표의 비교 연구를 수행하였다. 정확성이 검증되고 장기의 정보가 담긴 CT의 좌표는 자체 개발된 프로그램으로 2 차원의 필름 좌표로 변환되었다. 본 연구에 사용된 모든 프로그램은 ILD 5.5를 사용하여 개발되었다. 결과 : 두 시스템의 좌표 비교 결과 x, y 축은 차이가 2mm 이내로 비교적 정확한 실험 결과를 얻을 수 있었고, z 축의 경우 CT 슬라이드의 굵기에 따라 2mm-3mm 이내의 차이가 있음을 관찰할 수 있었다. z 축을 제외한 좌표의 차이는 획득한 영상에서 컴퓨터로 좌표를 옮기는 localizer 좌표 선택 과정에 발생했을 것으로 예상된다. 또한, 이 검증된 좌표와 개발된 프로그램을 이용하여 우리는 CT의 좌표를 2차원의 필름 좌표로 정확하게 변환할 수 있었다. 결론 : 이 연구로부터 기존의 C-arm 재구성 방법과 CT 재구성 방법의 비교를 통해 각 치료 기기의 신뢰성을 직접 확인할 수 있었으며, 비교를 통해 검증된 CT의 좌표를 필름 좌표로 변환시킴으로서, 각 시스템의 장점만을 결합한 효과적인 치료 계획을 세울 수 있는 가능성을 제시하였다. 또한 물과 아크릴을 사용한 비교적 간단하고 경제적인 방법으로 C-arm, CT 그리고 MRI에 모두 이용 가능한 팬톰을 제작하여 쉽고 정확하게 위치를 확인할 수 있었다. 더 나아가, 본 연구에서 제작된 자궁경부암 팬톰은 근접치료를 포함하여 관련 팬톰 개발에 도움을 줄 수 있을 것으로 예상된다.

• Journal of radiological science and technology
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• v.39 no.3
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• pp.337-344
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• 2016

The purpose of this study was to evaluate the radiolucency for the phantom output to the 3D printing technology. The 3D printing technology was applied for FDM (fused deposition modeling) method and was used the material of ABS (acrylonitrile butadiene styrene) resin. The phantom was designed in cylindrical uniformity. An image uniformity was measured by a cross-sectional images of the 3D printed phantom obtained from the CT equipment. The evaluation of radiolucency was measured exposure dose by the inserted ion-chamber from the 3D printed phantom. As a results, the average of uniformity in the cross-sectional CT image was 2.70 HU and the correlation of radiolucency between PMMA CT phantom and 3D printed ABS phantom is found to have a high correlation to 0.976. In the future, this results will be expected to be used as the basis for the phantom production of the radiation quality control by used 3D printing technology.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.451-456
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• 1997

각 사업소의 교정용 팬톰에 대한 유효성 여부를 판정하고, 측정결과의 정확도와 조직적 오차의 발생여부를 확인할 목적으로 현재 국내 원전에서 사용중인 In Vivo 시스템에 대한 성능 시험을 수행하였다. 성능시험의 내용과 절차는 미국의 관련 지침인 ANSI N13.30에 기초를 두었다. 전신 측정에 대한 성능시험 결과, 시험핵종의 편중, 정밀도 및 최소검출방사능은 ANSI N13.30에서 정한 용인한도 이내로 나타났으며, 또 폐, 하복부 및 갑상선 측정에 대한 성능시험결과에 있어서도 성능평가 항목의 값은 모두 용인한도 이내였다. 각 사업소의 교정용 팬톰과 성능시험용 팬톰이 기하학적 구조에서 다소 차이가 있다 할지라도 측정결과의 편중이 용인한도 이하였다는 사실로부터 각 사업소에서 보유하고 있는 교정용 팬톰의 유효성을 간접적으로 입증할 수 있었다.

• Radiation Oncology Journal
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• v.26 no.2
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• pp.118-125
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• 2008

Purpose: On-line image guided radiation therapy(on-line IGRT) and(kV X-ray images or cone beam CT images) were obtained by an on-board imager(OBI) and cone beam CT(CBCT), respectively. The images were then compared with simulated images to evaluate the patient's setup and correct for deviations. The setup deviations between the simulated images(kV or CBCT images), were computed from 2D/2D match or 3D/3D match programs, respectively. We then investigated the correctness of the calculated deviations. Materials and Methods: After the simulation and treatment planning for the RANDO phantom, the phantom was positioned on the treatment table. The phantom setup process was performed with side wall lasers which standardized treatment setup of the phantom with the simulated images, after the establishment of tolerance limits for laser line thickness. After a known translation or rotation angle was applied to the phantom, the kV X-ray images and CBCT images were obtained. Next, 2D/2D match and 3D/3D match with simulation CT images were taken. Lastly, the results were analyzed for accuracy of positional correction. Results: In the case of the 2D/2D match using kV X-ray and simulation images, a setup correction within $0.06^{\circ}$ for rotation only, 1.8 mm for translation only, and 2.1 mm and $0.3^{\circ}$ for both rotation and translation, respectively, was possible. As for the 3D/3D match using CBCT images, a correction within $0.03^{\circ}$ for rotation only, 0.16 mm for translation only, and 1.5 mm for translation and $0.0^{\circ}$ for rotation, respectively, was possible. Conclusion: The use of OBI or CBCT for the on-line IGRT provides the ability to exactly reproduce the simulated images in the setup of a patient in the treatment room. The fast detection and correction of a patient's positional error is possible in two dimensions via kV X-ray images from OBI and in three dimensions via CBCT with a higher accuracy. Consequently, the on-line IGRT represents a promising and reliable treatment procedure.

• Progress in Medical Physics
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• v.23 no.4
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• pp.229-233
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• 2012

A small water phantom (dual-window phantom) was developed to improve the output measurement efficiency of medical linacs. This phantom is suitable for determining the quality index and output dose for high-energy photon beams. The phantom has two opposite windows and two independently rotating axes. The two axes measure the tissue phantom ratio (TPR) and the percentage depth dose (PDD) simply without requiring chamber movement by rotating the phantom around its axis. High-energy photon beams from a Co-60 irradiator and a medical linac were used to evaluate the phantom. The measured quality index is in good agreement with the reference values; the measured and reference values are within 0.2% of each other for the Co-60 gamma rays and within 1.4% for 6 and 10 MV X-rays. This phantom is more practical for routine output measurements, resulting in the prevention of potential human errors.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.139-145
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• 2007

Dose evaluation for small field such as stereotactic radiosurgery was performed using $Gafchromic^{(R)}$ EBT film. Every film which irradiated 6MV photon beam was scanned and obtained the optical density(OD) by flat bed scanner after 24 hours of irradiation. This study compared dose from diode in water and Gafchromic $EBT^{(R)}$ film in acrylic phantom to verify the reliability of the film, and to evaluate the SRS in clinical dose distributions from calculation and measurement in the region of virtual target in humanoid and cylindrical phantoms were compared. The Gafchromic $EBT^{(R)}$ film was found to be linear up to 9Gy. The $D_{max}$ for 6 MV was measured at 1.5 cm from the surface by both of diode and the film. As the depth is deeper, the error was measured within $2{\sim}3%$ at $10{\sim}20\;cm$ depth. Comparing between distribution from calculation and measurement, we found that there is 5% error at 90% isodose line. We found that given dose could be measured accurately by using the phantoms. It was feasible to use the Gafchromic $EBT^{(R)}$ film in quality assurance of SRS.

• Progress in Medical Physics
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• v.17 no.4
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• pp.187-191
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• 2006

The purpose of this study was to measure the dose distribution from the moving phantom for the respiratory motion. The phantom for TLD measurement was designed and built for this study based on the multiple plates for placing TLD and film. The TLDs may be inserted at 3 mm intervals in each TLD plate. For the measurements, TLD plate was inserted into the phantom at 1.5 cm ($d_{max}$) depth, and phantom was allowed to move in SI directions in the range of 1 to 2 cm with 0.5 cm interval for 6 MV X-ray beams. Penumbra and FWHM were measured at both moving state and compared stationary. It was found that penumbra increased 0.71 cm at stationary and 2.10 cm at moving state in 2 cm movement, and that FWHM are 7.52 cm for stationary state and 7.02 cm for moving state (2 cm movement). In this study, film was used to compared with TLD results of measurements and simitar results were observed. Therefore, it is expected that TLD moving phantom may be useful for the treatment of tumors that move due to the respiratory motion.

• The Journal of Korean Society for Radiation Therapy
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• v.21 no.1
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• pp.33-39
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• 2009

Purpose: The aim of this study is to compare patient's body posture and its position at the time of simulation with one at the treatment room using On-board Imaging (OBI) and CT (CBCT). The detected offsets are compared with position errors of Rando Phantom that are practically applied. After that, Rando Phantom's position is selected by moving couch based on detected deviations. In addition, the errors between real measured values of Rando Phantom position and theoretical ones is compared. And we will evaluate target position's accuracy of KV X-ray imaging's 2D and CBCT's 3D one. Materials and Methods: Using the Rando Phantom (Alderson Research Laboratories Inc. Stanford. CT, USA) which simulated human body's internal structure, we will set up Rando Phantom on the treatment couch after implementing simulation and RTP according to the same ways as the real radioactive treatment. We tested Rando Phantom that are assumed to have accurate position with different 3 methods. We measured setup errors on the axis of X, Y and Z, and got mean standard deviation errors by repeating tests 10 times on each tests. Results: The difference between mean detection error and standard deviation are as follows; lateral 0.4+/-0.3 mm, longitudinal 0.6+/-0.5 mm, vertical 0.4+/-0.2 mm which all within 0~10 mm. The couch shift variable after positioning that are comparable to residual errors are 0.3+/-0.1, 0.5+/-0.1, and 0.3+/-0.1 mm. The mean detection errors by longitudinal shift between 20~40 mm are 0.4+/-0.3 in lateral, 0.6+/-0.5 in longitudinal, 0.5+/-0.3 in vertical direction. The detection errors are all within range of 0.3~0.5 mm. Residual errors are within 0.2~0.5 mm. Each values are mean values based on 3 tests. Conclusion: Phantom is based on treatment couch shift and error within the average 5mm can be gained by the diminution detected by image registration based on OBI and CBCT. Therefore, the selection of target position which depends on OBI and CBCT could be considered as useful.

• Progress in Medical Physics
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• v.14 no.1
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• pp.15-19
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• 2003

High dose rate (HDR) brachytherapy for treating a cervix carcinoma has become popular, because it eliminates many of the problems associated with conventional brachytherapy. In order to improve the clinical effectiveness with HDR brachytherapy, a dose calculation algorithm, optimization procedures, and image registrations need to be verified by comparing the dose distributions from a planning computer and those from a phantom. In this study, the phantom was fabricated in order to verify the absolute doses and the relative dose distributions. The measured doses from the phantom were then compared with the treatment planning system for the dose verification. The phantom needs to be designed such that the dose distributions can be quantitatively evaluated by utilizing the dosimeters with a high spatial resolution. Therefore, the small size of the thermoluminescent dosimeter (TLD) chips with a dimension of <1/8"and film dosimetry with a spatial resolution of <1mm used to measure the radiation dosages in the phantom. The phantom called a pelvic phantom was made from water and the tissue-equivalent acrylic plates. In order to firmly hold the HDR applicators in the water phantom, the applicators were inserted into the grooves of the applicator holder. The dose distributions around the applicators, such as Point A and B, were measured by placing a series of TLD chips (TLD-to-TLD distance: 5mm) in the three TLD holders, and placing three verification films in the orthogonal planes. This study used a Nucletron Plato treatment planning system and a Microselectron Ir-192 source unit. The results showed good agreement between the treatment plan and measurement. The comparisons of the absolute dose showed agreement within $\pm$4.0 % of the dose at point A and B, and the bladder and rectum point. In addition, the relative dose distributions by film dosimetry and those calculated by the planning computer show good agreement. This pelvic phantom could be a useful to verify the dose calculation algorithm and the accuracy of the image localization algorithm in the high dose rate (HDR) planning computer. The dose verification with film dosimetry and TLD as quality assurance (QA) tools are currently being undertaken in the Catholic University, Seoul, Korea.

• Radiation Oncology Journal
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• v.14 no.2
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• pp.167-173
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• 1996

Purpose : This analysis was to evaluate the radiation dose around a tracheostoma and spinal cord in the case of advanced laryngeal cancers in which a total laryngectomy was done before radiotherapy. Materials and Methods : The radiation dose around a tracheostoma and spinal cord was measured by thermoluminescence and film dosimetry in the phantom, Radiotherapy treatment planning was done in 12 cases of advanced laryngeal cancer and compared with the measured dose in the phantom. Results : Mean spinal cord doses in the phantom by thermoluminescence dosimetry were $86.4\%$ (with a tracheostoma), $80.1\%$ (without a tracheostoma), and the difference was $6.3\%$. Mean spinal cord doses in the phantom by film dosimetry were $84.7\%$ (with a tracheostoma), $79.0\%$ (without a tracheostoma). and the difference were $5.7\%$. Calculated spinal cord doses in the phantom were $84.0\%$ (with a tracheostoma), $78.0\%$ (without a tracheostoma), and the difference was $6.0\%$. Mean calculated spinal cord doses in 12 patients were $83.1\%$ (with a tracheostoma), $76.9\%$ (without a tracheostoma). and the difference was $6.2\%$. Measured dose of lateral and posterior wall of the tracheostoma by film was low (depth of maximum dose = 12 mm). Conclusion : In the treatment planning of the advanced laryngeal cancers, the radiation dose of the tracheostoma and spinal cord should be evaluated and be followed by an appropriate management such as a bouls or a brachytherapy boost if the dose around the tracheostoma is low.