• 한국콘텐츠학회논문지
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• 제16권1호
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• pp.75-81
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• 2016

최근 방사선 치료 분야에서는 다양한 영상유도 방사선 치료(IGRT) 장치들을 이용한 환자 셋업으로 고도의 정밀성이 보장된 치료가 가능해 졌다. 그러나 환자의 정상 조직에 받는 추가 선량 또한 더불어 증가되고 있다. 이에 본 연구에서는 영상유도 방사선 치료 장치 중 OBI, CBCT, ExacTrac를 이용한 환자 셋업에 주변 정상 조직에 받는 피폭선량을 측정하였다. 결과 팬텀 중심부의 선량이 CBCT의 경우 두부 12.57 mGy, 흉부 20.82 mGy, 복부 82.93 mGy, 골반부위 52.70 mGy로 측정되었으며 OBI는 0.76 ~ 8.58 mGy, ExacTrac의 경우 0.14 ~ 0.63 mGy로 CBCT의 피폭선량이 다른 장비에 비해 월등히 높게 나타나는 것을 알 수 있었다. 표면 선량의 경우에서도 CBCT가 다른 장비에 비해 높게 나타났으나 입사 피부표면 선량(Enterance skin dose)의 경우 OBI도 CBCT의 피폭선량과 거의 비슷한 흡수선량이 측정 되었다.

• 한국방사선학회논문지
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• 제10권1호
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• pp.39-44
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• 2016

본 연구는 전립선암의 치료방법 중 근접치료 시 환자 주변의 공간에 대한 선량을 평가한 것으로 환자, 시술자 그리고 보호자에 대한 선량을 예측함으로서 피폭을 최소한으로 예방하고자 수행하였다. 실험방법은 몬테칼로법을 기반으로 한 MCNPX를 사용하여 가상의 공간에서 모의피폭체를 만들어 실험하였으며, 선원은 $^{192}Ir$, $^{125}I$, $^{103}Pd$를 seed 형태로 이식하였다. 환자를 중심으로 전방 30, 50, 100, 200 cm 거리에 관심영역을 설정하여 공간 선량을 평가하였다. 그 결과 거리에 관계없이 $^{192}Ir$에서 가장 높은 선량을 나타내었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.248-251
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• 2002

The intensity modulated radiation therapy (IMRT) with a multileaf collimator (MLC) requires the conversion of a radiation fluence map into a leaf sequence file that controls the movement of the MLC during radiation treatment of patients. Patient dose verification is clinically one of the most important parts in the treatment delivery of the radiation therapy. The three dimensional (3D) reconstruction of dose distribution delivered to the target helps to verify patient dose and to determine the physical characteristics of beams used in IMRT. A new method is presented for the pretreatment dosimetric verification of two dimensional distributions of photon intensity by means of Beam Intensity Scanner System (BISS) as a radiation detector with a custom-made software for dose calculation of fluorescence signals from scintillator. The scintillator is used to produce fluorescence from the irradiation of 6MV photons on a Varian Clinac 21EX. The BISS reproduces 3D- relative dose distribution from the digitized fluoroscopic signals obtained by digital video camera-based scintillator(DVCS) device in the IMRT. For the intensity modulated beams (IMBs), the calculations of absorbed dose are performed in absolute beam fluence profiles which are used for calculation of the patient dose distribution. The 3D-dose profiles of the IMBs with the BISS were demonstrated by relative measurements of photon beams and shown good agreement with radiographic film. The mechanical and dosimetric properties of the collimating of dynamic and/or step MLC system alter the generated intensity. This is mostly due to leaf transmission, leaf penumbra and geometry of leaves. The variations of output according to the multileaf opening during the irradiation need to be accounted for as well. These phenomena result in a fluence distribution that can be substantially different from the initial and calculative intensity modulation and therefore, should be taken into account by the treatment planning for accurate dose calculations delivered to the target volume in IMRT.

• 한국방사선학회논문지
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• 제14권7호
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• pp.931-936
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• 2020

본 연구는 자동노출선량장치을 사용했을 때 생식선 차폐체의 유무와 크기 변화에 따른 소아 환자의 방사선 피폭선량과 화질의 변화를 관찰하기 위하여 수행되었다. X-ray 장비를 이용하여 소아 팬텀의 복부와 생식선에서 차폐체가 없을 때와 3가지 크기의 차폐체를 사용했을 때의 방사선 피폭선량을 측정하였으며, 얻어진 영상을 통하여 SNR과 CNR을 측정하였다. 연구 결과 방사선 차폐체의 크기에 비례하여 생식선의 방사선 피폭선량은 감소하였으나 복부의 방사선 피폭선량은 오히려 증가되는 것으로 나타났으며 화질의 변화는 나타나지 않았다. AEC System 사용으로 인하여 방사선 차폐체로 인하여 증가된 방사선으로 인하여과 피폭되지 않도록 소아 환자의 연령과 몸무게, 신체 크기에 최적화된 크기의 차폐체를 사용하는 것이 효과적이라는 것을 확인할 수 있었다.

• 한국의학물리학회지:의학물리
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• 제1권1호
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• pp.23-29
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• 1990

In order to explane the stereotactic procedure, the three steps of the procedure (target localization, dose planning, and radiation treatment) must be examined separately. The ultimate accuracy of the full procedure is dependent on each of these steps and on the consistancy of the approach The concern in this article was about dose planning, which is a important factor to the success of radiation treatment. The major factor in dose planning is a dosimetry system to evaluate the dose delivered to the target and normal tissues in the patient, while it generates an optimal dose distribution that will satisfy a set of clinical criteria for the patient. A three-dimensional treatment planning program is a prerequisite for treatment plan optimization. It must cover 3-D methods for representing the patient, the dose distributions, and beam settings. The major problems and possible modelings about 3-D factors and optimization technique were discussed to simplify and solve the problems associatied with 3-D optimization, with relative ease and efficiency. These modification can simplify the optimization problem while saving time, and can be used to develop reference dose planning system to prepare standard guideline for the selection of optimum beam parameters, such as the target position, collimator size, arc spacing, the variation in arc length and weight. The method yields good results which can then be simulated and tailored to the individual case. The procedure needed for dose planning in stereotactic radiosurgery is shown in figure 1.

• 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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• 제12권2호
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• pp.97-101
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• 2010

This experimental study is carried out one of the General Hospital in Kyungbok providence. Abdomen Phantom being located Anterior-posterior(AP) position on portable bed, and the portable X-ray generating device was placed the phantom at $-90^{\circ}$ direction. The experiment were set 65 kVp, 10 mAs, $10{\times}10\;cm^2$, 100 cm(FOD) for the measurement. Digital proportional counting tube survey meter was used for measuring the space scatter dose. Measurement points of horizontal distribution was set up at $30^{\circ}$ interval by increasing 50 cm radius of upside, downside, left and right. Vertical distribution of measurement points were set up for the vertical plane with a radius of at $30^{\circ}$ intervals with 50cm increments. It is concluded that longer distance from the soure of X-ray significantly decrease radiation dose to the patient and use of the radiation protection device should be applied in clinical practice to reduce dose to the patient.

• 한국의학물리학회지:의학물리
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• 제30권1호
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• pp.32-38
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• 2019

Purpose: The objective of this study is to evaluate the geometrical accuracy of a patient-specific bolus based on a three-dimensional (3D) printed mold and casting method. Materials and Methods: Three breast cancer patients undergoing treatment for a superficial region were scanned using computed tomography (CT) and a designed bolus structure through a treatment planning system (TPS). For the fabrication of patient-specific bolus, we cast harmless certified silicone into 3D printed molds. The produced bolus was also imaged using CT under the same conditions as the patient CT to acquire its geometrical shape. We compared the shapes of the produced bolus with the planned bolus structure from the TPS by measuring the average distance between two structures after a surface registration. Results and Conclusions: The result of the average difference in distance was within 1 mm and, as the worst case, the absolute difference did not exceed ${\pm}2mm$. The result of the geometric difference in the cross-section profile of each bolus was approximately 1 mm, which is a similar property of the average difference in distance. This discrepancy was negligible in affecting the dose reduction. The proposed fabrication of patient-specific bolus is useful for radiation therapy in the treatment of superficial regions, particularly those with an irregular shape.

• 한국콘텐츠학회논문지
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• 제10권2호
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• pp.258-267
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• 2010

방사선피폭에 대한 관심이 높아지면서 X선 검사시에 환자에게 조사되는 피폭선량을 정확히 알고 있다는 것은 환자의 불안을 해소하고 또 방사선사나 의사가 피폭선량 경감의식을 향상시키는 데 중요하지만, 임상에서 측정기를 보유하고 있는 시설은 극소수에 불과하다. 본 연구에서는 bit system 및 NDD-M법의 특징을 살려서 우리나라에 사용되고 있는 진단용 X선장치의 출력선량을 직접 측정하여 도표화 하고, X선 출력선량을 아는 경우 또는 모르는 경우 모두에서 적절히 적용할 수 있게 두 가지 방법을 제시하여 실측선량과 비교 실험을 하였다. 그 결과 bit system 및 NDD-M법보다 정확도가 우수한 결과를 나타내어 임상에서 환자가 받는 선량을 더욱 쉽게 알 수 있게 됨으로 방사선관련 종사자들의 의료피폭에 대한 관심이 더욱 높아지고 의료선량감소에 한층 더 노력하는 계기가 될 것으로 사료된다.

• Journal of Radiation Protection and Research
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• 제42권1호
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• pp.9-15
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• 2017

Background: The purpose of this study is to assign an appropriate density to virtual phantom for 2D diode array detector with different dose calculation algorithms to guarantee the accuracy of patient-specific QA. Materials and Methods: Ten VMAT plans with 6 MV photon beam and ten VMAT plans with 15 MV photon beam were selected retrospectively. The computed tomography (CT) images of MapCHECK2 with MapPHAN were acquired to design the virtual phantom images. For all plans, dose distributions were calculated for the virtual phantoms with four different materials by AAA and AXB algorithms. The four materials were polystyrene, 455 HU, Jursinic phantom, and PVC. Passing rates for several gamma criteria were calculated by comparing the measured dose distribution with calculated dose distributions of four materials. Results and Discussion: For validation of AXB modeling in clinic, the mean percentages of agreement in the cases of dose difference criteria of 1.0% and 2.0% for 6 MV were $97.2%{\pm}2.3%$, and $99.4%{\pm}1.1%$, respectively while those for 15 MV were $98.5%{\pm}0.85%$ and $99.8%{\pm}0.2%$, respectively. In the case of 2%/2 mm, all mean passing rates were more than 96.0% and 97.2% for 6 MV and 15 MV, respectively, regardless of the virtual phantoms of different materials and dose calculation algorithms. The passing rates in all criteria slightly increased for AXB as well as AAA when using 455 HU rather than polystyrene. Conclusion: The virtual phantom which had a 455 HU values showed high passing rates for all gamma criteria. To guarantee the accuracy of patent-specific VMAT QA, each institution should fine-tune the mass density or HU values of this device.