• 한국의학물리학회지:의학물리
• /
• 제9권3호
• /
• pp.175-184
• /
• 1998

감마나이프를 이용하는 정위적 방사선 수술 치료계획 프로그램 중에서 선량계산 프로그램을 PC에서 작성하고, 작성한 프로그램 GP1(Gamma Project 1) 을 상용화된 치료계획 프로그램인 KULA와 비교하여 선량분포 50% 지점에서 등선량분포의 차이와 편차를 계산함으로써 GPI을 평가하고자 한다. 또한 radiochromic 필름에 감마나이프로 방사선을 조사하여 선량분포를 계산하고, 이를 KULA, GPI에 의한 선량분포와 비교하여 GPI을 검증하고자 한다. 프로그램 작성은 프로그램 제작 언어인 IDL(Interactive Data Language)을 사용하였으며, 선량계산 알고리듬은 상용 치료계획 프로그램인 KULA의 알고리듬을 사용하였다. GP1을 평가하기 위해 반경이 80 mm인 구형 팬톰 중심에서 각 콜리메이터마다 세 방향 (축상면, 시상면, 관상면)에서의 선량분포를 계산하고, 이를 KULA에 의한 선량분포와 비교하였다. 또한 팬톰내 임의의 한 지점에서 GPl과 KULA에 의한 선량분포를 비교하여 두 프로그램간의 선량분포 차이를 계산하였다. 이를 검증하기 위해 팬톰 내부에 radiochromic 필름올 장치하여 방사선을 조사한 후 필름의 선량분포를 상용화된 프로그램 KULA와 본 연구에서 작성한 프로그램 GP1에 의한 선량분포와 비교하여 그 차이를 확인하였다. 그 결과 팬톰 중심에서 GPl과 KULA에 의한 선량분포는 50% 선량분포에서 $\pm$3% 이내의 편차를 나타내었으며, 임의의 지점에서도 같은 결과를 보여주었다. 콜리메이터 크기가 작고 선량분포의 값이 작을수록 두 프로그램의 차이가 커짐을 알 수 있었다. GPl 검증을 위한 필름에서의 선량분포 또한 두 프로그램에서의 선량분포와 잘 일치함을 알 수 있었다. 이로써 치료계획시 GPl에 의한 선량분포의 사용이 가능성을 확인하였다.

• 대한디지털의료영상학회논문지
• /
• 제11권1호
• /
• pp.5-13
• /
• 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
• /
• 제9권1호
• /
• pp.87-93
• /
• 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.

• 대한방사선치료학회지
• /
• 제10권1호
• /
• pp.88-93
• /
• 1998

Multileaf collimator is essential equipment in conformal radiation therapy, however the use is limitted by increase of penumbra width and undulating dose distribution at the field edge. The purpose of this study is to improve the penumbra and dose distribution in the multileaf collimator field edge. Measurement were performed with X-omat V film in solid water phantom using 6MV photon beam from Siemens linear accelerator. All the measurement were made along the central axis of $5{\times}5cm,\;10{\times}10cm$ circular field for constant SSD of 100 cm. To improve the penumbra and dose distribution collimator was rotated by 15 degrees from 0 to 90 degrees (collimator rotation method) and center was shifted to the longitudinal direction by fourth of lead width (center shift method). We compare the penumbra and dose distribution at the field edge to alloy block. Dose distribution and penumbra width at the feild edge of MLC showed undulated dose pattern and increased penumbra compared with alloy block. However, in the collimator rotation method and center shift method we abtained simular results with alloy block. Through the study we expected that clinical use of MLC will be increase.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.260-262
• /
• 2002

An accurate measurement of dose distribution is indispensable to perform radiation therapy planning. A measurement technique using a radiographic film, which is called a film dosimetry, is widely used because it is easy to obtain a dose distribution with a good special resolution. In this study, we tried to develop an analyzing system for the film dosimetry using usual office automation equipments such as a personal computer and an image scanner. A film was sandwiched between two solid water phantom blocks (30 ${\times}$ 30 ${\times}$ 15cm). The film was exposed with Cobalt-60 ${\gamma}$-ray whose beam axis was parallel to the film surface. The density distribution on the exposed film was stored in a personal computer through an image scanner (8bits) and the film density was shown as the digital value with NIH-image software. Isodose curves were obtained from the relationship between the digital value and the absorbed dose calculated from percentage depth dose and absorbed dose at the reference point. The isodose curves were also obtained using an Isodose plotter, for reference. The measurements were carried out for 31cGy (exposure time: 120seconds) and 80cGy (exposure time: 300seconds) at the reference point. While the isodose curves obtained with our system were drawn up to 60% dose range for the case of 80cGy, the isodose curves could be drawn up to 80% dose range for the case of 31cGy. Furthermore, the isodose curves almost agreed with that obtained with the isodose plotter in low dose range. However, further improvement of our system is necessary in high dose range.

• Radiation Oncology Journal
• /
• 제2권2호
• /
• pp.271-280
• /
• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• 대한방사선기술학회지:방사선기술과학
• /
• 제41권6호
• /
• pp.561-566
• /
• 2018

Field-in-Field Technique is applied to the radiation therapy of breast cancer patients, and it is possible to compensate the difference in breast thickness and deliver uniform dose in the breast. However, there are several fields in the treatment field that result in a more complex dose delivery than a single field dose delivery. If the patient's respiration is irregular during the delivery of the dose by several fields and the change of respiration occurs, the dose distribution in the breast changes. Therefore, based on the computed tomography images of breast cancer patients, a human model was created by using a 3D printer (Builder Extreme 1000) to describe the volume in the same manner. A computerized tomography (CT) of the human body model was performed and a treatment plan of 260 cGy / fx was established using a 6-MV field-in-field technique using a computerized treatment planning system (Eclipse 13.6, Varian, USA). The distribution of the dose in the breast according to the change of the respiration was measured using a moving phantom at 0.1 cm, 0.3 cm, 0.5 cm amplitude, using a MOSOXIDE Silicon Field Effect Transistor (MOSFET, Best Medical, Canada) Were measured and compared. The distribution of dose in the breast according to the change of respiration showed similar value within ${\pm}2%$ in the movement up to 0.3 cm compared to the treatment plan. In this experiment, we found that the dose distribution in the breast due to the change of respiration when the change of respiration was increased was not much different from the treatment plan.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.244-247
• /
• 2002

We examined a possibility to use inorganic plastic scintillator, which has the effective atomic number close to that of human soft tissue, for the measurement of dose distributions in a shorter time period. The method was to irradiate a block of plastic scintillator as a phantom, and to measure the distribution of the scintillation light by a wave length analyzer through a thread of plastic optical fiber. By irradiating the diagnostic x-ray, we observed the emission spectrum of the scintillation light from the scintillator. It showed a peak at around 420nm with a full width of 140 nm. The emission spectrum was integrated to determine the total number of photons. The dependences of the amount of photons on the irradiated dose were measured. The results of the experiment show that the amount of emission light is in proportional to the irradiated dose. From this fact, we conclude that the present method can be used for the measurement of the depth dose distribution of the diagnostic x-rays.

• 한국의학물리학회지:의학물리
• /
• 제21권2호
• /
• pp.218-222
• /
• 2010

세기조절방사선치료(intensity modulated radiation therapy, IMRT)는 치료면적을 소조사면으로 나누어 여러 방향에서 방사선이 조사되기 때문에 기존의 치료방법에 비해 많은 MU와 더 긴 치료시간이 요구된다. 통증 및 장애 등으로 인해 장시간 같은 자세를 유지하기 어려운 환자의 경우, 효과적인 치료를 위해서는 선량율을 증가시켜 치료시간을 줄이는 것이 한 방법이다. 본 연구에서는 선량율 변화에 따른 선량 및 선량분포를 측정하고 그 변화를 알아보았다. IMRT 치료계획은 ECLIPSE 시스템(Varian, SomaVision 6.5, USA)을 이용하여, $0^{\circ}$, $72^{\circ}$, $144^{\circ}$, $216^{\circ}$, $288^{\circ}$ 방향의 5문 조사로 계획하였다. 선량율 변화에 따른 선량 및 선량분포 확인을 위해 선량율은 100, 300, 500 MU/min으로 설정하였으며, 선량과 선량분포는 이온함(PTW, TN31014)과 필름(EDR2, Kodak)을 이용하여 각각 측정하였다. 이때 필름 선량계는 아크릴 팬톰에 삽입 후 빔의 조사방향과 나란하게 설치되었고 방사선조사를 위한 선형가속기는 21EX-S (Varian, USA)를 이용하였다. 측정된 필름 선량계는 VXR-16 (Vidar System Corporation)을 이용하여 분석함으로써 선량분포를 확인하였다. 선량율이 증가할수록 CTV를 포함하는 100% 선량분포의 면적이 거의 선형적으로 감소함을 보였다.

• Nuclear Engineering and Technology
• /
• 제49권1호
• /
• pp.189-195
• /
• 2017

Gel dosimeters have unique advantages in comparison with other dosimeters. Until now, these gels have been used in different radiotherapy techniques as a reliable dosimetric tool. Because dose distribution measurement is an important factor for appropriate treatment planning in different radiotherapy techniques, in this study, we evaluated the ability of the N-isopropylacrylamide (NIPAM) polymer gel to record the dose distribution resulting from the mixed neutron-gamma field of boron neutron capture therapy (BNCT). In this regard, a head phantom containing NIPAM gel was irradiated using the Tehran Research Reactor BNCT beam line, and then by a magnetic resonance scanner. Eventually, the $R_2$ maps were obtained in different slices of the phantom by analyzing T2-weighted images. The results show that NIPAM gel has a suitable potential for recording three-dimensional dose distribution in mixed neutron-gamma field dosimetry.