• Title, Summary, Keyword: Dose distribution

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Bi-material Bolus for Minimizing the Non-uniformity of Proton Dose Distribution

  • Takada, Yoshihisa;Kohno, Syunsuke
    • Proceedings of the Korean Society of Medical Physics Conference
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    • pp.214-215
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    • 2002
  • Generally uniform dose distribution is assumed to be formed in a target region when a conventional dose formation method using a broad proton beam, a fixed modulation technique, a bolus and an aperture is employed. However, actual situations differ. We usually find non-uniformity in the target region. This is due to the insertion of a range-compensating bolus before the patient. Since the range-compensating bolus has an irregular shape, the scattering in the bolus depends on the lateral position. Dose distribution is overlapping results of dose distribution of pencil-proton beams traversing different lateral positions of the bolus. The lateral extent of dose distribution of each pencil beam traversing the different position differs each other at the same depth in the target object. This is a cause of the non-uniformity of the dose distribution. Therefore the same lateral extent of dose distribution should be attained for different pencil beams at the same depth to obtain a uniform dose distribution. For that purpose, we propose here a bi-material bolus. The bi-material bolus consists of a low-Z material determining mainly the range loss and a high-Z material defining mainly the scattering in the bolus. After passing through the bi-material bolus, protons traversing different lateral positions will have different residual range yet with the same lateral spread at a certain depth. Using the optimized bi-material bolus, we can obtain a more uniform dose distribution in the target region as expected.

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Geant4-DICOM Interface-based Monte Carlo Simulation to Assess Dose Distributions inside the Human Body during X-Ray Irradiation

  • Kim, Sang-Tae
    • International Journal of Contents
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    • v.8 no.2
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    • pp.52-59
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    • 2012
  • This study uses digital imaging and communications in medicine (DICOM) files acquired after CT scan to obtain the absorbed dose distribution inside the body by using the patient's actual anatomical data; uses geometry and tracking (Geant)4 as a way to obtain the accurate absorbed dose distribution inside the body. This method is easier to establish the radioprotection plan through estimating the absorbed dose distribution inside the body compared to the evaluation of absorbed dose using thermo-luminescence dosimeter (TLD) with inferior reliability and accuracy because many variables act on result values with respect to the evaluation of the patient's absorbed dose distribution in diagnostic imaging and the evaluation of absorbed dose using phantom; can contribute to improving reliability accuracy and reproducibility; it makes significance in that it can implement the actual patient's absorbed dose distribution, not just mere estimation using mathematical phantom or humanoid phantom. When comparing the absorbed dose in polymethly methacrylate (PMMA) phantom measured in metal oxide semiconductor field effect transistor (MOSFET) dosimeter for verification of Geant4 and the result of Geant4 simulation, there was $0.46{\pm}4.69%$ ($15{\times}15cm^2$), and $-0.75{\pm}5.19%$ ($20{\times}20cm^2$) difference according to the depth. This study, through the simulation by means of Geant4, suggests a new way to calculate the actual dose of radiation exposure of patients through DICOM interface.

Development of Diode Based High Energy X-ray Spatial Dose Distribution Measuring Device

  • Lee, Jeonghee;Kim, Ikhyun;Park, Jong-Won;Lim, Yong-Kon;Moon, Myungkook;Lee, Sangheon;Lim, Chang Hwy
    • Journal of Radiation Protection and Research
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    • v.43 no.3
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    • pp.97-106
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    • 2018
  • Background: A cargo container scanner using a high-energy X-ray generates a fan beam X-ray to acquire a transmitted image. Because the generated X-rays by LINAC may affect the image quality and radiation protection of the system, it is necessary to acquire accurate information about the generated X-ray beam distribution. In this paper, a diode-based multi-channel spatial dose measuring device for measuring the X-ray dose distribution developed for measuring the high energy X-ray beam distribution of the container scanner is described. Materials and Methods: The developed high-energy X-ray spatial dose distribution measuring device can measure the spatial distribution of X-rays using 128 diode-based X-ray sensors. And precise measurement of the beam distribution is possible through automatic positioning in the vertical and horizontal directions. The response characteristics of the measurement system were evaluated by comparing the signal gain difference of each pixel, response linearity according to X-ray incident dose change, evaluation of resolution, and measurement of two-dimensional spatial beam distribution. Results and Discussion: As a result, it was found that the difference between the maximum value and the minimum value of the response signal according to the incident position showed a difference of about 10%, and the response signal was linearly increased. And it has been confirmed that high-resolution and two-dimensional measurements are possible. Conclusion: The developed X-ray spatial dose measuring device was evaluated as suitable for dose measurement of high energy X-ray through confirmation of linearity of response signal, spatial uniformity, high resolution measuring ability and ability to measure spatial dose. We will perform precise measurement of the X-ray beamline in the container scanning system using the X-ray spatial dose distribution measuring device developed through this research.

Determination of Dose Distribution under Nonequivalent Condition by Prosthesis in Radiotherapy (방사선 치료시 인공고관절 삽입에 의한 불균질면에서의 선량분포 평가)

  • Lee, Joon-Il;Kim, Sung-Hwan
    • Journal of radiological science and technology
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    • v.21 no.2
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    • pp.43-46
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    • 1998
  • When a patient was irradiated with prosthetic hip, the dose distribution was changed according to inhomogeneous materials. The density, effective atomic number, and the composition of material had influence on absorbed dose distribution. In this study, the influence of inhomogeneous material(Ti) was measured using a polyethylene phantom, which consisted of various diameter of titanium, with film dosimetry. As a result, the backward dose showed 29.5% increas by backscattering, the forward dose showed 28% decreas by absorption, and the side dose showed 7% increas by scattering, when 25 mm diameter Ti was used. In addition forward dose was in inverse proportion to the thickness of prosthetic material. When the prosthetic hip of patient is in an irradiated field, we must carefully study the absorbed dose distribution.

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A New Method for Measuring the Dose Distribution of the Radiotherapy Domain using the IP

  • Homma, Mitsuhiko;Tabushi, Katsuyoshi;Obata, Yasunori;Tamiya, Tadashi;Koyama, Shuji;Kurooka, Masahiko;Shimomura, Kouhei;Ishigaki, Takeo
    • Proceedings of the Korean Society of Medical Physics Conference
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    • pp.237-240
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    • 2002
  • Knowing the dose distribution in a tissue is as important as being able to measure exposure or absorbed dose in radiotherapy. Since the Dry Imager spread, the wet type automatic processor is no longer used. Furthermore, the waste fluid after film development process brings about a serious problem for prevention of pollution. Therefore, we have developed a measurement method for the dose distribution (CR dosimetry) in the phantom based on the imaging plate (IP) of the computed radiography (CR). The IP was applied for the dose measurement as a dosimeter instead of the film used for film dosimetry. The data from the irradiated IP were processed by a personal computer with 10 bits and were depicted as absorbed dose distributions in the phantom. The image of the dose distribution was obtained from the CR system using the DICOM form. The CR dosimetry is an application of CR system currently employed in medical examinations to dosimetry in radiotherapy. A dose distribution can be easily shown by the Dose Distribution Depiction System we developed this time. Moreover, the measurement method is simpler and a result is obtained more quickly compared with film dosimetry.

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Solution to Decrease Spatial Dose Rate in Laboratory of Nuclear Medicine through System Improvement (시스템 개선을 통한 핵의학 검사실의 공간 선량률 감소방안)

  • Moon, Jae-Seung;Shin, Min-Yong;Ahn, Seong-Cheol;Yoo, Mun-Gon;Kim, Su-Geun
    • Quality Improvement in Health Care
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    • v.20 no.1
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    • pp.60-73
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    • 2014
  • Objectives: This study aims at decreasing spatial dose rate through work improvement whilst spatial dose rate is the cause of increasing personal exposure dose which occurs in the process of handling radioisotope. Methods: From February 2013 until July 2013, divided into "before" and "after" the improvement, spatial dose rate in laboratory of nuclear medicine was measured in gamma image room, PET/CT-1 image room, and PET/CT-2 image room as its locations. The measurement time was 08:00, 12:00 and 17:00, and SPSS 21.0 USA was opted for its statistical analysis. Result: The spatial dose rate at distribution worktable, injection table, the entrance to the distribution room, and radioisotope storage box, which had showed high spatial dose rate, decreased by more than 43.7% a monthly average. The distribution worktable, that had showed the highest spatial dose rate in PET/CT-1 image room, dropped the rate to 42.3% as of July. The injection table and distribution worktable in the PET/CT-2 image room also showed the decline of spatial dose rate to 89% and 64.4%, respectively. Conclusion: By improving distribution process and introducing proper radiation shielding material, we were able to drop the spatial dose rate substantially at distribution worktable, injection table, and nuclide storage box. However, taking into account of steadily increasing amount of radioisotope used, strengthening radiation related regulations, and safe utilization of radioisotope, the process of system improvement needs to be maintained through continuous monitoring.

Dose Distribution of Total Body Irradiation for Bone Marrow Transplantation in Leukemia (백혈병에서 골수이식을 위한 전신방사선조사시 선량분포 특성)

  • 김성규;김명세;신세원
    • Progress in Medical Physics
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    • v.7 no.2
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    • pp.47-55
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    • 1996
  • Total Body Irradiation(TBI) is one of the essential treatment modalities in bone marrow transplantation for leukemia and lymphoma. Various techniques and dose regimens were introduced with sevelal advantages and disadvantages. In TBI, lung block could reduce lung dose to 75% of original beam for decreasing lung dose with homogenous total body irradiation. Accurate provision for specified dose and the desired homogeneity are essential before clinical total body irradiation. When performed in total body irradiation, the problem obtain uniform dose distribution in brain, neck, lung, umbilicus, pelvis and leg. Authors compared to dose distribution with method 1 and method 2. The method 1 used compensating filters for homogeneous dose distribution(Minesota University Method). The method 2 used fixing frame made in aeryl developing authors. Results were following. 1. Method 1 was showed dose distribution from 95.6% to 100%, method 2 showed dose distribution from 95.4% to 100%. 2. Method 2 was showed different to 3.4% at skin region and midline in the brain. In the neck, showed different to 1.5%. In the umbilicus. showed different to 2.3%.

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Dose Distribution of $^{11}C$ Beams for Spot Scanning Radiotherapy

  • Urakabe, Eriko;Kanai, Tatsuaki;Kanazawa, Mitsutaka;Kitagawa, Atsushi;Noda, Koji;Tomitani, Takehiro;Suda, Mitsuru;Mizuno, Hideyuki;Iseki, Yasushi
    • Proceedings of the Korean Society of Medical Physics Conference
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    • pp.202-205
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    • 2002
  • This paper describes the spot scanning with $^{11}$ C beams for the Heavy Ion Medical Accelerator in Chiba (HIMAC). The concave-shaped irradiation field was optimized and the dose distribution was measured by 128-ch ionization chamber. Because of the wide momentum spread inherent in $^{11}$ C beams, the dispersion caused from the beam line and the scanning magnets should be taken into account to calculate the dose distribution of $^{11}$ C beams and their irradiated field. The reconstructed dose distribution is in good agreement with the experimental results.

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Analysis of Dose Distribution of IORT Cone (IORT CONE의 선량분포에 관한 연구)

  • 김명세;김성규;신세원
    • Progress in Medical Physics
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    • v.2 no.2
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    • pp.141-148
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    • 1991
  • A since authors started IORT for stomach cancer patient on 198, we developed various sized, shaped IORT cones for better clinical application and homogeneous surface and depth dose distribution. Authors concluded as following. 1. The shaping block should be fixed on the tray, not under the tray for homogeneous dose distribution. 2. The straight cone was showed better dose distribution than divergence cone. 3. The acryl cone was superior than the stainless-steel cone. 4. The acryl cover fixed on the end for IORT cone not only improvement of surface dose, but also homogenity of depth dose.

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Measurement of the Spatial Dose Rate for Distribution Room in Department of Nuclear Medicine (핵의학과 분배실 내의 공간선량률 측정)

  • Park, Jeong-Kyu;Cho, Euy-Hyun
    • Journal of Digital Contents Society
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    • v.13 no.2
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    • pp.151-157
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    • 2012
  • Even though the protective facility is well made with the development of medicine, the spatial dose within the radiation section could increase the exposure of the workers. The spatial dose is always present in distribution room within the Department of Nuclear Medicine, so the spatial dose of the interior distribution room is measured and analyzed for the prediction of the exposure dose. The spatial dose rate was $6.78{\pm}0.083{\mu}Sv/h$ in the $^{18}F$ distribution room of department of Nuclear Medicine, $9.248{\pm}0.013{\mu}Sv/h$ in $^{99m}Tc$, and $^{131}I$ distribution room. In addition, in case of $^{18}F$ distribution room, the yearly external exposure dose was $42.5{\mu}Sv$ when the nurse does IV in 1m in distance. It also showed that the spatial dose rate on the direction of right oblique showed higher than others by the standard of distribution window of distribution room. Therefore, the staying time of the workers should be short during distributing radiopharmaceuticals in the distribution room and the design of the distribution protection is necessary to reduce the exposure in the direction of right oblique of the protection. The utmost endeavors are required to reduce the worker's individual exposure dose while doing IV.