• Title/Summary/Keyword: 전자선량분포

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Effect of an Acrylic Plate and SSD on Dose Profile and Depth Dose Distribution of 9 MeV Electron Beams (에너지 저하체로서 아크릴과 SSD 가 9MeV 전자선의 측방 및 깊이선량분포에 미치는 효과)

  • 강위생
    • Progress in Medical Physics
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    • v.9 no.2
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    • pp.65-71
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    • 1998
  • The aims are to evaluate the effects of an 1.0 cm acrylic plate and SSD on the dose profile and depth dose distribution of 9 MeV electron beam and to analyse adequacy for using an acrylic plate to reduce energy of electron beams. An acrylic plate of 1.0 cm thickness was used to reduce energy of 9 MeV electron beam to 7 MeV. The plate was put on an electron applicator at 65.4 cm distance from x-ray target. The size of the applicator was 10${\times}$l0cm at 100 cm SSD. For 100cm, l05cm and 110cm SSD, depth dose on beam axis and dose profiles at d$\_$max/ on two principal axes were measured using a 3D water phantom. From depth dose distributions, d$\_$max/, d$\_$85/, d$\_$50/ and R$\_$p/, surface dose, and mean energy and peak energy at surface were compared. From dose profiles flatness, penumbra width and actual field size were compared. For comparison, 9 MeV electron beams were measured. Surface dose of 7 MeV electron beams was changed from 85.5% to 82.2% increasing SSD from 100 cm to 110 cm, and except for dose buildup region, depth dose distributions were independent of SSD. Flatness of 7 MeV ranged from 4.7% to 10.4% increasing SSD, comparing 1.4% to 3.5% for 9 MeV. Penumbra width of 7 MeV ranged from 1.52 cm to 3.03 cm, comparing 1.14 cm to 1.63 cm for 9 MeV. Actual field size increased from 10.75 cm to 12.85 cm with SSD, comparing 10.32 cm to 11.46 cm for 9 MeV. Virtual SSD's of 7 and 9 MeV were respectively 49.8 cm and 88.5cm. In using energy reducer in electron therapy, depth dose distribution were independent of SSD except for buildup region as well as open field. In case of using energy reducer, increasing SSD made flatness to deteriorate more severely, penumbra width more wide, field size to increase more rapidly and virtual SSD more short comparing with original electron beam. In conclusion, it is desirable to use no energy reducer for electron beam, especially for long SSD.

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Evaluation of Electron Beam Dose Distribution by Age Diffusion Equation (연령 확산 이론에 의한 전자선의 조직내 선량분포 평가)

  • 추성실
    • Progress in Medical Physics
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    • v.4 no.1
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    • pp.29-39
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    • 1993
  • Electron beams have found unique and complementary used in the treatment of cancer, but it's very difficult to delineate dose distribution, because of multi-collisions. Numerical solution is more usefull to describe electron distributed in tissue. A semi-empirical eqution is given for the dose at any point at various depths in water. This equation is a modificated model which was based on solutions of a general age diffusion equation. Parameters have been calulated from electron beams data with energies 6~18MeV form a LINAC for use in computerised dosimetry calculations. The depth doses and isodose curves are predicted as a function of the practical range, source skin distance and field size. Depth dose accuracy have been achieved 2% above 50% depth dose and 5% at lower doses, relative to maximum dose. Also, the shape of the isodose curves with the constrictions at higher dose and bulging ot lower values are accurately predicted. Computer calculated beams have been used to generate ever isodose distribution for certain clinical situations.

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Development of Dose Verification Method for In vivo Dosimetry in External Radiotherapy (방사선치료에서 투과선량을 이용한 체내선량 검증프로그램 개발)

  • Hwang, Ui-Jung;Baek, Tae Seong;Yoon, Myonggeun
    • Progress in Medical Physics
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    • v.25 no.1
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    • pp.23-30
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    • 2014
  • The purpose of this study is to evaluate the developed dose verification program for in vivo dosimetry based on transit dose in radiotherapy. Five intensity modulated radiotherapy (IMRT) plans of lung cancer patients were used in the irradiation of a homogeneous solid water phantom and anthropomorphic phantom. Transit dose distribution was measured using electronic portal imaging device (EPID) and used for the calculation of in vivo dose in patient. The average passing rate compared with treatment planning system based on a gamma index with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit was 95% for the in vivo dose with the homogeneous phantom, but was reduced to 81.8% for the in vivo dose with the anthropomorphic phantom. This feasibility study suggested that transit dose-based in vivo dosimetry can provide information about the actual dose delivery to patients in the treatment room.

Comparison of Electron Beam Dosimetries by Means of Several Kinds of Dosimeters (수종의 측정기에 의한 전자선의 선량 측정의 비교)

  • Kang Wee-Saing
    • Radiation Oncology Journal
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    • v.7 no.1
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    • pp.93-100
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    • 1989
  • Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon Pmt junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and $90\%$ doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of $10\times10cm^2$ field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed $4\%$ difference between maximum and minimum. For 18MeV, depths of 80 and $90\%$ doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18MeV.

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Fabrication and Dosimetry Characteristics of Intracavitary Cones for Radiotherapy (방사선 강내치료를 위한 소조사면 전자선cone의 선량분포 특성)

  • 나수경;권수일
    • Progress in Medical Physics
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    • v.12 no.1
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    • pp.95-102
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    • 2001
  • The intracavitary cones were designed which were made of stainless steel and have scratched inside cone to be generated electron scatter and designed to be attached easily to the LINAC collimator and controlled cones length to be contacted smoothly between the patient and the cone tip. Two types of intracavitary cones were designed. One is the straight end cones with circular opening on the distal end and the other is 30 degree beveled end cones with elliptical opening on the distal end. Each type of intracavitary cone ranged in daimeter from 2.5 cm to 3.5 cm and required a separate set of lower trimmer annulias cone diameter. The film phantom was designed with an internal cassette that accurately aligned the film edge with the film phantom surface. Film optical density data were measured by photodensitometer(Wellhofer 700i) Dosimetry measurements were made to commission the LINAC for 6 - 20 MeV electron using the intracavitary cones. Isodose curves were measured for all energy and cones combinations. Output is defined as the maximum dose per MU along the clinical central axis in water at 113 cm SSD. Calibration output, defined to be the output for the 15cm$\times$15cm diameter straight cone, was adjusted to 1.00 cGy/MU at each energy according to the TG-21 protocol.

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Dose Characteristics of Total-Skin Electron-Beam Irradiation with Six-Dual Electron Fields (Six-Dual 전자선 조사면에 의한 전신 피부 조사의 선량 특성)

  • Choi, Tae-Jin;Kim, Jin-Hee;Kim, Ok-Bae
    • Radiation Oncology Journal
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    • v.16 no.3
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    • pp.337-345
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    • 1998
  • Purpose : To obtain the uniform dose at limited depth to entire surface of the body, the dose characteristics of degraded electron beam of the large target-skin distance and the dose distribution of the six-dual electron fields were investigated Materials and Method : The experimental dose distributions included the depth dose curve, spatial dose and attenuated electron beam were determined with 300 cm of target-skin distance (TSD) and full collimator size (35*35 $cm^2$ on TSD 100 cm) in 4 MeV electron beam energy. Actual collimated field size of 105 cm * 105 cm at the distance of 300 cm could include entire hemibody. A patient was standing on step board with hands up and holding the pole to stabilize his/her positions for the six-dual fields technique. As a scatter-degrader, 0.5 cm of acrylic plate was inserted at 20 cm from the body surface on the electron beam path to induce ray scattering and to increase the skin dose. Results : The full width at half maximum(FWHM) of dose profile was 130 cm in large field of 105*105 $cm^2$ The width of $100\pm10\%$ of the resultant dose from two adjacent fields which were separated at 25 cm from field edge for obtaining the dose unifomity was extended to 186 cm. The depth of maximum dose lies at 5 mm and the 80$\%$ depth dose lies between 7 and 8 mm for the degraded electron beam by using the 0.5 cm thickness of acrylic absorber. Total skin electron beam irradiation (TSEBI) was carried out using the six dual fields has been developed at Stanford University. The dose distribution in TSEBI showed relatively uniform around the flat region of skin except the protruding and deeply curvatured portion of the body, which showed excess of dose at the former and less dose at the latter. Conclusion : The percent depth dose, profile curves and superimposed dose distribution were investigated using the degraded electron beam through the beam absorber. The dose distribution obtained by experiments of TSEBI showed within$\pm10\%$ difference except the protruding area of skin which needs a shield and deeply curvatured region of skin which needs boosting dose.

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Characteristics of Dose Distribution at Junctional Area Using the Divergency Cutout Block in the Abutted Field of Photon and Electron Beams (광자선과 전자선의 인접조사에서 선속 퍼짐현상이 고려된 전자선 차폐물을 이용한 접합 조사면의 선량분포 특성)

  • Im, In-Chul;Lee, Jae-Seung
    • Journal of Radiation Protection and Research
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    • v.36 no.3
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    • pp.168-173
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    • 2011
  • This study investigated characteristics of dose distribution at junction field of X-ray and electron beams according to the method for fabricating the insert block on the electron cone. Insert block were fabricated to the divergency cutout block and the straight cutout block. For the 6 MV X-ray and 10 MeV nominal energy of electron beam, we was adjacent to the light field of X-ray and electron beam at a surface of matrix chamber and measured to beam profile of abutted field in the 0, 1, 2, 3 cm measurement depth. As a result, characteristics of dose distribution at junction field, straight block was existent that over dose area exceed the give dose more than 5% and under dose area with a rapid change in dose distribution. However, divergency block had remarkably decreased the over dose area caused by the lateral scattering effects of decrease, and being existed uniformity dose distribution in the junction field. Therefore, divergency block were the benefits of radiation dose delivery, in order to applied the clinical, measurement of electron beams according to the fabrication method of the block should be considered carefully.

Dosimetry by Using EBT2 Film for Total Skin Electron Beam Therapy (TSET) (전신 피부 전자선 치료(TSET)에서 EBT2 필름을 사용한 선량측정)

  • Hwang, Ui-Jung;Rah, Jeong-Eun;Jeong, Ho-Jin;Ahn, Sung-Hwan;Kim, Dong-Wook;Lee, Sang-Yeob;Lim, Young-Gyung;Yoon, Myong-Geun;Shin, Dong-Ho;Lee, Se-Byeong;Park, Sung-Young;Pyo, Hong-Ryull;Chung, Weon-Kuu
    • Progress in Medical Physics
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    • v.21 no.1
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    • pp.60-69
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    • 2010
  • For treatment of Total Skin Electron beam Therapy (TSET), measurement of dose at various conditions is need on the contrary to usual radiotherapy. When treating TSET with modified Stanford technique based on linear accelerator, the energy of treatment electron beam, the spatial dose distribution and the actual doses deposited on the surface of the patient were measured by using EBT2. The measured energy of the electron beam was agreed with the value that measured by ionization chamber, and the spatial dose distribution at the patient position and the doses at several point on the patient's skin could be easily measured by EBT2 film. The dose on the patient that was measured by EBT2 film showed good agreement with the data measured simultaneously by TLD. With the results of this study, it was proven that the EBT2 film can be one of the useful dosimeter for TSET.

Dose Distribution According to the Tissue Composition Using Wedge Filter by Radiochromic Film (쐐기필터 사용 시 레디오크로믹 필름을 이용한 조직에 따른 선량분포 연구)

  • Kim, Yon-Lae;Lee, Jeong-Woo;Park, Byung-Moon;Jung, Jae-Yong;Park, Ji-Yeon;Suh, Tae-Suk
    • Journal of radiological science and technology
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    • v.35 no.2
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    • pp.157-164
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    • 2012
  • The purpose of this study is to analyze the dose distribution when wedge filter is used in the various tissue electron density materials. The dose distribution was assessed that the enhanced dynamic wedge filter and physical wedge filter were used in the solid water phantom, cork phantom, and air cavity. The film dosimetry was suitable simple to measure 2D dose distribution. Therefore, the radiochromic films (Gafchromic EBT2, ISP, NJ, USA) were selected to measure and to analyze the dose distributions. A linear accelerator using 6 MV photon were irradiated to field size of $10{\times}10cm^2$ with 400 MUs. The dose distributions of EBT2 films were analyzed the in-field area and penumbra regions by using dose analysis program. In the dose distributions of wedge field, the dose from a physical wedge was higher than that from a dynamic wedge at the same electron density materials. A dose distributions of wedge type in the solid water phantom and the cork phantom were in agreements with 2%. However, the dose distribution in air cavity showed the large difference with those in the solid water phantom or cork phantom dose distributions. Dose distribution of wedge field in air cavity was not shown the wedge effect. The penumbra width, out of the field of thick and thin, was observed larger from 1 cm to 2 cm at the thick end. The penumbra of physical wedge filter was much larger average 6% than the dynamic wedge filter. If the physical wedge filter is used, the dose was increased to effect the scatter that interacted with photon and physical wedge. In the case of difference in electron like the soft tissue, lung, and air, the transmission, absorption, and scattering were changed in the medium at high energy photon. Therefore, the treatment at the difference electron density should be inhomogeneity correction in treatment planning system.

The Calculation of Energy Distributions for Clinical Electron Beams from Mono Energetic Depth dose Data (단일에너지 깊이선량률 자료에 의한 치료용 전자선의 에너지분포 계산)

  • 이정옥;정동혁
    • Progress in Medical Physics
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    • v.15 no.1
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    • pp.39-44
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    • 2004
  • The energy distributions for clinically used electron beams from measured and calculated mono energetic depth dose values were calculated. The energy distributions having the minimum difference between the measured and reduced values of depth dose are determined by iterations based on least square method. The nominal energies of 6, 9, 12, 15 MeV clinical electron beams were examined. The Monte Carlo depth dose calculations with determined energy distributions were peformed to evaluate those distributions. In a comparison of the calculated and measured depth dose data, the standard errors are estimated within $\pm$ 3% from surface to R$_{80}$ depth and within $\pm$4% from the surface to near the range for all electron beams. This can be practically applied to determine the energy distributions for clinically used electron beams.

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