• Title, Summary, Keyword: 투과선량

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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.

Transmission Dose Estimation Algorithm for Irregularly Shaped Radiation Field (부정형 방사선 조사면에 대한 투과선량 보정 알고리즘)

  • Yun Hyong Geun;Chie Eui Kyu;Huh Soon Nyung;Wu Hong Gyun;Lee Hyoung Koo;Shin Kyo Chul;Kim Siyong;Ha Sung Whan
    • Radiation Oncology Journal
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    • v.20 no.3
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    • pp.274-282
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    • 2002
  • Purpose : Measurement of transmission dose is useful for in vivo dosimetry. In this study, the algorithm for estimating the transmission dose for open radiation fields was modified for application to partially blocked radiation fields. Materials and Methods : The beam data was measured with a flat solid phantom with various blocked fields. A new correction algorithm for partially blocked radiation field was developed from the measured data. This algorithm was tested in some settings simulating clinical treatment with an irregular field shape. Results : The correction algorithm for the beam block could accurately reflect the effect of the beam block, with an error within ${\pm}1.0\%$, with both square fields and irregularly shaped fields. Conclusion : This algorithm can accurately estimate the transmission dose in most radiation treatment settings, including irregularly shaped field.

Feasibility Study for Development of Transit Dosimetry Based Patient Dose Verification System Using the Glass Dosimeter (유리선량계를 이용한 투과선량 기반 환자선량 평가 시스템 개발을 위한 가능성 연구)

  • Jeong, Seonghoon;Yoon, Myonggeun;Kim, Dong Wook;Chung, Weon Kuu;Chung, Mijoo;Choi, Sang Hyoun
    • Progress in Medical Physics
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    • v.26 no.4
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    • pp.241-249
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    • 2015
  • As radiation therapy is one of three major cancer treatment methods, many cancer patients get radiation therapy. To exposure as much radiation to cancer while normal tissues near tumor get little radiation, medical physicists make a radiotherapy plan treatment and perform quality assurance before patient treatment. Despite these efforts, unintended medical accidents can occur by some errors. In order to solve the problem, patient internal dose reconstruction methods by measuring transit dose are suggested. As feasibility study for development of patient dose verification system, inverse square law, percentage depth dose and scatter factor are used to calculate dose in the water-equivalent homogeneous phantom. As a calibration results of ionization chamber and glass dosimeter to transit radiation, signals of glass dosimeter are 0.824 times at 6 MV and 0.736 times at 10 MV compared to dose measured by ionization chamber. Average scatter factor is 1.4 and Mayneord F factor was used to apply percentage depth dose data. When we verified the algorithm using the water-equivalent homogeneous phantom, maximum error was 1.65%.

Empirical Determination of a CT X-ray Spectra by Numerical Analysis using Transmission Data (투과선량의 수치해석에 의한 전산화단층영상장치 X선의 에너지 분포결정)

  • 최태진;김옥배;서수지
    • Progress in Medical Physics
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    • v.8 no.2
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    • pp.35-43
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    • 1997
  • The knowledge of x-ray spectra is highly desirable in some investigation involves the differential penetrating power and absorption coefficient correction of various photon beam. The transmission data were obtained from the 80 kVp and 120 kVp of CT x-ray beam with the aluminium filter which is designed in a 30 cm of diameter and pipe-typed filter was prepared from 5.0 mm upto 92.3 mm of thickness. To obtain the reconstructed spectra of CT x-ray, the investigator used the iterative numerical analysis which has been extended to include the tungsten characteristics from experimental transmission data with energy interval of 2 keV. Comparison of the calculated transmission data from the reconstructed spectra with that of measurement shows good agreement in both 80 kVp and 120 kVp x-ray beams. This numerical analysis based on iteratively calculation of fractional exposure per energy interval shows the high potential of usefulness of determination the x-ray spectra from the attenuated beam in diagnostic energy range.

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Transmission Dose Estimation Algorithm for in vivo Dosimertry (투과선량을 이용한 생체내 (in vivo) 선량측정을 위한 알고리즘)

  • Yun, Hyong-Geun;Chie, Eui-Kyu;Huh, Soon-Nyung;Lee, Hyoung-Koo;Woo, Hong-Gyun;Shin, Kyo-Chul;Kim, Si-Yong;Ha, Sung-Whan
    • Journal of Radiation Protection and Research
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    • v.27 no.3
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    • pp.147-154
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    • 2002
  • Purpose : Measurement of transmission dose is useful for in vivo dosimetry of QA purpose. The objective of this study is to develope an algorithm for estimation of tumor dose using measured transmission dose for open radiation field. Materials and Methods : Transmission dose was measured with various field size (FS), phantom thickness (Tp), and phantom chamber distance (PCD) with a acrylic phantom for 6 MV and 10 MV X-ray. Source to chamber distance (SCD) was set to 150 cm. Measurement was conducted with a 0.6 co Farmer type ion chamber. Using measured data and regression analysis, an algorithm was developed lot estimation of expected reading of transmission dose. Accuracy of the algorithm was tested with flat solid phantom with various settings. Results : The algorithm consisted of quadratic function of log(A/P) (where A/P is area-perimeter ratio) and tertiary function of PCD. The algorithm could estimate dose with very high accuracy for open square field, with errors within ${\pm}0.5%$. For elongated radiation field, the errors were limited to ${\pm}1.0%$. Conclusion : The developed algorithm can accurately estimate the transmission dose in open radiation fields with various treatment settings.

Compare the Clinical Tissue Dose Distributions to the Derived from the Energy Spectrum of 15 MV X Rays Linear Accelerator by Using the Transmitted Dose of Lead Filter (연(鉛)필터의 투과선량을 이용한 15 MV X선의 에너지스펙트럼 결정과 조직선량 비교)

  • Choi, Tae-Jin;Kim, Jin-Hee;Kim, Ok-Bae
    • Progress in Medical Physics
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    • v.19 no.1
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    • pp.80-88
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    • 2008
  • Recent radiotherapy dose planning system (RTPS) generally adapted the kernel beam using the convolution method for computation of tissue dose. To get a depth and profile dose in a given depth concerened a given photon beam, the energy spectrum was reconstructed from the attenuation dose of transmission of filter through iterative numerical analysis. The experiments were performed with 15 MV X rays (Oncor, Siemens) and ionization chamber (0.125 cc, PTW) for measurements of filter transmitted dose. The energy spectrum of 15MV X-rays was determined from attenuated dose of lead filter transmission from 0.51 cm to 8.04 cm with energy interval 0.25 MeV. In the results, the peak flux revealed at 3.75 MeV and mean energy of 15 MV X rays was 4.639 MeV in this experiments. The results of transmitted dose of lead filter showed within 0.6% in average but maximum 2.5% discrepancy in a 5 cm thickness of lead filter. Since the tissue dose is highly depend on the its energy, the lateral dose are delivered from the lateral spread of energy fluence through flattening filter shape as tangent 0.075 and 0.125 which showed 4.211 MeV and 3.906 MeV. In this experiments, analyzed the energy spectrum has applied to obtain the percent depth dose of RTPS (XiO, Version 4.3.1, CMS). The generated percent depth dose from $6{\times}6cm^2$ of field to $30{\times}30cm^2$ showed very close to that of experimental measurement within 1 % discrepancy in average. The computed dose profile were within 1% discrepancy to measurement in field size $10{\times}10cm$, however, the large field sizes were obtained within 2% uncertainty. The resulting algorithm produced x-ray spectrum that match both quality and quantity with small discrepancy in this experiments.

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Evaluation of Radiolucent Considering the Compression Paddle Materials in Mammography (유방촬영장치의 압박대 재질을 고려한 투과선량 평가)

  • Hong, Dong-Hee
    • The Journal of the Korea Contents Association
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    • v.15 no.11
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    • pp.307-312
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    • 2015
  • Mammography improves image quality that is on the increase day by day and get a picture with the pressure it is essential to reduce the dose. However, because due to the thickness of the cuff itself may increase the dose scattering lines is necessary study on the cuff material. Material that is currently being used in clinical Polycarbonate is a plastic and family. If you try to reduce the exposure of patients than itgie need to consider for the better material in this study to compare against a radiolucent line for amorphous plastic material of the plastic. results radiolucent and half layer, transmitting dose Pixel values HIPS, GPPS, ABS, Tritan, PC, PMMA showed high results in the net.

Transmission Dose Estimation Algorithm for Tissue Deficit (조직 결손에 대한 투과선량 계산 알고리즘 보정)

  • Yun Hyong Geun;Chie Eui Kyu;Huh Soon Nyung;Lee Hyoung Koo;Woo Hong Gyun;Shin Kyo Chul;Ha Sung Whan
    • Radiation Oncology Journal
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    • v.20 no.2
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    • pp.186-192
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    • 2002
  • Purpose : Measurement of transmission dose is useful for in vivo dosimetry. In this study, previous algorithm for estimation of transmission dose was modified for use in cases with tissue deficit. Materials and Methods : The beam data was measured with flat solid phantom in various conditions of tissue deficit. New algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. The algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients using multiple sheets of solid phantoms. Results : The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within ${\pm}1.0\%$ in most situations and within ${\pm}3.0\%$ in experimental settings with irregular contours mimicking breast cancer treatment set-up. Conclusion : Developed algorithm could accurately reflect the effect of tissue deficit and irregularly shaped body contour on transmission dosimetry.

Radiation Dose during Transmission Measurement in Whole Body PET/CT Scan (전신 PET/CT 영상 획득 시 투과 스캔에서의 방사선 선량)

  • Son Hye-Kyung;Lee Sang-Hoon;Nam So-Ra;Kim Hee-Joung
    • Progress in Medical Physics
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    • v.17 no.2
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    • pp.89-95
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    • 2006
  • The purpose of this study was to evaluate the radiation doses during CT transmission scan by changing tube voltage and tube current, and to estimate the radiation dose during our clinical whole body $^{137}Cs$ transmission scan and high quality CT scan. Radiation doses were evaluated for Philips GEMINI 16 slices PET/CT system. Radiation dose was measured with standard CTDI head and body phantoms in a variety of CT tube voltage and tube current. A pencil ionization chamber with an active length of 100 mm and electrometer were used for radiation dose measurement. The measurement is carried out at the free-in-air, at the center, and at the periphery. The averaged absorbed dose was calculated by the weighted CTDI ($CTDI_w=1/3CTDI_{100,c}+2/3CTDI_{100,p}$) and then equivalent dose were calculated with $CTDI_w$. Specific organ dose was measured with our clinical whole body $^{137}Cs$ transmission scan and high quality CT scan using Alderson phantom and TLDs. The TLDs used for measurements were selected for an accuracy of ${\pm}5%$ and calibrated in 10 MeV X-ray radiation field. The organ or tissue was selected by the recommendations of ICRP 60. The radiation dose during CT scan is affected by the tube voltage and the tube current. The effective dose for $^{137}Cs$ transmission scan and high qualify CT scan are 0.14 mSv and 29.49 mSv, respectively. Radiation dose during transmission scan in the PET/CT system can measure using CTDI phantom with ionization chamber and anthropomorphic phantom with TLDs. further study need to be peformed to find optimal PET/CT acquisition protocols for reducing the patient exposure with same image qualify.

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Tissue Inhomogeneity Correction in Clinical Application of Transmission Dosimetry to Head and Neck Cancer Radiation Treatment (두경부 방사선 치료 환자에서 투과선량 알고리즘의 임상 적용시 불균질 조직 보정에 관한 연구)

  • Kim Suzy;Ha Sung Whan;Wu Hong Gyun;Huh Soon Nyung
    • Radiation Oncology Journal
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    • v.22 no.2
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    • pp.155-163
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    • 2004
  • Purpose : To confirm the reproducibility of in vivo transmission dosimetry system and the accuracy of the a1gorithms for the estimation of transmission dose in head and neck radiation therapy patients. Materials and Methods : From September 5 to 18, 2001, transmission dose measurements were peformed when radiotherapy was given to brain or head and neck cancer patients. The data of 35 patients who were treated more than three times and whose central axis of the beam was not blocked were analyzed in this study. To confirm the reproducibility of this system, transmission dose was measured before dally treatment and then repetitively every hour during the treatment time, with a field size of 10$\times$10 cm$^{2}$ and a delivery of 100 MU. The accuracy of the transmission dose calculation algorithms was confirmed by comparing estimated dose with measured dose. To accurately estimate transmission dose, tissue inhomogeneity correction was done. Results : The measurement variations during a day were within $\pm$0.5$\%$ and the dally variations in the checked period were within $\pm$ 1.0$\%$, which were acceptable for system reproducibility. The mean errors between estimated and measured doses were within $\pm$5.0$\%$ in Patients treated to the brain, $\pm$2.5$\%$ in head, and $\pm$ 5.0%$\%$in neck. Conclusion : The results of this study confirmed the reproducibility of our system and its usefulness and accuracy for dally treatment. We also found that tissue inhomogeneity correction was necessary for the accurate estimation of transmission dose in patients treated to the head and neck.