• Radiation Oncology Journal
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• v.12 no.2
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• pp.263-267
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• 1994

In clinical radiotherapy, the use of wide and irregular field techniques frequently results in considerable tumor dose inhomogeneity because of, the variation in physical characteristics of irradiated volumes. This report describes an analysis of the dosimetry of the irregular fields such as radiation fields for Hodgkin's disease(mantle field), esophageal cancer, and lung cancer when a 6 MV and a 15 MV linear accelerators are utilized. Doses were measured in a Rando phantom using methods of thermoluminescence dosimetry(TLD), and were calculated by radiotherapy planning computer system with the Clarkson's method for calculation of a irregular field. A dose variation of $5-22\%,\;6-9\%,\;6-14\%$ were found in the mantle field, esophageal cancer field, lung cancer field respectively. Higher doses occurred in the superior portion of the irregular field. The sites of maximum dose variation were the supraclavicular and the upper spinal cord region. To adjust for these substantial differences, a compensator or a shrinking field technique should be adopted.

• Nuclear Engineering and Technology
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• v.43 no.4
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• pp.399-404
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• 2011

A LEGO-type multi-purpose dosimetry phantom was developed for intensity-modulated radiation therapy (IMRT), which requires various types of challenging dosimetry. Polystyrene, polyethylene, polytetrafluoroethylene (PTFE), and polyurethane foam (PU-F) were selected to represent muscle, fat, bone, and lung tissue, respectively, after considering the relevant mass densities, elemental compositions, effective atomic numbers, and photon interaction coefficients. The phantom, which is composed of numerous small pieces that are similar to LEGO blocks, provides dose and dose distribution measurements in homogeneous and heterogeneous media. The phantom includes dosimeter holders for several types of dosimeters that are frequently used in IMRT dosimetry. An ion chamber and a diode detector were used to test dosimetry in heterogeneous media under radiation fields of various sizes. The data that were measured using these dosimeters were in disagreement when the field sizes were smaller than $1.5{\times}1.5\;cm^2$ for polystyrene and PTFE, or smaller than $3{\times}3\;cm^2$ for an air cavity. The discrepancy was as large as 41% for the air cavity when the field size was $0.7{\times}0.7\;cm^2$, highlighting one of the challenges of IMRT small field dosimetry. The LEGO-type phantom is also very useful for two-dimensional dosimetry analysis, which elucidates the electronic dis-equilibrium phenomena on or near the heterogeneity boundaries.

• Journal of radiological science and technology
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• v.43 no.6
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• pp.443-451
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• 2020

This study is to evaluate absorbed dose from right lung for brachytherapy and to estimate the effects of tissue heterogeneities on dose distribution for Iridium-192 source using Monte Carlo simulation. The study employed Geant4 code as Monte Carlo simulation to calculate the dosimetry parameters. The dose distribution of Iridium-192 source in solid water equivalent phantom including aluminium plate or steel plate inserted was calculated and compared with the measured dose by the ion chamber at various distances. And the simulation was used to evaluate the dose of gamma radiation absorbed in the lung organ and other organs around it. The dose distribution embedded in right lung was calculated due to the presence of heart, thymus, spine, stomach as well as left lung. The geometry of the human body was made up of adult male MIRD type of the computational human phantom. The dosimetric characteristics obtained for aluminium plate inserted were in good agreement with experimental results within 4%. The simulation results of steel plate inserted agreed well with a maximum difference 2.75%. Target organ considered to receive a dose of 100%, the surrounding organs were left the left lung of 3.93%, heart of 10.04%, thymus of 11.19%, spine of 12.64% and stomach of 0.95%. When the statistical error is performed for the computational human phantom, the statistical error of value is under 1%.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3816-3823
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• 2022

This work analyzed the dosimetric difference between the intensity modulated radiotherapy (IMRT), partial/single/double-arc volumetric modulated arc therapy (PA/SA/DA-VMAT) techniques in treatment planning for treating more than one target of lung cancer at different isocenters. IMRT and VMAT plans at different isocenters were created systematically using a Harold heterogeneous lung phantom. The conformity index (CI), homogeneity index (HI), gradient index (GI), dose-volume histogram and mean and maximum dose of the PTV were calculated and analyzed. Furthermore, the dose-volume histogram and mean and maximum doses of the OARs such as right lung, contralateral lung and non GTV were determined from the plans. The IMRT plans showed the superior target dose coverage, higher mean and maximum values than other VMAT techniques. PA-VMAT technique shows more lung sparing and DA-VMAT increases the V_5/10/20 values of contralateral lung than other VMAT and IMRT techniques. The IMRT technique achieves highly conformal dose distribution to the target than other VMAT techniques. Comparing to the IMRT plans, the higher V_5/10/20 and mean lung dose were observed in the contralateral lung in the DA-VMAT.

• The Journal of Korean Society for Radiation Therapy
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• v.35
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• pp.15-21
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• 2023

Purpose: The purpose of this study is to compare the performance of the anisotropic analytical algorithm (AAA) and portal dose image prediction (PDIP) for patient-specific quality assurance based on electronic portal imaging device, and to evaluate the clinical feasibility of portal dosimetry using AAA. Subjects and methods: We retrospectively selected a total of 32 patients, including 15 lung cancer patients and 17 liver cancer patients. Verification plans were generated using PDIP and AAA. We obtained gamma passing rates by comparing the calculated distribution with the measured distribution and obtained MLC positional difference values. Results: The mean gamma passing rate for lung cancer patients was 99.5% ± 1.1% for 3%/3 mm using PDIP and 90.6% ± 5.8% for 1%/1 mm. Using AAA, the mean gamma passing rate was 98.9% ± 1.7% for 3%/3 mm and 87.8% ± 5.2% for 1%/1 mm. The mean gamma passing rate for liver cancer patients was 99.9% ± 0.3% for 3%/3 mm using PDIP and 96.6% ± 4.6% for 1%/1 mm. Using AAA, the mean gamma passing rate was 99.6% ± 0.5% for 3%/3 mm and 89.5% ± 6.4% for 1%/1 mm. The MLC positional difference was small at 0.013 mm ± 0.002 mm and showed no correlation with the gamma passing rate. Conclusion: The AAA algorithm can be clinically used as a portal dosimetry calculation algorithm for patientspecific quality assurance based on electronic portal imaging device.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.2
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• pp.167-174
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• 2015

Purpose : The pre-treatment QA using Portal dosimetry for Volumetric Arc Therapy To analyze whether maintaining the reproducibility depending on various factors. Materials and Methods : Test was used for TrueBeam STx$^{TM}$ (Ver.1.5, Varian, USA). Varian Eclipse Treatment planning system(TPS) was used for planning with total of seven patients include head and neck cancer, lung cancer, prostate cancer, and cervical cancer was established for a Portal dosimetry QA plan. In order to measure these plans, Portal Dosimetry application (Ver.10) (Varian) and Portal Vision aS1000 Imager was used. Each Points of QA was determined by dividing, before and after morning treatment, and the after afternoon treatment ended (after 4 hours). Calibration of EPID(Dark field correction, Flood field correction, Dose normalization) was implemented before Every QA measure points. MLC initialize was implemented after each QA points and QA was retried. Also before QA measurements, Beam Ouput at the each of QA points was measured using the Water Phantom and Ionization chamber(IBA dosimetry, Germany). Results : The mean values of the Gamma pass rate(GPR, 3%, 3mm) for every patients between morning, afternoon and evening was 97.3%, 96.1%, 95.4% and the patient's showing maximum difference was 95.7%, 94.2% 93.7%. The mean value of GPR before and after EPID calibration were 95.94%, 96.01%. The mean value of Beam Output were 100.45%, 100.46%, 100.59% at each QA points. The mean value of GPR before and after MLC initialization were 95.83%, 96.40%. Conclusion : Maintain the reproducibility of the Portal Dosimetry as a VMAT QA tool required management of the various factors that can affect the dosimetry.

• 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.

• Journal of Radiation Protection and Research
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• v.16 no.1
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• pp.1-13
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• 1991

Effective dose equivalents resulting from inhalation of indoor radon-222 daughters at 12 residential areas in Korea were assessed by a simple mathematical lung dosimetry model based on the measurements of long-term averaged radon concentrations at 340 dwellings. The long-term averaged indoor radon-222 concentrations and corresponding eqilibrium equivalent radon $concentration(EEC_{Rn})$ measured by passive time-integrating CR-39 radon cups are in the range of $33.82{\sim}61.42Bq/m^3(median\;:\;48.90Bq/m^3)$ and of $13.53{\sim}24.57Bq/m^3(median\;:\;19.55Bq/m^3)$, respectively. The effective dose equvalent conversion factor for the exposure to unit $EEC_{Rn}$ derived in this study was estimated $1.07{\times}10^{-5}mSv/Bq\;h\;m^{-3}$ for a reference adult and agreed well with those recommended by the ICRP and UNSCEAR. The annual average dose equivalent to the lung $(H_{LUNG})$ from inhalation exposure to measured $EEC_{Rn}$ was estimated to be 20.90 mSv and resulting effective dose $equivalent(H_E)$ was to be 1.25 mSv, which is about 50% of the natural radiation exposure of 2.40 mSv/y to the public reported by the UNSCEAR.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.1
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• pp.57-67
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• 2013

Purpose: Replacing the film which used to be used for checking the set-up of the patient and dosimetry during radiation therapy, more and more EPID equipped devices are in use at present. Accordingly, this article tried to evaluated the accuracy of the position check-up and the usefulness of dosimetry during the use of an electronic portal imaging device. Materials and Methods: On 50 materials acquired with the search of Korea Society Radiotherapeutic Technology, The Korean Society for Radiation Oncology, and Pubmed using "EPID", "Portal dosimetry", "Portal image", "Dose verification", "Quality control", "Cine mode", "Quality - assurance", and "In vivo dosimetry" as indexes, the usefulness of EPID was analyzed by classifying them as history of EPID and dosimetry, set-up verification and characteristics of EPID. Results: EPID is developed from the first generation of Liquid-filled ionization chamber, through the second generation of Camera-based fluoroscopy, and to the third generation of Amorphous-silicon EPID imaging modes can be divided into EPID mode, Cine mode and Integrated mode. When evaluating absolute dose accuracy of films and EPID, it was found that EPID showed within 1% and EDR2 film showed within 3% errors. It was confirmed that EPID is better in error measurement accuracy than film. When gamma analyzing the dose distribution of the base exposure plane which was calculated from therapy planning system, and planes calculated by EDR2 film and EPID, both film and EPID showed less than 2% of pixels which exceeded 1 at gamma values (r%>1) with in the thresholds such as 3%/3 mm and 2%/2 mm respectively. For the time needed for full course QA in IMRT to compare loads, EDR2 film recorded approximately 110 minutes, and EPID recorded approximately 55 minutes. Conclusion: EPID could easily replace conventional complicated and troublesome film and ionization chamber which used to be used for dosimetry and set-up verification, and it was proved to be very efficient and accurate dosimetry device in quality assurance of IMRT (intensity modulated radiation therapy). As cine mode imaging using EPID allows locating tumors in real-time without additional dose in lung and liver which are mobile according to movements of diaphragm and in rectal cancer patients who have unstable position, it may help to implement the most optimal radiotherapy for patients.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.1
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• pp.18-24
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• 2017

Patient-specific image-based internal dosimetry involves using the patient's individual anatomy and spatial distribution of radioactivity over time to obtain an absorbed dose calculation. Individual absorbed dose was calculated by accumulated activity multiply S-value of each organs. The aim of this study was to calculate the S-values using Monte Carlo simulation in monkey and mouse and evaluation of absorbed dose in each organ. Self-irradiation S-value of monkey heart self-irradiation was 3.15E-03 mGy-g/MBq-s, lung self-irradiation was 8.94E-04 mGy-g/MBq-s and liver self-irradiation S-value was 2.23E-03 mGy-g/MBq-s. Mouse heart self-irradiation S-value was 1.95E-01 mGy-g/MBq-s, lung was 9.59E-02 mGy-g/MBq-s, and liver was 1.40E-03 mGy-g/MBq-s. The results of this study show that the calculation protocol of image based individual absorbed dose of each organ using Monte Carlo simulation. Therefore, this study may be applied to calculate human specific absorbed dose.