• Radiation Oncology Journal
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• v.30 no.1
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• pp.27-35
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• 2012

Purpose: To evaluate the effect of common three photon energies (6-MV, 10-MV, and 15-MV) on intensity-modulated radiation therapy (IMRT) plans to treat prostate cancer patients. Materials and Methods: Twenty patients with prostate cancer treated locally to 81.0 Gy were retrospectively studied. 6-MV, 10-MV, and 15-MV IMRT plans for each patient were generated using suitable planning objectives, dose constraints, and 8-field setting. The plans were analyzed in terms of dose-volume histogram for the target coverage, dose conformity, organs at risk (OAR) sparing, and normal tissue integral dose. Results: Regardless of the energies chosen at the plans, the target coverage, conformity, and homogeneity of the plans were similar. However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV. The $V_{20Gy}$ of rectal wall with 6-MV, 10-MV, and 15-MV were 95.6%, 88.4%, and 89.4% while the mean dose to femoral heads were 31.7, 25.9, and 26.3 Gy, respectively. Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%. Overall, integral doses in mid and low dose regions in 6-MV plans were increased by up to 13%. Conclusion: In this study, 10-MV prostate IMRT plans showed better OAR sparing and less integral doses than the 6-MV. The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.

• The Journal of Korean Society for Radiation Therapy
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• v.5 no.1
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• pp.126-130
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• 1992

• Journal of radiological science and technology
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• v.19 no.1
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• pp.81-87
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• 1996

When high energy photon beam is incident upon an air cavity interface the effect of ionization build-up observed. This phenomenon is resulting from the surface layers of the lesions are significant deficiency of electrons reaching the layers because of the replacement of solid scattering material by the air cavity, that is lack of electronic equilibrium. Measurement have been made in an acrylic phantom with a parallel plate chamber and high energy Photon beams, CO-60, 4MV, 6MV and 10MV X-rays have been investigated. The result of our study show that a significant effect was measured and was determined to be very dependent on field size, air cavity dimension and photon energy. The reductions were much larger for 10MV beam, underdosage at the interface was 12, 12.2, 16.9 and 20.6% for the CO-60, 4 MV, 6MV and 10MV, respectively. It was found that this non-equilibrium effect at the interface is more severe for the higher energy beams than that of lower energy beams and the larger cavity dimensions it is, the larger beam reductions we have. This problem is of clinical concern when lesions such as carcinoma beyond air cavities are irradiated, such as larynx, glottic and the patients with maxillectomy and ethmoidectomy and so forth.

• Radiation Oncology Journal
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• v.17 no.3
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• pp.256-260
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• 1999

Purpose : An investigation has been carried out on the factors which affect the response reading of thermoluminescent dosimeters (TLD-100) loaded with thin material in high energy Photon. The aim of the study was to assess the energy response of TLD-100 to the therapeutic ranges of photon beam. Materials and Methods : In this technique, TLD-100 (abbreviated as TLD) chips and three different thin material (Tin, Gold, and Tissue equivalent plastic plate) which mounted on the TLD chip were used in the clinical photon beam. The thickness of each metal plates was 0.1 mm and TE plastic plate was 1 mm thick. These compared with the photon energy dependence of the sensitivities of TLD (normal chip), TLD loaded with Tin or Gold plate, for the photon energy range 6 MV to 15 MV, which was of interest in radiotherapy. Results : The enhancement of surface dose in the TLD with metal plate was clearly detected. The TLD chips with a Gold plate was found to larger response by a factor of 1.83 in 10 MV photon beam with respect to normal chip. The sensitivity of TLD loaded with Tin was less than that for normal TLD and TLD loaded with Gold. The relative sensitivity of TLD loaded with metal has little energy dependence. Conclusion : The good stability and linearity with respect to monitor units of TLD loaded with metal were demonstrated by relative measurements in high energy Photon ($6\~15$ MV) beams. The TLD laminated with metals embedded system in solid water phantom is a suitable detector for relative dose measurements in a small beam size and surface dose.

• Progress in Medical Physics
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• v.21 no.1
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• pp.120-125
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• 2010

For the measurements of an absorbed dose using the standard dosimetry based on an absorbed dose to water the variety of factors, whether big, small, or tiny, may influence the accuracy of dosimetry. The beam quality correction factor ${\kappa}_{Q,Q_0}$ of an ionization chamber might also be one of them. The cylindrical type of ionization chamber, the PTW30013 chamber, was chosen for this work and 9 chambers of the same type were collected from several institutes where the chamber types are used for the reference dosimetry. They were calibrated from the domestic Secondary Standard Dosimetry Laboratory with the same electrometer and cable. These calibrated chambers were used to measure absorbed doses to water in the reference condition for the photon beam of 6 MV and 10 MV and the electron beam of 12 MeV from Siemens ONCOR. The biggest difference among chambers amounts to 2.4% for the 6 MV photon beam, 0.8% for the 10 MV photon beam, and 2.4% for the 12 MeV electron beam. The big deviation in the photon of 6 MV demonstrates that if there had been no problems with the process of measurements application of the same ${\kappa}_{Q,Q_0}$ to the chambers used in this study might have influenced the deviation in the photon 6 MV and that how important an external audit is.

• Progress in Medical Physics
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• v.27 no.2
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• pp.79-85
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• 2016

The objective of this study is to increase the accuracy of dose transmission in radiation therapy using two types of treatment tables, standard exact couch (Varian 21EX, Varian Medical Systems, Milpitas, CA) and 6D robotic couch (Novalis, BrainLAB A.G., Heimstetten, Germany)). We examined the dose attenuation based on the two types of treatment tables and studied the dose of attenuation using the phase (In/Out) for the standard exact couch. We measured the relative dose according to the incident angle of a penetrative photon beam under a treatment table. The incident angle of the photon beam was from $0^{\circ}$ to $360^{\circ}$ in the increments of $5^{\circ}$. The reference angle was set to $0^{\circ}$. Furthermore, the relative dose of the 6D robotic couch was measured using 6 MV and 15 MV, and that of the standard exact couch was measured at the sliding rail position (In-Out) using 6 MV and 10 MV. In the case of the standard exact couch, the measured relative dose was 16.53% (rails at the "In position," $175^{\circ}$, 6 MV), 12.42% (rails at the "In position," $175^{\circ}$, 10 MV), 13.13% (rails at the "Out position," $175^{\circ}$, 6 MV), and 9.96% (rails at the "Out position," $175^{\circ}$, 10 MV). In the case of the 6D robotic couch, the measured relative dose was 6.82% ($130^{\circ}$, 6 MV) and 4.92% ($130^{\circ}$, 15 MV). The photon energies were surveyed at the same incident angle. The dose attenuation for an energy of 10 MV was 4~5% lower than that for 6 MV. This indicated that the higher photon energy, lesser is the attenuation. The results of this study indicated that the attenuation rate for the 6D robotic couch was confirmed to be 1% larger than that for the standard exact couch at 6 MV and $180^{\circ}$. In the case of the standard exact couch, the dose attenuation was found to change rapidly in accordance with the phase ("In position" and "Out position") of the sliding rail.

• Progress in Medical Physics
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• v.17 no.3
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• pp.179-186
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• 2006

Purpose: Photon beam data of linear accelerators in Korea are collected, analyzed, and a simple method for checking and verifying the dose calculations in a TPS are suggested. Materials and Methods: Photon beam data such as output calibration condition, output factor, wedge factor, percent depth dose, beam profile, and beam quality were collected from 26 institutions in Korea. In order to verify the accuracy of dose calculation, ten sample planning tests were peformed. These Include square, elongated, and blocked fields, wedge fields, off-axis dose calculation, SSD variation. The planned data were compared to that of manual calculations. Results: The average and standard deviation of photon beam quality for 6, 10, and 15 MV were $0.576{\pm}0.005,\;0.632{\pm}0.004,\;and\;0.647{\pm}0.006$, respectively. The output factors of 6 MV photon beam measured at depth of dose maximum for $5{\times}5cm,\;15{\times}15cm,\;20{\times}20cm\;were\;0.944{\pm}0.006,\;1.031{\pm}0.006,\;and\;1.055{\pm}0.007$. For 10 MV photon beam, the values were $0.935{\pm}0.006,\;1.031{\pm}0.007,\;1.054{\pm}0.0005$. The collected data were not enough to calculate average, the output factors for 15MV photon beam with field size of $5{\times}5cm,\;15{\times}15cm,\;20{\times}20cm\;were\;0.941{\pm}0.008,\;1.032{\pm}0.004,\;1.049{\pm}0.014$. There was seven institutions $e{\times}ceeding$ tolerance when monitor unit values calculated from treatment planning system and manually were compared. The measured average MU values for the machines calibrated at SAD setup were 3 MU and 5 MU higher than the machines calibrated at SSD for 6 MV and 10 MV, respectively except the wedge case. When the wedges were inserted, the MU values to deliver 100 cGy to 5 cm depends on manufactures. When the same wedge angle was used, Siemens machine requires more MUs then Varian machine. Conclusion: In this study, photon beam data are collected and analyzed to provide a baseline value for chocking beam data and the accuracy of dose calculation for a treatment planning system.

• The Journal of Korean Society for Radiation Therapy
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• v.6 no.1
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• pp.142-145
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• 1994

• Progress in Medical Physics
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• v.10 no.1
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• pp.55-62
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• 1999

In an effort to study the characteristics of x-rays utilized in radiation therapy, we calculated the energy distribution and the mean energy of x-rays generated from a tungsten target bombarded by 6, 10, and 15 MeV electron beams, using a Monte Carlo technique. The average photon energies calculated as a function of the beam radius lied in 1.4 ∼ 1.6, 2.1 ∼ 2.5 and 2.8 ∼ 3.3 MeV ranges for 4, 10, and 15 MV electron beams, respectively, which turned out to have no strong dependence on the radius. Using the energy distributions of 6,10, and 15 MV x-rays obtained for the target distance of 100 cm, percentage depth doses were determined using Monte Carlo calculations. For the case 10 MV, a comparison was made between our calculation and measurement performed by others. The calculated percentage depth dose appeared somewhat smaller than the measured one except in the surface region. We conclude that this is due to the fact that the beam hardening effect resulting from the flattening filter was not properly allowed for in our Monte Carlo calculations.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.65-73
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• 2017

Purpose: Machine Performance Check (MPC) is a self-checking software based on the Electronic Portal Imaging Device (EPID) to measure daily beam outputs without external installation. The purpose of this study is to verify the usefulness of MPC by comparing and correlating daily beam output of QA Beamchecker PLUS. Materials and Methods: Linear accelerator (Truebeam 2.5) was used to measure 10 energies which are composed of photon beams(6, 10, 15 MV and 6, 10 MV-FFF) and electron beams(6, 9, 12, 16 and 20 MeV). A total of 80 cycles of data was obtained by measuring beam output measurement before treatment over five months period. The Pearson correlation coefficient was used to evaluate the consistency of the beam output between the MPC and the QA Beamchecker PLUS. In this study, if the Pearson correlation coefficient is; (1) 0.8 or higher, the correlation is very strong (2) between 0.6 and 0.79, the correlation is strong (3) between 0.4 and 0.59, the correlation is moderate (4) between 0.2 and 0.39, the correlation is weak (5) lower than 0.2, the correlation is very weak. Results: Output variations observed between MPC and QA Beamchecker PLUS were within 2 % for photons and electrons. The beam outputs variations of MPC were $0.29{\pm}0.26%$ and $0.30{\pm}0.26%$ for photon and electron beams, respectively. QA Beamchecker PLUS beam outputs were $0.31{\pm}0.24%$ and $0.33{\pm}0.24%$ for photon and electron beams, respectively. The Pearson correlation coefficient between MPC and QA Beamchecker PLUS indicated that photon beams were very strong at 15 MV, and strong at 6 MV, 10 MV, 6 MV-FFF and 10 MV-FFF. For electron beams, the Pearson correlation coefficient were strong at 16 MeV and 20 MeV, moderate at 9 MeV and 12 MeV, and very weak at 6 MeV. Conclusion: MPC showed significantly strong correlation with QA Beamchecker PLUS when testing with photon beams and high-energy electron beams in the evaluation of daily beam output, but the correlation when testing with low-energy electron beams (6 MeV) appeared to be low. However, MPC and QA Beamchecker PLUS are considered to be suitable for checking daily beam output, as they performed within 2 % of beam output consistency during the observation. MPC which can perform faster than the conventional daily beam output measurement tool, is considered to be an effective method for users.