• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.119-120
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• 2002

The aim is to urge the need of elaborate commissioning of 3D RTP system from the firsthand experience. A 3D RTP system requires so much data such as beam data and patient data. Most data of radiation beam are directly transferred from a 3D dose scanning system, and some other data are input by editing. In the process inputting parameters and/or data, no error should occur. For RTP system using algorithm-bas ed-on beam-modeling, careless beam-data processing could also cause the treatment error. Beam data of 3 different qualities of photon from two linear accelerators, patient data and calculated results were commissioned. For PDD, the doses by Clarkson, convolution, superposition and fast superposition methods at 10 cm for 10${\times}$10 cm field, 100 cm SSD were compared with the measured. An error in the SCD for one quality was input by the service engineer. Whole SCD defined by a physicist is SAD plus d$\sub$max/, the value was just SAD. That resulted in increase of MU by 100${\times}$((1_d$\sub$max//SAD)$^2$-1)%. For 10${\times}$10 cm open field, 1 m SSD and at 10 cm depth in uniform medium of relative electron density (RED) 1, PDDs for 4 algorithms of dose calculation, Clarkson, convolution, superposition and fast-superposition, were compared with the measured. The calculated PDD were similar to the measured. For 10${\times}$10 cm open field, 1 m SSD and at 10 cm depth with 5 cm thick inhomogeneity of RED 0.2 under 2 cm thick RED 1 medium, PDDs for 4 algorithms were compared. PDDs ranged from 72.2% to 77.0% for 4 MV X-ray and from 90.9% to 95.6% for 6 MV X-ray. PDDs were of maximum for convolution and of minimum for superposition. For 15${\times}$15 cm symmetric wedged field, wedge factor was not constant for calculation mode, even though same geometry. The reason is that their wedge factor is considering beam hardness and ray path. Their definition requires their users to change the concept of wedge factor. RTP user should elaborately review beam data and calculation algorithm in commissioning.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.183-188
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• 2012

Purpose: The concern of improving the quality of life and reducing side effects related to cancer treatment has been a subject of interest in recent years with advances in cancer treatment techniques and increasing survival time. This study is an analysis of differing scattered dose to the contralateral breast using common different treatment techniques. Materials and Methods: Eclipse 10.0 (Varian, USA) based $30^{\circ}$ EDW (Enhanced dynamic wedge) plan, $15^{\circ}$ wedge plan, $30^{\circ}$ wedge plan, Open beam plan, FiF (field in field) plan were established using CT image of breast phantom which in our hospital. Each treatment plan were designed to exposure 400 cGy using CL-6EX (VARIAN, USA) and we measured scattered dose at 1 cm, 3 cm, 5 cm, 9 cm away from medial side of the phantom at 1 cm depth using ionization chamber (FC 65G, IBA). We carried out measurement by separating effect of medial tangential field and lateral tangential field and analyze. Results: The evaluation of scattered dose to contralateral breast, $30^{\circ}$ EDW plan, $15^{\circ}$ wedge plan, $30^{\circ}$ wedge plan, Open beam plan, FIF plan showed 6.55%, 4.72%, 2.79%, 2.33%, 1.87% about prescription dose of each treatment plan. The result of scattered dose measurement by separating effect of medial tangential field and lateral tangential field results were 4.94%, 3.33%, 1.55%, 1.17%, 0.77% about prescription dose at medial tangential field and 1.61%, 1.40%, 1.24%, 1.16%, 1.10% at lateral tangential field along with measured distance. Conclusion: In our experiment, FiF treatment technique generates minimum of scattered dose to contralateral breast which come from mainly phantom scatter factor. Whereas $30^{\circ}$ wedge plan generates maximum of scattered doses to contralateral breast and 3.3% of them was scattered from gantry head. The description of treatment planning system showed a loss of precision for a relatively low scatter dose region. Scattered dose out of Treatment radiation field is relatively lower than prescription dose but, in decision of radiation therapy, it cannot be ignored that doses to contralateral breast are related with probability of secondary cancer.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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• pp.75-83
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• 2004

Ice rubble pieces broken by the bow impact load and side hull of an icebreaking vessel usually pass along the ship's bottom hull and may hit the propeller/rudder or other stern structures causing serious damage to ship's hull . Therefore it is important to estimate the size of broken ice pieces during the icebreaking process. The dynamic interaction process of icebreaker with infinite ice sheet is simplified as a wedge type beam of finite length supported by elastic foundation. The wedge type ice beam is leaded with vertical impact forces due to the inclined bow stem of icebreaking vessels. The numerical model provides locations of maximum dynamic bending moment where extreme tensile stress arises and also possible fracture occurs. The model can predict a failure length of broken ice sheet given design parameters. The results are compared to Nevel(1961)'s analytical solution for static load and observed pattern of ice sheet failure onboard an icebreaker. Also by comparing computed failure length with the characteristic length, the meaning of ice rubble sizes is discussed.

• Radiation Oncology Journal
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• v.7 no.2
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• pp.279-285
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• 1989

Central axis depth dose data for 6 MV X-rays, including tissue maximum ratios, were measured for wedge fields according to Tatcher's equation. In wedge fields, the differences in magnitude which increased with depth, field size, and wedge thickness increased when compared with the corresponding open field data. However, phantom scatter correction factors for wedge fields differed less than $1\%$ from the corresponding open field factors. The differences in central axis percent depth dose between two types of fields indicated beam hardening by the wedge filter The deviation of percent depth doses and scatter correction factors between the effective wedge field and the nominal wedge field at same angle was negligible. The differences were less than $3.20\%$ between the nominal or effective wedge fields and the open fields for percent depth doses to the depth 7cm in $6cm{\times}6cm$ field. For larger $(10cm{\times}10cm)$ field size, however, the deviation of percnet depth doses between the nominal or effective wedge fields and the open fields were greater-dosimetric errors were $3.56\%$ at depth 7cm and nearly $5.30\%$ at 12cm. We suggest that the percent depth doses of individual wedge and wedge transmission factors should be considered for the dose calculation or monitor setting in the treatment of deep seated tumor.

• 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.5 no.1
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• pp.115-119
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• 1992

The beam characteristics and dosimetric measurements of the 6MV X-ray and 6MeV electron beam from a ML-6M linear accelerator are examined. The Percent Depth Dose(PDD) table and the tissue Maximum Ratio(TMR) table are taken from measurement as a function of the field size and the depth. The calculated TMR table from PDD table is compared with those from measurement. Other beam characteristics such as output factor, beam profile(including flatness, symmetry and penumbra), wedge, and the variation of Dmax are presented. All of these dosimetric measurements sufficiently characterized the beam to permit safe clinical use.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.946-949
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• 2007

This paper discusses the lateral vibration of a beam with boundary condition of one end fixed and the other end free. The uniform beam has a solution by summation of some simple exponential functions. But if its shape is not uniform, its solution could be by Bessel's function or mathematical solution could not exist. Even if the solution of Bessel's function exists, as Bessel function is a series function, we must get the solution by numerical method. Author had proposed the solution of the matrix method by Ritz's method and a new mode shape function, and had earned the good results for a wedge beam. Hereby a vibration analysis for the tapered beam with circle cross section was executed, and so good results were showed.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.851-856
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• 2022

The purpose of this study is to confirm the effect of reducing the surface dose around the radiation field in breast cancer radiotherapy using the Field-in-Field (FIF) technique. X-ray was exposed from a linear accelerator (Linac) was used for irradiation, and the surface dose was measured with a glass dosimeter. The source-to-surface distance (SSD) was 90 cm, the field size is 10 × 10 cm², and the X-ray energy was 6 MV and 10 MV, respectively. The surface dose of the FIF was compared with the dose measured in the physical wedge (PW) and dynamic wedge (DW). Wedge angles of 15° and 30° were used in the PW and DW, respectively. Surface dose was measured at 1 cm, 3 cm, and 5 cm from the center of the field size, respectively. According to the results, FIF showed lower surface dose compared to PW and DW regardless of the energy of the X-ray beam, wedge angle, and dose measurement point. Since FIF could reduce the radiation dose in periphery of the field size in breast cancer treatment, it is expected to be able to reduce the secondary damage caused by the radiation beam as well as to obtain a uniform dose distribution on the target.

• Transactions of the Society of Information Storage Systems
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• v.2 no.4
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• pp.224-229
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• 2006

There has been studied flow to minimize the spot size to increase data capacity. Optical data storage devices are being developed near practical limits with wavelength and NA of 405nm and 0.85. There has been studied many types of next generation storage devices such as blu-ray multilayer system, probe based data storage and holographic data storage. Among these data storage devices, solid immersion lens(SIL) based near field recording (NFR) has been widely studied. In this system, SIL is the key component that focuses the laser beam with a very small size which enables ultra high data capacity. Therefore, optical performance evaluation system is required for SIL assembly. In this dissertation, a simple and accurate SIL assembly measurement method is proposed with wedge plate lateral shearing interferometer(LSI). Wedge plate LSI is cheaper than commercialized interferometer, robust to the vibration and the moving distance for phase shifting is large that is order of micrometer. We designed the thickness, wedge angle, material, surface quality and wavelength of wedge plate as 1mm, 0.02degree, fused silica, lamda/10(10-5) and 405nm, respectively. Also, we confirmed simulation and experimental results with quantitative analysis. This simple wedge plate LSI can be applied to different types of SIL such as solid immersion mirror(SIM), hemispherical, super-hemispherical and elliptical SIL.

• Progress in Medical Physics
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• v.18 no.1
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• pp.7-12
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• 2007

In the radiation therapy for breast cancer patients, wedge shaped compensators are essentially used to achieve appropriate dose distribution because of thickness difference according to breast shapes. Tangential Irradiation technique has usually been applied to radiation therapy for breast cancer patients treated with breast conservative surgery. When a primary beam is incident on wedge shaped compensators from medial direction In tangential irradiation technique, low energy scattered radiation is generated and gives additional dose to the breast surface. As a method to reduced additional dose to breast surface, the use of virtual wedge shaped compensator is possible. Eclipse radiation treatment planning (RTP) systems Installed at our institution have virtual wedge shaped compensator for radiation therapy treatment planning. The dose distributions of 15, 30, 45, 60 degree physical wedges and virtual wedges were measured and compared. Results showed that there was no significant differences In symmetry of $10{\times}10$ field among various wedge angles. When the transmission factor was compared, transmission factor Increased linearly as the wedge angle Increased. These results Indicates that the appilcation of virtual wedge in clinical use is appropriate.