• Radiation Oncology Journal
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• v.13 no.3
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• pp.291-296
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• 1995

Purpose : In general, the wedge factors which are used clinical practices are ignored of dependency on field sizes and depths. In this present, we investigated systematically the depth and field size dependency to determine the absorbed dose more accurately. Methods : The wedge factors for each wedge filter were measured at various depths (depth of Dmax, 5cm, 10cm, and 15cm) and field sizes ($5cm{\times}5cm,\;10cm{\times}10cm,\;15cm{\times}15cm, and 20cm{\times}20cm$) by using 4-, 6-, and 10-MVX rays. By convention, wedge factors are determined by taking the ratio of the central axis ionization readings when the wedge filter is in place to those of the open field in same field size and measurement depth. In this present work, we determined the wedge factors for 4-, 6-, and 10-MV X rays from Clinac 600C and 2100C linear accelerators (manufactured by Varian Associates, Inc., Palo Alto, CA). To confirm that the wedge was centered, measurements were done with the two possible wedge position and various collimator orientations. Results : The standard deviations of measured values are within $0.3\;\%$ and the depth dependence of wedge factor is greater for the lower energies. Especially, the variation of wedge factor is no less than $5\%$ for 4- and 6- MV X rays with more than $45^{\circ}$ wedge filters. But there seems to be a small dependence on field size. Conclusion : The results of this study show a dependence on the point of measurement. There also seems to be a small dependence on field size. And so, we should consider the depth and field size dependence in determining the wedge factors. If one wedge factor were to be used for each wedge filter it seems that the measurement for a 10cm x 10cm field size at a depth of loom would be a reasonable choice.

• Progress in Medical Physics
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• v.15 no.4
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• pp.237-246
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• 2004

Even though the wedge factor was defined by ICRU, RTPS uses other definition different from the wedge factor to consider the wedge effect to correct dose. Because the factors with different concept are defined in a very different way, replacement of different factor could make severe error of dose and is unacceptable because their values are very different from each other. Radiotherapy machine installed in department includes physical wedges and function of dynamic wedge by upper jaws, and Eclipse and Pinnacle$^{3}$ such as RTPS are used. The wedge factors, relative wedge output factors and wedge field output factors of physical wedges and dynamic wedges were measured by an ionization chamber in water phantom. They are analyzed and compared in according to wedge position, field size, wedge angle, X-ray quality, measurement condition. Wedge factor, relative wedge output factors and wedge field output factors of dynamic wedges comparing physical wedges have an effect of several factors. Main factors effecting to the factors of dynamic wedges were field size and wedge angle. Beam quality of X-ray introduces a few effect to the factors. Because the factors related to wedge and defined with different concepts are different from each other, to reduce dose error it should be input by values proper to RTPS.

• Progress in Medical Physics
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• v.11 no.1
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• pp.1-18
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• 2000

For wedged photon beams, the variation of the wedge factor with field size was reported by several authors. However, until now such variation with field size had not been explained quantitatively. Therefore, the variation of the wedge factor was investigated by measuring outputs with field sizes increasing from 4 cm $\times$ 4 cm to 25 cm $\times$ 25 cm for open and wedged 6 and 10MV X-ray beams. The relative outputs for wedged fields to 10 cm $\times$ 10 cm have been obtained. The results show the Increase of the wedge factor caused by the change in fluence of high energy Photon beam with field size, up to 8.0% for KD77-6MV X-ray beam. This increase could be explained as a linear function of the irradiated wedge volume except small field size up to about 10 cm. In the cases of the narrow rectangular beam parallel to the wedge direction, the wedge factor decreases slightly with increasing field size up to about 10-15 cm due to a relatively reduced photon fluence from the change of the wedge thickness. We could explain the causes of a wedge factor variation with field size as the fluences of primary photon passed throughout the wedge, contributing to the dose at the central beam axis and that the fluences were affected by the gradient of the wedge with the change of field size. For clinical use, the formula developed to describe the wedge factor variation with field size has been corrected.

• Progress in Medical Physics
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• v.3 no.2
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• pp.13-22
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• 1992

Traditionally. the wedge factor of universal wedge is regarded as constant for small depth. Recently. some investigators have reported the beam hardening effect from wedged beam even in small depth. suggesting that the wedge factors are depth dependent values. Here authors performed the study to determine the proper depth of measurement for wedge factor. In this study. we have measured the wedge factors (nominal wedge angles 15, 30, 45, and 60) not only for depth maximum. but also for each depth, for several energies (4MV, 6MV, 10MV, and 15MV) of various machines (Varian, Siemens, Mitsubishi). And we have analysed the treatment depth of 614 patients who had been treated with wedged field at our hospitals to determine of the proper depth of the measurement point for wedge factor. More than 60% of the patients are treated at the depth of 8cm$\pm$2.5cm with the wedged field for various machines. energies, and wedge angles. The results of the wedge factor measurements show that the systemic error of average 2% (maximum 4%) might be inherently originated for the patients who had been treated with wedged field if we adapt the depth maximum as the wedge factor determination depth due to beam hardening effect. But we could achieve average error less than 0.5% (maximum within 1.7%) if we use 8cm for wedge factor measurement point We conclude that the measurement depth point for wedge factor should be 8cm in order to deliver more accurate dose to target for Korean patients. instead of depth maximum.

• Progress in Medical Physics
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• v.6 no.2
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• pp.29-34
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• 1995

The wedge factor is defined as a ratio of the absorbed dose in a phantom at a depth of reference point on the central axis with the wedge in the place to the absorbed dose at the same point with the wedge removed. We attempted to show the wedge factors dependence on the field sizes. The wedge factors were measured at various field sizes on 6MV and 15MV x-ray of Varian Clinac 1800 and 5MV x-ray of Philips SL75/5. The single wedge factor measured for a reference field size(10cmx10cm) may not be valid for all field sizes. For the thick wedge, especially an autowedge on Philips SL75/5 for maximum field size width 30cm. the error can be significant(6.6％). Therefore, in the presence of a wedge filter in the beam, a field size dependent wedge factor may be necessary in the treatment dose calculations.

• Journal of radiological science and technology
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• v.22 no.2
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• pp.57-60
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• 1999

Therapy equipment have taken progress for Cancer make use of Radiation for the normal tissue system make much of important for shielding. In modern times independent jaw setting to used equipment as possible make use of asymmetric field. Therefore, the asymmetric field be leave out of consideration wedge factor because of with used wedge for the most of part. These experimentation find out have an effect on the dosimetry of out put compared with of the difference between the symmetric field and asymmetic field for the wedge factor.

• The Journal of Korean Society for Radiation Therapy
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• v.7 no.1
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• pp.103-110
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• 1995

Dynamic wedge system has been introduced to modify the beam profile and to make homogeneous isodose curves in the mass of irregular shape. Before the clinical use of dynamic wedge, several factors such as wedge transmission factor, dose profile, percent depth dose, and wedge angle have to be measured quantitatively. Film dosimetry is used to evaluate these factors in this study. A comparison of the result of the dynamic wedge to physical wedge system is made. A positive result for the application of the dynamic wedge to clinic is derived even though there is a limitation in accuracy of the dosimetry system used. To measure all factors quantitatively, more accurate dosimetry systems are required.

• Radiation Oncology Journal
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• v.15 no.1
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• pp.71-78
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• 1997

Purpose : To collect beam data for dynamic wedge fields using conventional measurement tools without the multi-detector system, such as the linear diode detectors or ionization chambers. Materials and Methods : The accelerator CL 2100 C/D has two photon energies of 6MV and 15MV with dynamic wedge an91es of 15o, 30o, 45o and 60o. Wedge transmission factors, percentage depth doses(PDD's) and dose Profiles were measured. The measurements for wedge transmission factors are performed for field sizes ranging from $4\times4cm^2\;to\;20\times20cm^2$ in 1-2cm steps. Various rectangular field sizes are also measured for each photon energy of 6MV and 15MV, with the combination of each dynamic wedge angle of 15o 30o. 45o and 60o. These factors are compared to the calculated wedge factors using STT(Segmented Treatment Table) value. PDD's are measured with the film and the chamber in water Phantom for fixed square field. Converting parameters for film data to chamber data could be obtained from this procedure. The PDD's for dynamic wedged fields could be obtained from film dosimetry by using the converting parameters without using ionization chamber. Dose profiles are obtained from interpolation and STT weighted superposition of data through selected asymmetric static field measurement using ionization chamber. Results : The measured values of wedge transmission factors show good agreement to the calculated values The wedge factors of rectangular fields for constant V-field were equal to those of square fields The differences between open fields' PDDs and those from dynamic fields are insignificant. Dose profiles from superposition method showed acceptable range of accuracy(maximum 2% error) when we compare to those from film dosimetry. Conclusion : The results from this superposition method showed that commissionning of dynamic wedge could be done with conventional dosimetric tools such as Point detector system and film dosimetry winthin maximum 2% error range of accuracy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.151-158
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• 2007

The mechanism of power transmission from motor torque to stem thrust and the operation characteristic of each stroke position are analyzed using the diagnostic signal, and effects of differential pressure on the performance of motor operated flexible wedge gate valve are investigated. Test facility consists of 76 mm motor operated valve(flexible wedge type), pump and pipe system. Static and dynamic test are performed separately, and two differential pressure conditions are applied in the dynamic test. To evaluate the performance of valve, test signals for the torque, thrust, current, voltage and stroke length are acquired by using UDS which is diagnosis device for motor operated valve, and each diagnostic signal is analyzed and compared. The characteristic of valve performance factors such as stem factor, rate of loading, valve factor, are evaluated, and these factors are found to be severely influenced by the fluid differential pressure.

• Geomechanics and Engineering
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• v.15 no.1
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• pp.669-676
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• 2018

The "pseudo-wedge" failure is a name for a complex instability occurring at the Sarcheshmeh open-pit mine (Iran). The pseudo-wedge failure contains both the rock bridge failure and sliding along pre-existing discontinuities. In this paper, a cross section of the failure area was first modeled using a bonded-particle method. The results indicated development of tensile cracks at the slope toe which explains the freedom of pseudo-wedge blocks to slide. Then, a three-dimensional discrete element method was used to perform a block analysis of the instability. The technique of shear strength reduction was used to calculate the factor of safety. Finally, the influence of geometrical characteristics of the mine wall on the pseudo-wedge failure was investigated. The safety factor significantly increases as the dip and dip direction of the wall decrease, and reaches an acceptable value with a 10-degree decrease of them.