The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Taesuk Suh - One of the best experts on this subject based on the ideXlab platform.
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optimal set of Grid Size and angular increment for practical dose calculation using the dynamic conformal arc technique a systematic evaluation of the dosimetric effects in lung stereotactic body radiation therapy
Radiation Oncology, 2014Co-Authors: Jiyeon Park, Siyong Kim, Haejin Park, Jeong Woo Lee, Yeonsil Kim, Taesuk SuhAbstract:Purpose: To recommend the optimal plan parameter set of Grid Size and angular increment for dose calculations in treatment planning for lung stereotactic body radiation therapy (SBRT) using dynamic conformal arc therapy (DCAT) considering both accuracy and computational efficiency. Materials and methods: Dose variations with varying Grid Sizes (2, 3, and 4 mm) and angular increments (2°, 4°, 6°, and 10°) were analyzed in a thorax phantom for 3 spherical target volumes and in 9 patient cases. A 2-mm Grid Size and 2° angular increment are assumed sufficient to serve as reference values. The dosimetric effect was evaluated using dose–volume histograms, monitor units (MUs), and dose to organs at risk (OARs) for a definite volume corresponding to the dose–volume constraint in lung SBRT. The times required for dose calculations using each parameter set were compared for clinical practicality. Results: Larger Grid Sizes caused a dose increase to the structures and required higher MUs to achieve the target coverage. The discrete beam arrangements at each angular increment led to over- and under-estimated OARs doses due to the undulating dose distribution. When a 2° angular increment was used in both studies, a 4-mm Grid Size changed the dose variation by up to 3–4% (50 cGy) for the heart and the spinal cord, while a 3-mm Grid Size produced a dose difference of <1% (12 cGy) in all tested OARs. When a 3-mm Grid Size was employed, angular increments of 6° and 10° caused maximum dose variations of 3% (23 cGy) and 10% (61 cGy) in the spinal cord, respectively, while a 4° increment resulted in a dose difference of <1% (8 cGy) in all cases except for that of one patient. The 3-mm Grid Size and 4° angular increment enabled a 78% savings in computation time without making any critical sacrifices to dose accuracy. Conclusions: A parameter set with a 3-mm Grid Size and a 4° angular increment is found to be appropriate for predicting patient dose distributions with a dose difference below 1% while reducing the computation time by more than half for lung SBRT using DCAT.
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verification of the Grid Size and angular increment effects in lung stereotactic body radiation therapy using the dynamic conformal arc technique
Journal of the Korean Physical Society, 2013Co-Authors: Taesuk Suh, Jiyeon Park, Haejin Park, Jeong Woo Lee, Mihwa Kim, Mison Chun, Kyu O Noh, Susie SuhAbstract:The dosimetric effects of variable Grid Size and angular increment were systematically evaluated in the measured dose distributions of dynamic conformal arc therapy (DCAT) for lung stereotactic body radiation therapy (SBRT). Dose variations with different Grid Sizes (2, 3, and 4 mm) and angular increments (2, 4, 6, and 10°) for spherical planning target volumes (PTVs) were verified in a thorax phantom by using EBT2 films. Although the doses for identical PTVs were predicted for the different Grid Sizes, the dose discrepancy was evaluated using one measured dose distribution with the gamma tool because the beam was delivered in the same set-up for DCAT. The dosimetric effect of the angular increment was verified by comparing the measured dose area histograms of organs at risk (OARs) at each angular increment. When the difference in the OAR doses is higher than the uncertainty of the film dosimetry, the error is regarded as the angular increment effect in discretely calculated doses. In the results, even when a 2-mm Grid Size was used with an elaborate dose calculation, 4-mm Grid Size led to a higher gamma pass ratio due to underdosage, a steep-dose descent gradient, and lower estimated PTV doses caused by the smoothing effect in the calculated dose distribution. An undulating dose distribution and a difference in the maximum contralateral lung dose of up to 14% were observed in dose calculation using a 10° angular increment. The DCAT can be effectively applied for an approximately spherical PTV in a relatively uniform geometry, which is less affected by inhomogeneous materials and differences in the beam path length.
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dose variations with varying calculation Grid Size in head and neck imrt
Physics in Medicine and Biology, 2006Co-Authors: H Chung, H Jin, Jatinder R Palta, Taesuk Suh, Siyong KimAbstract:Ever since the advent and development of treatment planning systems, the uncertainty associated with calculation Grid Size has been an issue. Even to this day, with highly sophisticated 3D conformal and intensity-modulated radiation therapy (IMRT) treatment planning systems (TPS), dose uncertainty due to Grid Size is still a concern. A phantom simulating head and neck treatment was prepared from two semi-cylindrical solid water slabs and a radiochromic film was inserted between the two slabs for measurement. Plans were generated for a 5400 cGy prescribed dose using Philips Pinnacle3 TPS for two targets, one shallow (~0.5 cm depth) and one deep (~6 cm depth). Calculation Grid Sizes of 1.5, 2, 3 and 4 mm were considered. Three clinical cases were also evaluated. The dose differences for the varying Grid Sizes (2 mm, 3 mm and 4 mm from 1.5 mm) in the phantom study were 126 cGy (2.3% of the 5400 cGy dose prescription), 248.2 cGy (4.6% of the 5400 cGy dose prescription) and 301.8 cGy (5.6% of the 5400 cGy dose prescription), respectively for the shallow target case. It was found that the dose could be varied to about 100 cGy (1.9% of the 5400 cGy dose prescription), 148.9 cGy (2.8% of the 5400 cGy dose prescription) and 202.9 cGy (3.8% of the 5400 cGy dose prescription) for 2 mm, 3 mm and 4 mm Grid Sizes, respectively, simply by shifting the calculation Grid origin. Dose difference with a different range of the relative dose gradient was evaluated and we found that the relative dose difference increased with an increase in the range of the relative dose gradient. When comparing varying calculation Grid Sizes and measurements, the variation of the dose difference histogram was insignificant, but a local effect was observed in the dose difference map. Similar results were observed in the case of the deep target and the three clinical cases also showed results comparable to those from the phantom study.
Ryo Mizuta - One of the best experts on this subject based on the ideXlab platform.
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changes in precipitation intensity over east asia during the 20th and 21st centuries simulated by a global atmospheric model with a 60 km Grid Size
Journal of Geophysical Research, 2013Co-Authors: Shoji Kusunoki, Ryo MizutaAbstract:[1] We conducted three-member ensemble simulations using a global atmospheric model with a high horizontal resolution of a 60 km Grid Size for the period 1872–2099 (228 years). Between 1872 and 2005, the model was forced with observed historical sea surface temperatures (SST), while between 2006 and 2099, the boundary SST data were estimated using the multimodel ensemble of the Coupled Model Intercomparison Project Phase 3 models and assuming A1B emission scenario. Annual mean precipitation (PAVE), the Simple Daily Precipitation Intensity Index (SDII), and the maximum 5 day precipitation total (R5d) averaged over East Asia increase almost monotonically through the 21st century. The statistically significant area of precipitation intensity increase is larger for 2080–2099 than for 2046–2065. In particular, intense rainfall will increase over northern and southern China during 2080–2099. The conversion rate from water vapor to precipitation per 1°C rise in surface air temperature for SDII and R5D is much larger than that for PAVE during the 21st century. This suggests that extreme rainfall events will occur more frequently than moderate rainfall events even if the amount of temperature rise is same. Future changes in the horizontal transport of water vapor also lead to more intense precipitation over East Asia. In particular, the increase in clockwise water vapor transport due to intensification of the subtropical high contributes to increased intense precipitation over southern China.
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change of baiu rain band in global warming projection by an atmospheric general circulation model with a 20 km Grid Size
Journal of the Meteorological Society of Japan, 2006Co-Authors: Shoji Kusunoki, Jun Yoshimura, Hiromasa Yoshimura, Akira Noda, Kazuyoshi Oouchi, Ryo MizutaAbstract:A global warming projection experiment was conducted on the Earth Simulator using a very high horizontal resolution atmospheric general circulation model, with 20-km Grid Size (the 20-km model). Such high horizontal resolution in a global climate model is unprecedented for a global warming projection. Experiments using the 20-km model were conducted by adopting the time-slice method, in which future changes in sea surface temperature (SST) were predicted by an atmosphere-ocean general circulation model (AOGCM) called MRI-CGCM2.3. The A1B emission scenario, proposed by the Intergovernmental Panel on Climate Change (IPCC), was assumed in the experiment.The model reproduces a realistic Baiu rain band under the present-day climate conditions in terms of geographical distribution and northward seasonal march. Experiments of the dependency of the horizontal resolution on the reproducibility of the Baiu rain band have revealed that the 20-km model generally exhibits higher performance than a model with a lower horizontal resolution. The future climate simulation shows that precipitation, and its intensity increases over the Yangtze River valley of China, the East China Sea, Western Japan, and the ocean to the south of the Japan archipelago. Conversely, precipitation and its intensity decrease over the Korean peninsula and Northern Japan. The termination of the Baiu season tends to be delayed until August.The future precipitation change is mainly attributable to the change in the horizontal transport of water vapor flux and its convergence associated with the intensification of a subtropical high. This can be interpreted as an atmospheric response to the El Nino condition of the ocean. The change in the wind field mainly contributes to the change in the water vapor flux in the case of the Baiu rain band.
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change of baiu rain band in global warming projection by an atmospheric general circulation model with a 20 km Grid Size
Journal of the Meteorological Society of Japan, 2006Co-Authors: Shoji Kusunoki, Jun Yoshimura, Hiromasa Yoshimura, Akira Noda, Kazuyoshi Oouchi, Ryo MizutaAbstract:A global warming projection experiment was conducted on the Earth Simulator using a very high horizontal resolution atmospheric general circulation model, with 20-km Grid Size (the 20-km model). Such high horizontal resolution in a global climate model is unprecedented for a global warming projection. Experiments using the 20-km model were conducted by adopting the time-slice method, in which future changes in sea surface temperature (SST) were predicted by an atmosphere-ocean general circulation model (AOGCM) called MRI-CGCM2.3. The A1B emission scenario, proposed by the Intergovernmental Panel on Climate Change (IPCC), was assumed in the experiment.The model reproduces a realistic Baiu rain band under the present-day climate conditions in terms of geographical distribution and northward seasonal march. Experiments of the dependency of the horizontal resolution on the reproducibility of the Baiu rain band have revealed that the 20-km model generally exhibits higher performance than a model with a lower horizontal resolution. The future climate simulation shows that precipitation, and its intensity increases over the Yangtze River valley of China, the East China Sea, Western Japan, and the ocean to the south of the Japan archipelago. Conversely, precipitation and its intensity decrease over the Korean peninsula and Northern Japan. The termination of the Baiu season tends to be delayed until August.The future precipitation change is mainly attributable to the change in the horizontal transport of water vapor flux and its convergence associated with the intensification of a subtropical high. This can be interpreted as an atmospheric response to the El Nino condition of the ocean. The change in the wind field mainly contributes to the change in the water vapor flux in the case of the Baiu rain band.
Haejin Park - One of the best experts on this subject based on the ideXlab platform.
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optimal set of Grid Size and angular increment for practical dose calculation using the dynamic conformal arc technique a systematic evaluation of the dosimetric effects in lung stereotactic body radiation therapy
Radiation Oncology, 2014Co-Authors: Jiyeon Park, Siyong Kim, Haejin Park, Jeong Woo Lee, Yeonsil Kim, Taesuk SuhAbstract:Purpose: To recommend the optimal plan parameter set of Grid Size and angular increment for dose calculations in treatment planning for lung stereotactic body radiation therapy (SBRT) using dynamic conformal arc therapy (DCAT) considering both accuracy and computational efficiency. Materials and methods: Dose variations with varying Grid Sizes (2, 3, and 4 mm) and angular increments (2°, 4°, 6°, and 10°) were analyzed in a thorax phantom for 3 spherical target volumes and in 9 patient cases. A 2-mm Grid Size and 2° angular increment are assumed sufficient to serve as reference values. The dosimetric effect was evaluated using dose–volume histograms, monitor units (MUs), and dose to organs at risk (OARs) for a definite volume corresponding to the dose–volume constraint in lung SBRT. The times required for dose calculations using each parameter set were compared for clinical practicality. Results: Larger Grid Sizes caused a dose increase to the structures and required higher MUs to achieve the target coverage. The discrete beam arrangements at each angular increment led to over- and under-estimated OARs doses due to the undulating dose distribution. When a 2° angular increment was used in both studies, a 4-mm Grid Size changed the dose variation by up to 3–4% (50 cGy) for the heart and the spinal cord, while a 3-mm Grid Size produced a dose difference of <1% (12 cGy) in all tested OARs. When a 3-mm Grid Size was employed, angular increments of 6° and 10° caused maximum dose variations of 3% (23 cGy) and 10% (61 cGy) in the spinal cord, respectively, while a 4° increment resulted in a dose difference of <1% (8 cGy) in all cases except for that of one patient. The 3-mm Grid Size and 4° angular increment enabled a 78% savings in computation time without making any critical sacrifices to dose accuracy. Conclusions: A parameter set with a 3-mm Grid Size and a 4° angular increment is found to be appropriate for predicting patient dose distributions with a dose difference below 1% while reducing the computation time by more than half for lung SBRT using DCAT.
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verification of the Grid Size and angular increment effects in lung stereotactic body radiation therapy using the dynamic conformal arc technique
Journal of the Korean Physical Society, 2013Co-Authors: Taesuk Suh, Jiyeon Park, Haejin Park, Jeong Woo Lee, Mihwa Kim, Mison Chun, Kyu O Noh, Susie SuhAbstract:The dosimetric effects of variable Grid Size and angular increment were systematically evaluated in the measured dose distributions of dynamic conformal arc therapy (DCAT) for lung stereotactic body radiation therapy (SBRT). Dose variations with different Grid Sizes (2, 3, and 4 mm) and angular increments (2, 4, 6, and 10°) for spherical planning target volumes (PTVs) were verified in a thorax phantom by using EBT2 films. Although the doses for identical PTVs were predicted for the different Grid Sizes, the dose discrepancy was evaluated using one measured dose distribution with the gamma tool because the beam was delivered in the same set-up for DCAT. The dosimetric effect of the angular increment was verified by comparing the measured dose area histograms of organs at risk (OARs) at each angular increment. When the difference in the OAR doses is higher than the uncertainty of the film dosimetry, the error is regarded as the angular increment effect in discretely calculated doses. In the results, even when a 2-mm Grid Size was used with an elaborate dose calculation, 4-mm Grid Size led to a higher gamma pass ratio due to underdosage, a steep-dose descent gradient, and lower estimated PTV doses caused by the smoothing effect in the calculated dose distribution. An undulating dose distribution and a difference in the maximum contralateral lung dose of up to 14% were observed in dose calculation using a 10° angular increment. The DCAT can be effectively applied for an approximately spherical PTV in a relatively uniform geometry, which is less affected by inhomogeneous materials and differences in the beam path length.
Shoji Kusunoki - One of the best experts on this subject based on the ideXlab platform.
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changes in precipitation intensity over east asia during the 20th and 21st centuries simulated by a global atmospheric model with a 60 km Grid Size
Journal of Geophysical Research, 2013Co-Authors: Shoji Kusunoki, Ryo MizutaAbstract:[1] We conducted three-member ensemble simulations using a global atmospheric model with a high horizontal resolution of a 60 km Grid Size for the period 1872–2099 (228 years). Between 1872 and 2005, the model was forced with observed historical sea surface temperatures (SST), while between 2006 and 2099, the boundary SST data were estimated using the multimodel ensemble of the Coupled Model Intercomparison Project Phase 3 models and assuming A1B emission scenario. Annual mean precipitation (PAVE), the Simple Daily Precipitation Intensity Index (SDII), and the maximum 5 day precipitation total (R5d) averaged over East Asia increase almost monotonically through the 21st century. The statistically significant area of precipitation intensity increase is larger for 2080–2099 than for 2046–2065. In particular, intense rainfall will increase over northern and southern China during 2080–2099. The conversion rate from water vapor to precipitation per 1°C rise in surface air temperature for SDII and R5D is much larger than that for PAVE during the 21st century. This suggests that extreme rainfall events will occur more frequently than moderate rainfall events even if the amount of temperature rise is same. Future changes in the horizontal transport of water vapor also lead to more intense precipitation over East Asia. In particular, the increase in clockwise water vapor transport due to intensification of the subtropical high contributes to increased intense precipitation over southern China.
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change of baiu rain band in global warming projection by an atmospheric general circulation model with a 20 km Grid Size
Journal of the Meteorological Society of Japan, 2006Co-Authors: Shoji Kusunoki, Jun Yoshimura, Hiromasa Yoshimura, Akira Noda, Kazuyoshi Oouchi, Ryo MizutaAbstract:A global warming projection experiment was conducted on the Earth Simulator using a very high horizontal resolution atmospheric general circulation model, with 20-km Grid Size (the 20-km model). Such high horizontal resolution in a global climate model is unprecedented for a global warming projection. Experiments using the 20-km model were conducted by adopting the time-slice method, in which future changes in sea surface temperature (SST) were predicted by an atmosphere-ocean general circulation model (AOGCM) called MRI-CGCM2.3. The A1B emission scenario, proposed by the Intergovernmental Panel on Climate Change (IPCC), was assumed in the experiment.The model reproduces a realistic Baiu rain band under the present-day climate conditions in terms of geographical distribution and northward seasonal march. Experiments of the dependency of the horizontal resolution on the reproducibility of the Baiu rain band have revealed that the 20-km model generally exhibits higher performance than a model with a lower horizontal resolution. The future climate simulation shows that precipitation, and its intensity increases over the Yangtze River valley of China, the East China Sea, Western Japan, and the ocean to the south of the Japan archipelago. Conversely, precipitation and its intensity decrease over the Korean peninsula and Northern Japan. The termination of the Baiu season tends to be delayed until August.The future precipitation change is mainly attributable to the change in the horizontal transport of water vapor flux and its convergence associated with the intensification of a subtropical high. This can be interpreted as an atmospheric response to the El Nino condition of the ocean. The change in the wind field mainly contributes to the change in the water vapor flux in the case of the Baiu rain band.
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change of baiu rain band in global warming projection by an atmospheric general circulation model with a 20 km Grid Size
Journal of the Meteorological Society of Japan, 2006Co-Authors: Shoji Kusunoki, Jun Yoshimura, Hiromasa Yoshimura, Akira Noda, Kazuyoshi Oouchi, Ryo MizutaAbstract:A global warming projection experiment was conducted on the Earth Simulator using a very high horizontal resolution atmospheric general circulation model, with 20-km Grid Size (the 20-km model). Such high horizontal resolution in a global climate model is unprecedented for a global warming projection. Experiments using the 20-km model were conducted by adopting the time-slice method, in which future changes in sea surface temperature (SST) were predicted by an atmosphere-ocean general circulation model (AOGCM) called MRI-CGCM2.3. The A1B emission scenario, proposed by the Intergovernmental Panel on Climate Change (IPCC), was assumed in the experiment.The model reproduces a realistic Baiu rain band under the present-day climate conditions in terms of geographical distribution and northward seasonal march. Experiments of the dependency of the horizontal resolution on the reproducibility of the Baiu rain band have revealed that the 20-km model generally exhibits higher performance than a model with a lower horizontal resolution. The future climate simulation shows that precipitation, and its intensity increases over the Yangtze River valley of China, the East China Sea, Western Japan, and the ocean to the south of the Japan archipelago. Conversely, precipitation and its intensity decrease over the Korean peninsula and Northern Japan. The termination of the Baiu season tends to be delayed until August.The future precipitation change is mainly attributable to the change in the horizontal transport of water vapor flux and its convergence associated with the intensification of a subtropical high. This can be interpreted as an atmospheric response to the El Nino condition of the ocean. The change in the wind field mainly contributes to the change in the water vapor flux in the case of the Baiu rain band.
Siyong Kim - One of the best experts on this subject based on the ideXlab platform.
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optimal set of Grid Size and angular increment for practical dose calculation using the dynamic conformal arc technique a systematic evaluation of the dosimetric effects in lung stereotactic body radiation therapy
Radiation Oncology, 2014Co-Authors: Jiyeon Park, Siyong Kim, Haejin Park, Jeong Woo Lee, Yeonsil Kim, Taesuk SuhAbstract:Purpose: To recommend the optimal plan parameter set of Grid Size and angular increment for dose calculations in treatment planning for lung stereotactic body radiation therapy (SBRT) using dynamic conformal arc therapy (DCAT) considering both accuracy and computational efficiency. Materials and methods: Dose variations with varying Grid Sizes (2, 3, and 4 mm) and angular increments (2°, 4°, 6°, and 10°) were analyzed in a thorax phantom for 3 spherical target volumes and in 9 patient cases. A 2-mm Grid Size and 2° angular increment are assumed sufficient to serve as reference values. The dosimetric effect was evaluated using dose–volume histograms, monitor units (MUs), and dose to organs at risk (OARs) for a definite volume corresponding to the dose–volume constraint in lung SBRT. The times required for dose calculations using each parameter set were compared for clinical practicality. Results: Larger Grid Sizes caused a dose increase to the structures and required higher MUs to achieve the target coverage. The discrete beam arrangements at each angular increment led to over- and under-estimated OARs doses due to the undulating dose distribution. When a 2° angular increment was used in both studies, a 4-mm Grid Size changed the dose variation by up to 3–4% (50 cGy) for the heart and the spinal cord, while a 3-mm Grid Size produced a dose difference of <1% (12 cGy) in all tested OARs. When a 3-mm Grid Size was employed, angular increments of 6° and 10° caused maximum dose variations of 3% (23 cGy) and 10% (61 cGy) in the spinal cord, respectively, while a 4° increment resulted in a dose difference of <1% (8 cGy) in all cases except for that of one patient. The 3-mm Grid Size and 4° angular increment enabled a 78% savings in computation time without making any critical sacrifices to dose accuracy. Conclusions: A parameter set with a 3-mm Grid Size and a 4° angular increment is found to be appropriate for predicting patient dose distributions with a dose difference below 1% while reducing the computation time by more than half for lung SBRT using DCAT.
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dose variations with varying calculation Grid Size in head and neck imrt
Physics in Medicine and Biology, 2006Co-Authors: H Chung, H Jin, Jatinder R Palta, Taesuk Suh, Siyong KimAbstract:Ever since the advent and development of treatment planning systems, the uncertainty associated with calculation Grid Size has been an issue. Even to this day, with highly sophisticated 3D conformal and intensity-modulated radiation therapy (IMRT) treatment planning systems (TPS), dose uncertainty due to Grid Size is still a concern. A phantom simulating head and neck treatment was prepared from two semi-cylindrical solid water slabs and a radiochromic film was inserted between the two slabs for measurement. Plans were generated for a 5400 cGy prescribed dose using Philips Pinnacle3 TPS for two targets, one shallow (~0.5 cm depth) and one deep (~6 cm depth). Calculation Grid Sizes of 1.5, 2, 3 and 4 mm were considered. Three clinical cases were also evaluated. The dose differences for the varying Grid Sizes (2 mm, 3 mm and 4 mm from 1.5 mm) in the phantom study were 126 cGy (2.3% of the 5400 cGy dose prescription), 248.2 cGy (4.6% of the 5400 cGy dose prescription) and 301.8 cGy (5.6% of the 5400 cGy dose prescription), respectively for the shallow target case. It was found that the dose could be varied to about 100 cGy (1.9% of the 5400 cGy dose prescription), 148.9 cGy (2.8% of the 5400 cGy dose prescription) and 202.9 cGy (3.8% of the 5400 cGy dose prescription) for 2 mm, 3 mm and 4 mm Grid Sizes, respectively, simply by shifting the calculation Grid origin. Dose difference with a different range of the relative dose gradient was evaluated and we found that the relative dose difference increased with an increase in the range of the relative dose gradient. When comparing varying calculation Grid Sizes and measurements, the variation of the dose difference histogram was insignificant, but a local effect was observed in the dose difference map. Similar results were observed in the case of the deep target and the three clinical cases also showed results comparable to those from the phantom study.
