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Matthew R. Palmer - One of the best experts on this subject based on the ideXlab platform.
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Xinming Liu, Alexander A. Bankier, John RongAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced <±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. CONCLUSIONS The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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Estimating patient water Equivalent Diameter from CT localizer images ‐‐ A longitudinal and multi‐institutional study of the stability of calibration parameters
Medical physics, 2020Co-Authors: Da Zhang, Xinhui Duan, Xinming Liu, Alexander A. Bankier, John Rong, Matthew R. PalmerAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Alexander A. Bankier, John RongAbstract:PURPOSE: Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 CT scanners from 3 medical centers, and their stability over 3~29 months for 14 of those scanners. METHODS: Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS: Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners (R2 > 0:999). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced less than ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. CONCLUSIONS: The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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A new method for CT dose estimation by determining patient water Equivalent Diameter from localizer radiographs: Geometric transformation and calibration methods using readily available phantoms.
Medical physics, 2018Co-Authors: Da Zhang, Georgeta Mihai, Larry Barbaras, Olga R. Brook, Matthew R. PalmerAbstract:PURPOSE Water Equivalent Diameter (Dw) reflects patient's attenuation and is a sound descriptor of patient size, and is used to determine size-specific dose estimator from a CT examination. Calculating Dw from CT localizer radiographs makes it possible to utilize Dw before actual scans and minimizes truncation errors due to limited reconstructed fields of view. One obstacle preventing the user community from implementing this useful tool is the necessity to calibrate localizer pixel values so as to represent water Equivalent attenuation. We report a practical method to ease this calibration process. METHODS Dw is calculated from water Equivalent area (Aw) which is deduced from the average localizer pixel value (LPV) of the line(s) in the localizer radiograph that correspond(s) to the axial image. The calibration process is conducted to establish the relationship between Aw and LPV. Localizer and axial images were acquired from phantoms of different total attenuation. We developed a program that automates the geometrical association between axial images and localizer lines and manages the measurements of Dw and average pixel values. We tested the calibration method on three CT scanners: a GE CT750HD, a Siemens Definition AS, and a Toshiba Acquilion Prime80, for both posterior-anterior (PA) and lateral (LAT) localizer directions (for all CTs) and with different localizer filters (for the Toshiba CT). RESULTS The computer program was able to correctly perform the geometrical association between corresponding axial images and localizer lines. Linear relationships between Aw and LPV were observed (with R2 all greater than 0.998) on all tested conditions, regardless of the direction and image filters used on the localizer radiographs. When comparing LAT and PA directions with the same image filter and for the same scanner, the slope values were close (maximum difference of 0.02 mm), and the intercept values showed larger deviations (maximum difference of 2.8 mm). Water Equivalent Diameter estimation on phantoms and patients demonstrated high accuracy of the calibration: percentage difference between Dw from axial images and localizers was below 2%. With five clinical chest examinations and five abdominal-pelvic examinations of varying patient sizes, the maximum percentage difference was approximately 5%. CONCLUSIONS Our study showed that Aw and LPV are highly correlated, providing enough evidence to allow for the Dw determination once the experimental calibration process is established.
Da Zhang - One of the best experts on this subject based on the ideXlab platform.
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Xinming Liu, Alexander A. Bankier, John RongAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced <±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. CONCLUSIONS The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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Estimating patient water Equivalent Diameter from CT localizer images ‐‐ A longitudinal and multi‐institutional study of the stability of calibration parameters
Medical physics, 2020Co-Authors: Da Zhang, Xinhui Duan, Xinming Liu, Alexander A. Bankier, John Rong, Matthew R. PalmerAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Alexander A. Bankier, John RongAbstract:PURPOSE: Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 CT scanners from 3 medical centers, and their stability over 3~29 months for 14 of those scanners. METHODS: Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS: Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners (R2 > 0:999). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced less than ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. CONCLUSIONS: The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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A new method for CT dose estimation by determining patient water Equivalent Diameter from localizer radiographs: Geometric transformation and calibration methods using readily available phantoms.
Medical physics, 2018Co-Authors: Da Zhang, Georgeta Mihai, Larry Barbaras, Olga R. Brook, Matthew R. PalmerAbstract:PURPOSE Water Equivalent Diameter (Dw) reflects patient's attenuation and is a sound descriptor of patient size, and is used to determine size-specific dose estimator from a CT examination. Calculating Dw from CT localizer radiographs makes it possible to utilize Dw before actual scans and minimizes truncation errors due to limited reconstructed fields of view. One obstacle preventing the user community from implementing this useful tool is the necessity to calibrate localizer pixel values so as to represent water Equivalent attenuation. We report a practical method to ease this calibration process. METHODS Dw is calculated from water Equivalent area (Aw) which is deduced from the average localizer pixel value (LPV) of the line(s) in the localizer radiograph that correspond(s) to the axial image. The calibration process is conducted to establish the relationship between Aw and LPV. Localizer and axial images were acquired from phantoms of different total attenuation. We developed a program that automates the geometrical association between axial images and localizer lines and manages the measurements of Dw and average pixel values. We tested the calibration method on three CT scanners: a GE CT750HD, a Siemens Definition AS, and a Toshiba Acquilion Prime80, for both posterior-anterior (PA) and lateral (LAT) localizer directions (for all CTs) and with different localizer filters (for the Toshiba CT). RESULTS The computer program was able to correctly perform the geometrical association between corresponding axial images and localizer lines. Linear relationships between Aw and LPV were observed (with R2 all greater than 0.998) on all tested conditions, regardless of the direction and image filters used on the localizer radiographs. When comparing LAT and PA directions with the same image filter and for the same scanner, the slope values were close (maximum difference of 0.02 mm), and the intercept values showed larger deviations (maximum difference of 2.8 mm). Water Equivalent Diameter estimation on phantoms and patients demonstrated high accuracy of the calibration: percentage difference between Dw from axial images and localizers was below 2%. With five clinical chest examinations and five abdominal-pelvic examinations of varying patient sizes, the maximum percentage difference was approximately 5%. CONCLUSIONS Our study showed that Aw and LPV are highly correlated, providing enough evidence to allow for the Dw determination once the experimental calibration process is established.
Abdelmalek Bouazza - One of the best experts on this subject based on the ideXlab platform.
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Reply to the discussion by Wu and Hu on "numerical assessment of Equivalent Diameter equations for prefabricated vertical drains"
Canadian Geotechnical Journal, 2013Co-Authors: H.m. .abuel-naga, Abdelmalek Bouazza, Dennes T. BergadoAbstract:where w and t are the width and thickness of the prefabricated vertical drain (PVD), respectively. Therefore, it is clear that the correct form of the Atkinson and Eldred (1981) equation is similar to the Rixner et al. (1986) equation. However, as this equation was first introduced by Atkinson and Eldred (1981), Rixner et al. (1986) was not cited in the paper under discussion. The results of the Atkinson and Eldred (1981) equation in Fig. 3 of the paper under discussion were developed using the correct equation: eq. (R1). However in their Discussion, Wu and Hu have used the wrong form of the Atkinson and Eldred (1981) equation, which could produce a smaller deq than what can be obtained by the Abuel-Naga and Bouazza (2009) equation. Therefore, Wu and Hu have observed a conflict between the expected behaviour of the Abuel-Naga and Bouazza (2009) equation and the Atkinson and Eldred (1981) equation. Based on the above explanation, the results of the Abuel-Naga and Bouazza (2009) equation and the Atkinson and Eldred (1981) equation will follow the concept introduced in Fig. 5 of the paper under discussion, where U is a function of deq and it decreases as deq increases. Regarding the need to conduct a three-dimensional (3D) instead of a two-dimensional (2D) numerical analysis to assess the validity of the different Equivalent Diameter equations, the authors would like to highlight the fact that as vertical consolidation could get activated in the 3D analysis, the rate of the overall degree of consolidation will be slightly higher than the results of a 2D analysis where only radial consolidation is activated. However, including the vertical consolidation process will have no effect on the ranking result of the different Equivalent Diameter equations as shown in Fig. D3 of the Discussion. Therefore, conducting a 3D numerical analysis to answer the research question raised by Abuel-Naga et al. (2012) is not required.
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Numerical assessment of Equivalent Diameter equations for prefabricated vertical drains
Canadian Geotechnical Journal, 2012Co-Authors: H.m. .abuel-naga, Abdelmalek Bouazza, Dennes T. BergadoAbstract:The design approaches to prefabricated vertical drains (PVDs) for different geotechnical and geoenvironmental engineering applications involve converting the PVD’s rectangular band shape to an Equivalent circular shape to simplify the analytical analysis. Several Equivalent Diameter equations for PVDs are available in the literature. However, these equations produce different Equivalent Diameters and no definitive recommendation is available regarding their validity. The aim of this study is to assess numerically the validity of these equations and identify the most appropriate one for use in design.
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Equivalent Diameter of a prefabricated vertical drain
Geotextiles and Geomembranes, 2009Co-Authors: H M Abuelnaga, Abdelmalek BouazzaAbstract:The aim of this study is to evaluate numerically the Equivalent Diameter of a prefabricated vertical drain (PVD) using an equal flow rate approach. This approach requires that the Equivalent circular well to be able to yield similar discharge as a PVD well when subjected to similar pressure-controlled pumping condition. Simple Equivalent Diameter equation was obtained from the numerical study. The proposed equation is discussed in light of the Equivalent Diameter equations and experimental results currently available in the literature. The outcomes of this study give more insight in this subject and improve the method of calculating the Equivalent Diameter of a PVD well.
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technical noteEquivalent Diameter of a prefabricated vertical drain
Geotextiles and Geomembranes, 2009Co-Authors: H M Abuelnaga, Abdelmalek BouazzaAbstract:The aim of this study is to evaluate numerically the Equivalent Diameter of a prefabricated vertical drain (PVD) using an equal flow rate approach. This approach requires that the Equivalent circular well to be able to yield similar discharge as a PVD well when subjected to similar pressure-controlled pumping condition. Simple Equivalent Diameter equation was obtained from the numerical study. The proposed equation is discussed in light of the Equivalent Diameter equations and experimental results currently available in the literature. The outcomes of this study give more insight in this subject and improve the method of calculating the Equivalent Diameter of a PVD well.
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On the Equivalent Diameter of Prefabricated Vertical Drain: Numerical Study
Geotextiles and Geomembranes, 2009Co-Authors: H.m. .abuel-naga, Abdelmalek BouazzaAbstract:The aim of this study is to evaluate numerically the Equivalent Diameter of a prefabricated vertical drain (PVD) using an equal flow rate approach. This approach requires that the Equivalent circular well to be able to yield similar discharge as a PVD well when subjected to similar pressure-controlled pumping condition. Simple Equivalent Diameter equation was obtained from the numerical study. The proposed equation is discussed in light of the Equivalent Diameter equations and experimental results currently available in the literature. The outcomes of this study give more insight in this subject and improve the method of calculating the Equivalent Diameter of a PVD well.
M Khatonabadi - One of the best experts on this subject based on the ideXlab platform.
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MO‐D‐134‐04: Calculating Size Specific Dose Estimates (SSDE): The Effect of Using Water Equivalent Diameter (WED) Vs. Effective Diameter (ED) On Organ Dose Estimates When Applying the Conversion Coefficients of TG204
Medical Physics, 2013Co-Authors: M Khatonabadi, D Oria, K Mok, Chris H. Cagnon, John J. Demarco, M Mcnitt‐grayAbstract:Purpose: AAPM Task Group (TG) 204 described the Size‐Specific Dose Estimate (SSDE) using effective Diameter (ED) as the size parameter in the conversion tables. The purpose of this investigation was to assess the effect on SSDE when a different size metric, water Equivalent Diameter (WED), was used with the conversion tables; and to compare these values to results from detailed Monte Carlo (MC) simulations. Methods: For a set of 101 thoracic and 82 abdomen/pelvis scans, including adult and pediatric patients, both ED and WED were calculated at the middle of the scan length. Each size metric was used as the input value to the SSDE conversion tables in TG204 to obtain two sets of SSDE values (SSDEED and SSDEWED). Additionally, voxelized patient models were generated from original scans and used in MC simulations to estimate dose to liver, spleen, and kidneys in the abdomen/pelvis, as well as lung and glandular breast tissue in the thoracic examinations under fixed tube current mode. SSDEED, SSDEWED were compared to organ doses by calculating percent differences and Root Mean Square errors. Results: For the abdomen, SSDEED and SSDEWED resulted in different RMSE from organ dose (for kidneys 8.8% and 6.4%, respectively) while SSDEWED demonstrated higher correlation with kidney dose than SSDEED (0.89 and 0.78, respectively). Similarly, for thorax, SSDEED and SSDEWED showed different RMSE (for lung 17.0% and 13.1%, respectively), with higher correlation for SSDEWED than SSDEED (0.92 and 0.78, respectively). Conclusion: Generated conversion factors based on ED appear to be applicable to WED and as originally assumed using WED not only improves dose estimates in the thorax but it also improves estimates in the abdomen. It is worth mentioning that these conclusions only apply to fixed tube current examinations while for tube current modulated (TCM) exams new set of conversion factors are recommended. Dr. Michael McNitt‐Gray Institutional research agreement, Siemens AG Recipient research support Siemens AG Consultant, Flaherty Sensabaugh Bonasso PLLC Consultant, Fulbright and Jaworski, LLC Maryam Khatonabadi: ipient research support Siemens AG
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mo d 134 04 calculating size specific dose estimates ssde the effect of using water Equivalent Diameter wed vs effective Diameter ed on organ dose estimates when applying the conversion coefficients of tg204
Medical Physics, 2013Co-Authors: M Khatonabadi, D Oria, K Mok, Chris H. Cagnon, J Demarco, Michael F McnittgrayAbstract:Purpose: AAPM Task Group (TG) 204 described the Size‐Specific Dose Estimate (SSDE) using effective Diameter (ED) as the size parameter in the conversion tables. The purpose of this investigation was to assess the effect on SSDE when a different size metric, water Equivalent Diameter (WED), was used with the conversion tables; and to compare these values to results from detailed Monte Carlo (MC) simulations. Methods: For a set of 101 thoracic and 82 abdomen/pelvis scans, including adult and pediatric patients, both ED and WED were calculated at the middle of the scan length. Each size metric was used as the input value to the SSDE conversion tables in TG204 to obtain two sets of SSDE values (SSDEED and SSDEWED). Additionally, voxelized patient models were generated from original scans and used in MC simulations to estimate dose to liver, spleen, and kidneys in the abdomen/pelvis, as well as lung and glandular breast tissue in the thoracic examinations under fixed tube current mode. SSDEED, SSDEWED were compared to organ doses by calculating percent differences and Root Mean Square errors. Results: For the abdomen, SSDEED and SSDEWED resulted in different RMSE from organ dose (for kidneys 8.8% and 6.4%, respectively) while SSDEWED demonstrated higher correlation with kidney dose than SSDEED (0.89 and 0.78, respectively). Similarly, for thorax, SSDEED and SSDEWED showed different RMSE (for lung 17.0% and 13.1%, respectively), with higher correlation for SSDEWED than SSDEED (0.92 and 0.78, respectively). Conclusion: Generated conversion factors based on ED appear to be applicable to WED and as originally assumed using WED not only improves dose estimates in the thorax but it also improves estimates in the abdomen. It is worth mentioning that these conclusions only apply to fixed tube current examinations while for tube current modulated (TCM) exams new set of conversion factors are recommended. Dr. Michael McNitt‐Gray Institutional research agreement, Siemens AG Recipient research support Siemens AG Consultant, Flaherty Sensabaugh Bonasso PLLC Consultant, Fulbright and Jaworski, LLC Maryam Khatonabadi: ipient research support Siemens AG
Xinhui Duan - One of the best experts on this subject based on the ideXlab platform.
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Xinming Liu, Alexander A. Bankier, John RongAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced <±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20 and 30-cm WED. CONCLUSIONS The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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Estimating patient water Equivalent Diameter from CT localizer images ‐‐ A longitudinal and multi‐institutional study of the stability of calibration parameters
Medical physics, 2020Co-Authors: Da Zhang, Xinhui Duan, Xinming Liu, Alexander A. Bankier, John Rong, Matthew R. PalmerAbstract:PURPOSE Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. METHODS Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners ( R2>0.999 ). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and
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estimating patient water Equivalent Diameter from ct localizer images a longitudinal and multi institutional study of the stability of calibration parameters
Medical Physics, 2020Co-Authors: Xinhui Duan, Da Zhang, Matthew R. Palmer, Alexander A. Bankier, John RongAbstract:PURPOSE: Water Equivalent Diameter (WED) is a robust patient-size descriptor. Localizer-based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 CT scanners from 3 medical centers, and their stability over 3~29 months for 14 of those scanners. METHODS: Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion-One, Aquilion-Prime80, and Aquilion-64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water Equivalent area (WEA) and averaged LPV were established through regression analysis. RESULTS: Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners (R2 > 0:999). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced less than ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20-cm and 30-cm WED. CONCLUSIONS: The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.
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Size-specific Dose Estimates for Chest, Abdominal, and Pelvic CT: Effect of Intrapatient Variability in Water-Equivalent Diameter
Radiology, 2015Co-Authors: Shuai Leng, Maria Shiung, Xinhui Duan, Yi Zhang, Cynthia H. MccolloughAbstract:Although water-Equivalent Diameter (Dw) can vary substantially along the z-axis within any given patient, using the mean volume CT dose index over the whole scan range and the Dw from the image located at the center of the scan range provides an accurate and easily obtained estimation of the size-specific dose estimate for the whole scan range, with a root mean square error of less than 1.4 mGy or 9% for a scan range of the complete chest, abdomen, and pelvis.