The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with are...The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.展开更多
Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to ...Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to a water phantom planned by a clinical TPS.Methods:A Monte Carlo based track repeating algorithm was incorporated into an in-house treatment planning system for proton and carbon ion beams.Calculations were performed in a flat water phantom for both a traditional pencil beam algorithm and a new Monte Carlo algorithm,and then compared to measurements made at multiple depths with a 2D ionization array for 44 patient portals.The comparisons utilized a Gamma analysis.Results:A total of 124 measurements were performed for proton and carbon ion patient portals.Using a small Gamma criteria of 2%/2 mm,an average of 93%and 97%of measurement points passed for each portal for pencil beam and Monte Carlo calculations,respectively.The passing rate was substantially higher for Monte Carlo calculations than for pencil beam calculations for portals that used a range shifter.Conclusions:The implemented independent method has been verified against measurements.The high passing rate with small tolerances leads to the possibility of reducing the number of required quality assurance measurements.展开更多
文摘The spatial resolution of a commercial two-dimensional(2D)ionization chamber(IC)array is limited by the size of the individual detector and the center-to-center distance between sensors.For dose distributions with areas of steep dose gradients,inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements.This may introduce significant errors,particularly in proton spot scanning radiotherapy.In this study,by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method,a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution.Meanwhile,the similarity between the measured original data and the downsampled logfilebased reconstructed dose is regarded as the confidence of the reformatted dose distribution.Furthermore,we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements.The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements.The reformatted dose distributions generally yield a confidence exceeding 95%.
文摘Objective:To verify the accuracy of an independent dose calculation method,as incorporated into an in-house developed treatment planning system(TPS),for performing quality assurance of dose distributions delivered to a water phantom planned by a clinical TPS.Methods:A Monte Carlo based track repeating algorithm was incorporated into an in-house treatment planning system for proton and carbon ion beams.Calculations were performed in a flat water phantom for both a traditional pencil beam algorithm and a new Monte Carlo algorithm,and then compared to measurements made at multiple depths with a 2D ionization array for 44 patient portals.The comparisons utilized a Gamma analysis.Results:A total of 124 measurements were performed for proton and carbon ion patient portals.Using a small Gamma criteria of 2%/2 mm,an average of 93%and 97%of measurement points passed for each portal for pencil beam and Monte Carlo calculations,respectively.The passing rate was substantially higher for Monte Carlo calculations than for pencil beam calculations for portals that used a range shifter.Conclusions:The implemented independent method has been verified against measurements.The high passing rate with small tolerances leads to the possibility of reducing the number of required quality assurance measurements.
