<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison wi...<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imag</span><span style="font-family:Verdana;">ing limited to the target. On each phase-specific image, gross tumor </span><span style="font-family:Verdana;">volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.</span> </div>展开更多
Objective:To evaluate the dose uncertainty in stereotactic body radiation therapy induced by respiratory motion using a 4D dynamic dose(4DDD)reconstruction method.Methods:A retrospective analysis was conducted on five...Objective:To evaluate the dose uncertainty in stereotactic body radiation therapy induced by respiratory motion using a 4D dynamic dose(4DDD)reconstruction method.Methods:A retrospective analysis was conducted on five lung cancer patients who received static intensitymodulated radiation therapy.The 4DDD was constructed using beam delivery log files,four-dimensional computed tomography(4DCT)scans,and treatment plans.To evaluate the impact of respiratory motion,4DDD calculations were performed with 10 starting phases for each field.A total of 270 field doses were simulated and calculated.The differences between the cumulative volume histogram in whole-course treatment and the field doses'gamma passing rate(GPR)were compared.The correlations between plan complexity metrics and the dose deviation caused by respiratory motion were evaluated independently.The phase distributions of 398 subfields were calculated and evaluated for the influence of dose rate and breathing frequency.Results:The GPRs of all fields were different among various starting phases,with the highest range from 62.20% to 76.87% for 2 mm/3%GPR.The deviation of mean point dose was(5.42±5.21)%,and the deviation in the mean dose and D98% within the internal gross tumor volume were(0.97±0.71)% and(0.77±0.53)%,respectively.There was a significant correlation between the beam aperture-to-volume(BA2V)ratio and the average 2 mm/2%GPR(R?0.601,P<0.01).Lower dose rates led to a more homogeneous distribution of phases among subfields(t?44.100,P<0.001).Conclusions:Different beam starting phases had a limited impact on the overall treatment evaluation.However,the respiratory motion could be observed to induce dose deviations using the 4DDD reconstruction model,particularly for fields with small BA2V.展开更多
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">The purpose of this study was to evaluate a planning strategy based on Acuros with density override in comparison with AAA without and with the override. Ten lung-tumor patients were selected with each PTV size around 2 - 4 cm and were imaged using slow scan, followed by four-dimensional (4D) imag</span><span style="font-family:Verdana;">ing limited to the target. On each phase-specific image, gross tumor </span><span style="font-family:Verdana;">volume (GTV) was contoured. Summed over all phases, an integrated GTV (iGTV) was generated and copied to the slow scan. A treatment plan was created using a dynamic-conformal-arc technique with AAA to prescribe 60 Gy to 95% of PTV (iGTV + 0.5 cm). Each AAA-based plan was regenerated by overriding the density of the setup margin of PTV by GTV density (modeling tumor-position uncertainty). It was also regenerated with Acuros and the override. The three plans were validated in 4D dose to PTV, after similarly overriding PTV density (phase-specific), accurately calculating with Acuros, and summing the phase-specific plans through organ/dose registration. The Acuros-based plan with the override, the AAA-based plan, and the AAA-based plan with the override provided 4D PTV doses of 63.9, 67.9, and 62 Gy at D95%, respectively, averaged over all patients. The override with Acuros and AAA produced lesser 4D doses, closer to the associated 3D doses, respectively, than that without the override, with better conformity and inhomogeneity. With the override in common, Acuros provided a greater dose to PTV than that by AAA. The Acuros with the override, which was more accurate than the AAA without the override, is clinically recommended.</span> </div>
基金supported by National Key R&D Program of China.(No.2016YFC0105311)National Natural Science Foundation of China(No.81803047)the Fundamental Research Funds for the Central Universities of China(No.2019kfyXKJC061).
文摘Objective:To evaluate the dose uncertainty in stereotactic body radiation therapy induced by respiratory motion using a 4D dynamic dose(4DDD)reconstruction method.Methods:A retrospective analysis was conducted on five lung cancer patients who received static intensitymodulated radiation therapy.The 4DDD was constructed using beam delivery log files,four-dimensional computed tomography(4DCT)scans,and treatment plans.To evaluate the impact of respiratory motion,4DDD calculations were performed with 10 starting phases for each field.A total of 270 field doses were simulated and calculated.The differences between the cumulative volume histogram in whole-course treatment and the field doses'gamma passing rate(GPR)were compared.The correlations between plan complexity metrics and the dose deviation caused by respiratory motion were evaluated independently.The phase distributions of 398 subfields were calculated and evaluated for the influence of dose rate and breathing frequency.Results:The GPRs of all fields were different among various starting phases,with the highest range from 62.20% to 76.87% for 2 mm/3%GPR.The deviation of mean point dose was(5.42±5.21)%,and the deviation in the mean dose and D98% within the internal gross tumor volume were(0.97±0.71)% and(0.77±0.53)%,respectively.There was a significant correlation between the beam aperture-to-volume(BA2V)ratio and the average 2 mm/2%GPR(R?0.601,P<0.01).Lower dose rates led to a more homogeneous distribution of phases among subfields(t?44.100,P<0.001).Conclusions:Different beam starting phases had a limited impact on the overall treatment evaluation.However,the respiratory motion could be observed to induce dose deviations using the 4DDD reconstruction model,particularly for fields with small BA2V.
