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
In response to the challenge inherent in classical high-dimensional models of random ground motions, a family of simulation methods for nonstationary seismic ground motions was developed previously through employing a...In response to the challenge inherent in classical high-dimensional models of random ground motions, a family of simulation methods for nonstationary seismic ground motions was developed previously through employing a wave-group propagation formulation with phase spectrum model built up on the frequency components’ starting-time of phase evolution. The present paper aims at extending the formulation to the simulation of non-stationary random seismic ground motions. The ground motion records associated with N–S component of Northridge Earthquake at the type-II site are investigated. The frequency components’ starting-time of phase evolution of is identified from the ground motion records, and is proved to admit the Gamma distribution through data fitting. Numerical results indicate that the simulated random ground motion features zeromean, non-stationary, and non-Gaussian behaviors, and the phase spectrum model with only a few starting-times of phase evolution could come up with a sound contribution to the simulation.展开更多
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.
文摘In response to the challenge inherent in classical high-dimensional models of random ground motions, a family of simulation methods for nonstationary seismic ground motions was developed previously through employing a wave-group propagation formulation with phase spectrum model built up on the frequency components’ starting-time of phase evolution. The present paper aims at extending the formulation to the simulation of non-stationary random seismic ground motions. The ground motion records associated with N–S component of Northridge Earthquake at the type-II site are investigated. The frequency components’ starting-time of phase evolution of is identified from the ground motion records, and is proved to admit the Gamma distribution through data fitting. Numerical results indicate that the simulated random ground motion features zeromean, non-stationary, and non-Gaussian behaviors, and the phase spectrum model with only a few starting-times of phase evolution could come up with a sound contribution to the simulation.
