The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stere...The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stereotactic body radiation therapy (SBRT) and other motion-managed therapies. However, it is known that 4DCT and 4DCBCT differ in aspects of image acquisition and reconstruction that may lead to discrepancies between the two modalities. To evaluate quantitative differences between 4DCT and 4DCBCT imaging under respiratory motion, we performed a phantom study in the ground truth setting. A programmable respiratory motion phantom was used to simulate the 1D S-I position of a known-size lesion. Ten sinusoidal and twenty patient-specific breathing waveforms were applied to drive lesion motion during the 4DCT and 4DCBCT acquisitions. The difference in lesion volume acquired between the two imaging modalities was as high as 34.4% and 18.4% for sinusoidal and patient-specific breathing motions, respectively. When compared to the true volume, 4DCT measurement often underestimated the lesion size whereas 4DCBCT overestimated the lesion volume in most of the cases. 4DCBCT gave more accurate recovery of the volume than 4DCT for most settings tested in this study. These findings may be helpful for improving the definition of internal target and planning target volume margins, and extracting quantitative information from on-board treatment verification imaging.展开更多
Objective: The purpose of this study was to evaluate the performance of the phase-binning algorithm and amplitude-binning algorithm for four-dimensional computed tomography(4DCT) reconstruction in lung cancer radiatio...Objective: The purpose of this study was to evaluate the performance of the phase-binning algorithm and amplitude-binning algorithm for four-dimensional computed tomography(4DCT) reconstruction in lung cancer radiation therapy. Methods: Quasar phantom data were used for evaluation. A phantom of known geometry was mounted on a four-dimensional(4D) motion platform programmed with twelve respiratory waves(twelve lung patients trajectories) and scanned with a Philips Brilliance Big bore 16-slice CT simulator. The 4DCT images were reconstructed using both phase- and amplitude-binning algorithms. Internal target volumes(ITVs) of the phase- and amplitude-binned image sets were compared by evaluation of shape and volume distortions. Results: The phantom experiments illustrated that, as expected, maximum inhalation occurred at the 0% amplitude and maximum exhalation occurred at the 50% amplitude of the amplitude-binned 4DCT image sets. The amplitude-binned algorithm rendered smaller ITV than the phase-binning algorithm. Conclusion: The amplitude-binning algorithm for 4DCT reconstruction may have a potential advantage in reducing the margin and protecting normal lung tissue from unnecessary irradiation.展开更多
Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was ge...Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was generated in this study. To avoid the uncertainties from target delineation and imaging artifacts, a sphere with diameter of 3 cm representing a rigid mobile target (GTV) was inserted into the right side of the lung. The target motion is set in superior-inferior (SI) direction from ?5 mm to 5 mm. Four SFUD planning strategies were used based on: 1) Maximum-In-tensity-Projection Image (MIP-CT);2) CT_average with ITV overridden to muscle density (CTavg_muscle);3) CT_average with ITV overridden to tumor density (CTavg_tumor);4) CT_average without any override density (CTavg_only). Dose distributions were recalculated on each individual phase and accumulated together to assess the “actual” treatment. To estimate the impact of proton range uncertainties, +/?3.5% CT calibration curve was applied to the 4DCT phase images. Results: Comparing initial plan to the dose accumulation: MIP-CT based GTV D98 degraded 2.42 Gy (60.10 Gy vs 57.68 Gy). Heart D1 increased 6.19 Gy (1.88 Gy vs 8.07 Gy);CTavg_tumor based GTV D98 degraded 0.34 Gy (60.07 Gy vs 59.73 Gy). Heart D1 increased 2.24 Gy (3.74 Gy vs 5.98 Gy);CTavg_muscle based initial GTV D98 degraded 0.31 Gy (60.4 Gy vs 60.19 Gy). Heart D1 increased 3.44 Gy (4.38 Gy vs 7.82 Gy);CTavg_only based Initial GTV D98 degraded 6.63 Gy (60.11 Gy vs 53.48 Gy). Heart D1 increased 0.30 Gy (2.69 Gy vs 2.96 Gy);in the presence of ±3.5% range uncertainties, CTavg_tumor based plan’s accumulated GTV D98 degraded to 57.99 Gy (+3.5%) 59.38 Gy (?3.5%), and CTavg_muscle based plan’s accumulated GTV D98 degraded to 59.37 Gy (+3.5%) 59.37 Gy (?3.5%). Conclusion: This study shows that CTavg_Tumor and CTavg_Muscle based planning strategies provide the most robust GTV coverage. However, clinicians need to be aware that the actual dose to OARs at distal end of target may increase. The study also indicates that the current SFUD PBS planning strategy might not be sufficient to compensate the CT calibration uncertainty.展开更多
文摘The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stereotactic body radiation therapy (SBRT) and other motion-managed therapies. However, it is known that 4DCT and 4DCBCT differ in aspects of image acquisition and reconstruction that may lead to discrepancies between the two modalities. To evaluate quantitative differences between 4DCT and 4DCBCT imaging under respiratory motion, we performed a phantom study in the ground truth setting. A programmable respiratory motion phantom was used to simulate the 1D S-I position of a known-size lesion. Ten sinusoidal and twenty patient-specific breathing waveforms were applied to drive lesion motion during the 4DCT and 4DCBCT acquisitions. The difference in lesion volume acquired between the two imaging modalities was as high as 34.4% and 18.4% for sinusoidal and patient-specific breathing motions, respectively. When compared to the true volume, 4DCT measurement often underestimated the lesion size whereas 4DCBCT overestimated the lesion volume in most of the cases. 4DCBCT gave more accurate recovery of the volume than 4DCT for most settings tested in this study. These findings may be helpful for improving the definition of internal target and planning target volume margins, and extracting quantitative information from on-board treatment verification imaging.
文摘Objective: The purpose of this study was to evaluate the performance of the phase-binning algorithm and amplitude-binning algorithm for four-dimensional computed tomography(4DCT) reconstruction in lung cancer radiation therapy. Methods: Quasar phantom data were used for evaluation. A phantom of known geometry was mounted on a four-dimensional(4D) motion platform programmed with twelve respiratory waves(twelve lung patients trajectories) and scanned with a Philips Brilliance Big bore 16-slice CT simulator. The 4DCT images were reconstructed using both phase- and amplitude-binning algorithms. Internal target volumes(ITVs) of the phase- and amplitude-binned image sets were compared by evaluation of shape and volume distortions. Results: The phantom experiments illustrated that, as expected, maximum inhalation occurred at the 0% amplitude and maximum exhalation occurred at the 50% amplitude of the amplitude-binned 4DCT image sets. The amplitude-binned algorithm rendered smaller ITV than the phase-binning algorithm. Conclusion: The amplitude-binning algorithm for 4DCT reconstruction may have a potential advantage in reducing the margin and protecting normal lung tissue from unnecessary irradiation.
文摘Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was generated in this study. To avoid the uncertainties from target delineation and imaging artifacts, a sphere with diameter of 3 cm representing a rigid mobile target (GTV) was inserted into the right side of the lung. The target motion is set in superior-inferior (SI) direction from ?5 mm to 5 mm. Four SFUD planning strategies were used based on: 1) Maximum-In-tensity-Projection Image (MIP-CT);2) CT_average with ITV overridden to muscle density (CTavg_muscle);3) CT_average with ITV overridden to tumor density (CTavg_tumor);4) CT_average without any override density (CTavg_only). Dose distributions were recalculated on each individual phase and accumulated together to assess the “actual” treatment. To estimate the impact of proton range uncertainties, +/?3.5% CT calibration curve was applied to the 4DCT phase images. Results: Comparing initial plan to the dose accumulation: MIP-CT based GTV D98 degraded 2.42 Gy (60.10 Gy vs 57.68 Gy). Heart D1 increased 6.19 Gy (1.88 Gy vs 8.07 Gy);CTavg_tumor based GTV D98 degraded 0.34 Gy (60.07 Gy vs 59.73 Gy). Heart D1 increased 2.24 Gy (3.74 Gy vs 5.98 Gy);CTavg_muscle based initial GTV D98 degraded 0.31 Gy (60.4 Gy vs 60.19 Gy). Heart D1 increased 3.44 Gy (4.38 Gy vs 7.82 Gy);CTavg_only based Initial GTV D98 degraded 6.63 Gy (60.11 Gy vs 53.48 Gy). Heart D1 increased 0.30 Gy (2.69 Gy vs 2.96 Gy);in the presence of ±3.5% range uncertainties, CTavg_tumor based plan’s accumulated GTV D98 degraded to 57.99 Gy (+3.5%) 59.38 Gy (?3.5%), and CTavg_muscle based plan’s accumulated GTV D98 degraded to 59.37 Gy (+3.5%) 59.37 Gy (?3.5%). Conclusion: This study shows that CTavg_Tumor and CTavg_Muscle based planning strategies provide the most robust GTV coverage. However, clinicians need to be aware that the actual dose to OARs at distal end of target may increase. The study also indicates that the current SFUD PBS planning strategy might not be sufficient to compensate the CT calibration uncertainty.
