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Evaluation of 4D Cone Beam Computed Tomography for Target Localization in Stereotactic Body Radiation Therapy for Early Lung Cancer
Oral Scientific Sessions S143
Volume 90 Number 1S Supplement 2014 Results: For the 59 images analyzed, the template-based matching algorithm was able to localize the GTV on only 74.6% (44/59) of the SE images vs. 94.9% (56/59) of the DE images (p Z 0.004). For 3 cases, the algorithm was unable to localize the GTV on both the SE and DE images. In the 12 cases in which the algorithm localized the GTV on the DE image but not on the SE image, 8 of the GTVs were < 5 cc in volume (p Z 0.39). Median vector differences in the position of the GTV centroids for the template-based match and the “ground truth” images were 0.5 mm (95% CI Z 0.3 mm, 1.0 mm) for SE images, versus 0.6 mm (95% CI Z 0.4 mm, 1.0 mm) for DE images (p Z 0.63). Conclusions: While the accuracy is comparable, DE imaging provides a higher tracking rate than SE imaging using a template-based matching algorithm on kV planar images for patients with lung tumors. By combining such an algorithm with DE imaging, this approach has the potential to allow for accurate and reliable real-time, markerless-motion tracking of lung tumors. Author Disclosure: A.M. Block: None. R. Patel: E. Research Grant; Varian Medical Systems. J. Panfil: E. Research Grant; Varian Medical Systems. J. Breunig: None. M. Surucu: None. M.M. Harkenrider: None. J.C. Roeske: E. Research Grant; Varian Medical Systems.
314 Robust Optimization in Intensity Modulated Proton Therapy Reduces Dose Variation Due to Setup Uncertainty and Anatomy Change H. Li,1 P. Peter,2 J.Y. Chang,1 Z. Liao,1 X. Zhang,1 W. Liu,3 Y. Li,4 F. Poenisch,1 R. Mohan,1 S.J. Frank,1 and X. Zhu1; 1M.D. Anderson Cancer Center, Houston, TX, 2University of Emory, Atlanta, GA, 3Mayo Clinic, Phoenix, AZ, 4Varian Medical Systems, Palo Alto, CA Purpose/Objective(s): The purpose of this study was to evaluate efficacy of the clinically implemented robust optimization technique used in intensity-modulated proton therapy (IMPT) plans and understand the relationship between robustness and the magnitude of dose variation due to setup uncertainty and anatomical change. Materials/Methods: Nine lung cancer patients who underwent IMPT at our center between 08/12-07/13 were selected for this retrospective study. For a given patient, PTV based multi-field optimized (MFO) and multifield optimized with robustness constrains (RbMFO) plans were generated on a simulation CT (CT0). The RbMFO plans were used for patient treatment. The plan robustness against setup and range uncertainty was evaluated on the CT0 with a statistical technique to compute standard deviation of the dose-volume histogram (SD-DVH) of the target volumes and critical structures for 600 combinations of setup and range uncertainties. In order to assess dose variation due to setup uncertainty and anatomy change, the original plans beam data were used to compute dose on subsequent weekly CTs (CTn). On Average, 4 repeated weekly CTs were acquired for each patient and total of 39 repeated CTs were evaluated. All dose distributions calculated were accumulated on the CT0 coordinate by deformable image registration. The DVHs of weekly doses, equivalent uniform dose (EUD), as well as the accumulated dose were compared on CT0 with the anticipated SD-DVH variations predicted by the statistical plan robustness evaluation system. Results: SD-DVHs were calculated as an indicator of robustness for both RbMFO and MFO plans, t-test showed there were statistical significant reduction in SD-DVH for RbMFO for GTV, CTV, lung and esophagus with p < 0.05. For RbMFO plans, 3/9 patients required adaptive planning because of loss coverage on target volume on the weekly CTs. Three of 9 patients and 11/ 39 repeated CT sessions showed EUD change of > 5% for CTV compared to the planned dose distribution. For MFO plans, 6/9 patients and 17/39 repeated CT sessions show EUD change of > 5% for CTV. In 7/9 patients and 28/39 repeated CT sessions CTV received higher EUD for RbMFO plan. The t-test showed there were statistical significant differences in the accumulated EUD for GTV and CTV between RbMFO and MFO plans with p < 0.05. Conclusions: Robust optimization in IMPT reduces the dose variation due to setup uncertainty and anatomy change during patient treatment.
Required re-plan during course of treatment was substantially reduced with robust optimization. Author Disclosure: H. Li: E. Research Grant; Varian. P. Peter: None. J.Y. Chang: None. Z. Liao: None. X. Zhang: None. W. Liu: None. Y. Li: None. F. Poenisch: None. R. Mohan: None. S.J. Frank: None. X. Zhu: None.
315 Evaluation of 4D Cone Beam Computed Tomography for Target Localization in Stereotactic Body Radiation Therapy for Early Lung Cancer D. Glick,1,2 T. Karan,3,1 K. Le,3 Z. Allibhai,3 M.M. Taremi,3,2 and D.J. Moseley2,2; 1University of Toronto, Toronto, ON, Canada, 2 Princess Margaret Cancer Centre, Toronto, ON, Canada, 3Stronach Regional Cancer Centre, Newmarket, ON, Canada Purpose/Objective(s): To assess the accuracy and reproducibility of automated registration of 4D cone-beam CT (CBCT) in target localization and verification for lung stereotactic body radiation therapy (SBRT) compared to 3D CBCT (manual and automatic soft tissue localization). Materials/Methods: Early stage non-small cell lung carcinoma patients were treated with image guided SBRT using a VMAT technique. Localization images were obtained using CBCT before shift, after shift and after treatment on each treatment day. Tumor registration on 3D CBCT was performed by four independent observers as well as automatically with dual registration using vertebral clipbox and soft tissue mask. Dual registration with clipbox and mask was also performed on 4D reconstructed CBCT. Krippendorff’s alpha was used to assess agreement and Bland-Altman analysis was used to assess limits of agreement. Results: Six patients and 114 cone beam images were analyzed. Four right-sided and 2 left-sided tumors were assessed with an equal number of central and peripheral tumors. Mean (+/- SD) shift amplitude for manual registration was 2.54 2.65 mm, 2.98 2.83 mm, and 1.93 1.40 mm in the right-left (RL), cranio-caudal (CC) and anterior posterior (AP) direction respectively. Agreement between observers was very high with Krippendorff’s alpha greater than 0.87 in all directions. Automatic dual registration on 3D CBCT produced similar shifts with the mean difference between mean manual and automatic techniques of 0.4 mm in all directions. Dual registration on 4D CBCT produced differences of 0.2 mm RL, 0.4 mm CC and 0.02 mm AP. Agreement between both manual and 3D automatic and manual and 4D automatic was high with Krippendorff’s alpha greater than 0.9 in all directions. Maximum limits of agreement were -0.21 to 0.13 and -0.10 to 0.19 for the 3D and 4D automatic techniques, respectively. Linear regression analysis revealed association between maximum respiratory motion and disagreement between manual and automatic 3D registration (R2 Z 0.41, p < 0.01), but did not reveal a similar correlation with 4D CBCT (R2 Z 0.02, p Z 0.10). Conclusions: Automatic dual registration using 4D CBCT provides accurate tumor localization and unlike automatic dual registration using 3D CBCT is unaffected by large respiratory motion. Four-dimensional CBCT reduces the potential for systematic error making it a desirable approach for image guidance. Author Disclosure: D. Glick: None. T. Karan: None. K. Le: None. Z. Allibhai: None. M.M. Taremi: None. D.J. Moseley: None.
316 Evaluation of Lung Ventilation and Strain From Direct Measurements of Lung Deformation During Breathing Using Hyperpolarized Helium-3 Tagging MRI T. Cui,1 Q. Huang,1 W.G. Miller,2 X. Zhong,3 F. Yin,4 and J. Cai4; 1Duke University, Durham, NC, 2University of Virginia, Charlottesville, VA, 3 Siemens Healthcare, Atlanta, GA, 4Duke University Medical Center, Durham, NC Purpose/Objective(s): Direct measurement of lung ventilation is often more favorable than the calculated ones using deformable image registration (DIR), which has been found susceptible to many uncertainties and
Volume 90 Number 1S Supplement 2014 Results: For the 59 images analyzed, the template-based matching algorithm was able to localize the GTV on only 74.6% (44/59) of the SE images vs. 94.9% (56/59) of the DE images (p Z 0.004). For 3 cases, the algorithm was unable to localize the GTV on both the SE and DE images. In the 12 cases in which the algorithm localized the GTV on the DE image but not on the SE image, 8 of the GTVs were < 5 cc in volume (p Z 0.39). Median vector differences in the position of the GTV centroids for the template-based match and the “ground truth” images were 0.5 mm (95% CI Z 0.3 mm, 1.0 mm) for SE images, versus 0.6 mm (95% CI Z 0.4 mm, 1.0 mm) for DE images (p Z 0.63). Conclusions: While the accuracy is comparable, DE imaging provides a higher tracking rate than SE imaging using a template-based matching algorithm on kV planar images for patients with lung tumors. By combining such an algorithm with DE imaging, this approach has the potential to allow for accurate and reliable real-time, markerless-motion tracking of lung tumors. Author Disclosure: A.M. Block: None. R. Patel: E. Research Grant; Varian Medical Systems. J. Panfil: E. Research Grant; Varian Medical Systems. J. Breunig: None. M. Surucu: None. M.M. Harkenrider: None. J.C. Roeske: E. Research Grant; Varian Medical Systems.
314 Robust Optimization in Intensity Modulated Proton Therapy Reduces Dose Variation Due to Setup Uncertainty and Anatomy Change H. Li,1 P. Peter,2 J.Y. Chang,1 Z. Liao,1 X. Zhang,1 W. Liu,3 Y. Li,4 F. Poenisch,1 R. Mohan,1 S.J. Frank,1 and X. Zhu1; 1M.D. Anderson Cancer Center, Houston, TX, 2University of Emory, Atlanta, GA, 3Mayo Clinic, Phoenix, AZ, 4Varian Medical Systems, Palo Alto, CA Purpose/Objective(s): The purpose of this study was to evaluate efficacy of the clinically implemented robust optimization technique used in intensity-modulated proton therapy (IMPT) plans and understand the relationship between robustness and the magnitude of dose variation due to setup uncertainty and anatomical change. Materials/Methods: Nine lung cancer patients who underwent IMPT at our center between 08/12-07/13 were selected for this retrospective study. For a given patient, PTV based multi-field optimized (MFO) and multifield optimized with robustness constrains (RbMFO) plans were generated on a simulation CT (CT0). The RbMFO plans were used for patient treatment. The plan robustness against setup and range uncertainty was evaluated on the CT0 with a statistical technique to compute standard deviation of the dose-volume histogram (SD-DVH) of the target volumes and critical structures for 600 combinations of setup and range uncertainties. In order to assess dose variation due to setup uncertainty and anatomy change, the original plans beam data were used to compute dose on subsequent weekly CTs (CTn). On Average, 4 repeated weekly CTs were acquired for each patient and total of 39 repeated CTs were evaluated. All dose distributions calculated were accumulated on the CT0 coordinate by deformable image registration. The DVHs of weekly doses, equivalent uniform dose (EUD), as well as the accumulated dose were compared on CT0 with the anticipated SD-DVH variations predicted by the statistical plan robustness evaluation system. Results: SD-DVHs were calculated as an indicator of robustness for both RbMFO and MFO plans, t-test showed there were statistical significant reduction in SD-DVH for RbMFO for GTV, CTV, lung and esophagus with p < 0.05. For RbMFO plans, 3/9 patients required adaptive planning because of loss coverage on target volume on the weekly CTs. Three of 9 patients and 11/ 39 repeated CT sessions showed EUD change of > 5% for CTV compared to the planned dose distribution. For MFO plans, 6/9 patients and 17/39 repeated CT sessions show EUD change of > 5% for CTV. In 7/9 patients and 28/39 repeated CT sessions CTV received higher EUD for RbMFO plan. The t-test showed there were statistical significant differences in the accumulated EUD for GTV and CTV between RbMFO and MFO plans with p < 0.05. Conclusions: Robust optimization in IMPT reduces the dose variation due to setup uncertainty and anatomy change during patient treatment.
Required re-plan during course of treatment was substantially reduced with robust optimization. Author Disclosure: H. Li: E. Research Grant; Varian. P. Peter: None. J.Y. Chang: None. Z. Liao: None. X. Zhang: None. W. Liu: None. Y. Li: None. F. Poenisch: None. R. Mohan: None. S.J. Frank: None. X. Zhu: None.
315 Evaluation of 4D Cone Beam Computed Tomography for Target Localization in Stereotactic Body Radiation Therapy for Early Lung Cancer D. Glick,1,2 T. Karan,3,1 K. Le,3 Z. Allibhai,3 M.M. Taremi,3,2 and D.J. Moseley2,2; 1University of Toronto, Toronto, ON, Canada, 2 Princess Margaret Cancer Centre, Toronto, ON, Canada, 3Stronach Regional Cancer Centre, Newmarket, ON, Canada Purpose/Objective(s): To assess the accuracy and reproducibility of automated registration of 4D cone-beam CT (CBCT) in target localization and verification for lung stereotactic body radiation therapy (SBRT) compared to 3D CBCT (manual and automatic soft tissue localization). Materials/Methods: Early stage non-small cell lung carcinoma patients were treated with image guided SBRT using a VMAT technique. Localization images were obtained using CBCT before shift, after shift and after treatment on each treatment day. Tumor registration on 3D CBCT was performed by four independent observers as well as automatically with dual registration using vertebral clipbox and soft tissue mask. Dual registration with clipbox and mask was also performed on 4D reconstructed CBCT. Krippendorff’s alpha was used to assess agreement and Bland-Altman analysis was used to assess limits of agreement. Results: Six patients and 114 cone beam images were analyzed. Four right-sided and 2 left-sided tumors were assessed with an equal number of central and peripheral tumors. Mean (+/- SD) shift amplitude for manual registration was 2.54 2.65 mm, 2.98 2.83 mm, and 1.93 1.40 mm in the right-left (RL), cranio-caudal (CC) and anterior posterior (AP) direction respectively. Agreement between observers was very high with Krippendorff’s alpha greater than 0.87 in all directions. Automatic dual registration on 3D CBCT produced similar shifts with the mean difference between mean manual and automatic techniques of 0.4 mm in all directions. Dual registration on 4D CBCT produced differences of 0.2 mm RL, 0.4 mm CC and 0.02 mm AP. Agreement between both manual and 3D automatic and manual and 4D automatic was high with Krippendorff’s alpha greater than 0.9 in all directions. Maximum limits of agreement were -0.21 to 0.13 and -0.10 to 0.19 for the 3D and 4D automatic techniques, respectively. Linear regression analysis revealed association between maximum respiratory motion and disagreement between manual and automatic 3D registration (R2 Z 0.41, p < 0.01), but did not reveal a similar correlation with 4D CBCT (R2 Z 0.02, p Z 0.10). Conclusions: Automatic dual registration using 4D CBCT provides accurate tumor localization and unlike automatic dual registration using 3D CBCT is unaffected by large respiratory motion. Four-dimensional CBCT reduces the potential for systematic error making it a desirable approach for image guidance. Author Disclosure: D. Glick: None. T. Karan: None. K. Le: None. Z. Allibhai: None. M.M. Taremi: None. D.J. Moseley: None.
316 Evaluation of Lung Ventilation and Strain From Direct Measurements of Lung Deformation During Breathing Using Hyperpolarized Helium-3 Tagging MRI T. Cui,1 Q. Huang,1 W.G. Miller,2 X. Zhong,3 F. Yin,4 and J. Cai4; 1Duke University, Durham, NC, 2University of Virginia, Charlottesville, VA, 3 Siemens Healthcare, Atlanta, GA, 4Duke University Medical Center, Durham, NC Purpose/Objective(s): Direct measurement of lung ventilation is often more favorable than the calculated ones using deformable image registration (DIR), which has been found susceptible to many uncertainties and