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Evaluation of Lung Toxicity Risk with Computed Tomography Ventilation Functional Image for Lung Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiation Therapy
E708
International Journal of Radiation Oncology Biology Physics
None. J. Pukala: None. P. Kelly: None. N.R. Ramakrishna: None. T. Willoughby: Independent Contractor; Calypso. Honoraria; Calypso Medical. AAPM.
3685
3684 Technique for Assessing Stopping Power Ratio of Implantable Materials and Devices Commonly Used in Pencil Beam Scanning Proton Therapy for Thoracic Malignancies N.E. Onyeuku,1 H. Chung,1 J.W. Snider III,1 J.K. Molitoris Jr,1 S.N. Badiyan,1 S. Carr,1 E.M. Pickering,1 A. Sachdeva,1 S.J. Feigenberg,2 K.M. Langen,2 C.B. Simone II,1 and P. Mohindra1; 1University of Maryland Medical Center, Baltimore, MD, 2University of Maryland School of Medicine, Baltimore, MD Purpose/Objective(s): Implantable materials can significantly impact the dose-distribution of proton pencil beam scanning (PBS) and pose a unique clinical dilemma. A measurement-based methodology is essential for the accurate estimation of stopping power ratio (SPR) of these implants due to potential extreme dosimetric effects. This is particularly critical in thoracic oncology considering the variety of shapes, sizes, and materials of implantable devices used. Commonly encountered materials and devices include drug-delivery ports, sternotomy fixation plates/screws/wires, esophageal stents, chest wall reconstructive polytetrafluoroethylene (PTFE) mesh, and pacemakers. We aim to provide a reproducible measurement-based methodology to estimate SPR for commonly used implantable materials/devices in thoracic oncology. Materials/Methods: Implants were characterized as homogeneous in material and geometry (e.g. PTFE mesh); homogenous in material but heterogeneous in geometry (e.g. mesh stents); or heterogeneous in material and geometry (e.g. ports and pacemakers). For homogeneous in material and geometry and for homogeneous materials but heterogeneous in geometry, a single-step approach of measuring SPR using a multi-layer ionization chamber (MLIC) was used. In this approach, a stream of pencil beam is delivered through the implant. SPR was defined as the quotient of the change in the depth of distal 80% of Bragg peak with and without the device divided by the physical thickness of the device. For heterogeneous devices (material and geometry), a two-step measurement was performed. We first measured the SPR at the center of the implant using the MLIC approach as above. This was followed by measurement of two-dimensional dose distribution with GafChromic films using a single energy 10 x 10 cm2field size proton beam. The exposed GafChromic films were used to determine the relative Bragg peak distal fall-off of the proton beams which was normalized to the MLIC measurement at the center of the implant. Specifically, the ratio of the depth of the Bragg peak distal fall-off at the center of the implant and the distal fall-off that is off-axis to the center of the implant was obtained. To estimate the SPR of the heterogeneous geometry, the distal fall-off ratio was divided by the MLIC measured SPR value at the center of the implant. Results: SPRs of various implants are listed: PTFE 0.4; Esophageal Stent 0.8; Port Injector (#1 - Center) 0.827; Port Injector (#1 - Outer Frame) 1.24; Port Injector (#2 - Center) 0.704; Port Injector (#2 - Outer Frame) 0.782; Pacemaker 1.601; Thoracic Microfixation System 3.24. Conclusion: Measurement of SPR for implanted devices in thoracic PBS is complicated by the variety of materials used. Accurate methods for estimating SPR should be explored further. We report a reproducible step wise process to estimate the measurement-based SPR for commonly used implantable materials and devices in thoracic oncology. Author Disclosure: N.E. Onyeuku: None. H. Chung: None. J.W. Snider: None. J.K. Molitoris: None. S.N. Badiyan: None. S. Carr: None. E.M. Pickering: None. A. Sachdeva: None. S.J. Feigenberg: None. K.M. Langen: Editor; IJROBP. C.B. Simone: Annals of Palliative Medicine, Proton Collaborative Group (PCG). P. Mohindra: None.
Evaluation of Lung Toxicity Risk with Computed Tomography Ventilation Functional Image for Lung Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiation Therapy M. Otsuka,1 H. Monzen,2 N. Kadoya,3 M. Inada IV,4 K. Matsumoto,1 and Y. Nishimura4; 1Department of Medical Physics, Graduate School of Medical Science, Kindai University, Osakasayama, Japan, 2Department of Medical Physics, Graduate School of Medical Science, Kindai university, Osaka-sayama, Japan, 3Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan, 4Department of Radiation Oncology, Kindai University Faculty of Medicine, Osaka, Japan Purpose/Objective(s): Ventilated regions using 4D-CT ventilation may reduce lung toxicity after radiation therapy. This study evaluated clinical correlations between 4D-CT ventilation-based dosimetric parameters and clinical outcomes. Materials/Methods: Pre-treatment 4D-CT data were used to compute ventilation images for 40 lung cancer patients. Ventilation images were calculated from 4D-CT data using a DIR and Jacobian-based algorithm. We normalized each ventilation map by converting it to percentile images. Ventilation-based dosimetric parameters (Mean Dose, V5, and V20 in highly and poorly ventilated regions) were calculated. To test whether the ventilation-based dosimetric parameters can be used for prediction of radiation pneumonitis of Grade 2, the area under the curve (AUC) was determined from receiver operating characteristic analysis. Results: For Mean Dose, poorly ventilated lung regions in the 0e30% observed the highest AUC value (0.809) (95% confidence interval (CI), 0.663 to 0.955). For V20, poorly ventilated lung regions in the 0e20% had the highest AUC value (0.774)(95% CI, 0.598 to 0.915). For V5, poorly ventilated lung regions in the 0e30% observed the highest AUC value (0.843)(95% CI, 0.732 to 0.954). These results showed that the highest AUC values for Mean Dose, V20, and V5 were obseved in poorly ventilated regions (0-20%, 0-30%). Conclusion: Our results showed that poorly ventilated lung regions had higher AUC values than highly ventilated regions, suggesting that 4D-CT ventilation-based functional planning may reduce the lung toxicity risk after radiation therapy. Author Disclosure: M. Otsuka: None. H. Monzen: None. N. Kadoya: None. M. Inada: None. K. Matsumoto: None. Y. Nishimura: None.
3686 Dosimetric Effect of Internal Metallic Ports in Temporary Tissue Expanders on Postmastectomy Radiation Therapy: A Monte Carlo Study J.M. Park,1 K. Kim,2 J.I. Park,3 and J.I. Kim1,4; 1Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of (South), 2Ewha Womans University School of Medicine, Seoul, Korea, Republic of (South), 3Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Korea, Republic of (South), 4Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea, Republic of (South) Purpose/Objective(s): To investigate the dosimetric effect of the internal metallic port (IMP) in a tissue expander (TE) on the dose distribution of postmastectomy radiation therapy (PMRT). Materials/Methods: A total of 10 patients who have received PMRT with a TE were selected retrospectively. For each patient, the dose distributions of treatment plans with a 10 MV photon beam were calculated using the Monte Carlo (MC) method with CT images. The dose distributions without the TE were also calculated by designating the mass densities of the TE including the IMP as those of tissue. From
International Journal of Radiation Oncology Biology Physics
None. J. Pukala: None. P. Kelly: None. N.R. Ramakrishna: None. T. Willoughby: Independent Contractor; Calypso. Honoraria; Calypso Medical. AAPM.
3685
3684 Technique for Assessing Stopping Power Ratio of Implantable Materials and Devices Commonly Used in Pencil Beam Scanning Proton Therapy for Thoracic Malignancies N.E. Onyeuku,1 H. Chung,1 J.W. Snider III,1 J.K. Molitoris Jr,1 S.N. Badiyan,1 S. Carr,1 E.M. Pickering,1 A. Sachdeva,1 S.J. Feigenberg,2 K.M. Langen,2 C.B. Simone II,1 and P. Mohindra1; 1University of Maryland Medical Center, Baltimore, MD, 2University of Maryland School of Medicine, Baltimore, MD Purpose/Objective(s): Implantable materials can significantly impact the dose-distribution of proton pencil beam scanning (PBS) and pose a unique clinical dilemma. A measurement-based methodology is essential for the accurate estimation of stopping power ratio (SPR) of these implants due to potential extreme dosimetric effects. This is particularly critical in thoracic oncology considering the variety of shapes, sizes, and materials of implantable devices used. Commonly encountered materials and devices include drug-delivery ports, sternotomy fixation plates/screws/wires, esophageal stents, chest wall reconstructive polytetrafluoroethylene (PTFE) mesh, and pacemakers. We aim to provide a reproducible measurement-based methodology to estimate SPR for commonly used implantable materials/devices in thoracic oncology. Materials/Methods: Implants were characterized as homogeneous in material and geometry (e.g. PTFE mesh); homogenous in material but heterogeneous in geometry (e.g. mesh stents); or heterogeneous in material and geometry (e.g. ports and pacemakers). For homogeneous in material and geometry and for homogeneous materials but heterogeneous in geometry, a single-step approach of measuring SPR using a multi-layer ionization chamber (MLIC) was used. In this approach, a stream of pencil beam is delivered through the implant. SPR was defined as the quotient of the change in the depth of distal 80% of Bragg peak with and without the device divided by the physical thickness of the device. For heterogeneous devices (material and geometry), a two-step measurement was performed. We first measured the SPR at the center of the implant using the MLIC approach as above. This was followed by measurement of two-dimensional dose distribution with GafChromic films using a single energy 10 x 10 cm2field size proton beam. The exposed GafChromic films were used to determine the relative Bragg peak distal fall-off of the proton beams which was normalized to the MLIC measurement at the center of the implant. Specifically, the ratio of the depth of the Bragg peak distal fall-off at the center of the implant and the distal fall-off that is off-axis to the center of the implant was obtained. To estimate the SPR of the heterogeneous geometry, the distal fall-off ratio was divided by the MLIC measured SPR value at the center of the implant. Results: SPRs of various implants are listed: PTFE 0.4; Esophageal Stent 0.8; Port Injector (#1 - Center) 0.827; Port Injector (#1 - Outer Frame) 1.24; Port Injector (#2 - Center) 0.704; Port Injector (#2 - Outer Frame) 0.782; Pacemaker 1.601; Thoracic Microfixation System 3.24. Conclusion: Measurement of SPR for implanted devices in thoracic PBS is complicated by the variety of materials used. Accurate methods for estimating SPR should be explored further. We report a reproducible step wise process to estimate the measurement-based SPR for commonly used implantable materials and devices in thoracic oncology. Author Disclosure: N.E. Onyeuku: None. H. Chung: None. J.W. Snider: None. J.K. Molitoris: None. S.N. Badiyan: None. S. Carr: None. E.M. Pickering: None. A. Sachdeva: None. S.J. Feigenberg: None. K.M. Langen: Editor; IJROBP. C.B. Simone: Annals of Palliative Medicine, Proton Collaborative Group (PCG). P. Mohindra: None.
Evaluation of Lung Toxicity Risk with Computed Tomography Ventilation Functional Image for Lung Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiation Therapy M. Otsuka,1 H. Monzen,2 N. Kadoya,3 M. Inada IV,4 K. Matsumoto,1 and Y. Nishimura4; 1Department of Medical Physics, Graduate School of Medical Science, Kindai University, Osakasayama, Japan, 2Department of Medical Physics, Graduate School of Medical Science, Kindai university, Osaka-sayama, Japan, 3Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan, 4Department of Radiation Oncology, Kindai University Faculty of Medicine, Osaka, Japan Purpose/Objective(s): Ventilated regions using 4D-CT ventilation may reduce lung toxicity after radiation therapy. This study evaluated clinical correlations between 4D-CT ventilation-based dosimetric parameters and clinical outcomes. Materials/Methods: Pre-treatment 4D-CT data were used to compute ventilation images for 40 lung cancer patients. Ventilation images were calculated from 4D-CT data using a DIR and Jacobian-based algorithm. We normalized each ventilation map by converting it to percentile images. Ventilation-based dosimetric parameters (Mean Dose, V5, and V20 in highly and poorly ventilated regions) were calculated. To test whether the ventilation-based dosimetric parameters can be used for prediction of radiation pneumonitis of Grade 2, the area under the curve (AUC) was determined from receiver operating characteristic analysis. Results: For Mean Dose, poorly ventilated lung regions in the 0e30% observed the highest AUC value (0.809) (95% confidence interval (CI), 0.663 to 0.955). For V20, poorly ventilated lung regions in the 0e20% had the highest AUC value (0.774)(95% CI, 0.598 to 0.915). For V5, poorly ventilated lung regions in the 0e30% observed the highest AUC value (0.843)(95% CI, 0.732 to 0.954). These results showed that the highest AUC values for Mean Dose, V20, and V5 were obseved in poorly ventilated regions (0-20%, 0-30%). Conclusion: Our results showed that poorly ventilated lung regions had higher AUC values than highly ventilated regions, suggesting that 4D-CT ventilation-based functional planning may reduce the lung toxicity risk after radiation therapy. Author Disclosure: M. Otsuka: None. H. Monzen: None. N. Kadoya: None. M. Inada: None. K. Matsumoto: None. Y. Nishimura: None.
3686 Dosimetric Effect of Internal Metallic Ports in Temporary Tissue Expanders on Postmastectomy Radiation Therapy: A Monte Carlo Study J.M. Park,1 K. Kim,2 J.I. Park,3 and J.I. Kim1,4; 1Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of (South), 2Ewha Womans University School of Medicine, Seoul, Korea, Republic of (South), 3Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Korea, Republic of (South), 4Biomedical Research Institute, Seoul National University Hospital, Seoul, Korea, Republic of (South) Purpose/Objective(s): To investigate the dosimetric effect of the internal metallic port (IMP) in a tissue expander (TE) on the dose distribution of postmastectomy radiation therapy (PMRT). Materials/Methods: A total of 10 patients who have received PMRT with a TE were selected retrospectively. For each patient, the dose distributions of treatment plans with a 10 MV photon beam were calculated using the Monte Carlo (MC) method with CT images. The dose distributions without the TE were also calculated by designating the mass densities of the TE including the IMP as those of tissue. From