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Functional Lung Avoidance using SPECT Ventilation Imaging and IMRT for Advanced Non-small Cell Lung Cancer
Proceedings of the 50th Annual ASTRO Meeting Materials/Methods: Real-time tracking of the position of a gold marker surgically embedded in the lung was performed using the RTRT system at Hokkaido University Hospital. Measurements were carried out prior to the first radiation therapy session of each patient. The marker motion was determined for 4 set-up, with and without the SBF. Population for this study consisted of 18 patients at various cancer stages. Patient data were classified based on the location of the marker. Histograms of the displacement of the marker positions relative to its median were constructed for the x-axis (medio-lateral), yaxis (cranio-caudal) and z-axis (dorso-ventral). The effect of the SBF on respiratory organ motion was evaluated by considering the displacement from the median position of the marker along each of the coordinate axes that included a cumulative frequency of 90% or greater of all recorded the marker positions. Smaller displacements of the gold marker indicated less organ motion. Results from measurements without the SBF were used as the benchmark. Results: Marker displacements confirmed that the range of respiratory organ motion is highest in the y-axis and least in the x-axis, regardless of whether the SBF is used or not. The range of motion along the coordinate axes of the markers in the upper right and left lobes of the lung were not influenced by the SBF. However, using it in combination with an abdominal press resulted in 1.4 mm reduction in the marker range of motion along the y-axis for the upper right lobe but increased by about 3mm for the upper left lobe. For markers placed in the lower right lobe, the range of motion along the x-axis was 1.4mm and 0.8mm shorter when an SBF and an SBF together with an abdominal press was used, respectively. The y-axis motion was reduced by as much as 4.4 mm with the SBF but only by 0.8 mm with the SBF plus abdominal press. This may have been brought about by the large deviation in the individual data for this set of patients. Motion along the z-axis was not significantly changed with the use of the SBF. No significant differences in the x- and z-axes motion between all set-ups for markers embedded in the lower left lobe. In the y-axis, using the SBF alone reduce the motion by 1 mm and by 2 mm when the body frame was used together with the abdominal press. Conclusions: The stereotactic body frame used together with an abdominal press may be useful in restricting respiratory organ motion during RTRT, particularly in the cranio-caudal direction. Author Disclosure: G. Bengua, None; M. Ishikawa, None; K. Sutherland, None; K. Horita, None; R. Yamazaki, None; K. Fujita, None; R. Onimaru, None; S. Shimizu, None; H. Shirato, None.
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Functional Lung Avoidance using SPECT Ventilation Imaging and IMRT for Advanced Non-small Cell Lung Cancer
B. P. Yaremko1, I. Munawar2, S. Gaede1, J. R. Craig1, J. Z. Chen1, G. Rodrigues1, E. Yu1, R. H. Reid1, E. Leung3, E. Wong1 1 University of Western Ontario - London Regional Cancer Centre, London, ON, Canada, 2University of Western Ontario, London, ON, Canada, 3University of Ottawa - Ottawa Regional Cancer Centre, Ottawa, ON, Canada
Purpose/Objective(s): To correlate lung doses from inverse planning with patterns of ventilation SPECT scans. Materials/Methods: Fifteen stage III lung radiotherapy patients underwent SPECT ventilation/perfusion scans (GE Hawkeye SPECT-CT) prior to their planning CT. Ventilation scans were performed with patient inhaling 99mTc labeled ultrafine graphite particles (Technegas). Ventilation scans were reconstructed with attenuation corrections prior to importing into the treatment planning system (Pinnacle v8.0, Philips Medical Systems) for image fusion. The hot spots from the Technegas that was trapped in the bifurcation of the bronchus were excluded when we determined the maximum ventilation activities in lung. The volumes of ventilation activities were then normalized by the maximum ventilation. In particular, we automatically segment out the 50% and 70% well ventilated lung sub-volume (50%, 70%-Vent-Vol). For each patient, two inverse treatment plans were generated using 9 equally spaced beams for a prescription dose of 70 Gy, one with dose volume constraints for total lung volume, and one with dose volume constraints for the 50% and 70% well ventilated volumes. All other normal tissue constraints were identical. Results: Using dose-volume constraints for the 70% ventilated lung [(5 Gy, 20%), (10 Gy, 10%), (20 Gy, 5%), (30 Gy, 3%)] and 50% ventilated lung [(5 Gy, 30%), (10 Gy, 15%), (20 Gy, 8%), (30 Gy, 5%)], we produced plans with reduced ventilated lung dose (reduction of volume at 20 Gy for 70%-ventilation ranged from 5-20%), while the reduction came at the expense of total lung volume at 20 Gy (increase of 0-5%) when compared to the plans without ventilation information. Based on these plans, a ventilation heterogeneity index is proposed, separating out patients with uniformly ventilated lungs from those with relatively larger ventilation defects. Conclusions: In inverse treatment planning, replacing the conventional dose volume constraint of total lung volume receiving 20 Gy or more with dose volume constraints for functional lung is feasible, and produced plans that reduce the doses to the functioning lung, at slight expense of the dose to the total lung volume. A ventilation heterogeneity index has been derived based on this patient group to select patients that will gain significantly in avoiding dose to well ventilated regions of the lung. Author Disclosure: B.P. Yaremko, None; I. Munawar, None; S. Gaede, None; J.R. Craig, None; J.Z. Chen, None; G. Rodrigues, None; E. Yu, None; R.H. Reid, None; E. Leung, None; E. Wong, None.
2986
Dosimetric and Technical Aspects of Lung Cancer Radiotherapy with Respiratory Motion Management and CT-fluoroscopic Image Guidance
A. Tai, J. Christensen, E. Gore, A. X. Li Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): To report our initial experience of treating lung tumor with gating and CT and fluoroscopic image guidance. Materials/Methods: Data collected for 9 lung cancer patients, treated with either the conventional 3D conformal radiation therapy (3DCRT) or stereotactic body radiation therapy (SBRT) with respiratory motion management and image guidance in our clinic, were analyzed. The 4DCT images were sorted into 10 breathing phases and the maximum intensity projection (MIP) images were generated for (1) all 10 phases (non-gating), (2) the 3 phases around end of inspiration (EI), and (3) the 3 phases around end of expiration (EE). SBRT followed the treatment guidelines for RTOG 0236 lung protocol. For patients whose tumor motion
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2985
Functional Lung Avoidance using SPECT Ventilation Imaging and IMRT for Advanced Non-small Cell Lung Cancer
B. P. Yaremko1, I. Munawar2, S. Gaede1, J. R. Craig1, J. Z. Chen1, G. Rodrigues1, E. Yu1, R. H. Reid1, E. Leung3, E. Wong1 1 University of Western Ontario - London Regional Cancer Centre, London, ON, Canada, 2University of Western Ontario, London, ON, Canada, 3University of Ottawa - Ottawa Regional Cancer Centre, Ottawa, ON, Canada
Purpose/Objective(s): To correlate lung doses from inverse planning with patterns of ventilation SPECT scans. Materials/Methods: Fifteen stage III lung radiotherapy patients underwent SPECT ventilation/perfusion scans (GE Hawkeye SPECT-CT) prior to their planning CT. Ventilation scans were performed with patient inhaling 99mTc labeled ultrafine graphite particles (Technegas). Ventilation scans were reconstructed with attenuation corrections prior to importing into the treatment planning system (Pinnacle v8.0, Philips Medical Systems) for image fusion. The hot spots from the Technegas that was trapped in the bifurcation of the bronchus were excluded when we determined the maximum ventilation activities in lung. The volumes of ventilation activities were then normalized by the maximum ventilation. In particular, we automatically segment out the 50% and 70% well ventilated lung sub-volume (50%, 70%-Vent-Vol). For each patient, two inverse treatment plans were generated using 9 equally spaced beams for a prescription dose of 70 Gy, one with dose volume constraints for total lung volume, and one with dose volume constraints for the 50% and 70% well ventilated volumes. All other normal tissue constraints were identical. Results: Using dose-volume constraints for the 70% ventilated lung [(5 Gy, 20%), (10 Gy, 10%), (20 Gy, 5%), (30 Gy, 3%)] and 50% ventilated lung [(5 Gy, 30%), (10 Gy, 15%), (20 Gy, 8%), (30 Gy, 5%)], we produced plans with reduced ventilated lung dose (reduction of volume at 20 Gy for 70%-ventilation ranged from 5-20%), while the reduction came at the expense of total lung volume at 20 Gy (increase of 0-5%) when compared to the plans without ventilation information. Based on these plans, a ventilation heterogeneity index is proposed, separating out patients with uniformly ventilated lungs from those with relatively larger ventilation defects. Conclusions: In inverse treatment planning, replacing the conventional dose volume constraint of total lung volume receiving 20 Gy or more with dose volume constraints for functional lung is feasible, and produced plans that reduce the doses to the functioning lung, at slight expense of the dose to the total lung volume. A ventilation heterogeneity index has been derived based on this patient group to select patients that will gain significantly in avoiding dose to well ventilated regions of the lung. Author Disclosure: B.P. Yaremko, None; I. Munawar, None; S. Gaede, None; J.R. Craig, None; J.Z. Chen, None; G. Rodrigues, None; E. Yu, None; R.H. Reid, None; E. Leung, None; E. Wong, None.
2986
Dosimetric and Technical Aspects of Lung Cancer Radiotherapy with Respiratory Motion Management and CT-fluoroscopic Image Guidance
A. Tai, J. Christensen, E. Gore, A. X. Li Medical College of Wisconsin, Milwaukee, WI Purpose/Objective(s): To report our initial experience of treating lung tumor with gating and CT and fluoroscopic image guidance. Materials/Methods: Data collected for 9 lung cancer patients, treated with either the conventional 3D conformal radiation therapy (3DCRT) or stereotactic body radiation therapy (SBRT) with respiratory motion management and image guidance in our clinic, were analyzed. The 4DCT images were sorted into 10 breathing phases and the maximum intensity projection (MIP) images were generated for (1) all 10 phases (non-gating), (2) the 3 phases around end of inspiration (EI), and (3) the 3 phases around end of expiration (EE). SBRT followed the treatment guidelines for RTOG 0236 lung protocol. For patients whose tumor motion
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