Program Information
Larger Ventilation Allows More Lung Sparing
I Mihaylov1*, K Latifi2 , E Moros3 , G Zhang4 , (1) Univ Miami, Miami, FL, (2) H. Lee Moffitt Cancer Center, Tampa, Florida, (3) H. Lee Moffitt Cancer Center, Tampa, FL, (4) H. Lee Moffitt Cancer Center, Tampa, FL
Presentations
WE-RAM2-GePD-J(B)-6 (Wednesday, August 2, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Lounge - B
Purpose: To explore the effects of ventilation on dose-volume (Dvh) and integral dose (Energy) inverse optimization approaches and lung ventilation in NSCLC
Methods: Six cases were studied. For each case ventilation was computed on voxel-by-voxel basis, derived from the time-resolved (4D) CT scans. Ventilation is defined as voxel volume change between full inspiration and full expiration, divided by voxel volume. The ventilation volume was mapped to full expiration phase. For each patient case two IMRT plans were created - one with Dvh quadratic and one with Energy-based cost function, applied to the OARs. The OARs used as dose limiting structures were lung, spinal cord, esophagus, and heart. After obtaining the IMRT solutions average doses as well as 2000 cGy isovolumes and isomases were extracted for ventilation volumes of 0.5, 0.9, 1.1, 1.2, and 1.5. Ventilation volume of 0.5 incorporates all CT voxels having a voxel volume change (exhale-to-inhale) 50% and more. Similarly, ventilation volume of 1.5 encompasses all CT voxels with volume change of 150% and more. Thereby, ventilation volume of 0.5 encompasses almost the entire lung, while ventilation volume of 1.5 represents ~1% of ventilation 0.5 volume. The doses, the isovolumes, and the isomasses derived from the Dvh optimization were used as references.
Results: The results indicate that with increasing ventilation (0.5 to 1.5) the differences between Dvh and Energy derived doses increase. For some cases the differences between the average doses for the different ventilation volumes are up to almost 25%. The changes in the isovolumes and the isomasses for the different ventilation volumes are similar with differences of avout 30%.
Conclusion: The findings herein indicate that the larger the ventilation the more dramatic the differences between the Dvh and the Energy optimization schemes.
Funding Support, Disclosures, and Conflict of Interest: US patent 9254396B2
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