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Modeling the impact of out-of-phase ventilation on normal lung tissue response to radiation dose
Journal article   Peer reviewed

Modeling the impact of out-of-phase ventilation on normal lung tissue response to radiation dose

Eric M Wallat, Mattison J Flakus, Antonia E Wuschner, Wei Shao, Gary E Christensen, Joseph M Reinhardt, Andrew M Baschnagel and John E Bayouth
Medical physics (Lancaster), Vol.47(7), pp.3233-3242
07/2020
DOI: 10.1002/mp.14146
PMCID: PMC9486957
PMID: 32187683
url
https://www.ncbi.nlm.nih.gov/pmc/articles/9486957View
Open Access

Abstract

To create a dose-response model that predicts lung ventilation change following radiation therapy, and examine the effects of out-of-phase ventilation. The dose-response model was built using 27 human subjects who underwent radiation therapy (RT) from an IRB-approved trial. For each four-dimensional computed tomography, two ventilation maps were created by calculating the N-phase local expansion ratio (LER ) using most or all breathing phases and the 2-phase LER (LER ) using only the end inspiration and end expiration breathing phases. A polynomial regression model was created using the LER ventilation maps pre-RT and post-RT and dose distributions for each subject, and crossvalidated with a leave-one-out method. Further validation of the model was performed using 15 additional human subjects using common statistical operating characteristics and gamma pass rates. For voxels receiving 20 Gy or greater, there was a significant increase from 52% to 59% (P = 0.03) in the gamma pass rates of the LER model predicted post-RT Jacobian maps to the actual post-RT Jacobian maps, relative to the LER model. Additionally, accuracy significantly increased (P = 0.03) from 68% to 75% using the LER model, relative to the LER model. The LER model was significantly more accurate than the LER model at predicting post-RT ventilation maps. More accurate post-RT ventilation maps will aid in producing a higher quality functional avoidance treatment plan, allowing for potentially better normal tissue sparing.
Four-Dimensional Computed Tomography Humans Lung - diagnostic imaging Lung Neoplasms Radiation Dosage Radiotherapy Planning, Computer-Assisted Respiration

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