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Modeling the impact of out‐of‐phase ventilation on normal lung tissue response to radiation dose
Author(s) -
Wallat Eric M.,
Flakus Mattison J.,
Wuschner Antonia E.,
Shao Wei,
Christensen Gary E.,
Reinhardt Joseph M.,
Baschnagel Andrew M.,
Bayouth John E.
Publication year - 2020
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.14146
Subject(s) - ventilation (architecture) , medicine , nuclear medicine , physics , thermodynamics
Purpose To create a dose‐response model that predicts lung ventilation change following radiation therapy, and examine the effects of out‐of‐phase ventilation. Methods 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 N ) using most or all breathing phases and the 2‐phase LER (LER 2 ) using only the end inspiration and end expiration breathing phases. A polynomial regression model was created using the LER N 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. Results 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 N model predicted post‐RT Jacobian maps to the actual post‐RT Jacobian maps, relative to the LER 2 model. Additionally, accuracy significantly increased ( P = 0.03) from 68% to 75% using the LER N model, relative to the LER 2 model. Conclusions The LER N model was significantly more accurate than the LER 2 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.