Functionally weighted airway sparing (FWAS): a functional avoidance method for preserving post-treatment ventilation in lung radiotherapy

Recent changes to the guidelines for screening and early diagnosis of lung cancer have increased the interest in preserving post-radiotherapy lung function. Current investigational approaches are based on spatially mapping functional regions and generating regional avoidance plans that preferentiall...

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Bibliographic Details
Published in:Physics in medicine & biology 2020-08, Vol.65 (16), p.165010-165010
Main Authors: Vicente, E, Modiri, A, Kipritidis, J, Hagan, A, Yu, K, Wibowo, H, Yan, Y, Owen, D R, Matuszak, M M, Mohindra, P, Timmerman, R, Sawant, A
Format: Article
Language:English
Subjects:
Aged
airways
Algorithms
Female
functional lung avoidance
Humans
Lung - physiopathology
Lung Neoplasms - radiotherapy
lung SAbR
Male
Middle Aged
Organ Sparing Treatments - methods
Organs at Risk - radiation effects
Pulmonary Ventilation - physiology
radiotherapy
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted - methods
Radiotherapy, Conformal - methods
Respiration
Retrospective Studies
ventilation map
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Summary:Recent changes to the guidelines for screening and early diagnosis of lung cancer have increased the interest in preserving post-radiotherapy lung function. Current investigational approaches are based on spatially mapping functional regions and generating regional avoidance plans that preferentially spare highly ventilated/perfused lung. A potentially critical, yet overlooked, aspect of functional avoidance is radiation injury to peripheral airways, which serve as gas conduits to and from functional lung regions. Dose redistribution based solely on regional function may cause irreparable damage to the 'supply chain'. To address this deficiency, we propose the functionally weighted airway sparing (FWAS) method. FWAS (i) maps the bronchial pathways to each functional sub-lobar lung volume; (ii) assigns a weighting factor to each airway based on the relative contribution of the sub-volume to overall lung function; and (iii) creates a treatment plan that aims to preserve these functional pathways. To evaluate it, we used four cases from a retrospective cohort of SAbR patients treated for lung cancer. Each patient's airways were auto-segmented from a diagnostic-quality breath-hold CT using a research virtual bronchoscopy software. A ventilation map was generated from the planning 4DCT to map regional lung function. For each terminal airway, as resolved by the segmentation software, the total ventilation within the sub-lobar volume supported by that airway was estimated and used as a function-based weighting factor. Upstream airways were weighted based on the cumulative volumetric ventilation supported by corresponding downstream airways. Using a previously developed model for airway radiosensitivity, dose constraints were determined for each airway corresponding to a
ISSN:0031-9155
1361-6560
1361-6560
DOI:10.1088/1361-6560/ab9f5d