ESTRO 2024 - Abstract Book

S4998

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

857

Digital Poster

Lung ventilation assessment using 4DCT scans before and after radiotherapy

Liam Walker, Alex Flynn, Nick West, Spyros Manolopoulos

Northern Centre for Cancer Care - Newcastle upon Tyne Hospitals NHS Foundation Trust, Radiotherapy Physics, Newcastle, United Kingdom

Purpose/Objective:

4DCT scans can be used to produce lung ventilation images, where function throughout the lungs is quantified by the relative amounts of distortion and airflow between breathing phases [1, 2]. There is potential to then tailor radiotherapy to avoid the highest functioning regions, with the aim of reducing rates of radiation pneumonitis [3]. We retrospectively generated ventilation images to look for distinguishing features before and after radiotherapy, and to establish whether they correlated with other respiratory metrics. Showing that ventilation maps can capture physiological changes encourages confidence in their use, and provides new ways to study the effects of radiotherapy using existing patient data.

Material/Methods:

Lung compliance is a measure of a lung's ability to stretch and expand, and is a key concept in respiratory physiology. Compliance is proportional to a change in air volume ΔV, and the difference in HU values from the inhale and exhale phases of a 4DCT can be related to regional changes in volume,

The workflow requires outlining the lungs on the maximum inhale and exhale scans, and deformably registering the lung volumes, in order to make a full 3D ventilation map. We did this for 10 consecutive patients with repeat referrals for lung SABR treatment, who had consequently received two 4DCT scans for the purposes of motion management. In order to compare the maps we collapsed the data into histograms, binning voxels by how much they expanded. We then looked for correlation between the mean voxel expansion, and records of forced expiratory volumes (FEV1); measurements which are routinely used to quantify patients' lung function before prescribing treatment.

Results: