ESTRO 2021 Abstract Book

S172

ESTRO 2021

a DVF histogram (Fig.1). DVF distributions within diaphragm sub-regions D1, D2, and D3 were also investigated. Peak values of displacement extracted from each histogram were used to plot ROI displacement over time. The velocity was then determined by linear fit of the data-points. Results On average, subjects sustained PIBHs (median 315s; IQR 271-436s) longer than PEBHs (median 293s; IQR 260- 359s). For both manoeuvres, DVF histograms of the liver and right diaphragm dome exhibited elastic distributions with multiple peaks (Fig.1). Conversely, D1, D2, D3, and the right kidney yielded more rigid distributions allowing for extraction of single peaks that displaced linearly over time (Fig.2), primarily directed craniodorsally. The median velocity VM was greatest for D3 (5.7mm/min and 5.8mm/min during PIBH and PEBH, respectively), and lowest for D1 (PIBH 2.1mm/min; PEBH 2.4mm/min). The median velocity VM for D2 (PIBH 3.7mm/min; PEBH 3.9mm/min) strongly correlated with that of the right kidney (PIBH 3.5mm/min; PEBH 4mm/min), overall R 2 >0.9.