TH-E-218-03: On the significance of density-induced speed of sound variations on ultrasound-guided radiotherapy

US systems assume that speed of sound (SOS) is constant in human soft tissues (at a value of 1540 m/s), while its actual non homogeneous distribution produces small but systematic errors of up to a few millimeters in the positions of scanned structures. This work aims at showing the effect of SOS aberration on ultrasound guided radiotherapy (US-gRT) as a function of implemented workflow.