Estimation of respiratory breathing signal from 2D US sequences and 4DCT of the liver

One challenge of High Intensity Focused Ultrasound (HIFU) for treating primary liver tumors is the management of the breathing motion during treatment. An extracorporeal HIFU transducer with an integrated ultrasound (US) imaging probe has been specifically designed for treating the liver. The imaging probe produces 2D images and the tumor itself may not always be visible in US images. A pre-operative 4D-Computed Tomography (CT) image is acquired to infer the tumor location. To retrieve spatio-temporal correspondence between the 4DCT and 2D+t US sequences to guide extracorporeal HIFU treatments temporal Principal Component Analysis and Hilbert transform was applied. The correspondence was visually verified by radiologist.