Ultrasound Liver Imaging in Minimally Invasive Interventions

Ultrasound imaging is one of the most used imaging techniques due to its wide availability, low cost, bed-side nature and real-time capabilities. However, conventional ultrasound is mainly limited to a role of follow up or initial modality to assess patients with suspicious liver disease. Then, a CT or MR scan is performed in case of abnormal ultrasound images. Nevertheless, ultrasound imaging has proved its utility for guiding biopsy or local ablative therapies and the appearance of dedicated probes has increased its use during intra-operative phase of minimally invasive interventions. But with the advent of echo-enhancers and nonlinear imaging modes, contrast-enhanced ultrasound is becoming a valid alternative to established modalities for detection and characterization of focal liver lesions. The quality and the readability of ultrasound images are improved considerably, leading to a redefinition of the ultrasound liver imaging role in clinical practice. Contrast-enhanced imaging could provide a full package of detecting, staging, planning, guidance and early assessment of therapy response. Moreover it could also open a new era for image processing applications since contrast agents reduce the speckle noise of ultrasound images. After tumor, hepatic vessels are also of primary importance to be delineated accurately. In fact, the liver vasculature influences directly minimally invasive interventions planning and can be used as natural landmarks to register pre-operative information to intraoperative reality.