Review of Techniques and Technologies for Mosaicking Ultrasound Volumes.

Ultrasound imaging, known for its affordability, portability and real-time capabilities, has become a crucial diagnostic tool worldwide. However, the limited field of view in 2-D ultrasound and reduced anatomical coverage in current 3-D systems have prompted the development of volumetric compounding. This review aims to outline the techniques and technologies used in mosaicking ultrasound volumes to overcome these challenges and enhance clinical imaging capabilities. This review adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. A search was conducted in four bibliographic databases and grey literature to identify articles that utilised 3-D ultrasound transducers for the registration or compounding of ultrasound volumes. Review selection and characterisation were performed by two independent reviewers. The search identified 72 papers published from 2013 to 2024, with most studies focused on cardiovascular applications (54.2%). The primary goal of these studies was to improve the visualisation of structures (45.8%) and extend the field of view (30.6%). Automation was a significant focus, with 46.6% of studies using automated methods for improved efficiency and accuracy. However, a larger proportion of semi-automated methods indicates that certain tasks still require human intervention. While significant progress has been made in enhancing image quality, future research should focus on refining these methods, exploring under-represented clinical applications, and leveraging state-of-the-art artificial intelligence methods to improve efficiency, accuracy and clinical integration.