Design, implementation, and analysis of a three-dimensional ultrasound system for image-guided surgery

Two-dimensional freehand ultrasound is an imaging modality often used by surgeons because of its real-time, interactive nature. During interventions under two-dimensional ultrasound image-guidance, however, clinicians report difficulty in ascertaining when a surgical instrument is in the middle of a region of interest, such as a tumor. A biopsy or ablation tool may appear to be centered in one cross-sectional view of complex or asymmetric tissue, while it is in fact located peripherally in the lesion. Three-dimensional medical imaging increased understanding of anatomical relationships, reduces the time spent evaluating images, minimizes disruption of the surgical area, and improves surgical outcomes. Most current three-dimensional imaging techniques, including those using freehand ultrasound, do not however offer real-time performance: data acquisition is separated temporally from visualization because the scanned data is stored before rendering, and therefore only static data is available for viewing. While sufficient for diagnostic purposes, static datasets are inadequate in surgical situations when anatomical changes need to be visualized in near real-time. The research presented in this thesis has leveraged the interactive nature of ultrasound by developing a near real-time, freehand, three-dimensional ultrasound visualization system for image-guided surgery.; The system uses an optical tracking device to determine the position of a freehand probe during acquisition of a two-dimensional cross-section. The position and orientation of the probe allow each cross-sectional slice to be properly inserted into the volume through a mapping algorithm involving a series of homogenous transformations. With fast algorithms for frame insertion, volume maintenance, and two-dimensional texture-based rendering, the system is able to simultaneously acquire, update, and display three-dimensional volume-rendered ultrasound data.; The work presented in this thesis quantifies and analyzes the implementation of a novel thee-dimensional imaging system that uses conventional ultrasound equipment to generate volumetric representations of lesions that can be acquired and displayed in near real time. The system has been designed for use in clinical situations, specifically for navigation and guidance of surgical tools during interventions of breast and liver tumors.