Design of a programmable micro-ultrasound research platform

To foster innovative uses of micro-ultrasound in biomedicine, it is beneficial to develop flexible research-purpose systems that allow researchers to easily reconfigure its system-level operations such as transmit firing sequence and receive processing. In this paper, we present the development of a programmable micro-ultrasound research platform that is capable of realizing various micro-imaging algorithms. The research platform comprises a linear-array-based scanning front-end and a PC-based data processing back-end, which employs a graphical processing unit (GPU) as the processor core. The front-end operations can be configured from the PC via the parallel port and the two blocks are synchronized by an external clock. Acquired data from the front-end is first digitized and relayed to the PC through an data acquisition card (200 MHz, 14-bit). They are then transferred to the GPU (GTX 275) in which the image formation is carried out via multi-thread processing. Results are displayed on-screen in real-time and can be saved to the PC's hard disk for offline analysis. Through a module-based programming approach, this platform can facilitate realization of custom-designed imaging algorithms developed by researchers. In this work, B-mode imaging and adaptive color flow imaging have been implemented as demonstrations of the research platform's programmability. The performance results show that real-time processing frame rates can be achieved for both imaging modes. © 2010 IEEE.published_or_final_versionThe 2010 IEEE International Ultrasonics Symposium, San Diego, CA., 11-14 October 2010. In Proceedings of IEEE IUS, 2010, p. 1980-198

Precise scatterer localization for ultrasound contrast imaging

This thesis is concerned with developing algorithms for the precise localization of ultrasound point scatterers with an eye to super-resolution ultrasound contrast imaging. In medical ultrasound, the conventional resolution is limited by diffraction and, in contrast to other sensing fields, point source imaging has not been extensively investigated. Here, two independent methods were proposed aiming to increase the lateral and the axial resolution respectively, by improving the localization accuracy of a single scatterer. The methods were examined with simulated and experimental data by using standard transmission protocols. Where a technique is applicable to imaging of more complicated structures than point sources, this was also examined. Further, a preliminary study was included with algorithm application to microbubbles that are currently used in contrast enhanced ultrasound. It was demonstrated that it is feasible to translate to ultrasonics, adaptive processes or techniques from optical imaging/astronomy. This way, it was possible to overcome the diffraction limit and achieve sub-wavelength localization. The accuracy gains are subject to many parameters but may reach up to two orders of magnitude, and are based exclusively on array signal processing. The latter is an important advantage since current attempts for super-resolution ultrasound are image-based which is generally undesired