High frequency subharmonic imaging: practical implementations and recent developments

• Published in: The Journal of the Acoustical Society of America 2012-04, Vol.131 (4_Supplement), p.3323-3323
• Main Authors: Needles, Andrew, Daeichin, Verya, Bosch, Hans, de Jong, Nico, van der Steen, AFW, Foster, F. Stuart
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4708435

High-frequency ultrasound systems have been developed to provide appropriate imaging resolution for small anatomical structures. Typical applications include small animal preclinical research as well as intravascular ultrasound (IVUS) in larger animals and humans. In addition to traditional B-Mode (structural) and Doppler (functional) imaging, contrast detection modes have been implemented on these systems to improve the sensitivity to microbubbles in the microcirculation. This talk will overview some examples of these implementations and their respective advantages and disadvantages. Examples include direct radio frequency (RF) filtering and pulse sequence approaches, on both single element and array based systems. Additionally, subharmonic imaging will be compared to other harmonic detection approaches (namely nonlinear fundamental and second harmonic) and cases where subharmonic only detection is optimal at high frequencies. Recent advances explore the use of the self-demodulation phenomena to enhance to contribution of the subharmonic signal from microbubbles and improve detection. Examples of in vivo data from mice and rats will be shown, illustrating the ability to detect changes in blood perfusion by analyzing contrast uptake over time with curve fitting algorithms. Finally, the detection of microbubbles targeted to endothelial cells, using subharmonic imaging in small animals, will be demonstrated.