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High frequency nonlinear B-scan imaging of microbubble contrast agents
David E Goertz1, Emmanuel Cherin, Andrew Needles
1Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada. d.goertz@erasmusmc.nl
Summary
High-frequency nonlinear microbubble imaging is now feasible. New instrumentation enables subharmonic and ultraharmonic modes, successfully visualizing microvessels in vivo with improved contrast and tissue signal suppression.
Area of Science:
- Medical Imaging
- Biomedical Engineering
- Acoustics
Background:
- Nonlinear scattering from microbubble contrast agents was previously demonstrated at 14-32 MHz.
- This suggested the potential for high-frequency nonlinear microbubble imaging.
Purpose of the Study:
- To develop and validate nonlinear microbubble B-scan imaging instrumentation operating at high frequencies (10-50 MHz).
- To evaluate the performance of subharmonic, ultraharmonic, and second harmonic imaging modes.
Main Methods:
- Developed nonlinear microbubble B-scan imaging system (10-50 MHz).
- Validated system at 20 and 30 MHz using wall-less vessel phantoms.
- Performed nonlinear imaging utilizing subharmonic, ultraharmonic, and second harmonic frequencies.
- Conducted in vivo experiments on rabbit ear and mouse heart.
Main Results:
- Subharmonic and ultraharmonic imaging achieved significant tissue signal suppression (below noise floor).
- Contrast-to-noise ratios of up to 26 dB (subharmonic) and 17 dB (ultraharmonic) were obtained.
- Second harmonic imaging performance was limited by nonlinear propagation.
- Successfully detected microvessels in vivo using 20 MHz subharmonic imaging.
Conclusions:
- Demonstrated the feasibility of high-frequency nonlinear microbubble imaging.
- Subharmonic and ultraharmonic modes show promise for enhanced microvascular visualization.
- The developed system supports advanced nonlinear imaging techniques for biomedical applications.