Application of the probe beam deflection technique in photoacoustic and ultrasound imaging

Ultrasound imaging and Photoacoustic imaging methodologies, commonly utilize piezo-electric transducers, both ceramic-based and polymer-based, to detect the acoustic energy reflected or emitted from an imaging target. Ceramic based piezo-electric transducers, exhibit non-desirable traits including: limited bandwidth (<15 MHz), off-axis energy acceptance, and requirement of a perfectly matched layer (PML), due to the large impedance mismatch to soft tissue. Polymer based piezo-electric transducers such as PVDF, exhibit high bandwidth (up to 100 MHz), however exhibit low coupling efficiency (<0.2). An optical sensing method known as the Probe Beam Deflection Technique (PBDT), is applied to ultrasound and photoacoustic imaging, to detect the acoustic reflection/emission in ultrasound and photoacoustic imaging. It is shown that the PBDT exhibits: high bandwidth (>30 MHz), acoustic propagation directionality quantification, passive sensing, high coupling efficiency (>0.5) and impedance similar to soft tissue. A series of 2-D and 3-D ultrasound images are reconstructed utilizing the PBDT and compared to images reconstructed from piezo-electric transducers. It is shown that artifact reduction and improved contrast are exhibited by the PBDT.