Ultrasound-heated photoacoustic flowmetry

Journal of Biomedical Optics (Impact Factor: 2.86). 11/2013; 18(11):117003. DOI: 10.1117/1.JBO.18.11.117003
Source: PubMed


We report the development of photoacoustic flowmetry assisted by high-intensity focused ultrasound (HIFU). This novel method employs HIFU to generate a heating impulse in the flow medium, followed by photoacoustic monitoring of the thermal decay process. Photoacoustic flowmetry in a continuous medium remains a challenge in the optical diffusive regime. Here, both the HIFU heating and photoacoustic detection can focus at depths beyond the optical diffusion limit (∼1 mm in soft tissue). This method can be applied to a continuous medium, i.e., a medium without discrete scatterers or absorbers resolvable by photoacoustic imaging. Flow speeds up to 41 mm·s-1 have been experimentally measured in a blood phantom covered by 1.5-mm-thick tissue.

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    • "To apply existing PA blood flow measurement methods in deep tissue, a long-standing hurdle was their requirement of resolvable absorbers in the flowing medium, which was particularly challenging when only IEEE Photonics Journal Breakthroughs in Photonics 2013 acoustic-resolution was available. Wang et al. successfully resolved this issue by thermally tagging a small portion of the flowing blood and photoacoustically monitoring the tagged Bhot[ blood [see Fig. 2(a) and (b)] [21], [22]. Because the tagged blood serves as an acoustically defined Fvirtual absorber_, blood flow can be measured deep in tissue. "
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