Microbubbles And Nanodrops For Photoacoustic Tomography

Photoacoustic imaging holds a unique position in medical imaging technology by interlinking optical and acoustic techniques. Photoacoustic methods have shown potential for realtime, noninvasive imaging of structural and functional properties of biological tissues and organs based on optical transmission and acoustic reception, but with limited penetration depth and specificity due to strong light scattering and absorption in tissues and overlapping absorption spectra of various endogenous absorbers. Incorporation of tailor-made microbubbles and nanodrops comprising light-absorbing molecules or nanoparticles shows the potential to overcome such detection limitations. Microbubbles may be driven into powerful radial oscillations, thereby amplifying the acoustic emission and focusing it to the bubble's resonant frequency. Nanodrops may be vaporized into microbubbles, further amplifying the thermoelastic response. This review surveys advancements of this emerging imaging technology over the past decade.