High-sensitivity reflection-mode in vivo photoacoustic microscopy based on surface plasmon resonance sensing

摘要

Photoacoustic (PA) microscopy can measure the optical absorption properties of tissues with high specificity. However,most photoacoustic microscopy (PAM) systems use piezoelectric ultrasonic transducers for PA pressure detection. Due tothe limited bandwidth, the axial resolution of PA imaging is low (generally lager than 20-μm), resulting in inaccuratepositioning of light absorbing biomolecules. Moreover, the large difference in spatial resolution between the axial andlateral directions severely degrades the reconstruction of the three-dimensional image of the tissue. Surface plasmonresonance sensing (SPR) has an ultra-fast time response and thus is expected to increase the detection bandwidth of PAwaves. The disturbance of the PA pressure wave causes the refractive index change of the medium near the sensing layer,which modulates the SPR field. By detecting the change of the optical reflectivity, wideband PA detection can be realized.Here, we combine the SPR detector and an acoustic cavity with the ellipsoid inner surface for PA detection, which notonly enhances the signal detection sensitivity, but also realizes the reflection-mode PA imaging. The experimental resultsshow that the imaging signal-to-noise ratio (SNR) increases by around three times, and the detection bandwidth is morethan 70-MHz. High resolution and high contrast vascular imaging of mouse ear is acquired in vivo.