Spectroscopic Imaging of Deep Tissue through Photoacoustic Detection of Molecular Vibration

Abstract

The quantized vibration of chemical bonds provides a way of imaging target molecules in a complex tissue environment. Photoacoustic detection of harmonic vibrational transitions provides an approach to visualize tissue content beyond the ballistic photon regime. This method involves pulsed laser excitation of overtone transitions in target molecules inside a tissue. Fast relaxation of the vibrational energy into heat results in a local temperature rise on the order of mK and a subsequent generation of acoustic waves detectable with an ultrasonic transducer. In this perspective, we review recent advances that demonstrate the advantages of vibration-based photoacoustic imaging and illustrate its potential in diagnosing cardiovascular plaques. An outlook into future development of vibrational photoacoustic endoscopy and tomography is provided.

High-performance near-infrared imaging for breast cancer detection

“…[15][16][17][18][20][21][22][23][24][25][26][27][28] Also, by using this technique with the help of advanced digital image processing, we would be able to distinguish and differentiate between different grade levels of tumor and cancerous cells. The novelty of the current work lies in several areas as mentioned in this scenario; first, on the imaging front, we have been able to achieve high-resolution photothermal imaging of tumor with size less than 2 cm 3 using NIR laser.…”

High-speed intravascular photoacoustic imaging at 17 μm with a KTP-based OPO

“…As reported, the 1.2 and 1.7 µm spectral bands resonant with the second and first overtone vibrations of the C-H bond and are suitable for IVPA imaging of lipid-rich plaques [17][18][19]. Compared with 1.2 µm excitation, 1.7 µm is more favorable for IVPA imaging due to the high absorption coefficient and less optical scattering by blood [18,20,21]. A few groups have demonstrated the feasibility of IVPA imaging of lipid-laden plaques by excitation at 1.7 µm, even in the presence of blood [18,19,22].…”

Biological imaging with coherent Raman scattering microscopy: a tutorial

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