Plasmonic Intravascular Photoacoustic Imaging for Detection of Macrophages in Atherosclerotic Plaques

Abstract

To detect macrophages in atherosclerotic plaques, plasmonic gold nanoparticles are introduced as a contrast agent for intravascular photoacoustic imaging. The phantom and ex vivo tissue studies show that the individual spherical nanoparticles, resonant at 530 nm wavelength, produce a weak photoacoustic signal at 680 nm wavelength while photoacoustic signal from nanoparticles internalized by macrophages is very strong due to the plasmon resonance coupling effect. These results suggest that intravascular photoacoustic imaging can assess the macrophage-mediated aggregation of nanoparticles and therefore identify the presence and the location of nanoparticles associated with macrophage-rich atherosclerotic plaques.

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

“…To further assess the vulnerability of the plaques, we previously introduced intravascular photoacoustic ͑IVPA͒ imaging. [15][16][17][18][19][20][21] Photoacoustic imaging utilizes light absorption properties of tissues. After excitation of the tissues by short laser pulses, consequent acoustic transients generated as a result of thermal expansion are detected.…”

Biomedical photoacoustics beyond thermal expansion using triggered nanodroplet vaporization for contrast-enhanced imaging

“…Exogenous contrast in photoacoustic imaging can be achieved through use of contrast agents, such as plasmonic metal nanoparticles [9][10][11][12] . These nanoparticles have optical absorption cross-sections that are orders of magnitude higher than those of tissue components and are generally used to enhance the optical absorption of nanoparticle-labelled tissues.…”

“…These nanoparticles have optical absorption cross-sections that are orders of magnitude higher than those of tissue components and are generally used to enhance the optical absorption of nanoparticle-labelled tissues. Surface-functionalized nanoparticles also provide molecular functionality with the addition of specific targeting moieties 10,11,13 . However, the production of photoacoustic transients using these exogenous agents is still governed by thermal expansion, and therefore, the same fundamental limits of this mode of photoacoustic signal generation apply.…”

Feasibility ofin vivointravascular photoacoustic imaging using integrated ultrasound and photoacoustic imaging catheter

“…[11][12][13] Furthermore, imaging contrast agents were explored to identify molecular and cellular signatures associated with atherosclerosis. [14][15][16][17][18] Compared to IVUS imaging, IVPA has a similar imaging depth of several millimeters and imaging resolution within one hundred micrometers. 10 IVPA imaging was combined with IVUS imaging thus visualizing both morphology and composition of soft tissues.…”

“…Recently, combined IVUS/IVPA imaging was used ex vivo to characterize plaque composition including lipid and macrophages. 11,12,[15][16][17][18][19] In vivo IVUS/IVPA imaging can be performed using an integrated IVUS/IVPA imaging catheter capable of both delivering pulsed laser irradiation into an arterial lumen with consequent detection of photoacoustic transients (IVPA imaging) and probing the arterial walls in ultrasound pulse-echo mode (IVUS imaging). The first concepts of an integrated IVUS/ IVPA imaging catheter, consisting of a single element ultrasound transducer combined with a custom single optical fiber-based light delivery system, 20 were successfully evaluated in tissue-mimicking phantoms.…”