Intravascular Photoacoustics for Image-Guidance and Temperature Monitoring During Plasmonic Photothermal Therapy of Atherosclerotic Plaques: A Feasibility Study

Abstract

Recently, combined intravascular ultrasound and photoacoustic (IVUS/IVPA) imaging has been demonstrated as a novel imaging modality capable of visualizing both morphology (via IVUS) and cellular/molecular composition (via IVPA) of atherosclerotic plaques, using both endogenous tissue absorbers and exogenous contrast agents. Plasmonic gold nanoparticles were previously utilized as IVPA contrast agents which co-localize with atherosclerotic plaques, particularly phagocytically active macrophages. The present work demonstrates the use of IVUS/IVPA imaging as a tool for localized temperature monitoring during laser heating. The temperature dependent change in IVPA signal intensity of silica-coated gold nanorod contrast agents absorbing within the near-infrared optical wavelength range is evaluated and shown to have a linear relationship, with a slope greater than that of endogenous tissue. A continuous wave laser was subsequently incorporated into the IVUS/IVPA integrated catheter and utilized to selectively heat the nanoparticles with simultaneous IVPA temperature monitoring. IVUS/IVPA, therefore, provides a platform for detection and temperature monitoring of atherosclerotic plaques through the selective heating of plasmonic gold nanoparticle contrast agents.

Gold Nanoparticles for Photoacoustic Imaging

“…The IVPA signal intensity of silica-coated AuNRs absorbing within the NIR optical wavelength range is shown to have a linear relationship with temperature change. Therefore, IVUS/IVPA imaging can provide a platform for the detection and temperature monitoring of atherosclerotic plaques through the selective heating of AuNPs [136]. The examples provided in this section clearly indicate the potential of PA imaging with AuNPs as contrast agents for guiding and monitoring therapeutic procedures.…”

High speed intravascular photoacoustic imaging with fast optical parametric oscillator laser at 1.7 μm

“…[13][14][15] Based on the optical absorption contrast of the tissues within the vessel wall, intravascular photoacoustic (IVPA) imaging for characterizing plaque compositions has been studied. [16][17][18][19][20][21][22][23][24][25][26][27] Recently, due to the high optical absorption by first overtone of C-H bonds around 1720 nm, IVPA imaging of lipid-rich atherosclerotic plaque at 1.7 lm spectral band has been attracting great attention. 21,28 However, current IVPA imaging speed is limited by the repetition rate of commercial nanosecond lasers at 1.7 lm.…”

“…The phantom with a 2 mm-diameter lumen was molded from a solution containing 5% gelatin and 2% silica particles (5-lm average diameter) as an acoustic scattering agent. 27,31 As shown in Fig. 3(a), four 0.5-mm diameter cylindrical cavities were located at 0.2 mm (B1), 0.5 mm (G1), 1.0 mm (B2), and 1.0 mm (G2) from the lumen and filled with inclusions of butter (B1, B2) and graphite rods (G1, G2).…”

Angled-focused 45MHz PMN-PT single element transducer for intravascular ultrasound imaging

“…To improve the diagnostic capabilities of imaging modalities, research groups have been developing new approaches [8-12]. Our group has been intensively developing IVUS imaging transducers and systems [13-17].…”