Intravascular Photoacoustic Tomography of Coronary Atherosclerosis

Monitoring the Progression of Early Atherosclerosis Using a Fluorescence Nanoprobe for the Detection and Imaging of Phosphorylation and Glucose Levels

Monitoring the early stage of atherosclerosis (AS) without plaque formation is of great significance. Herein, we developed a metal organic framework (MOF)-based fluorescence nanoprobe to analyze the progression of AS by assessing the levels of protein phosphorylation and glucose in blood and tissue. The probe was prepared by post-modification of the MOF with iodine (I3 - )-rhodamine B (RhB) associate, which realizes the specific recognition of target object through the metal joint ZrIV and I3 - -RhB, respectively. We investigated different stages of target object changes in the early non-plaque stage of AS in blood. It was found that the levels of phosphate and glucose in the blood were higher than those of the normal mice. The results of two-photon images showed that early AS mice had higher levels of protein phosphorylation and glucose than that of the normal mice. The present study provides a suitable fluorescence tool for further revealing the pathogenesis and progression of AS.

Photoacoustic Imaging in Biomedicine and Life Sciences

Photo-acoustic imaging, also known as opto-acoustic imaging, has become a widely popular modality for biomedical applications. This hybrid technique possesses the advantages of high optical contrast and high ultrasonic resolution. Due to the distinct optical absorption properties of tissue compartments and main chromophores, photo-acoustics is able to non-invasively observe structural and functional variations within biological tissues including oxygenation and deoxygenation, blood vessels and spatial melanin distribution. The detection of acoustic waves produced by a pulsed laser source yields a high scaling range, from organ level photo-acoustic tomography to sub-cellular or even molecular imaging. This review discusses significant novel technical solutions utilising photo-acoustics and their applications in the fields of biomedicine and life sciences.

Photoacoustic Imaging: Contrast Agents and Their Biomedical Applications

Photoacoustic (PA) imaging as a fast-developing imaging technique has great potential in biomedical and clinical applications. It is a noninvasive imaging modality that depends on the light-absorption coefficient of the imaged tissue and the injected PA-imaging contrast agents. Furthermore, PA imaging provides superb contrast, super spatial resolution, and high penetrability and sensitivity to tissue functional characteristics by detecting the acoustic wave to construct PA images. In recent years, a series of PA-imaging contrast agents are developed to improve the PA-imaging performance in biomedical applications. Here, recent progress of PA contrast agents and their biomedical applications are outlined. PA contrast agents are classified according to their components and function, and gold nanocrystals, gold-nanocrystal assembly, transition-metal chalcogenides/MXene-based nanomaterials, carbon-based nanomaterials, other inorganic imaging agents, small organic molecules, semiconducting polymer nanoparticles, and nonlinear PA-imaging contrast agents are discussed. The applications of PA contrast agents as biosensors (in the sensing of metal ions, pH, enzymes, temperature, hypoxia, reactive oxygen species, and reactive nitrogen species) and in bioimaging (lymph nodes, vasculature, tumors, and brain tissue) are discussed in detail. Finally, an outlook on the future research and investigation of PA-imaging contrast agents and their significance in biomedical research is presented.

Emerging Technology Update Intravascular Photoacoustic Imaging of Vulnerable Atherosclerotic Plaque

The identification of vulnerable atherosclerotic plaques in the coronary arteries is emerging as an important tool for guiding atherosclerosis diagnosis and interventions. Assessment of plaque vulnerability requires knowledge of both the structure and composition of the plaque. Intravascular photoacoustic (IVPA) imaging is able to show the morphology and composition of atherosclerotic plaque. With imminent improvements in IVPA imaging, it is becoming possible to assess human coronary artery disease in vivo. Although some challenges remain, IVPA imaging is on its way to being a powerful tool for visualising coronary atherosclerotic features that have been specifically associated with plaque vulnerability and clinical syndromes, and thus such imaging might become valuable for clinical risk assessment in the catheterisation laboratory.

Mechanical characterization of intraluminal tissue with phase-resolved photoacoustic viscoelasticity endoscopy

We developed a phase-sensitive side-scanning photoacoustic viscoelasticity endoscopy (PAVEE) for mechanical characterization of intraluminal tissues. In PAVEE, the PA phase can be extracted from the optical absorption induced ultrasonic waves and provides an index of viscoelasticity that is closely linked to tissue compositions. The transverse resolution of the PAVEE measured by carbon fiber was about 32 μm. The imaging capability of the PAVEE was verified using a vessel-mimicking phantom with different agar density. Moreover, PAVEE was investigated in processed lumen-shaped vascular tissues to evaluate the biomechanical features, which was highly consistent with the histology. The results demonstrated that the PAVEE can obtain viscoelastic properties of intraluminal tissues, which puts a new insight into the intravascular disease and holds great promise for plaque vulnerability detection.