No abstract

Lipid is a common constituent in atherosclerotic plaques. The location and area of the lipid region is closely related to the progression of the disease. Intravascular photoacoustic (IVPA) imaging, a minimally invasive imaging modality, can spatially resolve the optical absorption property of arterial tissue. Based on the distinct optical absorption spectrum of fat in the near infrared wavelength range, spectroscopic IVPA imaging may distinguish lipid from other water-based tissue types in the atherosclerotic artery. In this study, a bench-top spectroscopic IVPA imaging system was used to ex-vivo image both atherosclerotic and normal rabbit aortas. By combing the spectroscopic IVPA image with the intravascular ultrasound (IVUS) image, lipid regions in the aorta were identified. The results demonstrated that IVUS-guided spectroscopic IVPA imaging is a promising tool to differentiate lipid in atherosclerosis.

Lipid is a common constituent in atherosclerotic plaques. The location and area of the lipid region is closely related to the progression of the disease. Intravascular photoacoustic (IVPA) imaging, a minimally invasive imaging modality, can spatially resolve the optical absorption property of arterial tissue. Based on the distinct optical absorption spectrum of fat in the near infrared wavelength range, spectroscopic IVPA imaging may distinguish lipid from other water-based tissue types in the atherosclerotic artery. In this study, a bench-top spectroscopic IVPA imaging system was used to ex-vivo image both atherosclerotic and normal rabbit aortas. By combing the spectroscopic IVPA image with the intravascular ultrasound (IVUS) image, lipid regions in the aorta were identified. The results demonstrated that IVUS-guided spectroscopic IVPA imaging is a promising tool to differentiate lipid in atherosclerosis. in the rabbit induced by feeding graded amounts of low-level cholesterol. Methodological considerations regarding individual variability in response to dietary cholesterol and development of lesion type," Arterioscler. photoacoustic imaging and plasmon resonance coupling of gold nanoparticles for selective detection of cancer," Nano Lett. (2009). 20. A. B. Karpiouk, B. Wang, and S. Y. Emelianov, "Development of a catheter for combined intravascular ultrasound and photoacoustic imaging," Rev. Sci. Instrum. 81(1), 1-7 (2010). 21. A. Roggan, M. Friebel, K. Dorschel, A. Hahn, and G. Muller, "Optical properties of circulating human blood in the wavelength range 400-2500 nm," J.

Intravascular photoacoustic (IVPA) imaging can characterize atherosclerotic plaque composition on the basis of the optical absorption contrast between different tissue types. Given the high optical absorption of lipid at 1720 nm wavelength, an atherosclerotic rabbit aorta was imaged at this wavelength ex vivo using an integrated intravascular ultrasound (IVUS) and IVPA imaging catheter in the presence of luminal blood. Strong optical absorption of lipid combined with low background signal from other tissues provides a high-contrast, depth-resolved IVPA image of lipid. The ability to image lipid at a single wavelength without removing luminal blood suggests that in vivo detection of lipid in atherosclerotic plaques using combined IVUS/IVPA imaging is possible.

We present a preliminary study demonstrating the capability of ultrasound-guided intravascular photoacoustic (IVPA) imaging to visualize the depth-resolved distribution of lipid deposits in atherosclerotic plaques in vivo. Based on the characteristic optical absorption of lipid in the near infrared wavelength range, IVPA imaging at a single, 1720 nm, wavelength was used to provide a spatially resolved direct measurement of lipid content in atherosclerotic arteries. By overlaying an IVPA image with a spatially co-registered intravascular ultrasound (IVUS) image, the combined IVPA/IVUS image was used to visualize the distribution of lipid within the vessel wall. Ultrasound-guided IVPA imaging was performed in vivo in the abdominal aorta of a Watanabe heritable hyperlipidemic (WHHL) rabbit. Subsequently, the excised rabbit aorta filled with a solution of red blood cells (RBC) was then imaged ex vivo, and the histology was obtained in the section adjacent to the imaged cross-section. To demonstrate the potential of future clinical application of IVPA/IVUS imaging, a sample of diseased human right coronary artery (RCA) was also imaged. Both in vivo and ex vivo IVPA images clearly showed the distribution of lipid in the atherosclerotic vessels. In vivo IVPA imaging was able to identify diffuse, lipid-rich plaques in the WHHL rabbit model of atherosclerosis. Furthermore, IVPA imaging at a single wavelength was able to identify the lipid core within the human RCA ex vivo. Our results demonstrate that ultrasound-guided IVPA imaging can identify lipid in atherosclerotic plaques in vivo. Importantly, the IVPA/IVUS images were obtained in presence of luminal blood and no saline flush or balloon occlusion was required. Overall, our studies suggest that ultrasound-guided IVPA imaging can potentially be used for depth-resolved visualization of lipid deposits within the anatomical context of the vessel wall and lumen. Therefore, IVUS/ IVPA imaging may become an important tool for the detection of rupture-prone plaques.