title: Characterization of lipid-rich aortic plaques by intravascular photoacoustic tomography: ex vivo and in vivo validation in a rabbit atherosclerosis model with histologic correlation.
abstract: BACKGROUND
  Histologic studies have demonstrated that lipid content and its spatial distribution is related to plaque vulnerability. However, in vivo imaging is still limited. Photoacoustic imaging may provide novel in vivo insights into these lipid-rich plaques.
  
  
  OBJECTIVE
  This study sought to examine whether intravascular photoacoustic tomography (IVPAT) allows localization and quantification of lipid content in atherosclerotic plaques.
  
  
  METHODS
  Rabbits fed with a high-fat/high-cholesterol diet served as the atherosclerotic model. Catheter-based IVPAT was used to evaluate pixel-based lipid relative concentration (LRC) of the vessel wall. The aorta of 4 groups of rabbits (n = 12) were examined ex vivo with IVPAT after 0, 5, 10, and 15 weeks of a high-fat diet, respectively. Six rabbits underwent 3-dimensional (3D) IVPAT after 20 weeks of the high-fat diet. Three rabbits were examined in vivo using IVPAT without interruption of blood flow. Concentration-based lipid map and quantitative index were calculated. For subsequent histologic correlation, all specimens were evaluated with Oil Red O staining.
  
  
  RESULTS
  Cross-sectional LRC maps allowed visualization of concentration and depth information of lipid content in the atherosclerotic plaques. Lipid accumulation within plaque, assessed by the maximum LRC, mean LRC, and high lipid content area correlated to duration of a high-fat diet. Three-dimensional LRC maps enabled overall evaluation of focal plaques in an intact explanted aorta including spatial and structural features. In vivo-obtained LRC maps accurately showed the structure of lipid core with high contrast. Ex vivo and in vivo IVPAT results were highly consistent with histological results.
  
  
  CONCLUSIONS
  In an animal model, IVPAT allowed characterization of spatial and quantitative features of lipid-rich plaques.
authors: Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, Guangdong Province, China.
authors: Jian
authors: J
authors: Zhang
authors: Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, Guangdong Province, China. Electronic address: yangsh@scnu.edu.cn.
authors: Sihua
authors: S
authors: Yang
authors: Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, Guangdong Province, China.
authors: Xuanrong
authors: X
authors: Ji
authors: Medical Imaging Center, First Affiliated Hospital of Jinan University, Guangzhou, Guangdong Province, China.
authors: Quan
authors: Q
authors: Zhou
authors: Ministry of Education Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, Guangdong Province, China. Electronic address: xingda@scnu.edu.cn.
authors: Da
authors: D
authors: Xing
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000473:pathology; D001013:Aorta, Thoracic / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000473:pathology; D001018:Aortic Diseases / Q000175:diagnosis / Q000378:metabolism; D050197:Atherosclerosis / Q000175:diagnosis* / Q000378:metabolism; D004195:Disease Models, Animal; D021621:Imaging, Three-Dimensional; D008055:Lipids / Q000032:analysis*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D061088:Photoacoustic Techniques; D058226:Plaque, Atherosclerotic / Q000737:chemistry / Q000175:diagnosis*; D011817:Rabbits; D015203:Reproducibility of Results; D018084:Ultrasonography, Interventional / Q000379:methods*
chemical_list: D008055:Lipids
keywords: atherosclerosis; histological imaging; intravascular photoacoustic tomography; lipid