title: Noninvasive detection of lipids in atherosclerotic plaque using ultrasound thermal strain imaging: in vivo animal study.
abstract: OBJECTIVE
  This study sought to examine the feasibility of in vivo detection of lipids in atherosclerotic plaque (AP) by ultrasound (US) thermal (or temporal) strain imaging (TSI).
  
  
  BACKGROUND
  Intraplaque lipid content is thought to contribute to plaque stability. Lipid exhibits a distinctive physical characteristic of temperature-dependent US speed compared with water-bearing tissues. As tissue temperature changes, US radiofrequency (RF) echoes shift in time of flight, which produces an apparent strain (thermal or temporal strain [TS]).
  
  
  METHODS
  US heating-imaging pulse sequences and transducers were designed and integrated into commercial US scanners for US-TSI of arterial segments. US-RF data were collected while gradually increasing tissue temperature. Phase-sensitive speckle tracking was applied to reconstruct TS maps coregistered to B-scans. Segments from injured atherosclerotic and uninjured nonatherosclerotic common femoral arteries (CFA) in cholesterol-fed New Zealand rabbits, and segments from control normal diet-fed rabbits (N =14) were scanned in vivo at different time points up to 12 weeks.
  
  
  RESULTS
  Lipid-rich atherosclerotic lesions exhibited distinct positive TS (+0.19 ± 0.08%) compared with that in nonatherosclerotic (-0.10 ± 0.13%) and control (-0.09 ± 0.09%) segments (p < 0.001). US-TSI enabled serial monitoring of lipids during atherosclerosis development. The coregistered set of morphological and compositional information of US-TSI showed good agreement with histology.
  
  
  CONCLUSIONS
  US-TSI successfully detected and longitudinally monitored lipid progression in atherosclerotic CFA. US-TSI of relatively superficial arteries may be a modality that could be integrated into a commercial US system for noninvasive lipid detection in AP.
authors.affiliation: Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine, Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania; Department of Biomedical Engineering and Systems, Cairo University, Giza, Egypt.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Mahmoud
authors.forename: Debaditya
authors.initials: D
authors.lastname: Dutta
authors.forename: Linda
authors.initials: L
authors.lastname: Lavery
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Stephens
authors.forename: Flordeliza S
authors.initials: FS
authors.lastname: Villanueva
authors.forename: Kang
authors.initials: K
authors.lastname: Kim
mesh_terms: D000818:Animals; D003952:Diagnostic Imaging / Q000379:methods*; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted; D008055:Lipids / Q000032:analysis*; D008297:Male; D058226:Plaque, Atherosclerotic / Q000737:chemistry* / Q000000981:diagnostic imaging; D011817:Rabbits; D011846:Radio Waves; D015203:Reproducibility of Results; D014463:Ultrasonography
chemical_list: D008055:Lipids
keywords: AP; CFA; LBT; RF; TS; TSI; US; WBT; atherosclerosis; atherosclerotic plaque; common femoral artery; lipid-bearing tissue; lipids; noninvasive; radiofrequency; thermal (or temporal) strain; thermal (or temporal) strain imaging; ultrasound; ultrasound thermal strain; water-bearing tissue
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