title: Distribution of ultrasonic radiofrequency signal amplitude detects lipids in atherosclerotic plaque of coronary arteries: an ex-vivo study.
abstract: BACKGROUND
  Accumulation of lipids within coronary plaques is an important process in disease progression. However, gray-scale intravascular ultrasound images cannot detect plaque lipids effectively. Radiofrequency signal analysis could provide more accurate information on preclinical coronary plaques.
  
  
  METHODS
  We analyzed 29 zones of mild atheroma in human coronary arteries acquired at autopsy. Two histologic groups, i.e., plaques with a lipid core (group L) and plaques without a lipid core (group N), were analyzed by automatic calculation of integrated backscatter. One hundred regions of interest were set on the target zone. Radiofrequency signals from a 50 MHz transducer were digitized at 240 MHz with 12-bit resolution. The intensity of integrated backscatter and its distribution within each plaque were compared between the two groups.
  
  
  RESULTS
  Although the mean backscatter was similar between the groups, intraplaque variation of backscatter and backscatter in the axial direction were larger in group L than in group N (p = 0.02). Conventional intravascular ultrasound showed extremely low sensitivity for lipid detection, despite a high specificity. In contrast, a cut-off value>32 for the total variance of integrated backscatter identified lipid-containing plaque with a high sensitivity (85%) and specificity (75%).
  
  
  CONCLUSIONS
  Compared with conventional imaging, assessment of the intraplaque distribution of integrated backscatter is more effective for detecting lipid. As coronary atheroma progresses, its composition becomes heterogeneous and multi-layered. This radiofrequency technique can portray complex plaque histology and can detect the early stage of plaque progression.
authors.affiliation: Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo, Japan. h.hisao1967@gmail.com
authors.forename: Hisao
authors.initials: H
authors.lastname: Hara
authors.forename: Taro
authors.initials: T
authors.lastname: Tsunoda
authors.forename: Naohiko
authors.initials: N
authors.lastname: Nemoto
authors.forename: Itaru
authors.initials: I
authors.lastname: Yokouchi
authors.forename: Masaya
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ono
authors.forename: Masao
authors.initials: M
authors.lastname: Moroi
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sugi
authors.forename: Masato
authors.initials: M
authors.lastname: Nakamura
mesh_terms: D000368:Aged; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D050356:Lipid Metabolism; D008297:Male; D012542:Scattering, Radiation; D014018:Tissue Distribution; D014463:Ultrasonography / Q000379:methods*