title: Image enhancement by noncontrast harmonic echocardiography. Part I. Qualitative assessment of endocardial visualization.
abstract: OBJECTIVE
  To determine whether harmonic imaging--use of signals with frequencies twice that of the transmitted ultrasound to produce ultrasound images--can improve endocardial border definition in patients who have technically difficult echocardiograms.
  
  
  METHODS
  We studied 29 patients with technically difficult echocardiograms (nonvisualization of 2 or more endocardial segments in a 16-segment model). Apical long-axis, four-chamber, and two-chamber images were acquired during fundamental imaging (at 2.0 and 3.5 MHz) and second harmonic imaging (3.5-MHz receive mode) in random order. Images were digitally stored and subsequently reviewed blindly for endocardial segment score (0 = not visualized; 1 = adequate; or 2 = excellent) and overall ranking of image quality (1 [best] to 3 [worst]).
  
  
  RESULTS
  Mean endocardial segment score was significantly better (P < 0.0001) for harmonic imaging (1.02 +/- 0.36) than for either fundamental mode (0.49 +/- 0.21 and 0.57 +/- 0.27 for the 2.0- and 3.5-MHz images, respectively). The harmonic images were ranked as better (P < 0.0001) than those of either fundamental mode: harmonic mean rank was 1.07 in comparison with 2.67 and 2.26 for the 2.0- and 3.5-MHz fundamental images, respectively.
  
  
  CONCLUSIONS
  Noncontrast harmonic imaging appreciably enhances endocardial definition in patients with technically difficult echocardiographic studies and significantly improves overall image quality.
authors.affiliation: Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic Rochester, Minnesota 55905, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Mulvagh
authors.forename: D A
authors.initials: DA
authors.lastname: Foley
authors.forename: M
authors.initials: M
authors.lastname: Belohlavek
authors.forename: J B
authors.initials: JB
authors.lastname: Seward
mesh_terms: D000328:Adult; D015986:Confounding Factors, Epidemiologic; D004452:Echocardiography / Q000379:methods*; D004699:Endocardium / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008297:Male