title: Illusion of contraction from out-of-plane translation: can Doppler tissue velocities resolve it?
abstract: BACKGROUND
  Assessment of wall motion is one of the most challenging aspects of echocardiography. Because of tapering cardiac shape, the impression of thickening can be produced by cardiac translation perpendicular to the image plane. Doppler tissue imaging (DTI) can potentially resolve this problem because in noncontracting myocardium, velocities (V) are uniform (V gradient [VG] = 0) and V measured by DTI should be unaffected by translation perpendicular to the imaging beam.
  
  
  METHODS
  A left ventricle-shaped phantom and a string model were translated at known angles to the ultrasound beam. Two-dimensional gray-scale, DTI, and M-mode images were acquired and analyzed.
  
  
  RESULTS
  During translation perpendicular to the image plane, 2-dimensional and M-mode images of the ventricular model showed apparent wall thickening, but analysis of the DTI images showed that V and VG across the walls were near 0 (V = 0.04 +/- 0.1 cm/s; VG = 0.02 +/- 0.02/s). Translation of both models at various angles relative to an M-mode beam also created the impression of wall thickening. However, DTI accurately measured the angle-corrected V component toward the transducer (r > 0.98, P <.0001), and VG corresponded to rigid body motion (0.003 +/- 0.02/s).
  
  
  CONCLUSIONS
  M-mode and 2-dimensional echocardiography images are subject to the illusion of myocardial thickening resulting from out-of-plane translation. Analysis of tissue Doppler V avoids such error by accurately measuring V components and VG, and it has the potential to improve assessment of left ventricular function.
authors.affiliation: Cardiac Ultrasound Laboratory, Cardiology Division and Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Playford
authors.forename: Robert A
authors.initials: RA
authors.lastname: Levine
authors.forename: Michael H
authors.initials: MH
authors.lastname: Picard
authors.forename: Mark D
authors.initials: MD
authors.lastname: Handschumacher
mesh_terms: D001185:Artificial Intelligence; D001783:Blood Flow Velocity / Q000502:physiology; D015150:Echocardiography, Doppler; D004699:Endocardium / Q000000981:diagnostic imaging / Q000503:physiopathology; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D007088:Illusions; D007090:Image Interpretation, Computer-Assisted; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D015588:Observer Variation; D010496:Pericardium / Q000000981:diagnostic imaging / Q000503:physiopathology; D013223:Statistics as Topic