title: Comparison of left ventricular contraction homogeneity index using SPECT gated blood pool imaging and planar phase analysis.
abstract: BACKGROUND
  There is growing interest in developing a practical technique to accurately assess ventricular synchrony. We describe a novel 3-dimensional (3D) gated blood pool single photon emission computed tomography (SPECT) approach, from which a contraction homogeneity index (CHI) is derived and compared with planar phase analyses.
  
  
  RESULTS
  Subjects underwent planar and SPECT blood pool acquisition. Planar images were processed for left ventricular ejection fraction computation and phase values. SPECT images were processed by our novel algorithm, with which CHI was computed. Overall, 235 patients (79% male; mean age, 62 +/- 11 years) completed the study. Left ventricular ejection fractions were similar by planar (33.5% +/- 13.5%) and 3D (34.7% +/- 12.7%) methods (r = 0.83, P < .0001). Mean phase angles for planar and tomographic methods were 126.3 degrees +/- 29.6 degrees and 124.4 degrees +/- 28.7 degrees , respectively (r = 0.53, P < .0001). Phase and amplitude signals were incorporated in the CHI, which was non-normally distributed with a median of 73.8% (interquartile range, 58.7%-84.9%). This index minimized the negative impact of dyskinetic wall segments with limited regional motion. The planar heterogeneity index (SDPhi) was 28.2 degrees (interquartile range, 17.5 degrees -46.8 degrees ) and correlated inversely with CHI (r = -0.61, P < .0001).
  
  
  CONCLUSIONS
  The novel 3D dispersion index CHI accounts for both phase delay of a dyssynchronous segment and its magnitude of contraction and is moderately correlated with planar phase analyses. Its potential in cardiac resynchronization therapy remains to be exploited.
authors.affiliation: Department of Nuclear Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada. francois_harel@hotmail.com
authors.forename: François
authors.initials: F
authors.lastname: Harel
authors.forename: Vincent
authors.initials: V
authors.lastname: Finnerty
authors.forename: Jean
authors.initials: J
authors.lastname: Grégoire
authors.forename: Bernard
authors.initials: B
authors.lastname: Thibault
authors.forename: Paul
authors.initials: P
authors.lastname: Khairy
mesh_terms: D005260:Female; D015637:Gated Blood-Pool Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging*