title: New hybrid count- and geometry-based method for quantification of left ventricular volumes and ejection fraction from ECG-gated SPECT: methodology and validation.
abstract: BACKGROUND
  We have previously developed a new method for quantitative assessment of left ventricular (LV) volumes and ejection fraction (EF) from electrocardiography-gated single photon emission computed tomography (SPECT). The aims of this study were to present the methodology, to validate the gated SPECT cardiac quantification (GSCQ) method in phantoms and patients, and to determine normal values of LVEF.
  
  
  RESULTS
  A simple thresholding technique was used to generate binary images from nongated SPECT images. The K-means cluster classification algorithm was used to separate the LV region from non-LV regions on the binary images. A count- and geometry-based algorithm was applied to define endocardial and epicardial boundaries for calculation of LV volumes and LVEF. Overall correlation between GSCQ-quantified volumes and actual phantom volumes was good ( r = 0.97 and standard error of estimation (SEE) = 9.99 mL for normal phantoms, r = 0.99 and SEE = 6.97 mL for phantoms with defects). In patient studies, LVEF derived by GSCQ from SPECT and from equilibrium radionuclide angiography also showed good correlation ( r = 0.90 and SEE = 6.2%). The lower limit of normal LVEF from 8-frame gated SPECT by use of GSCQ was 45%. Quantification of LVEF by the GSCQ method was highly producible and was not significantly affected by the presence of myocardial perfusion defects or intense gastrointestinal activity.
  
  
  CONCLUSIONS
  The GSCQ method provides reliable and consistent assessments of LV volumes and EF. This methodology is less affected by intense gastrointestinal activity than other methods.
authors.affiliation: Section of Cardiovascular Medicine, Department of Internal Medicine, Cardiovascular Nuclear Imaging Laboratory, Yale University School of Medicine, New Haven, CT 06520, USA. yihwa@liu.med.yale.edu
authors.forename: Yi-Hwa
authors.initials: YH
authors.lastname: Liu
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Sinusas
authors.forename: Daniel
authors.initials: D
authors.lastname: Khaimov
authors.forename: Beata I
authors.initials: BI
authors.lastname: Gebuza
authors.forename: Frans J Th
authors.initials: FJ
authors.lastname: Wackers
mesh_terms: D000328:Adult; D000465:Algorithms; D004562:Electrocardiography / Q000379:methods; D005260:Female; D015637:Gated Blood-Pool Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013318:Stroke Volume; D015899:Tomography, Emission-Computed, Single-Photon / Q000295:instrumentation / Q000379:methods; D018487:Ventricular Dysfunction, Left / Q000145:classification* / Q000000981:diagnostic imaging*