title: Improved quantification of small hearts for gated myocardial perfusion imaging.
abstract: OBJECTIVE
  In patients with a small heart, defined as an end-systolic volume (ESV) of ≤20 mL calculated using the Quantitative Gated SPECT (QGS) program, underestimation of ESV and overestimation of ejection fraction (EF) using gated myocardial perfusion imaging are considered errors caused by inappropriate delineation of the left ventricle (LV). The aim of this study was to develop a new method for delineation of the LV and to evaluate it in studies using a digital phantom, normal subjects and patients.
  
  
  METHODS
  The active shape-based method for LV delineation, EXINI heart (ExH), was adjusted to more accurately process small hearts. In small hearts, due to the partial volume effect and the short distance to the opposite ventricular wall, the endocardial and the epicardial surfaces are shifted in the epicardial direction depending on the midventricular volume. The adjusted method was evaluated using digital XCAT phantoms with Monte Carlo simulation (8 virtual patients), a Japanese multicentre normal database (69 patients) and consecutive Japanese patients (116 patients). The LV volumes, EF and diastolic parameters derived from ExH and QGS were compared.
  
  
  RESULTS
  The digital phantom studies showed a mean ESV of 87% ± 9% of the true volume calculated using ExH and 22 % ± 18% calculated using QGS. In the normal database, QGS gave higher EFs in women than in men (71.4 ± 6.0 % vs. 67.2 ± 6.0%, p = 0.0058), but ExH gave comparable EFs (70.7 ± 4.9% and 71.4 ± 5 % in men and women, respectively, p = ns). QGS gave higher EFs in subjects with a small heart than in those with a normal-sized heart (74.5 ± 5.1% vs. 66.1 ± 4.9%), but ExH gave comparable values (70.0 ± 5.9% vs. 71.6 ± 4.2%, respectively, p = ns). In consecutive patients, the average EFs with QGS in patients with ESV >20 mL, 11-20 mL and ≤10 mL were 57.9%, 71.9% and 83.2%, but with ExH the differences among these groups were smaller (65.2%, 67.8% and 71.5%, respectively).
  
  
  CONCLUSIONS
  The volume-dependent edge correction algorithm was able to effectively reduce the effects on ESV and EF of a small heart. The uniform normal values might be applicable to both men and women and to both small and normal-sized hearts.
authors: Kanazawa University Hospital, Kanazawa, Japan. nakajima@med.kanazawa-u.ac.jp
authors: Kenichi
authors: K
authors: Nakajima
authors: Koichi
authors: K
authors: Okuda
authors: Karin
authors: K
authors: Nyström
authors: Jens
authors: J
authors: Richter
authors: David
authors: D
authors: Minarik
authors: Hiroshi
authors: H
authors: Wakabayashi
authors: Shinro
authors: S
authors: Matsuo
authors: Seigo
authors: S
authors: Kinuya
authors: Lars
authors: L
authors: Edenbrandt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D055426:Cardiac-Gated Single-Photon Emission Computer-Assisted Tomography / Q000379:methods*; D005260:Female; D006352:Heart Ventricles / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D009929:Organ Size; D013318:Stroke Volume; D016276:Ventricular Function
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