title: Cause of apical thinning on attenuation-corrected myocardial perfusion SPECT.
abstract: OBJECTIVE
  Decreases in apical and apex activities - namely, 'apical thinning' - are a well-known phenomenon in attenuation-corrected (AC) myocardial perfusion. The aim of this study was to compare actual myocardial thickness derived from a multidetector-row computed tomography with AC myocardial perfusion count from a hybrid single-photon emission computed tomography/computed tomography to investigate the cause of apical thinning.
  
  
  METHODS
  We enrolled 21 participants with a low likelihood of coronary artery disease (mean age 65 ± 21 years, 13 men) from 185 consecutive patients and 11 healthy volunteers, who independently underwent ⁹⁹mTc-sestamibi single-photon emission computed tomography/computed tomography and 64-slice multidetector-row computed tomography scans. AC and non-AC myocardial perfusion counts and thickness were measured on the basis of a 17-segment model and averaged at the apex, apical, mid, and basal walls.
  
  
  RESULTS
  Myocardial thickness at the apex was significantly thinner than that at the apical and mid walls (5.1 ± 1.3, 7.3 ± 1.3, and 9.9 ± 2.4 mm, respectively; P<0.005). AC count at the apex was significantly lower than that at the apical and mid regions (76.0 ± 5.5, 82.8 ± 4.7, and 85.6 ± 3.8, respectively; P<0.002). Moderate relationship was observed between myocardial thickness and AC count (y=-10.5 + 0.22x, r=0.54, P<0.0001. No relationship was found between thickness and non-AC count (r=0.16, P=0.263).
  
  
  CONCLUSIONS
  The low apex and apical counts were caused by anatomical thinning of the myocardium in AC myocardial perfusion imaging. Attenuation correction provided an accurate relationship between myocardial count and thickness because of the partial volume effect.
authors: Department of Nuclear Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan. okuda@nmd.m.kanazawa-u.ac.jp
authors: Koichi
authors: K
authors: Okuda
authors: Kenichi
authors: K
authors: Nakajima
authors: Shinro
authors: S
authors: Matsuo
authors: Hiroshi
authors: H
authors: Wakabayashi
authors: Junichi
authors: J
authors: Taki
authors: Seigo
authors: S
authors: Kinuya
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi