title: Impact of time-of-flight on qualitative and quantitative analyses of myocardial perfusion PET studies using (13)N-ammonia.
abstract: BACKGROUND
  The impact of time-of-flight (TOF) in myocardial perfusion (13)N-ammonia positron emission tomography (PET) is unclear.
  
  
  RESULTS
  Twenty consecutive subjects underwent rest and adenosine stress (13)N-ammonia myocardial perfusion PET. Two sets of images were reconstructed using TOF-ordered subset expectation maximization (TOF-OSEM) and 3-dimensional row-action maximum likelihood algorithm (3D-RAMLA). Qualitative and quantitative analyses from the TOF-OSEM and 3D-RAMLA reconstructions were compared. Count profile curves revealed that TOF relatively increased the uptake of (13)N-ammonia at the lateral walls, and apical thinning was emphasized on the TOF images. Both segmental rest and stress myocardial blood flow (MBF) values were higher with TOF-OSEM use than with 3D-RAMLA use (rest MBF: 0.955 ± 0.201 vs 0.836 ± 0.185, P < .001; stress MBF: 2.149 ± 0.697 vs 2.058 ± 0.721, P < .001). The differentiation of MBF between reconstructions was more enhanced under rest conditions. Thus, segmental myocardial flow reserve (MFR) observed using TOF-OSEM reconstruction was lower than that observed using 3D-RAMLA (2.25 ± 0.57 vs 2.46 ± 0.75, P < .001). No remarkable differences were observed between segmental and territorial results.
  
  
  CONCLUSIONS
  TOF increased lateral wall counts and emphasized apical thinning. Quantitatively, TOF reconstruction showed increased MBF, especially under relatively low perfusion conditions.
authors.affiliation: Department of Radiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan. tk2@nms.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tomiyama
authors.affiliation: Clinical Imaging Center for Healthcare, Nippon Medical School, Tokyo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ishihara
authors.affiliation: Clinical Imaging Center for Healthcare, Nippon Medical School, Tokyo, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Suda
authors.affiliation: Clinical Imaging Center for Healthcare, Nippon Medical School, Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kanaya
authors.affiliation: Clinical Imaging Center for Healthcare, Nippon Medical School, Tokyo, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Sakurai
authors.affiliation: Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Takano
authors.affiliation: NM & RT System Sales Division, Hitachi Medical Corporation, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nitta
authors.affiliation: Clinical Imaging Center for Healthcare, Nippon Medical School, Tokyo, Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Hakozaki
authors.affiliation: Department of Radiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan.
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Kumita
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000641:Ammonia / Q000737:chemistry*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D003326:Coronary Circulation; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging; D009590:Nitrogen Radioisotopes / Q000737:chemistry*; D015588:Observer Variation; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000737:chemistry*; D012044:Regression Analysis
chemical_list: D009590:Nitrogen Radioisotopes; D019275:Radiopharmaceuticals; D000641:Ammonia
keywords: 13N-ammonia; Myocardial blood flow (MBF); Myocardial flow reserve (MFR); Positron emission tomography (PET); Time-of-flight (TOF)