title: [Improvement of quantitative accuracy using phase-based respiratory-gated PET/CT in phantom and clinical studies].
abstract: OBJECTIVE
  The present study aimed at determining the quantitative accuracy of phase-based respiratory-gated PET/CT imaging using phantom and clinical studies.
  
  
  METHODS
  The effects of target size, target-to-background ratio (TBR), and respiratory motion on PET images were estimated using a NEMA body phantom comprising six spheres (diameter 10-37mm) in a solution of F-18 of three different TBRs (4, 6, 8). The phantom was moved in a superior-inferior direction at motion displacements of 0, 10, 20 and 30 mm. Stationary images of the phantom as well as non-gated (3D) and gated (4D) images of the phantom while moving were reconstructed and the recovery coefficient (RC) of individual spheres was calculated from each image. We then determined the RC improvement rate to evaluate improvements conferred by 4D-PET/CT. We retrospectively analyzed data from 14 patients with lung cancer who were examined by 3D- and 4D-PET/CT. Each lesion on the 3D-PET/CT and each of the five phases of the 4D-PET/CT were analyzed.
  
  
  RESULTS
  Larger motion displacement and TBR resulted in increased RC degradation for small spheres. The RC improvement rate showed that 4D acquisition improved the RC of spheres with larger motion displacement exceeding 13 mm in diameter. 4D-PET/CT alone can reduce the effects of motion blurring, but partial volume effects may still be the dominant source of quantitative inaccuracy for small lesions. The trends of phantom and clinical studies for evaluating the improvement rate were similar.
  
  
  CONCLUSIONS
  4D-PET/CT significantly improved the quantitative accuracy of PET images particularly when larger motion displacement exceeded 17mm in diameter such as in lung cancer.
authors.affiliation: Department of Diagnostic Radiology Center, Cancer Institute Hospital of Japanese Foundation for Cancer Research.
authors.forename: Kenta
authors.initials: K
authors.lastname: Miwa
authors.forename: Kei
authors.initials: K
authors.lastname: Wagatsuma
authors.forename: Takuro
authors.initials: T
authors.lastname: Umeda
authors.forename: Noriaki
authors.initials: N
authors.lastname: Miyaji
authors.forename: Taisuke
authors.initials: T
authors.lastname: Murata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Osawa
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Takiguchi
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Koizumi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sasaki
mesh_terms: D000368:Aged; D005260:Female; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*