title: Importance of Defect Detectability in Positron Emission Tomography Imaging of Abdominal Lesions.
abstract: OBJECTIVE
  This study was designed to assess defect detectability in positron emission tomography (PET) imaging of abdominal lesions.
  
  
  METHODS
  A National Electrical Manufactures Association International Electrotechnical Commission phantom was used. The simulated abdominal lesion was scanned for 10 min using dynamic list-mode acquisition method. Images, acquired with scan duration of 1-10 min, were reconstructed using VUE point HD and a 4.7 mm full-width at half-maximum (FWHM) Gaussian filter. Iteration-subset combinations of 2-16 and 2-32 were used. Visual and physical analyses were performed using the acquired images. To sequentially evaluate defect detectability in clinical settings, we examined two middle-aged male subjects. One had a liver cyst (approximately 10 mm in diameter) and the other suffered from pancreatic cancer with an inner defect region (approximately 9 mm in diameter).
  
  
  RESULTS
  In the phantom study, at least 6 and 3 min acquisition durations were required to visualize 10 and 13 mm defect spheres, respectively. On the other hand, spheres with diameters ≥17 mm could be detected even if the acquisition duration was only 1 min. The visual scores were significantly correlated with background (BG) variability. In clinical settings, the liver cyst could be slightly visualized with an acquisition duration of 6 min, although image quality was suboptimal. For pancreatic cancer, the acquisition duration of 3 min was insufficient to clearly describe the defect region.
  
  
  CONCLUSIONS
  The improvement of BG variability is the most important factor for enhancing lesion detection. Our clinical scan duration (3 min/bed) may not be suitable for the detection of small lesions or accurate tumor delineation since an acquisition duration of at least 6 min is required to visualize 10 mm lesions, regardless of reconstruction parameters. Improvements in defect detectability are important for radiation treatment planning and accurate PET-based diagnosis.
authors.affiliation: Division of Radiology, Public Central Hospital of Matto Ishikawa, Hakusan, Japan; Department of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: PET Imaging Center, Public Central Hospital of Matto Ishikawa, Hakusan, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Department of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Masahisa
authors.initials: M
authors.lastname: Onoguchi
authors.affiliation: Division of Radiology, Public Central Hospital of Matto Ishikawa, Hakusan, Japan.
authors.forename: Haruki
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: Division of Radiology, Public Central Hospital of Matto Ishikawa, Hakusan, Japan.
authors.forename: Tetsu
authors.initials: T
authors.lastname: Nakaichi
authors.affiliation: PET Imaging Center, Public Central Hospital of Matto Ishikawa, Hakusan, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Tsuji
authors.affiliation: Department of Nuclear Medicine, Kanazawa University Hospital, Kanazawa, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nakajima
keywords: Abdominal Lesion; Defect Detectability; Positron Emission Tomography