title: Coincidence imaging using 2 dual-head gamma-camera systems, with and without attenuation correction.
abstract: OBJECTIVE
  Coincidence imaging enhances the potential for imaging a greater number of patients with 18F-FDG in centers that do not have dedicated PET systems. The purpose of this study was to compare, in a clinical setting, coincidence imaging for tumor detection using 2 dual-head gamma-camera systems, one equipped with a 5/8-in. (16 mm) detector (CoDe5) and the other equipped with a newly designed 1-in. (25.4 mm) detector (CoDe8) with an x-ray tube installed in its gantry.
  
  
  METHODS
  Thirty consecutive patients were studied by both systems during the same visit and had 4 image sets for comparison: CoDe5 without attenuation correction (CoDe5NC), CoDe8 with (CoDe8AC) and without (CoDe8NC) attenuation correction, and fused coincidence-CT images. The target-to-background ratio (T/Bg ratio) and target-to-nontarget ratio (T/NT ratio) were calculated for each tumor site.
  
  
  RESULTS
  On visual assessment, 61 tumor sites were detected on CoDe8AC images. Of these, 59 (97%) were detected on CoDe8NC and 54 (88%) were detected on CoDe5NC images. Fused images improved image interpretation in 10 patients (33%) compared with coincidence images alone. Data added by fusion were of clinical relevance in 6 patients (20%). On quantitative assessment, the number of accepted events by the CoDe8 was significantly higher than that by CoDe5 (5.21 +/- 1.46 million vs. 1.27 +/- 0.36 million, P <0.001). When comparing CoDe5 with CoDe8 images without attenuation correction, the T/Bg and T/NT ratios were significantly higher on the CoDe8 images (P <0.0005 and P <0.0005, respectively). When comparing CoDe8 images with and without attenuation correction, the T/Bg ratio was better on the attenuation-corrected images (P <0.0005).
  
  
  CONCLUSIONS
  Coincidence imaging with 1-in. detectors and attenuation correction improve image quality and, to a lesser extent, the tumor detection rate compared with the 5/8-in. detectors and noncorrected images. The data added by fusion of coincidence images to CT findings were clinically relevant in 20% of the patients.
authors.affiliation: Department of Nuclear Medicine, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel. evensap@tasmc.health.gov.il
authors.forename: Einat
authors.initials: E
authors.lastname: Even-Sapir
authors.forename: Bella
authors.initials: B
authors.lastname: Yuzefovich
authors.forename: Elka
authors.initials: E
authors.lastname: Miller
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Bouhnik
authors.forename: Osnat
authors.initials: O
authors.lastname: Zak
authors.forename: Hedva
authors.initials: H
authors.lastname: Lerman
authors.forename: Genady
authors.initials: G
authors.lastname: Lievshitz
authors.forename: Charles
authors.initials: C
authors.lastname: Levin
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis*; D005260:Female; D019788:Fluorodeoxyglucose F18; D015902:Gamma Cameras; D005770:Gastrointestinal Neoplasms / Q000175:diagnosis*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008175:Lung Neoplasms / Q000175:diagnosis*; D008228:Lymphoma, Non-Hodgkin / Q000175:diagnosis*; D008297:Male; D008545:Melanoma / Q000175:diagnosis*; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000175:diagnosis*; D019275:Radiopharmaceuticals; D014055:Tomography, Emission-Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18