title: [Evaluation of different breathing and contrast-protocols concerning quality and alignment in 18F-FDG PET/CT].
abstract: OBJECTIVE
  The purpose of this study was to establish a reliable and simple parameter for alignment evaluation and the evaluation and optimization of state-of-the-art contrast-enhanced examination protocols for (18)F FDG-PET/CT.
  
  
  METHODS
  44 consecutive patients were referred to 4 examination protocols. Group A and B underwent single-phase, contrast-enhanced CT (90 s delay) performed either during free shallow breathing (FA; group A) or normal expiration (NormExp; group B). Groups C and D underwent arterial and portal venous multiphase examinations performed during FA (group C) or during NormExp (group D) followed by a low-dose CT scan for attenuation correction. Organ displacement in the cranio-caudal direction was correlated with a 3D-vectorial shift. For alignment evaluation discrepancies with respect to size and liver location, the spleen and kidneys were calculated. Additionally, the groups were compared with regard to the presence of CT artifacts.
  
  
  RESULTS
  Cranio-caudal organ shift and 3D-vectorial shift showed a high correlation (r > 0.8). Single-phase CT scans performed during NormExp yielded better image quality (p < 0.001) and alignment (p < 0.01 for liver, spleen and right kidney) than those performed during FA. Differences in organ size did not differ during FA and NormExp. Depending on the evaluated organ, breathing and contrast protocol misalignment was in the cranio-caudal direction 0-27 mm (mean: 6.8; standard deviation: +/- 4.9) in multiphase CT compared to 0 - 11 mm (mean: 4.5 +/- 2.3) in single-phase examinations.
  
  
  CONCLUSIONS
  1. Organ shift in the cranio-caudal direction is a good and simple parameter for alignment evaluation. 2. Alignment and CT quality are best in expiration protocols. 3. Despite comparatively low alignment quality, integrated multiphase CT examinations show acceptable quality and alignment.
authors.affiliation: Diagnostische Radiologie, Eberhard-Karls-Universität Tübingen. monika.vogel@med.uni-tuebingen.de
authors.forename: M N
authors.initials: MN
authors.lastname: Vogel
authors.forename: K
authors.initials: K
authors.lastname: Brechtel
authors.forename: M D
authors.initials: MD
authors.lastname: Klein
authors.forename: P
authors.initials: P
authors.lastname: Aschoff
authors.forename: M
authors.initials: M
authors.lastname: Horger
authors.forename: S
authors.initials: S
authors.lastname: Eschmann
authors.forename: R
authors.initials: R
authors.lastname: Bares
authors.forename: C D
authors.initials: CD
authors.lastname: Claussen
authors.forename: C
authors.initials: C
authors.lastname: Pfannenberg
mesh_terms: D000368:Aged; D000465:Algorithms; D016477:Artifacts; D016009:Chi-Square Distribution; D002985:Clinical Protocols; D003287:Contrast Media; D003627:Data Interpretation, Statistical; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011169:Portal Vein / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D012119:Respiration; D013154:Spleen / Q000000981:diagnostic imaging*; D036542:Tomography, Spiral Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18