title: Positron emission tomography (PET) attenuation correction artefacts in PET/CT and PET/MRI.
abstract: OBJECTIVE
  To compare the effect of implanted medical materials on (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)/MRI using a Dixon-based segmentation method for MRI-based attenuation correction (MRAC), PET/CT and CT-based attenuation-corrected PET (PETCTAC).
  
  
  METHODS
  12 patients (8 males and 4 females; age 58±11 years) with implanted medical materials prospectively underwent whole-body (18)F-FDG PET/CT and PET/MRI. CT, MRI and MRAC maps as well as PETCTAC and PETMRAC images were reviewed for the presence of artefacts. Their morphology and effect on the estimation of the (18)F-FDG uptake (no effect, underestimation, overestimation compared with non-corrected images) were compared. In PETMRAC images, a volume of interest was drawn in the area of the artefact and in a reference site (contralateral body part); the mean and maximum standardised uptake values (SUVmean; SUVmax) were measured.
  
  
  RESULTS
  Of 27 implanted materials (20 dental fillings, 3 injection ports, 3 hip prostheses and 1 sternal cerclage), 27 (100%) caused artefacts in CT, 19 (70%) in T1 weighted MRI and 17 (63%) in MRAC maps. 20 (74%) caused a visual overestimation of the (18)F-FDG uptake in PETCTAC, 2 (7%) caused an underestimation and 5 (19%) had no effect. In PETMRAC, 19 (70%) caused spherical extinctions and 8 (30%) had no effect. Mean values for SUVmean and SUVmax were significantly decreased in artefact-harbouring sites (p<0.001).
  
  
  CONCLUSIONS
  Contrary to PET attenuation correction artefacts in PET/CT, which often show an overestimation of the (18)F-FDG uptake, MRAC artefacts owing to implanted medical materials in most cases cause an underestimation.
  
  
  CONCLUSIONS
  Being aware of the morphology of artefacts owing to implanted medical materials avoids interpretation errors when reading PET/MRI.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Medical Faculty, University of Dusseldorf, Dusseldorf, Germany. Christian.buchbender@med.uni-duesseldorf.de
authors.forename: C
authors.initials: C
authors.lastname: Buchbender
authors.forename: V
authors.initials: V
authors.lastname: Hartung-Knemeyer
authors.forename: M
authors.initials: M
authors.lastname: Forsting
authors.forename: G
authors.initials: G
authors.lastname: Antoch
authors.forename: T A
authors.initials: TA
authors.lastname: Heusner
mesh_terms: D016477:Artifacts; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008670:Metals; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods*; D019736:Prostheses and Implants; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging / Q000379:methods
chemical_list: D008670:Metals; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18