title: Metallic artifacts caused by dental metal prostheses on PET images: a PET/CT phantom study using different PET/CT scanners.
abstract: OBJECTIVE
  The objective of this study was to investigate the effects of computed tomography (CT) artifacts caused by dental metal prostheses on positron emission tomography (PET) images.
  
  
  METHODS
  A dental arch cast was fixed in a cylindrical water-bath phantom. A spherical phantom positioned in the vicinity of the dental arch cast was used to simulate a tumor. To simulate the tumor imaging, the ratio of the (18)F-fluoro-deoxy-glucose radioactivity concentration of the spherical phantom to that of the water-bath phantom was set at 2.5. A dental bridge composed of a gold-silver-palladium alloy on the right mandibular side was prepared. A spherical phantom was set in the white artifact area on the CT images (site A), in a slightly remote area from the white artifact (site B), and in a black artifact area (site C). A PET/CT scan was performed with and without the metal bridge at each simulated tumor site, and the artifactual influence was evaluated on the axial attenuation-corrected (AC) PET images, in which the simulated tumor produced the strongest accumulation. Measurements were performed using three types of PET/CT scanners (scanners 1 and 2 with CT-based attenuation correction, and 3 with Cesium-137 ((137)Cs)-based attenuation correction). The influence of the metal bridge was evaluated using the change rate of the SUVmean with and without the metal bridge.
  
  
  RESULTS
  At site A, an overestimation was shown (scanner 1: +5.0% and scanner 2: +2.5%), while scanner 3 showed an underestimation of -31.8%. At site B, an overestimation was shown (scanner 1: +2.1% and scanner 2: +2.0%), while scanner 3 showed an underestimation of -2.6%. However, at site C, an underestimation was shown (scanner 1: -25.0%, scanner 2: -32.4%, and scanner 3: -8.4%).
  
  
  CONCLUSIONS
  When CT is used for attenuation correction in patients with dental metal prostheses, an underestimation of radioactivity of accumulated tracer is anticipated in the dark streak artifact area on the CT images. In this study, the dark streak artifacts of the CT caused by metallic dental prostheses may cause false negative finding of PET/CT in detecting small and/or low uptake tumor in the oral cavity.
authors.affiliation: Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shimamoto
authors.forename: Naoya
authors.initials: N
authors.lastname: Kakimoto
authors.forename: Kouichi
authors.initials: K
authors.lastname: Fujino
authors.forename: Seiki
authors.initials: S
authors.lastname: Hamada
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: Shumei
authors.initials: S
authors.lastname: Murakami
authors.forename: Souhei
authors.initials: S
authors.lastname: Furukawa
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D016477:Artifacts; D017266:Dental Prosthesis; D006801:Humans; D008670:Metals; D009369:Neoplasms / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D008670:Metals