title: Radiofrequency-induced heating near fixed orthodontic appliances in high field MRI systems at 3.0 Tesla.
abstract: OBJECTIVE
  To assess radiofrequency (RF)-induced heating of fixed orthodontic appliances during acquisition of three different sequences in magnetic resonance imaging (MRI) at 3 Tesla.
  
  
  METHODS
  Ten commonly used fixed orthodontic appliances were investigated utilizing a phantom head and simulating the in vivo intraoral situation. A 3 Tesla MRI system (Intera, Philips Medical Systems, Best, The Netherlands) was used to acquire T1w spin-echo (T1 SE), T1w turbo spin-echo (T1 TSE) and T1w gradient-echo (T1 GRE) sequences in axial orientation. Continuous temperature measurement was performed with a dedicated four channel fluoroptic thermometry system. For each orthodontic appliance temperature probes were placed at three predefined sites in order to perform temperature measurements during MR imaging. The fourth temperature probe was fixed to the neck of the phantom head and served as the reference. Mean temperature alterations were determined for all appliances.
  
  
  RESULTS
  Temperature elevations ranged from -0.3 degrees C to 0.2 degrees C and were negligible for all orthodontic appliances investigated. There was no difference in mean temperature alteration for any of the three imaging sequences.
  
  
  CONCLUSIONS
  Based on the data of our experimental study the radiofrequency-induced heating of orthodontic brackets during high field MRI at 3 Tesla can be categorized as negligibly low. Even the clinical routine examination of the head at 3 Tesla using high-energetic pulse sequences can be applied without hesitation in patients with fixed orthodontic appliances.
authors: Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. mregier@uke.uni-hamburg.de
authors: Marc
authors: M
authors: Regier
authors: Jörn
authors: J
authors: Kemper
authors: Michael G
authors: MG
authors: Kaul
authors: Markus
authors: M
authors: Feddersen
authors: Gerhard
authors: G
authors: Adam
authors: Bärbel
authors: B
authors: Kahl-Nieke
authors: Arndt
authors: A
authors: Klocke
mesh_terms: D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D019544:Equipment Failure Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging; D009055:Mouth / Q000502:physiology* / Q000528:radiation effects*; D009967:Orthodontic Appliances; D019047:Phantoms, Imaging; D011846:Radio Waves; D013696:Temperature