Marc Regier, Presenter: Nothing to Disclose

Joern K. Kemper MD, Abstract Co-Author: Nothing to Disclose

Marcus Feddersen MD, Abstract Co-Author: Nothing to Disclose

Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose

Bärbel Kahl-Nieke MD, PhD, Abstract Co-Author: Nothing to Disclose

Arndt Klocke MD,PhD, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to assess the radio frequency (RF) induced heating near fixed orthodontic appliances during the acquisition of three different sequences in high-field magnetic resonance imaging (MRI) at 3 Tesla.

Ten commonly used fixed orthodontic appliances were investigated utilizing a head phantom and simulating the in vivo intraoral situation. In vitro testing was performed using an integrated quadrature body coil at a 3 Tesla scanner system (Intera, Philips Medical Systems, Best, the Netherlands). A T1w spin-echo (TR 150 ms; TE 25 ms; FOV 350 mm; slice thickness 4 mm; SAR 3.5 W/kg), T1w turbo spin-echo (TR 5995 ms; TE 92 ms; FOV 350 mm; slice thickness 3 mm; SAR 4 W/kg) and T1w gradient-echo (TR 4.5 ms; TE 1.7 ms; FOV 350 mm; slice thickness 5 mm; SAR 1.9 W/kg) sequence were acquired in axial orientation. For continuous temperature measurement a dedicated four channel fluoroptic thermometry system (Fotemp 4, Optocon, Dresden, Germany) was used. 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 head phantom and served as the reference. Mean temperature alterations were determined for all appliances.

Temperature elevations ranged from -0.3° to 0.2° and were negligible for all orthodontic appliances investigated. There was no difference in mean temperature alteration among the three imaging sequences performed.

Based on the results of an experimental setting, Radio frequency induced heating near orthodontic appliances does not seem to be a concern during MRI of patients undergoing orthodontic treatment.

The results of the study show, that even highfield MRI at 3T does not lead to a temperature increase near orthodontic appliances. Therefore, the evaluated appliances can be considered as safe for MRI.

Regier, M, Kemper, J, Feddersen, M, Adam, G, Kahl-Nieke, B, Klocke, A, Radiofrequency-induced Heating Near Fixed Orthodontic Appliances during Magnetic Resonance Imaging at 3.0 Tesla.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6017505.html