Evaluation of MR safety of a set of canine ear defenders (MuttMuffs®) at 1 T

Previous studies have indicated that loud noise produced during MR scanning is hazardous for human patients. Although loud noise can also be harmful to canine patients in MRI, ear protection is not routinely provided. The purpose of this study was to test the safety of a set of commercially available canine ear defenders (MuttMuffs®) during MRI scanning at 1 T. A metal fastening ring was removed and replaced with a plastic washer prior to testing. Torque, translation, heating and artifact production were tested. No torque, translation, or excessive heating were detected. No artifacts were observed. Clinical use demonstrated additional benefits of improved immobilisation of the dog, with no effect on signal-to-noise ratio. Results from this study indicate that following replacement of the metal ring with one made of plastic, these canine ear defenders are suitable for use at 1 T. The author recommends the use of ear defenders during canine MRI scans in order to reduce the risk of hearing damage, reduce the dose needed for anaesthetic maintenance and reduce the need for repeated MRI sequences due to movement of the dog.