Less than an hour of 3T MRI exposure could result in weeks of altered hearing ability, even if a patient wears hearing protection during the exam, researchers reported in Radiology this month.
MRIs are common diagnostic tools in the radiologic world, but a strong machine like a 3T MR system can reach sound pressure levels of up to 130.7 decibels during an exam, lead author Chao Jin, PhD, and colleagues wrote. To avoid hearing loss—which doesn’t always happen—clinicians recommend patients are fitted with earplugs, earmuffs or sponge mats before undergoing an MRI.
“The acoustic noise [of] MR imaging remains a well-recognized issue of concern for the person who is imaged, and the noise-induced hearing loss is also a public health concern,” Jin and co-authors said. “Despite the use of hearing protection, healthy volunteers who routinely participate in clinical research may have an increased risk of hearing loss, potentially causing permanent hearing threshold shift.”
Jin’s team studied 26 young adults, all of whom had clean bills of health at baseline. Each participant underwent 51-minute 3T MR neuroimaging scans, which included T1-weighted 3D gradient-echo sequence, T2-weighted fast spin-echo sequence, diffusion-tensor imaging, diffusion-kurtosis imaging, T2-weighted 3D multiecho gradient-echo sequence and blood oxygen level-dependent imaging. Automated auditory brainstem response (ABR) was used to calculate each patient’s hearing threshold 24 hours before, 20 minutes after and 25 days after the MRI, and all individuals wore earplugs and motion-refraining sponge mats during the procedure.
Automated ABR results showed a significantly increased mean threshold shift of five decibels—a change that still left patients below the temporary threshold shift of 40 to 50 decibels associated with cochlear nerve damage—immediately after the imaging exam, the authors wrote. Thirty-two ears and 23 ears were found to present threshold increases of 5 decibels or more and 10 decibels or more, respectively.
The same ABR statistics were restored to baseline values 25 days after the exam, suggesting a noise-induced threshold shift that was temporary, Jin et al. said.
“This finding further supports the importance of appropriate hearing protection in clinical practice,” the authors wrote. “Furthermore, developing protective apparatus with higher level of noise attenuation is desired for reducing the potential risk of hearing loss.”