Can MRI Noise Level Be Turned Down to a "Child's Level"?

[su bernadette]

Hi Dr Nagler,

I read somewhere on Tinnitus Talk that it was possible to ask for the noise level of an MRI scanning machine to be turned down to a child's level.

Can you tell me if this is correct?

Thank you,

Susanne

 

[Dr. Nagler]

I read somewhere on Tinnitus Talk that it was possible to ask for the noise level of an MRI scanning machine to be turned down to a child's level. Can you tell me if this is correct?

It's a bit complicated, Susanne. There are a number of different reasons that a doctor might order an MRI.

For infants and very young children, MRIs are generally done for assessment of myelenation in patients with significant developmental delays. The greatest concern in terms of accuracy and sensitivity in such studies is the introduction of artifact due to movement of the very young patient. Understandably the children must be sedated (so they do not move), and the noise of the machine is generally turned down so they are not startled from their sedated state (and hence move!) For reasons too complex for me to fully understand, turning down the noise decreases the sensitivity of the study somewhat because in order to turn down the noise you need to decrease the amount of electricity running through the gradient coils, which is what produces the noise and makes the study possible. So it's a trade-off: a less sensitive study but no motion artifact.

In the case of the evaluation of adults with unexplained unilateral tinnitus, MRIs are typically ordered to rule out an acoustic neuroma, which is a benign growth along an auditory nerve. Importantly, doctors want the most sensitive and accurate study possible because acoustic neuromas grow, and the smaller an acoustic neuroma is at the time of discovery, the greater the therapeutic options and the higher the likelihood of treatment success. [That is why the study is usually done both with and without contrast - to increase the possibility of picking up a very small acoustic neuroma if one is present.] Now, since lowering the sound level would decrease the accuracy and sensitivity of the study, it makes much more sense (to me, anyway) for the adult patient (who will lie still when asked), to use very good ear protection instead of turning the volume down "to a child's level."

Stephen M. Nagler, M.D.