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Re: MR-compatible headphones: Koss medical ESP 900

Dear Yoshiko:
We are currently using the Koss headphones and are reasonably pleased
with them. Others I know have been less enamoured. There are several
modifications that various labs have implemented, mainly to improve
sound isolation and reduce susceptibility artifact. I have prepared a
narrated PowerPoint presentation on the general topic of auditory fMRI
which should be posted in the online methodology seminars series at
NCRRN.org in the next two weeks.  This will have a discussion not not
only of the Koss headphones but other alternatives for auditory
presentation in fMRI environments. However, I can summarize some of the
changes that have been implemented to the Koss headphones here.
Firstly, it is common to remove the electrostatic transducers from the
factory enclosures and fit them into MRI compatible ear defenders to
improve sound isolation. Some labs have utilized Bilsom ear defenders
while we have found that a pair of 3M ear defenders is satisfactory.
This can improve isolation from scanner noise by 30+dB. The unmodified
Koss headphones produce a modest amount of susceptibility artifact,
probably oweing to residual copper wiring. So, some labs have replaced
the copper wiring to the transducers with carbon fiber cable.  Thirdly,
some labs have installed MRI compatible resistors. These modifications
are described by Featherstone and colleagues from the Institute of
Neurology in London. They have been working on developing and testing
various modifications to these units and have presented their findings
at some imaging meetings. Hope this is helpful.


Gerry A. Stefanatos, D. Phil.
Director, Cognitive Neurophysiology Laboratory
Moss Rehab Research Institute
Albert Einstein Medical Center
1200 W. Tabor Rd.
Philadelphia, PA 19141
Tel: (215) 456-5962
Fax: (215) 456-5926
>>> Yoshiko Yamada <yyamada@DARKWING.UOREGON.EDU> 11/08/04 6:58 PM >>>

I'm wondering if anyone on this list is using or knows someone (or a
who is using Koss 'medifcal ESP 900', which is a model of MR-compatible
headphones, for auditory fMRI studies.

When I talked to a sales rep at Koss, I was told that although this
is MR-compatible, each lab makes a bit of modification to meet their
needs.  We are wondering what kind of modification is made and why since
sales rep didn't know the details about what was done to the headphones.

Our lab has been looking for a set of MR-compatible electrostatic
headphones for auditory language fMRI studied and considering purchasing
this model, but we'd like to gether more information about compatibility
of the headphones with fMR image acquisition.

Thank you for your info!