Dear Diederick,
In Figure 2 of Foerster et al. 2005 there is actually a plot of
vibration amplitude as a function of EPI-readout bandwidth. As you can
se there can be a 12 dB difference in vibrational amplitude between
loud and quiet EPI protocols. The plot is for a Sonata gradient coil
on a 4T varian system, so you should make your own investigations
specific to the GE and Philips.
Best
Torben
Foerster et al. Magnetic field shift due to mechanical vibration in
functional magnetic resonance imaging. Magnetic resonance in
medicine : official journal of the Society of Magnetic Resonance in
Medicine / Society of Magnetic Resonance in Medicine (2005) vol. 54
(5) pp. 1261-7
http://dx.doi.org/10.1002/mrm.20695
Den 20/12/2009 kl. 22.41 skrev David Carmichael:
> Dear Diederick,
>
> I remember previously that running with sinusoidal rather than
> trapezoidal wave forms for the EPI readout can be benificial it can
> reduce the noise level and make it narrower in frequency so then
> changing the echospacing can be used to find the gradients
> vibrational minimum for your particular systems in addition to the
> steps below.
>
> Best regards
> David Carmichael
>
> ps hi helmut!!
>
>
> Quoting Helmut Laufs <[log in to unmask]>:
>
>>
>> Dear Diederick,
>>
>> According to our experience, the actual dB are not as relevant as
>> e.g. a really contiuous and hence monotonous sound (i.e. inter-
>> slice and inter-volume gap should be identical), proper sound
>> protection and bedding of the patient, time of day and anxiety
>> level of the subject.
>>
>> Hope this helps,
>>
>> Bw,
>>
>> Helmut
>>
>> -------------
>>
>>
>> Hi all,
>> A question not relating to software, but perhaps someone would be
>> wiling to help us out.
>> We
>> are trying to heave subjects fall asleep during fMRI acq, we would
>> like
>> to have a more "silent" EPI sequence. There are quite some
>> publications
>> from groups that have a relatively silent EPI sequence running on a
>> Siemens machine. We have a 3T GE Signa HD and a 3T Philips Intera
>> available. We have been playing around with the factory provided
>> silent
>> mode options on both, but are not particularly happy with the results
>> (high TR/TE/slice thickness, not much noise reduction). Does anyone
>> have a reasonably performing "silent" EPI on a GE or Philips system
>> running? Can anyone recommend what settings to use?
>> Thanks,
>> Diederick
>>
>>
>> _________________________________________________________________
>> Windows Live: Make it easier for your friends to see what you?re
>> up to on Facebook.
>> http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_2:092009
|