Hi all,
We experienced that 3D EPI (or EVI) and PRESTO has substantially reduced acoustic noise, especially when combined with SENSE parallel acquisition. It is a subjective impression, no dB was measured. But subjects are much better able to understand sounds from an MR headphone with those sequences as compared to conventional 2DEPI. I think that the lack of a slice selection gradient for 3D acquisition in combination with a more continous readout (for PRESTO, eg hardly any 'dead time') does the trick.
SENSE is mainly a Philips thing though, I think it is called Phased-array for Siemens.
But be careful though, 3D and SENSE have its own pros and cons.
Cheers,
Bas
--------------------------------------------------
Dr. S.F.W. Neggers
Division of Brain Research
Rudolf Magnus Institute for Neuroscience
Utrecht University Medical Center
Visiting : Heidelberglaan 100, 3584 CX Utrecht
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> -----Oorspronkelijk bericht-----
> Van: SPM (Statistical Parametric Mapping)
> [mailto:[log in to unmask]] Namens Jonathan Peelle
> Verzonden: maandag 21 december 2009 12:59
> Aan: [log in to unmask]
> Onderwerp: Re: [SPM] "silent" EPI
>
> Dear Diederick, others:
>
> A paper from last year by Schmitter et al. introduced a new
> sequence which significantly reduces the amount of acoustic
> noise through a combination of modifications (several of
> which have been mentioned in this discussion):
>
> Schmitter S, Diesch E, Amann M, Kroll A, Moayer M, Schad LR
> (2008) Silent echo-planar imaging for auditory FMRI. Magnetic
> Resonance Materials in Physics, Biology and Medicine 21, 317-325.
> http://dx.doi.org/10.1007/s10334-008-0132-4
>
> In our experience this sequence is noticeably quieter than
> our standard EPI sequence, and in a speech task resulted in
> significantly greater acoustic-related activity in primary
> auditory regions.
> However, as you would expect due to the use of a longer TE,
> there is greater signal dropout in regions typically
> associated with susceptibility effects.
>
> One other comment: reducing scanner noise using
> headphones/earplugs can only do so much, as there is a
> considerable amount of sound transmitted via bone conduction,
> which any hearing protection won't be able to reduce.
>
> That being said, I suspect in terms of people falling asleep,
> as long as the sound is continuous you won't have any
> problems...at least, given how hard it is to get subjects NOT
> to fall asleep sometimes, even with standard sequences! ;-)
>
> Hope this helps,
> Jonathan
>
>
> On Mon, Dec 21, 2009 at 9:03 AM, Torben Ellegaard Lund
> <[log in to unmask]> wrote:
> > 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
> >>>
> >>>
>
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