Are you sure that the value of the "PhaseEncodingLines" string is the same
as the first value of "AcquisitionMatrixText", in instances of GRAPPA,
partial Fourier, etc?
cheers,
-MH
--
Michael Harms, Ph.D.
-----------------------------------------------------------
Conte Center for the Neuroscience of Mental Disorders
Washington University School of Medicine
Department of Psychiatry, Box 8134
660 South Euclid Ave. Tel: 314-747-6173
St. Louis, MO 63110 Email: [log in to unmask]
On 3/12/14 2:05 PM, "Joel Bruss" <[log in to unmask]> wrote:
>Thanks for that, Matt. I'd read something similar before but the DICOM
>I have has "Unimplemented" in the 0019,1028 header field. 0051,100b
>doesn't exist as well. I had to use the ascii header to grab the same
>information:
>
>dcmPic=`ls *dcm | sort -t. -k 5 -n | head -1 | tail -1`
>BWpe=`strings $dcmPic | grep -A1 "BandwidthPerPixelPhaseEncode" | head
>-2 | tail -1`
>dimpe=`strings $dcmPic | grep -A1 "PhaseEncodingLines" | head -1 | awk
>'{print $3}'`
>dwellTime=`echo $BWpe $dimpe | awk '{print (1/($1*$2))}'`
>
>Hope this helps someone else.
>
>-Joel
>
>On 03/12/2014 01:58 PM, Matt Glasser wrote:
>> For Siemens:
>>
>> #Echo Spacing or Dwelltime of fMRI image in seconds =
>> 1/(BandwidthPerPixelPhaseEncode * # of phase encoding samples): DICOM
>> field (0019,1028) = BandwidthPerPixelPhaseEncode, DICOM field
>>(0051,100b)
>> AcquisitionMatrixText first value (# of phase encoding samples)
>>
>> I believe this accounts for GRAPPA factors and partial fourier does not
>> affect the echo spacing.
>>
>> Peace,
>>
>> Matt.
>>
>> On 3/12/14 1:33 PM, "Estrid Jakobsen" <[log in to unmask]> wrote:
>>
>>> Dear all,
>>>
>>> I am trying to do fieldmap correction of 7T EPI data using FUGUE, which
>>> requires input of a variable, 'dwell time'. If I've understood
>>>correctly,
>>> this variable actually refers to the 'effective echo spacing' (rather
>>> than simply the dwell time listed in the DICOM of the EPI data) but
>>>there
>>> seem to be several methods to calculate it.
>>>
>>> 1. DwellTime = (EchoSpacing/GRAPPA)-1
>>>
>>> 2. DwellTime = EchoSpacing*((MatrixLines*PartialFourier/GRAPPA)-1)
>>>
>>> Which of these options (if either) is correct for running FUGUE?
>>>
>>> Many thanks!
>>>
>>> Estrid
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