Do the images look the same? If not, they're probably still different
echo times. The Siemens default echo time difference at 3T is 2.46ms.
Peace,
Matt.
On 11/2/13 3:21 PM, "Jesper Andersson" <[log in to unmask]>
wrote:
>Dear Eric,
>
>one way to find out if the data has been collected with the same echo
>time would be to use it to generate "fake" fieldmaps using some arbitrary
>number as echo time difference. If the echo time was the same the
>resulting fieldmap would have no structure and look like just random
>noise. If on the other hand the data was acquired with different echo
>times it will have the same general appearance as a regular field map and
>you'll know it is worthwhile to try and find out the true echo time
>difference.
>
>Jesper
>
>On 2 Nov 2013, at 18:38, Eric Walden <[log in to unmask]> wrote:
>
>> Hello all. I inherited some data from a research assistant at fmrib
>>who has since moved on. I am trying to make sense of the field maps for
>>B0 correction. I have two files called gre_field_mapping_005 and
>>gre_field_mapping_006. However, when I look at the DICOM headers, both
>>show an echo time of 7.65. However, I thought that you were supposed to
>>have two different echo times--other gre_field_mappings that I have have
>>different echo times.
>>
>> Does this mean that there was an error in taking the field mappings?
>>
>> gre_field_mapping_005 header
>>
>> Series description: gre_field_mapping
>> Manufacturer: SIEMENS
>> Model name: Verio
>> Study id: 1
>> Series number: 5
>> Repetition time (ms): 400
>> Echo time (ms): 7.65
>> Flip angle: 60
>> Number of averages: 1
>> Slice thickness (mm): 3
>> Slice spacing (mm): 3.75
>> Image columns: 64
>> Image rows: 64
>> Phase encoding direction: ROW
>> Voxel size x (mm): 3
>> Voxel size y (mm): 3
>> Number of volumes: 1
>> Number of slices: 1
>> Number of files: 1
>> Number of frames: 14947920
>> Slice duration (ms) : 50602.5
>> Orientation: tra
>>
>> gre_field_mapping_006 header
>> Series description: gre_field_mapping
>> Manufacturer: SIEMENS
>> Model name: Verio
>> Study id: 1
>> Series number: 5
>> Repetition time (ms): 400
>> Echo time (ms): 7.65
>> Flip angle: 60
>> Number of averages: 1
>> Slice thickness (mm): 3
>> Slice spacing (mm): 3.75
>> Image columns: 64
>> Image rows: 64
>> Phase encoding direction: ROW
>> Voxel size x (mm): 3
>> Voxel size y (mm): 3
>> Number of volumes: 1
>> Number of slices: 1
>> Number of files: 1
>> Number of frames: 12160192
>> Slice duration (ms) : 50602.5
>> Orientation: tra
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