Siemens MULTI-ECHO EPI 4A21 - Manual (Page 7)

Multi-Echo EPI
Page 7 of 9 Numaris/4 VA21B
3 Sequences and Protocols
3.1 General Remarks
Since the sequence is derived from the standard EPI sequence, most of the user
interface and features are identical to this method. Due to the large number of images
created in a short time, the images are saved to the database in the mosaic format.
One mosaic-image contains all slices of one echo time for one repetition. Repetitions
can be saved in multiple series if desired (Contrast card or BOLD card).
Prior to the first run of the sequence, the 3D standard shim procedure is performed to
ensure best field homogeneity. As with standard EPI this option cannot be disabled.
Due to the high switching rates used in EPI imaging, the peripheral nerve stimulation
monitor will sometimes not allow the measurement to be performed with the
parameters selected. In general, a lower bandwidth will decrease the stimulation and
a different selection of the readout gradient may also help (read direction along L/R-
axis shows generally the lowest stimulation).
3.2 New Parameters
Number of echoes: The number of echo-images per excitation can be set on the
sequence card (part1) as the parameter contrasts. The number of echo-images can
be selected between 1 and 8. The number of TE-times is changes accordingly.
Please note that only the first echo time can be changed by the user. All other echo
times are set to the minimum value according to the remaining selected parameters.
!!Attention!!: Even echo time 1 is adjusted to longer times without warning if required
by another parameter! It is not set back to minimum if the parameter is changed back!
Please check echo time 1 after changing other timing relevant parameters of the
sequence.