Multi-Echo EPI

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.

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Numaris/4 VA21B

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Siemens 4A21 manual Sequences and Protocols, General Remarks, New Parameters
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4A21 specifications

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