Multi-Echo EPI

t-Test: The online t-test and display work as in the original EPI sequence. However, the t-test only works properly when motion correction is selected! Alternatively, T2*-Maps can be processed within the BOLD-card.

3.3 Remarks on reconstruction performance

The number of images that can be acquired with the Multi-Echo EPI method is very high (up to 30 images per second for 64*64 matrix). The processing (especially T2*- Fit and Motion Correction) requires computationally intensive calculations and may required slower acquisition speeds (increased TR) to be performed online. If the reconstruction system lags behind the acquisition, the raw data is saved to disk during acquisition and reconstructed afterwards. Therefore, long reconstruction times after the scan are possible. The scan is not aborted! However, no new scan can be started during reconstruction! Do not move the patient table to the home position during reconstruction, otherwise the reconstruction will stop and data is lost!

The number of images that can be processed online depends on the reconstruction hardware. Up to 20 slices with 4 echoes and a TR of 3s can be acquired without motion correction and without long reconstruction delays.

3.4 Protocols

When the default protocol is created, motion correction and t-test are selected! Please adjust to your needs. Remember, t-test only works correctly when motion correction is enabled (due to inflexibility in the BOLD task card t-test could not be disabled for this condition).

As in the standard EPI sequence, the sequence automatically introduces ‘dummy scans’ at the beginning if more than one measurement is specified! The number of dummy scans depends on the TR.

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Numaris/4 VA21B

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Siemens 4A21 manual Remarks on reconstruction performance, Protocols
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4A21 specifications

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