Siemens MULTI-ECHO EPI 4A21 Manual De Usuario

Page 9 of 9 

Numaris/4 VA21B 

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. 
 
 

 
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. 
 
 

 
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.