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MRI Sequences

Balanced gradient echo

by Denis Hoa

Type of sequence Philips Siemens GE Hitachi Toshiba
Balanced GE Balanced
FFE
True FISP FIESTA BASG True SSFP

 

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The steady state is perturbed by the phase shift linked to rapid flows. The shift alters phase encoding and degrades the quality of the image.
By applying balanced and symmetrical gradients in the 3 spatial directions, phase shifts induced by flow at constant speed are nulled. Balance indicates equal quantities of positive and negative lobes The recorded signal simultaneously cumulates the free induction signal (FID) and that of the spin/ stimulated echo.
The contrast varies according to T2/T1 ratio.
With these sequences, we obtain ultrafast (roughly one second per slice), and robust imagery with a liquid / tissue contrast and an excellent signal to noise ratio.
High TR is likely to produce band artifacts.

 

CISS

 

Combination of 2 True FISP acquisitions, with and without excitation pulse phase alternation, to eliminate band artifacts .
Interest: high resolution T2 -weighted 3D gradient echo.

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