Table 1 Summary of key differences between gradient echo and spin echo sequences
From: Cardiovascular magnetic resonance physics for clinicians: part I
| Â | Spin echo | Gradient echo (spoiled) | Gradient echo (bSSFP) |
|---|---|---|---|
Flip angle (excitation pulse) | 90° | variable 5°-40° | variable 50°-70° |
180° refocusing pulse | Yes | No | No |
Contrast weighting | T1, T2, 'proton density' | T1, T2* | T2/T1 ratio |
Short Repetition time (T1- weighting) | 400-800 ms | 3-400 ms (depends on flip angle) | 3-5 ms |
Short echo time (minimise T2 or T2* weighting) | 6-25 ms | 1-3 ms | 1-3 ms |
Long echo time (for T2 or T2* weighting) | 60-100 ms | 7-15 ms | N/A |
Long Repetition time (minimises T1 weighting) | 1500-2500 ms | 100 ms - (depends on flip angle) | N/A |
Shortest practical TR | 200 ms | 2-5 ms | 2-5 ms |
Intra-voxel signal loss (susceptibility, iron) | No | Yes | Yes |
Signal from blood flowing through the slice | Dark (spin washout) | Bright (inflow enhancement) | Bright (intrinsic T2/T1 contrast) |
Cardiac Applications | T1, T2 and 'proton density'-weighted anatomical imaging and tissue characterisation | Fast cine imaging, Contrast-enhanced MR angiography, flow imaging, T2*-weighted imaging for iron loading. | Fast cine imaging |