SHAPE Society

1. • three basic varieties
–conventional (GRASS, FAST)
–spoiled (spoiled grass, RF-FAST)
–“T2” enhanced (SSFP, CE-FAST)
Pulse Sequences
gradient echo

2. • TR has little effect on image contrastTR has little effect on image contrast
• TE behavior similar to conventional SETE behavior similar to conventional SE
imagingimaging
–more T2* effect with increased TEmore T2* effect with increased TE
• less T1 weighting with shorter flip anglesless T1 weighting with shorter flip angles
–maximum signal to noise between 30maximum signal to noise between 3000
and 60and 6000
Pulse Sequences
gradient echo - general principles
TE=9TE=9 TE=30TE=30

3. • Desired contrast
–T1: spoiled gradient echo
»TE ~10
»flip angle 450
to 900
–PD: gradient echo
»TE ~ 10-15
»flip angle 450
to 600
Pulse Sequences
gradient echo - general principles

4. • Desired contrast
–T2: gradient echo
»TE ~ 15-25
»flip angle 100
to 300
Pulse Sequences
gradient echo - general principles

5. • artifacts
–magnetic susceptibility
»black bones
»blooming effect
•air in bowel
•metal clips
•suture material
»artifact reduced with shorter TE
Pulse Sequences
gradient echo - general principles

6. • artifacts
–phase cancellation of water and fat
» alternates every ~2.2 msec at 1.5 T
–additional phase artifacts due to
absence of 1800
refocussing pulse
»avoid 0.5, 0.75 NEX or PCS
acquisition
Pulse Sequences
gradient echo - general principles

7. Fat and Water
gradient echo - phase cancellation
TR 450
TE 13.42
α=45°
TR 450
TE 15.7
α=45°
FESUM
in-phase
FEDIF
opposed-
phase
ν

8. Fat and Water
gradient echo - phase artifacts
»avoid 0.5, 0.75 NEX or PCS acquisition

9. • conventional gradient echo (MPGR, FE)
–usually a multislice 2D acquisition
–cartilage and joint visualization (e.g.
shoulder labrum)
»TR 450 +, TE 10-15, 450
•difficult to distinguish fluid from
cartilage, but signal to noise is good
Pulse Sequences
gradient echo - USE

10. • “magic” cartilage sequence (MPGR, FE)
–TR 600, TE 22, 150
»bright fluid, dark bones, gray
cartilage
•patellofemoral joint
»lower signal to noise
Pulse Sequences
gradient echo - USE

11. • tumor imaging
–conventional gradient echo (MPGR, FE)
–delineates relationship of vessels to tumor
–demonstrates bony cortex
Pulse Sequences
gradient echo - USE

12. • fast gradient echo (GRASS, SER FAST)
–usually a single slice 2D acquisition
–kinematic motion studies (shoulder)
»TR 50, TE 10, 450
• ≈ 20 second scan
Pulse Sequences
gradient echo - USE

13. • fast spoiled gradient echo (SPGR, RF-fast spoiled gradient echo (SPGR, RF-
FAST)FAST)
–usually a single slice 2D acquisitionusually a single slice 2D acquisition
–extremity MRA (2D time of flight)extremity MRA (2D time of flight)
»30-60 slices, 5-10 sec / slice30-60 slices, 5-10 sec / slice
Pulse Sequences
gradient echo - USE

14. • MT gradient echo (2D)MT gradient echo (2D)
–excellent joint visualizationexcellent joint visualization
–MTC contrast for muscle and fatMTC contrast for muscle and fat
–bright fluidbright fluid
–routine axial kneeroutine axial knee
Pulse Sequences
gradient echo - USE

15. • MT gradient echo (3D)
–multiplanar capability
Pulse Sequences
gradient echo - USE

16. • 3D spoiled gradient echo
–TR 35, TE 13.4, 500
, 124 slices, 128
phase encodings, 0.9-1 mm slice
thickness
–multiplanar joint and tendon visualization
Pulse Sequences
gradient echo - USE

17. CORONALCORONAL OBLIQUEOBLIQUE AXIALAXIAL
Pulse Sequences
3D spoiled gradient echo - USE

18. • DO NOT substitute gradient echo for T2
weighted
–CANNOT see bone marrow edema
–may miss significant pathologic findings
Pulse Sequences
gradient echo - USE

19. Pulse Sequences
gradient echo - USE
• DO NOT use gradient echo imaging for
primary diagnosis of rotator cuff disease or
meniscal tears
–CANNOT reliably distinguish a tear from
normal bright signal seen within
fibrocartilage on most gradient echo
sequences
• DO NOT use T2 enhanced sequences
(SSFP, CE-FAST)

20. Pulse Sequences
3D gradient echo - USE

21. Shoulder Volume
radial labral images

22. Shoulder Volume
radial labral images