Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Pulse sequences gradient echo

185 views

Published on

SHAPE Society

Published in: Health & Medicine
  • Be the first to comment

Pulse sequences gradient echo

  1. 1. • three basic varieties –conventional (GRASS, FAST) –spoiled (spoiled grass, RF-FAST) –“T2” enhanced (SSFP, CE-FAST) Pulse Sequences gradient echo
  2. 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. 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. 4. • Desired contrast –T2: gradient echo »TE ~ 15-25 »flip angle 100 to 300 Pulse Sequences gradient echo - general principles
  5. 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. 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. 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. 8. Fat and Water gradient echo - phase artifacts »avoid 0.5, 0.75 NEX or PCS acquisition
  9. 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. 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. 11. • tumor imaging –conventional gradient echo (MPGR, FE) –delineates relationship of vessels to tumor –demonstrates bony cortex Pulse Sequences gradient echo - USE
  12. 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. 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. 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. 15. • MT gradient echo (3D) –multiplanar capability Pulse Sequences gradient echo - USE
  16. 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. 17. CORONALCORONAL OBLIQUEOBLIQUE AXIALAXIAL Pulse Sequences 3D spoiled gradient echo - USE
  18. 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. 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. 20. Pulse Sequences 3D gradient echo - USE
  21. 21. Shoulder Volume radial labral images
  22. 22. Shoulder Volume radial labral images

×