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Evaluation of mcDESPOT Imaging with 3T MRI: Challenges and Performance Analysis

This study assesses the performance of mcDESPOT for T1 and T2 mapping using a 3T MRI system with specific acquisition parameters. Results showed mixed performance, particularly highlighting issues with T2 mapping likely due to off-resonance effects. Despite promising performance in T1 mapping with high fidelity SPGR sequences, SSFP methods introduced errors. Future directions include improving DESPOT-FM performance and exploring B1 correction implementation, as well as addressing issues with sampling on the low end of the SPGR signal curve.

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Evaluation of mcDESPOT Imaging with 3T MRI: Challenges and Performance Analysis

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  1. DISCO-mcDESPOT Nov. 6, 2011 Jason Su

  2. Methods • In vivo, 3T • 2mm in-plane resolution • 5mm slice resolution • Rect 200us SPGR (13 angles from up to 18) and SSFP (13 angles up to 65) • Left out B1 correction • Running into issues with HIFI producing completely wrong T1 • Still some work to do incorporating Ives’s Bloch-Siegert -> kappa map code into pipeline • Possible issue with collection • May need more samples on low end of SPGR signal curve, was enough for DESPOT1 but perhaps not mcDESPOT, only 1-2 points before Ernst angle

  3. Results • Performance is mixed for the different output maps • Overall good performance with T1 • Worse performance with T2, probably because bands caused by off-resonance affect high-freq. k-space • MWF % difference histogram is poor but looks decent, could be a dividing by small numbers issue • Stochastic nature of optimization makes interpretation difficult, i.e. how much variation is due to randomness or view sharing?

  4. MWF – offline.recon

  5. MWF – DISCO

  6. MWF – % Difference Mean: 11.3056 SD: 75.637

  7. Fast T1 – offline.recon

  8. Fast T1 – DISCO

  9. Fast T1 – % Difference Mean: -0.75528 SD: 11.4194

  10. Slow T1 – offline.recon

  11. Slow T1 – DISCO

  12. Slow T1 – % Difference Mean: -0.84407 SD: 10.024

  13. Fast T2 – offline.recon

  14. Fast T2 – DISCO

  15. Fast T2 – % Difference Mean: 1.9265 SD: 31.8879

  16. Slow T2 – offline.recon

  17. Slow T2 – DISCO

  18. Slow T2 – % Difference Mean: -0.34274 SD: 12.2981

  19. Off-Resonance – offline.recon

  20. Off-Resonance – DISCO

  21. Off-Resonance – % Difference Mean: 10.7222 SD: 105.1012

  22. Residence Time – offline.recon

  23. Residence Time – DISCO

  24. Residence Time – % Difference Mean: 0.0097232 SD: 16.17

  25. More Images • From the performance in T1 mapping, we know that our SPGRs are fairly high-fidelity • SSFPs are probably the source of error • The first flip angle is again problematic • In the future, should probably start with improving DESPOT-FM performance, much easier to look at

  26. SSFP fa5 – offline.recon

  27. SSFP fa5 – DISCO

  28. SSFP fa5 – % Difference

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