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DISCO- mcDESPOT. Nov. 6, 2011 Jason Su. 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
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DISCO-mcDESPOT Nov. 6, 2011 Jason Su
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
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?
MWF – % Difference Mean: 11.3056 SD: 75.637
Fast T1 – % Difference Mean: -0.75528 SD: 11.4194
Slow T1 – % Difference Mean: -0.84407 SD: 10.024
Fast T2 – % Difference Mean: 1.9265 SD: 31.8879
Slow T2 – % Difference Mean: -0.34274 SD: 12.2981
Off-Resonance – % Difference Mean: 10.7222 SD: 105.1012
Residence Time – % Difference Mean: 0.0097232 SD: 16.17
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