DISCO-mcDESPOT Nov. 6, 2011 Jason Su

Methods In vivo, 3T Possible issue with collection 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 – offline.recon

MWF – DISCO

MWF – % Difference Mean: 11.3056 SD: 75.637

Fast T1 – offline.recon

Fast T1 – DISCO

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

Slow T1 – offline.recon

Slow T1 – DISCO

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

Fast T2 – offline.recon

Fast T2 – DISCO

Fast T2 – % Difference Mean: 1.9265 SD: 31.8879

Slow T2 – offline.recon

Slow T2 – DISCO

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

Off-Resonance – offline.recon

Off-Resonance – DISCO Pattern shift is quite apparent here, I suspect because DISCO is losing a lot of the information that happens at the banding edges

Off-Resonance – % Difference Mean: 10.7222 SD: 105.1012 The histogram is clearly non-Gaussian, more reason to believe that this is a particularly affected map. Large SD is due to large tail on + side not shown in histogram.

Residence Time – offline.recon

Residence Time – DISCO

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

SSFP fa5 – offline.recon

SSFP fa5 – DISCO

SSFP fa5 – % Difference