Relaxometry tools

Estimation

T1 relaxation

We include an implementation of the DESPOT1 [1] algorithm for T1 relaxation time estimation: animaT1RelaxometryEstimation. It optionally can take a B1 inhomogeneity map as an input to correct for it (-b parameter). It outputs two images: T1 relaxation times (-o output) and M0 map (proportional to proton density, -O output).

T2 relaxation

We include two ways to estimate T2 relaxation times from T2 relaxometry sequences. Those two algorithms suppose acquisitions were made with an equal echo spacing that is specified to the algorithm. Those two tools are:

• animaT2RelaxometryEstimation estimates T2 relaxation using the regular exponential decay equation with a single T2 value. It may take an input T1 map for better estimation, and outputs M0 and T2 maps.
• animaT2EPGRelaxometryEstimation estimates T2 relaxation using the EPG algorithm with a single T2 value, to account for stimulated echoes due to B1 inhomogeneity [2]. It may take input T1 and B1 maps for better estimation, and outputs M0 and T2 maps.

MRI simulation

Several MR simulation tools are included in ANIMA, which simulate sequences from relaxation time maps. All of them are described in detail here.

References

1. Deoni, S. High-resolution T1 mapping of the brain at 3T with driven equilibrium single pulse observation of T1 with high-speed incorporation of RF field inhomogeneities (DESPOT1-HIFI). J Magn Reson Imaging 26(4):1106–1111, 2007.
2. Kelvin J Layton, Mark Morelande, David Wright, Peter M Farrell, Bill Moran, Leigh Johnston. Modelling and estimation of multicomponent T2 distributions. IEEE transactions on medical imaging, 32(8):1423–34, 2013.