PLANET: An Ellipse Fitting Approach for Simultaneous T1 and T2 Mapping Using Phase-Cycled Balanced Steady-State Free Precession

Shcherbakova, Y, van den Berg, CAT, Moonen, CTW, Bartels, LW


Magnetic Resonance in Medicine 79 (2), p. 711-722


Purpose: To demonstrate the feasibility of a novel, ellipse fitting
approach, named PLANET, for simultaneous estimation of
relaxation times T1 and T2 from a single 3D phase-cycled balanced
steady-state free precession (bSSFP) sequence.
Methods: A method is presented in which the elliptical signal
model is used to describe the phase-cycled bSSFP steadystate
signal. The fitting of the model to the acquired data is
reformulated into a linear convex problem, which is solved
directly by a linear least squares method, specific to ellipses.
Subsequently, the relaxation times T1 and T2, the banding free
magnitude, and the off-resonance are calculated from the fitting
Results: Maps of T1 and T2, as well as an off-resonance and
a banding free magnitude can be simultaneously, quickly, and
robustly estimated from a single 3D phase-cycled bSSFP
sequence. The feasibility of the method was demonstrated in
a phantom and in the brain of healthy volunteers on a clinical
MR scanner. The results were in good agreement for the phantom,
but a systematic underestimation of T1 was observed in
the brain.
Conclusion: The presented method allows for accurate mapping
of relaxation times and off-resonance, and for the reconstruction
of banding free magnitude images at realistic signalto-
noise ratios. Magn Reson Med 000:000–000, 2017.
VC 2017 The Authors Magnetic Resonance in Medicine published
by Wiley Periodicals, Inc. on behalf of International
Society for Magnetic Resonance in Medicine. This is an
open access article under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivs License, which
permits use and distribution in any medium, provided the
original work is properly cited, the use is non-commercial
and no modifications or adaptations are made.