Rapid 3D Relaxation Time and Proton Density Quantification Using a Modified Radial IR TrueFisp Sequence

Introduction: A promising approach for the simultaneous quantification of proton density, T1 and T2 is the IR TrueFISP sequence proposed by Schmitt et al. [1]. This sequence consists of an inversion pulse followed by a series of TrueFISP acquisitions, observing a quasirelaxation towards the steady-state. However, this sequence requires a delay between individual segments in order to allow the magnetization to recover. For adequate results this delay has to be on the order of 5 to 10s, resulting in relatively long scan times. Recently, a modified IR TrueFISP method for simultaneous T1, T2 and spin density quantification has been proposed, which does not necessitate relaxation delays [2]. The aim of this work was to develop a method for rapid parameter quantification in 3D. To this end, the modified IR TrueFISP method was combined with a 3D radial stack-of-stars acquisition with golden-ratio based profile order [3]. Theory: The signal in an IR TrueFISP as proposed by Schmitt et al. [1], follows a simple exponential relaxation curve (Fig.1a):