T2* quantification using multi-echo gradient echo sequences: a comparative study of different readout gradients

Scientific Reports, vol. 13, pp. 1138

Abstract

To quantify T2*, multiple echoes are typically acquired with a multi-echo gradient echo sequence using either monopolar or bipolar readout gradients. The use of bipolar readout gradients achieves a shorter echo spacing time, enabling the acquisition of a larger number of echoes in the same scan time. However, despite their relative time efficiency and the potential for more accurate quantification, a comparative investigation of these readout gradients has not yet been addressed. This work aims to compare the performance of monopolar and bipolar readout gradients for T2* quantification. The differences in readout gradients were theoretically investigated with a Cramér-Rao lower bound and validated with computer simulations with respect to the various imaging parameters (e.g., flip angle, TR, TE, TE range, and BW). The readout gradients were then compared at 3 T using phantom and in vivo experiments. The bipolar readout gradients provided higher precision than monopolar readout gradients in both computer simulations and experimental results. The difference between the two readout gradients increased for a lower SNR and smaller TE range, consistent with the prediction made using Cramér-Rao lower bound. The use of bipolar readout gradients is advantageous for regions or situations where a lower SNR is expected or a shorter acquisition time is required.

Authors 3

1. Seonyeong Shin Aachen

   RWTH Aachen University · Forschungszentrum Jülich

   Affiliation as printed

   Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich, INM-4, 52428, Jülich, Germany

   RWTH Aachen University, Aachen, Germany

2. Seong Dae Yun

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich, INM-4, 52428, Jülich, Germany

3. Nadim Jon Shah corresponding Aachen Department of Neurology

   RWTH Aachen University · Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Department of Neurology, RWTH Aachen University, Aachen, Germany. n.j.shah@fz-juelich.de

   Institute of Neuroscience and Medicine 11, JARA, Forschungszentrum Jülich, INM-11, Jülich, Germany. n.j.shah@fz-juelich.de

   Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich, INM-4, 52428, Jülich, Germany. n.j.shah@fz-juelich.de

   JARA-BRAIN-Translational Medicine, Aachen, Germany. n.j.shah@fz-juelich.de

   RWTH Aachen University, Aachen, Germany. n.j.shah@fz-juelich.de

   Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich, INM-4, 52428, Jülich, Germany

   RWTH Aachen University, Aachen, Germany