Fast model-based T2 mapping using SAR-reduced simultaneous multislice excitation

Tom Hilbert*, Jenni Schulz, José P. Marques, Jean Philippe Thiran, Gunnar Krueger, David G. Norris, Tobias Kober

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)

Abstract

Purpose: To obtain whole-brain high-resolution T2 maps in 2 minutes by combining simultaneous multislice excitation and low-power PINS (power independent of number of slices) refocusing pulses with undersampling and a model-based reconstruction. Methods: A multi-echo spin-echo sequence was modified to acquire multiple slices simultaneously, ensuring low specific absorption rate requirements. In addition, the acquisition was undersampled to achieve further acceleration. Data were reconstructed by subsequently applying parallel imaging to separate signals from different slices, and a model-based reconstruction to estimate quantitative T2 from the undersampled data. The signal model used is based on extended phase graph simulations that also account for nonideal slice profiles and B1 inhomogeneity. In vivo experiments with 3 healthy subjects were performed to compare accelerated T2 maps to fully sampled single-slice acquisitions. The accuracy of the T2 values was assessed with phantom experiments by comparing the T2 values to single-echo spin-echo measurements. Results: In vivo results showed that conventional multi-echo spin-echo, simultaneous multislice, and undersampling result in similar mean T2 values within regions of interest. However, combining simultaneous multislice and undersampling results in higher SDs (about 7 ms) in comparison to a conventional sequence (about 3 ms). The T2 values were reproducible between scan and rescan (SD < 1.2 ms) within subjects and were in similar ranges across subjects (SD < 4.5 ms). Conclusion: The proposed method is a fast T2 mapping technique that enables whole-brain acquisitions at 0.7-mm in-plane resolution, 3-mm slice thickness, and low specific absorption rate in 2 minutes.

Original languageEnglish
Pages (from-to)2090-2103
Number of pages14
JournalMagnetic resonance in medicine
Volume82
Issue number6
Early online date4 Jul 2019
DOIs
Publication statusPublished - Dec 2019

Keywords

  • UT-Hybrid-D
  • simultaneous multislice
  • T mapping
  • model-based reconstruction
  • T-2 mapping

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