Simultaneous QSM and metabolic imaging of the brain using SPICE: Further improvements in data acquisition and processing

Rong Guo, Yibo Zhao, Yudu Li, Tianyao Wang, Yao Li, Brad Sutton, Zhi Pei Liang

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: To achieve high-resolution mapping of brain tissue susceptibility in simultaneous QSM and metabolic imaging. Methods: Simultaneous QSM and metabolic imaging was first achieved using SPICE (spectroscopic imaging by exploiting spatiospectral correlation), but the QSM maps thus obtained were at relatively low-resolution (2.0 × 3.0 × 3.0 mm3). We overcome this limitation using an improved SPICE data acquisition method with the following novel features: 1) sampling (k, t)-space in dual densities, 2) sampling central k-space fully to achieve nominal spatial resolution of 3.0 × 3.0 × 3.0 mm3 for metabolic imaging, and 3) sampling outer k-space sparsely to achieve spatial resolution of 1.0 × 1.0 × 1.9 mm3 for QSM. To keep the scan time short, we acquired spatiospectral encodings in echo-planar spectroscopic imaging trajectories in central k-space but in CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration) trajectories in outer k-space using blipped phase encodings. For data processing and image reconstruction, a union-of-subspaces model was used, effectively incorporating sensitivity encoding, spatial priors, and spectral priors of individual molecules. Results: In vivo experiments were carried out to evaluate the feasibility and potential of the proposed method. In a 6-min scan, QSM maps at 1.0 × 1.0 × 1.9 mm3 resolution and metabolic maps at 3.0 × 3.0 × 3.0 mm3 nominal resolution were obtained simultaneously. Compared with the original method, the QSM maps obtained using the new method reveal fine-scale brain structures more clearly. Conclusion: We demonstrated the feasibility of achieving high-resolution QSM simultaneously with metabolic imaging using a modified SPICE acquisition method. The improved capability of SPICE may further enhance its practical utility in brain mapping.

Original languageEnglish (US)
Pages (from-to)970-977
Number of pages8
JournalMagnetic Resonance in Medicine
Volume85
Issue number2
DOIs
StateAccepted/In press - 2020

Keywords

  • MRSI
  • QSM
  • sparse sampling
  • subspace modeling

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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