Physiologic motion: Dealing with cardiac, respiratory, and other sporadic motion in MRS

Research output: Contribution to journalArticle

Abstract

Physiologic motion, such as respiration and cardiac motion, affects magnetic resonance (MR) spectroscopy (MRS) in different ways. Tissue displacement on the order of the MRS voxel size leads to contamination from neighboring tissue. Bulk motion, even that involving only small displacements that occurs during the application of localization gradients and RF pulses, induces phase shifts which can lead to signal loss when averaging and to ghosting in chemical shift imaging (CSI), even at locations away from the actual motion such as the brain, spine, and breast. Cardiac muscle motion with strain-induced thickening, thinning, and rotation leads to a range of induced signal phase shifts within single MRS voxels and, hence, to intravoxel dephasing. Reducing the strength of 'crusher' gradients that are used for dephasing extraneous transverse magnetization may reduce the amount of motion-induced phase variations. Cardiac triggering with either pulse oximetry sensors or electrocardiogram (ECG), and respiratory triggering or gating with either bellows or respiratory navigators, allow the synchronization of MRS acquisitions to cardiac and respiratory cycles. These techniques minimize the effects of motion - depending on its reproducibility - by facilitating a consistent tissue location, to enable MRS acquisitions even in the moving chest, liver and heart. Remaining shot-to-shot phase variations in the data can be corrected by constructive averaging or signal rejection techniques during post-processing.

Original languageEnglish (US)
Pages (from-to)1087-1096
Number of pages10
JournaleMagRes
Volume5
Issue number2
DOIs
StatePublished - 2016

Keywords

  • -Intravoxel phase dispersion
  • Constructive averaging
  • Double triggering
  • ECG triggering
  • Motion artifacts
  • Motion-induced phase
  • Respiratory navigator

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Biomedical Engineering
  • Biochemistry
  • Radiology Nuclear Medicine and imaging

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