Non-water-suppressed 1 H FID-MRSI at 3T and 9.4T

Paul Chang, Sahar Nassirpour, Nikolai Avdievitch, Anke Henning

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Purpose: This study investigates metabolite concentrations using metabolite-cycled 1 H free induction decay (FID) magnetic resonance spectroscopic imaging (MRSI) at ultra-high fields. Methods: A non-lipid-suppressed and slice-selective ultra-short echo time (TE) 1 H FID MRSI sequence was combined with a low-specific absorption rate (SAR) asymmetric inversion adiabatic pulse to enable non-water-suppressed metabolite mapping using metabolite-cycling at 9.4T. The results were compared to a water-suppressed FID MRSI sequence, and the same study was performed at 3T for comparison. The scan times for performing single-slice metabolite mapping with a nominal voxel size of 0.4 mL were 14 and 17.5 min on 3T and 9.4T, respectively. Results: The low-SAR asymmetric inversion adiabatic pulse enabled reliable non-water-suppressed metabolite mapping using metabolite cycling at both 3T and 9.4T. The spectra and maps showed good agreement with the water-suppressed FID MRSI ones at both field strengths. A quantitative analysis of metabolite ratios with respect to N-acetyl aspartate (NAA) was performed. The difference in Cre/NAA was statistically significant, ∼0.1 higher for the non-water-suppressed case than for water suppression (from 0.73 to 0.64 at 3T and from 0.69 to 0.59 at 9.4T). The difference is likely because of chemical exchange effects of the water suppression pulses. Small differences in mI/NAA were also statistically significant, however, are they are less reliable because the metabolite peaks are close to the water peak that may be affected by the water suppression pulses or metabolite-cycling inversion pulse. Conclusion: We showed the first implementation of non-water-suppressed metabolite-cycled 1 H FID MRSI at ultra-high fields. An increase in Cre/NAA was seen for the metabolite-cycled case. The same methodology was further applied at 3T and similar results were observed. Magn Reson Med 80:442–451, 2018.

Original languageEnglish (US)
Pages (from-to)442-451
Number of pages10
JournalMagnetic resonance in medicine
Volume80
Issue number2
DOIs
StatePublished - Aug 2018
Externally publishedYes

Keywords

  • metabolite cycling
  • MRSI
  • non-water-suppressed
  • spectroscopic imaging
  • ultra-high field strengths

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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