• Object ID: 00000018WIA304E8870GYZ
  • Topic ID: id_40025221 Version: 1.8
  • Date: Aug 21, 2022 7:28:03 PM

Spectroscopy

For spectroscopy data acquisitions there are two possible modes; 2D or MRS. The Spectroscopy Pulse Sequence Family in the MRS imaging mode allows you to choose one of the voxel localized pulse sequences:

  • PROBE-P
  • PROBE-S
  • PROSE
  • PRESS CSI
  • STEAM CSI
  • TEA-PRESS

Homogeneity and susceptibility

All spectroscopy acquisitions are strongly affected by magnetic field inhomogeneity that may arise in a patient at air/bone/tissue interfaces such as the sinuses, orbits, mouth, nasal passages, the skull, and the scalp. The main effect of large susceptibility changes at these interfaces is the broadening of the resonance peaks in the spectrum. The broadening can result in a loss of SNR, poor resolution of overlapping resonance peaks, and baseline artifacts. The shim process (part of Auto Prescan) should always be used to optimize the homogeneity through the prescribed volume. Whenever possible, prescribe the spectroscopy volume in regions of high magnetic field homogeneity. For spectroscopy in the brain, that is away from the sinuses, mouth, nasal passages, orbits, the skull, and the scalp; and, in the prostate gland, away from the rectum and endo-rectal coil.

Figure 1. Spectrum shim comparison
Table 1. Spectrum shim comparison image legend
ItemDescription
APoor shim
BImproved shim (Note the improved resolution and SNR of spectrum B