Recent advances in in-vivo spectroscopy methods at CNI
Background
CNI continues to support the research of its user community by developing and incorporating for general use new spectroscopy data acquisition and data analysis capabilities. For all spectroscopy research projects, CNI actively follows the recommended best practices from the ISMRM (International Society for Magnetic Resonance in Medicine) Spectroscopy Study Group and published experts’ consensus recommendations. Currently the s-LASER sequence is the ISMRM consensus method particularly for multi-site 3T MRS studies and is the sequence of choice for studies at CNI. If you are interested in learning more about these methods or joining the special interest group, please consult with Laima Baltusis. The link to the CNI Spectroscopy Wiki page is here.
The most recent spectroscopy methods developments and results were shared in a poster presented at the 67th ENC (Experimental Nuclear Magnetic Resonance Conference), the premier conference for nuclear magnetic resonance research (April 12 – 16, 2026, Asilomar, California). The key technical points in the poster are summarized below. Details and supporting figures for data acquisition and data processing are in the ENC poster attached.
Technical Notes
Subcortical brain regions, such as regions within the basal ganglia (caudate nucleus, putamen, globus pallidus, nucleus accumbens), are important and have been studied by investigators trying to understand movement, reward, cognition, and emotion. Unacceptable spectral quality in many of our earliest basal ganglia studies using single voxel spectroscopy (SVS) led us to examine alternatives including focal 2D MRSI. The added spatial resolution in focal MRSI was expected to reduce inhomogeneity and perhaps reduce out-of-band artifacts. For multiple voxels, a 14 x 14 2D grid with a FOV 140 was found to be competitive with SVS in time, especially considering the added benefits of acquiring multiple regions of interest and averaging over non rectilinear ROIs. MRSI data from the basal ganglia demonstrated the flexibility to separate basal ganglia subregions as well as other nearby regions of interest such as the insula and thalamus.
To rigorously test the hypothesis that focal 2D MRSI improves spectral quality relative to SVS methods in subcortical prescriptions, SVS and MRSI were run under matched conditions in the right basal ganglia.
Single voxel 13 x 13 x 10 mm3 spectra from a mostly putamen ROI and a mostly caudate ROI were compared with the corresponding ROIs extracted from a focal 45 x 50 x 10 mm3 MRSI data set. Data were collected using HOS (High Order Shimming) that was focally optimized for the MRSI volume. Spectral quality as judged by FWHM (Full Width at Half Maximum) was substantially improved with focal MRSI relative to SVS. However, a FWHM of 0.105 ppm for the caudate ROI was still broader than desirable. To understand this result, the HOS phase maps were evaluated to understand the source of the remaining inhomogeneity for the caudate ROI. As shown in poster Figure 3, strong susceptibility shifts from the sinus cavity were reduced but not eliminated by the focal HOS approach for the region as prescribed. As illustrated by the oblique prescription, the HOS shim data predicts a significant improvement for focal MRSI prescribed from near-axial ACPC plane that tilts the volume to a more superior position away from the sinus cavity. As illustrated in poster Figure 4 a 45 x 50 x 10 mm3 volume in the AC-PC plane includes all the structures we have been examining, with the added benefit of improving the caudate spectral quality. Poster Figure 5 illustrates the improvement of the focal MRSI sampled data compared with the SVS data collected under matched conditions.
