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Practical considerations of diffusion-weighted MRS with ultra-strong diffusion gradients
Christopher W Davies-Jenkins1,2,3, André Döring3,4, Fabrizio Fasano3,5
1The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
Frontiers in Neuroscience
|December 25, 2023
Summary
Ultra-strong gradients in diffusion-weighted magnetic resonance spectroscopy (DW-MRS) improve signal-to-noise ratio (SNR) and enable shorter diffusion times. Developed strategies effectively mitigate confounding effects for enhanced metabolite analysis.
Area of Science:
- Magnetic Resonance Imaging
- Neuroimaging
- Biophysics
Background:
- Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) provides cellular specificity but suffers from low spatial resolution and signal-to-noise ratio (SNR).
- High b-values are necessary for characterizing slow-diffusing metabolites, but achieving them with conventional gradients is time-consuming and limits SNR.
- Ultra-strong gradients offer potential for higher b-values per unit time and improved SNR but introduce technical challenges like eddy-current artifacts and gradient non-uniformity.
Purpose of the Study:
- To present initial Diffusion-Weighted Magnetic Resonance Spectroscopy (DW-MRS) data acquired using ultra-strong gradients (300 mT/m).
- To explore and mitigate practical issues associated with ultra-strong gradient acquisitions in DW-MRS.
- To evaluate the benefits of ultra-strong gradients for DW-MRS, including improved SNR and shorter diffusion times.
Main Methods:
- Acquisition of DW-MRS data on a 3T Siemens Connectom scanner with ultra-strong gradients.
- Development of an in-house DW-PRESS sequence and data processing pipeline to address gradient-related confounds.
- Investigation of the interplay between echo time (TE), b-value, and maximum gradient amplitude using simulations and pilot data.
Main Results:
- Experimental confirmation of T2-based SNR gains predicted by simulations.
- Demonstration that ultra-strong gradient acquisitions exhibit similar artifact profiles to lower gradient systems, validating mitigation strategies.
- Quantification of gradient field non-uniformity impact (up to 4% ADC error) and confirmation of metabolite estimates (tNAA, tCho, tCr) aligning with literature.
Conclusions:
- Successful implementation of acquisition and processing strategies for ultra-strong gradient DW-MRS.
- Demonstrated amelioration of confounding effects from strong gradient systems.
- Achieved shorter diffusion times and improved metabolite SNR, highlighting the potential of ultra-strong gradients for advanced DW-MRS.
