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Enhanced detection of paramagnetic fluorine-19 magnetic resonance imaging agents using zero echo time sequence and
Jiawen Chen1, Piya Pal1, Eric T Ahrens2
1Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California, USA.
NMR in Biomedicine
|March 9, 2022
Summary
Compressed sampling with zero echo time (CS-ZTE) significantly enhances Fluorine-19 MRI sensitivity and speed for cell tracking. This technique improves signal-to-noise ratio by over sixfold, enabling faster, clearer imaging of labeled cells in vivo.
Area of Science:
- Biomedical Imaging
- Magnetic Resonance Imaging
- Nanotechnology
Background:
- Fluorine-19 (19 F) MRI offers specific in vivo cell detection but faces challenges with speed and signal-to-noise ratio (SNR).
- Paramagnetic metallo-perfluorocarbon (MPFC) nanoemulsions improve 19 F MRI SNR but are limited by T2 reduction and linewidth broadening.
- Existing methods struggle with long acquisition times and modest SNR for 3D 19 F imaging.
Purpose of the Study:
- To develop and evaluate a compressed sampling (CS) scheme using a zero echo time (ZTE) sequence for accelerated 3D 19 F MRI.
- To improve SNR and imaging speed for MPFC-labeled cell detection in vivo.
- To enable accurate absolute quantification of 19 F spins with minimal artifacts.
Main Methods:
- Implementation of a compressed sampling (CS) scheme with a zero echo time (ZTE) sequence for 19 F MRI.
- Acquisition of k-space data using an undersampled spherical radial pattern and signal averaging.
- Image reconstruction via a sparsity-promoting algorithm, specifically a joint total variation and -norm regularized least square problem.
- Evaluation using simulations and 19 F MRI at 11.7 T in phantoms and mice with MPFC-labeled dendritic cells.
Main Results:
- Achieved ~6.3-fold SNR gains for MPFC-labeled cells in vivo with 8-fold undersampling.
- Demonstrated SNR enhancement through undersampling, increased signal averaging, CS denoising, and paramagnetic T1 reduction.
- Confirmed accurate absolute quantification of 19 F spins through image intensity analysis.
- Observed ultrafast imaging with minimal artifacts.
Conclusions:
- The CS-ZTE method significantly boosts 19 F MRI sensitivity and speed when used with MPFC probes.
- This technique overcomes previous limitations, enabling enhanced detection and accurate quantification of labeled cells.
- CS-ZTE represents a major advancement for in vivo cell imaging applications.
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