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Fast 19 F spectroscopic imaging with pseudo-spiral k-space sampling
Muhammed Yildirim1,2, Xenia Kovalyk2,3, Patrick Scholtz2,3
1Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey.
NMR in Biomedicine
|December 18, 2023
Summary
A new balanced spiral spectroscopic imaging (BaSSI) sequence enables efficient, ghosting-artifact-free fluorine-19 MRI. This technique significantly improves detection sensitivity for theranostics applications, outperforming existing methods.
Area of Science:
- Magnetic Resonance Imaging
- Medical Physics
- Theranostics
Background:
- Fluorine-19 MRI (19F MRI) is crucial for theranostics, requiring high-quality imaging of fluorinated contrast agents.
- Existing MRI techniques struggle with low signal-to-noise ratio and artifacts like chemical shift ghosting in 19F imaging.
- Efficient and artifact-free imaging is essential for clinical viability in 19F MRI applications.
Purpose of the Study:
- To introduce and validate a novel balanced spiral spectroscopic imaging (BaSSI) sequence for 19F MRI.
- To demonstrate BaSSI's capability for efficient, ghosting-artifact-free imaging of 19F hotspots.
- To compare BaSSI's performance, particularly detection sensitivity, against established 19F MRI methods.
Main Methods:
- Developed and implemented the BaSSI sequence on a 3.0T clinical scanner, utilizing an all-phase-encoded pseudo-spiral k-space trajectory.
- Performed in silico characterization of the excitation pulse and parameter space optimization.
- Benchmarked BaSSI against 3D ultrashort-echo-time balanced steady-state free precession (3D UTE BSSFP) using phantoms and postmortem mouse imaging, evaluating sensitivity with the Rose criterion (Rc).
Main Results:
- BaSSI acquired 64x64 images with 1mm x 1mm voxels in 14s, outperforming typical MRSI sequences.
- BaSSI demonstrated superior detection sensitivity compared to 3D UTE BSSFP, achieving approximately twice the Rc values.
- Postmortem imaging successfully localized 19F hotspots in mice, with data registered to 1H anatomical images, though scan times were substantial for 3D scans.
Conclusions:
- The BaSSI sequence is an efficient and effective tool for producing ghosting-artifact-free 19F MRI hotspot images.
- BaSSI offers significantly improved detection sensitivity, making it a promising technique for theranostics and preclinical applications.
- Further research into accelerated imaging techniques like compressed sensing is needed to enhance BaSSI's clinical applicability.
