Radial Hadamard-encoded ¹⁹F-MRI

Area of Science:

• Magnetic Resonance Imaging
• Fluorine-19 (¹⁹F) Spectroscopy
• Molecular Imaging

Background:

• ¹⁹F MRI offers unique molecular imaging capabilities.
• Perfluorooctyl bromide (PFOB) is a promising tracer for tracking myeloid cell responses.
• Imaging PFOB with ¹⁹F MRI is hindered by chemical shift artifacts due to its complex spectrum.

Purpose of the Study:

• To develop and validate a ¹⁹F MRI method for artifact-free imaging of the PFOB tracer.
• To assess the efficacy of Hadamard encoding (HE) in suppressing chemical shift artifacts for PFOB imaging.
• To evaluate the in vivo performance of the developed method in phantom and animal studies.

Main Methods:

• A Hadamard-encoded (HE) radial 3D UTE sequence was implemented for ¹⁹F MRI.
• The method was tested in phantoms and in vivo in a pig model.
• ¹⁹F signal in the spleen was measured at various time points post-injection of PFOB.

Main Results:

• Hadamard encoding (HE) effectively suppressed chemical shift artifacts in ¹⁹F PFOB imaging.
• A high signal-to-noise ratio (SNR) > 100 was achieved for the splenic ¹⁹F signal 2 days post-injection.
• The ¹⁹F signal intensity decreased by 30% from day 2 to day 7 post-injection.

Conclusions:

• HE-based ¹⁹F MRI enables artifact-free in vivo imaging of PFOB-labeled monocytes with high SNR.
• HE improved the PFOB ¹⁹F-MRI signal by 10% compared to spectrally selective excitation.
• The HE algorithm is simple and can be readily integrated into existing MRI system reconstruction pipelines.