High-Sensitivity, Low-Field ¹⁹F-MRI Approach Using High Manganese Ferrite Concentrations

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Biomedical Engineering

Background:

• Fluorine-19 MRI (¹⁹F-MRI) offers background-free quantification valuable for research and clinical applications.
• High-field MRI systems limit ¹⁹F-MRI accessibility; low-field systems are more prevalent.
• Improving detection sensitivity via reduced ¹⁹F spin-lattice relaxation time (T₁) and ultrashort echo time (UTE) imaging is crucial but challenging.

Purpose of the Study:

• To develop a hardware-friendly ultrashort echo time (UTE) ¹⁹F-MRI sequence compatible with low-field MRI systems.
• To enhance the detection sensitivity and quantification capabilities of ¹⁹F-MRI at low magnetic fields.

Main Methods:

• Introduction of the k-space scaling imaging (KSSI) MRI sequence for variable-scale k-space sampling.
• Implementation of KSSI on custom low-field MRI systems for experiments.
• Validation using swine bone, perfluorooctyl bromide (PFOB) phantoms, and a tumor-bearing mouse model.

Main Results:

• KSSI successfully validated ultrashort TE imaging on swine bone.
• High signal-to-noise ratio (SNR) achieved for 658 mM fluorine concentration, demonstrating high sensitivity.
• KSSI showed a 7.1x higher SNR than spin echo for 3.29 M PFOB phantom and demonstrated quantifiable capacity across various concentrations.
• Simultaneous ¹H/¹⁹F imaging was performed on a tumor-bearing mouse.

Conclusions:

• The KSSI sequence enables hardware-friendly, ultrashort TE ¹⁹F-MRI on low-field systems.
• KSSI significantly improves detection sensitivity and quantification, overcoming limitations of conventional UTE sequences.
• This method holds strong potential for the clinical translation of fluorine probes in low-field MRI settings.