Towards accurate MRF T₂ in structured material at 0.55T using MT-suppressed excitations

Area of Science:

• Biomedical Engineering
• Magnetic Resonance Imaging
• Neuroimaging

Background:

• Accurate T2 mapping is crucial for characterizing biological tissues.
• Structured materials like white matter present challenges for conventional MR imaging due to complex magnetic properties.
• Existing Magnetic Resonance Fingerprinting (MRF) methods can suffer from artifacts, particularly at lower field strengths.

Purpose of the Study:

• To develop a novel 0.55 Tesla Fast Imaging with Steady-state Free Precession-Magnetic Resonance Fingerprinting (FISP-MRF) technique.
• To enhance the accuracy of T2 quantification in structured biological tissues, such as white matter.
• To mitigate artifacts caused by off-resonance Magnetization Transfer (MT) effects.

Main Methods:

• Implementation of non-selective, low-bandwidth excitation pulses to minimize on-resonance MT effects.
• Simulation of MRF dictionaries using a conventional single-pool model.
• Comparison of T2 maps generated by the novel non-selective approach against conventional slab-selective MRF and slow, reference-based measurements.

Main Results:

• The proposed non-selective approach significantly reduced T2 underestimation in white matter from approximately 40% to below 10%.
• The precision of T2 measurements was maintained without compromise.
• The method demonstrated improved accuracy at 0.55 Tesla.

Conclusions:

• Non-selective, low-bandwidth excitations effectively reduce MT effects in 0.55T FISP-MRF.
• This advancement enables the use of a simplified single-pool model for T2 quantification.
• The developed technique is particularly valuable for MRF applications at low field strengths and in challenging materials like white matter.