Magnetization transfer in magnetic resonance fingerprinting

Area of Science:

• Biophysics
• Medical Imaging

Background:

• Magnetic Resonance Fingerprinting (MRF) is a quantitative imaging technique.
• Magnetization Transfer (MT) describes the interaction between semi-solid and free spin pools.
• Understanding MT effects is crucial for accurate MRF relaxometry.

Purpose of the Study:

• To investigate the influence of Magnetization Transfer (MT) on Magnetic Resonance Fingerprinting (MRF) signals.
• To develop and validate an MRF method incorporating MT effects for improved T1 and T2 quantification.
• To assess the feasibility of estimating fractional pool size using MT-aware MRF in the human brain.

Main Methods:

• Simulations and phantom experiments were conducted to assess MT impact on MRF signals.
• An MRF sequence with off-resonance MT pulses was implemented.
• A two-pool model was used to generate an MT-dimension dictionary for parameter estimation.
• The method was evaluated in vivo on the human brain.

Main Results:

• MT was shown to influence MRF signals in phantom studies, with MT-aware models yielding better signal matching.
• Off-resonance MT pulses enhanced the differentiation of MT from T1 and T2 effects.
• In vivo, MT was quantified in white matter (~16%) and gray matter (~10%).
• Accounting for MT led to longer T1 (~1060 ms vs. ~860 ms) and T2 (~47 ms vs. ~35 ms) values in white matter.

Conclusions:

• Magnetization transfer effects can significantly influence T1 and T2 quantification in MRF.
• An MRF model incorporating MT effects improves the accuracy of relaxation parameter estimation.
• This approach allows for the simultaneous quantification of relaxation times and fractional pool size.