Implementation of the QRAPMASTER data analysis using dictionary matching and quantitative evaluation of the...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysical Measurement Techniques
• Quantitative MRI

Background:

• Accurate measurement of T1 and T2 relaxation times is crucial for MRI-based tissue characterization.
• Magnetization transfer (MT) is a common phenomenon in biological tissues that can affect relaxation time measurements.
• The QRAPMASTER sequence is a novel method for acquiring MRI data, but its susceptibility to MT effects requires investigation.

Purpose of the Study:

• To investigate and quantify the effect of magnetization transfer (MT) on T1 and T2 relaxation time values obtained using the QRAPMASTER MRI sequence.
• To assess the accuracy and linearity of T1 and T2 measurements from the QRAPMASTER sequence compared to established methods.

Main Methods:

• Phantom and biological (chicken breast) samples were imaged using the QRAPMASTER and a multislice multiple spin-echo (MSMSE) sequence at 1.5T.
• T1 and T2 values were calculated via data matching using Bloch equation simulation-generated dictionaries.
• The MT effect was quantified by numerically solving Bloch equations with a two-pool model.

Main Results:

• Excellent linearity (R=0.9969-0.9986) was observed between QRAPMASTER and standard T1 measurements, excluding the chicken breast sample.
• Good linearity (R=0.963-0.985) was found for T2 values across all samples and slices.
• T2 accuracy showed limitations (slope=0.674-0.758), attributed to eddy currents, while MT effects on T1 were consistent with Bloch simulations.

Conclusions:

• The study demonstrates that the MT effect significantly shortens T1 values measured in biological samples using the QRAPMASTER sequence.
• Understanding and accounting for MT effects are essential for accurate quantitative MRI analysis with the QRAPMASTER sequence.