T1 measurements with clinical MR units

Area of Science:

• Medical Imaging
• Biophysics
• Magnetic Resonance

Background:

• Proton spin-lattice relaxation time (T1) is a crucial parameter in Magnetic Resonance Imaging (MRI).
• Accurate and feasible T1 measurements are essential for routine clinical applications.
• Existing T1 measurement techniques face challenges in precision and speed.

Purpose of the Study:

• To evaluate and compare different Magnetic Resonance Imaging (MRI) sequences for accurate and feasible proton spin-lattice relaxation time (T1) measurements.
• To assess the impact of sequence parameters and phantom properties on T1 quantification.

Main Methods:

• Utilized a phantom with polyvinyl alcohol gels and gadolinium solutions on 1.5T clinical MR units.
• Applied and analyzed inversion-recovery (IR) and Turbo-fast low angle shot (FLASH) sequences.
• Calculated T1 values by fitting various models to observed signal intensities, accounting for inversion pulse imperfections.

Main Results:

• The inversion-recovery sequence, when accounting for inversion pulse imperfections, provided precise T1 measurements.
• Turbo-fast low angle shot sequences achieved rapid T1 acquisition but suffered from limited precision due to low signal-to-noise ratio.
• Spin-echo (SE) sequences demonstrated signal intensity variations with the effective flip angle, rendering them unsuitable for T1 measurement.

Conclusions:

• The inversion-recovery sequence is a precise method for T1 measurement in MRI, especially when accounting for pulse imperfections.
• Turbo-fast FLASH sequences offer speed but require optimization to improve precision for T1 quantification.
• Standard spin-echo sequences are not recommended for accurate T1 measurements due to signal instability.