Minimum acquisition methods for simultaneously imaging T(1), T(2), and proton density with B(1) correction and no...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Medical Physics

Background:

• Spin lattice (T(1)) and spin-spin (T(2)) relaxation times, along with proton density (PD), are crucial for (1)H MRI but rarely imaged directly.
• Existing methods often require numerous acquisitions, limiting efficiency in clinical diagnosis and research.

Purpose of the Study:

• To develop and validate novel MRI methods for direct imaging of T(1), T(2), and PD with minimal data acquisition.
• To assess the accuracy and efficiency of these new methods compared to conventional techniques.

Main Methods:

• Three new methods were developed utilizing adiabatic pre-pulses for T(2) encoding and varying flip-angle (FA) or repetition period (TR) for T(1) encoding.
• The 'Four-FA' method incorporates an additional FA-dependent acquisition for self-correction of T(1), T(2), PD, and FA.
• Methods were validated using phantom studies and human brain imaging, with comparisons to standard partial saturation and spin-echo techniques.

Main Results:

• All three methods successfully imaged T(1), T(2), and PD with a minimum of three acquisitions.
• The 'Four-FA' method demonstrated superior accuracy and efficiency, especially when accounting for B(1) inhomogeneity.
• Slice profile errors were identified as a significant factor for T(1) measurements, addressable through Bloch equation analysis and calibration.

Conclusions:

• The presented methods offer efficient, minimum-acquisition options for simultaneous T(1), T(2), and PD imaging.
• The 'Four-FA' method provides the best overall performance in terms of accuracy and efficiency for quantitative MRI.
• Further calibration can address slice profile errors, enhancing the reliability of T(1) measurements.