Simultaneous quantification of T2 and T'2 using a combined gradient echo-spin echo sequence at ultrahigh field.

Area of Science:

• Magnetic Resonance Imaging
• Biophysics
• Neuroimaging

Background:

• Measuring T(2) relaxation times at high magnetic fields (7.0 T) is challenging due to radiofrequency (RF) inhomogeneity.
• Existing methods can be susceptible to RF pulse errors and image distortions.

Purpose of the Study:

• To evaluate gradient echo sampling of a spin echo (GESSE) for T(2) and T'(2) measurements at 7.0 T.
• To optimize GESSE acquisition and analysis parameters for improved accuracy and reduced noise sensitivity.

Main Methods:

• GESSE technique was employed to acquire data at 1.5, 3.0, and 7.0 T.
• Weighted linear fitting and optimized spin echo and gradient echo timing were utilized.
• T(2), T'(2), and T*(2) values were calculated for frontal gray matter, occipital gray matter, and white matter.

Main Results:

• GESSE is insensitive to RF pulse errors and image distortions, enabling simultaneous T(2) and T'(2) estimation.
• A weighted linear fit improved T(2) accuracy compared to nonlinear fitting.
• T(2), T'(2), and T*(2) values decreased with increasing field strength across all investigated brain regions.
• T(2) exhibited a linear dependence on field strength.

Conclusions:

• GESSE is a robust method for quantitative T(2) and T'(2) mapping at 7.0 T.
• Optimized fitting and timing parameters enhance the reliability of T(2) measurements.
• Field-dependent changes in T(2), T'(2), and T*(2) were observed in human brain tissues.