Robust T₂ estimation with balanced steady state free precession.

Area of Science:

• Magnetic Resonance Imaging
• Biophysics

Background:

• Balanced steady state free precession (bSSFP) is a widely used MRI technique.
• Accurate T2 quantification is crucial for various diagnostic applications.
• B1 field inhomogeneity and magnetization transfer (MT) effects can introduce errors in T2 measurements.

Purpose of the Study:

• To develop a novel signal representation for bSSFP.
• To demonstrate the independence of T2 quantification from B1 and MT effects.
• To establish a robust method for T2 measurement in bSSFP imaging.

Main Methods:

• A new bSSFP signal model was developed, explicitly dependent on T2 and a novel parameter c.
• Magnetization transfer effects were incorporated by redefining T1 and E1.
• Phase-cycled bSSFP brain scans were acquired at 3T with varying parameters.
• T2 and c were estimated using the Variable Projection (VARPRO) method.
• Monte-Carlo simulations assessed T2 estimation precision.

Main Results:

• The developed model confirmed T2 independence from TR, flip angle, B1 inhomogeneity, and RF pulse duration.
• Variations in protocol settings primarily affected the estimation of parameter c, not T2.
• Initial experiments validated the theoretical predictions.

Conclusions:

• The novel bSSFP signal model offers T2 quantification independent of B1 and MT effects.
• This approach presents a potentially robust methodology for accurate T2 measurement.
• Further validation against existing standards is recommended.