Finite RF pulse correction on DESPOT2.

Area of Science:

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

Background:

• Balanced steady state free precession (bSSFP) imaging is sensitive to magnetization transfer (MT) and radiofrequency (RF) pulse duration.
• Accurate quantification of transverse relaxation (T2) is crucial for various MRI applications.
• Existing T2 quantification methods using driven equilibrium single pulse observation of T2 (DESS-T2) can be affected by these bSSFP-specific phenomena.

Purpose of the Study:

• To investigate the impact of MT and finite RF pulse effects on DESS-T2 quantification.
• To develop and validate a method for obtaining accurate, MT-free T2 values in bSSFP imaging.
• To reduce the variability of T2 measurements in bSSFP sequences.

Main Methods:

• Implementation of a correction for finite RF pulse effects within the DESS-T2 framework.
• Acquisition of bSSFP images using elongated RF pulses to minimize MT effects.
• Comparison of T2 quantification results before and after applying the correction.

Main Results:

• Short RF pulses (TRF/TR≪1) in bSSFP lead to significant MT effects.
• Prolonged RF pulses (TRF/TR>0.2) minimize MT but increase finite pulse effects.
• The implemented correction successfully removes the dependency of DESS-T2 on RF pulse duration.
• T2 measurement variation was reduced from over 50% to less than 10%.

Conclusions:

• Elongated RF pulses enable MT-free bSSFP imaging.
• The developed correction method accurately quantifies T2 values in bSSFP.
• This approach provides a reliable means for accurate T2 mapping using bSSFP sequences.