Rapid Fourier imaging using steady-state free precession.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Biomedical Engineering

Background:

• Steady-state free precession (SSFP) is a pulse sequence used in MRI.
• Efficient collection of spin echoes is crucial for image quality and speed.
• Controlling tissue contrast and slice selection are key challenges in MRI.

Purpose of the Study:

• To develop a method for collecting full spin echoes within the SSFP sequence.
• To enable 2D and 3D Fourier transform imaging techniques.
• To investigate the manipulation of tissue contrast and slice selection.

Main Methods:

• Reversal of the read gradient to collect a full spin echo between RF pulses.
• Use of orthogonal gradient pulses for dephasing and rephasing transverse magnetization.
• Implementation of oscillating bipolar sawtooth gradients for slice selection in 2D imaging.

Main Results:

• Achieved minimum data collection times of 3.1s (3D) and 25s (2D).
• Demonstrated excellent slice selection with <5% signal outside the central lobe.
• Showed manipulation of gray/white matter contrast by altering RF pulse angles (30° vs. 90°).

Conclusions:

• The novel SSFP technique allows for efficient spin echo acquisition.
• Tissue contrast can be precisely controlled by adjusting the RF pulse angle.
• The method provides accurate slice selection, enhancing image quality and diagnostic potential.