SPARE: A robust method for magnetic resonance imaging in inhomogeneous fields

Area of Science:

• Magnetic Resonance Imaging
• Biophysics
• Medical Physics

Background:

• Main magnetic field inhomogeneity and chemical shifts in MRI can cause geometric distortions and artifacts.
• Radiofrequency (RF) field variations can lead to image amplitude fluctuations.
• Power deposition is a critical safety concern for in vivo MRI at high field strengths.

Purpose of the Study:

• To develop a novel spin-echo train imaging sequence.
• To eliminate geometric distortions in the imaging plane caused by main field inhomogeneity.
• To minimize artifacts and ensure safety for in vivo high-field MRI.

Main Methods:

• Development of a spin-echo train imaging sequence.
• Implementation of high gradient strengths and short radiofrequency pulses to minimize slice displacement.
• Utilized low-flip-angle refocusing pulses to reduce power deposition.
• Sequence tested on a Bruker whole-body 3T system.

Main Results:

• The developed sequence is free from geometric distortions in the imaging plane due to main field inhomogeneity.
• Chemical shifts and inhomogeneities cause only slice displacement, minimized by high gradients and short RF pulses.
• RF field variations cause amplitude variations but no other artifacts.
• Low-flip-angle pulses reduced power deposition to safe in vivo levels at 3T.

Conclusions:

• The novel spin-echo train sequence effectively eliminates geometric distortions in the imaging plane.
• The sequence minimizes artifacts and ensures safety for in vivo high-field MRI applications.
• Demonstrated feasibility with example images from a phantom and human head at 3T.