Accelerating fully phase-encoded MRI near metal using multiband radiofrequency excitation

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Radiology

Background:

• Metallic prostheses cause significant magnetic field distortions, leading to signal dropout in MRI.
• Accelerating imaging near metal implants is crucial for effective patient monitoring and diagnosis.

Purpose of the Study:

• To develop a multiband radiofrequency (RF) excitation strategy for simultaneous excitation of multiple RF offsets.
• To accelerate fully phase-encoded (FPE) imaging in the presence of metallic prostheses.

Main Methods:

• Designed and incorporated multiband RF excitation into a spectrally resolved FPE (SR-FPE) imaging scheme.
• Compared a triband acquisition with single-band acquisitions using a phantom with a hip prosthesis.
• Acquired in vivo data in the knee of a healthy volunteer and a volunteer with a total knee prosthetic implant.

Main Results:

• Phantom images with triband excitation were comparable to single-band acquisitions but achieved a threefold acceleration.
• In vivo multiband images of a healthy knee near metal showed excellent anatomical detail.
• In vivo images of a total knee replacement demonstrated reduced signal dropout compared to 2D-FSE.

Conclusions:

• FPE imaging with multiband excitation is feasible even with extreme off-resonance effects caused by metal.
• This approach significantly reduces scan time and broadens off-resonance coverage for in vivo FPE imaging near metallic prostheses.