External calibration of the spectral coverage for three-dimensional multispectral MRI

Area of Science:

• Medical Imaging
• Magnetic Resonance Imaging (MRI)

Background:

• Metal implants cause spatial frequency dispersion in MRI, degrading image quality.
• Three-dimensional multispectral imaging (3D-MSI) sequences mitigate this dispersion by combining images at different frequency offsets.
• The required spectral coverage for 3D-MSI varies with implant characteristics.

Purpose of the Study:

• To prospectively calibrate spectral coverage for MAVRIC 3D-MSI scans.
• To improve image quality and reduce scan time for MRI near orthopedic implants.
• To establish a calibration procedure for optimizing 3D-MSI near metallic implants.

Main Methods:

• A calibration scan generated a map of frequency offsets around the implant.
• Magnitude images removed outliers, and processed maps determined cutoff frequency offset and spectral bin count.
• The method was tested retrospectively on 13 subjects and prospectively on six subjects using MAVRIC-SL sequences.

Main Results:

• Both retrospectively and prospectively calibrated MAVRIC-SL images adequately delineated the implant boundary, even with fewer spectral bins.
• The calibration successfully determined the optimal number of spectral bins required for high-quality imaging.

Conclusions:

• This calibration procedure enhances signal-to-noise ratio and reduces scan time for 3D-MSI near orthopedic implants.
• Implementing this calibration improves clinical workflow for MRI near metallic implants.
• Optimized spectral coverage is crucial for effective 3D-MSI in the presence of metal artifacts.