AAPM Task Group Report 325: MRI static magnetic field homogeneity measurement and evaluation procedures – Guidance and resources

Measurement of static magnetic field (B₀) homogeneity is an essential component of routine MRI system evaluation. This report summarizes the work of AAPM Task Group (TG) 325 on vendor-specific methods of B₀ homogeneity measurement and evaluation. TG 325 was charged with producing a set of detailed, step-by-step instructions to implement B₀ homogeneity measurement methods discussed in the American College of Radiology (ACR) MRI Quality Control Manual using specific makes and models of MRI scanners. The TG produced such instructions for as many approaches as was relevant and practical on six currently available vendor platforms including details of software/tools, settings, phantoms, and other experimental details needed for a reproducible protocol. Because edits to these instructions may need to be made as vendors enter and exit the market and change available tools, interfaces, and access levels over time, the step-by-step instructions are published as a living document on the AAPM website. This summary document provides an introduction to B₀ homogeneity testing in MRI and several of the common methods for its measurement and evaluation. A living document on the AAPM website provides vendor-specific step-by-step instructions for performing these tests to facilitate accurate and reproducible B₀ homogeneity evaluation on a routine basis.