NEMA MS 3:2008 (R2014)

This document defines a method for measuring image-uniformity performance of diagnostic magnetic resonance imaging systems using single channel volume coils and performing proton imaging. This document does not address the use of surface coils, chemical shift imaging, or spectroscopy. Image uniformity can be characterized in a number of different ways. The choice of a measurement and reporting method was guided by a desire for simplicity, accuracy, and ease of implementation on all MR systems. The peak deviation method represents a single image test that can quickly determine and report uniformity with a single number. It works best with very high SNR images. The gray-scale uniformity map image represents a single image test that can visually describe image uniformity. Both the ACR MR Accreditation Procedure method and the Normalized Absolute Average Deviation method resolve some of the image SNR issues of the peak deviation method. Measurements are made over a volume that is representative of the region used for typical clinical studies. Due to the difficulty in handling large phantoms, it is permitted to use a test phantom that only covers 85% of the specification area. This document does not address the use of special purpose coils (see MS 6) or coils that require multiple receiver channels for operation (see MS 9).