NEMA recommends method for measuring non-uniformity of MR images

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The National Electrical Manufacturers Association (NEMA) has published its MS 3-2008 Determination of Image Uniformity in Diagnostic MRI, produced by the MR Section of Medical Imaging and Technology Alliance (MITA). 

According to Michael Steckner of the MR section at NEMA that developed the standard, MS 3 prescribes a method to characterize the low spatial frequency non-uniformities typical of such images.

The publication is one of a series of test standards developed by the medical diagnostic imaging industry for the measurement of performance parameters governing image quality of MRI systems.

“It is important to quantify image non-uniformity because of the impact it has on image quality,” Steckner said. “This standard characterizes image non-uniformity qualitatively with a gray-scale uniformity map and quantitatively with simple figures of merit that analyze the range of pixel intensities relative to some measure of the average image intensity. This newly revised standard now permits the ACR-MRAP and IEC performance standard methods for determining image uniformity, both methods being more robust against variations in measurement SNR [signal-to-noise ratio].”

To make this standard consistent with the structure of related standards, it covers single-channel volume coils exclusively, NEMA said.

The new edition has been modified to permit the gray-scale map definition of NEMA MS-6 Determination of SNR and Image Uniformity for Single-channel Non-Volume Coils in Diagnostic MR Imaging for added flexibility.