NEMA releases new MRI performance standards
The National Electrical Manufacturers Association (NEMA) on Wednesday published four standards that govern the overall quality of magnetic resonance imaging (MRI) systems. The standards are part of a series the organization is releasing to gauge performance of systems in a number of parameters, including noise levels, energy deposition, and electric field strength, the organization said.
The standards are as follows:
  • One standard has been revised: MS 4-2006, for Acoustic  Noise Measurement Procedure for Diagnostic Magnetic Resonance Imaging Devices;  and 
  • The following are new: MS 10-2006, Determination of  Local Specific Absorption Rate (SAR) in Diagnostic Magnetic Resonance Imaging;  MS 11-2006, Determination of Gradient-Induced Electric Fields in Diagnostic  Magnetic Resonance Imaging; and MS 12-2006, Quantification and Mapping of  Geometric Distortion for Special Applications.
NEMA puts out these standards for use by equipment manufacturers, testing houses, prospective purchasers, and users. Manufacturers are permitted to use them to help develop system performance specifications, and it is hoped the standards will benefit prospective buyers. The parameters, which are sometimes used to shape federal regulations, are also supplied as a guide to those factors that can influence the measurement. Additionally, they serve as reference procedures for acceptance testing and periodic quality assurance, NEMA said.

In the case of MS 4, it has undergone revision due to the gradient performance of modern MRI scanners that have advanced, making some basic assumptions and guidance in the original standard obsolete.

MS 10 is used for measuring local regions of high Specific Absorption Rate (SAR) from radiofrequency (RF) power deposition. NEMA standard MS 8 is useful for measuring whole-body average SAR. By using both MS 8 and MS 10, it is possible to completely characterize RF power deposition both whole-body and local. MS 11 presents a measurement method for determining gradient-induced electric fields, which affect the safety and comfort of patients. Lastly, MS 12 provides a series of recommendations on how to measure and present the distortion analysis information in order to meet this growing need, NEMA said.
The different standards can be found online at: