This international standard specifies measurement procedures for the determination of many essential medical MR equipment image quality parameters. Measurement procedures as addressed in this standard are suitable for: - quality assessment in the acceptance test; - quality assurance in the constancy test. In addition, the measurement procedures specified in this standard may also be useful for type tests, although that is not an objective of this standard. The scope of this standard is also limited to measuring image quality characteristics in test devices, not in patient images. The measurement procedures specified in this standard are directed to: a) manufacturers, who can demonstrate compliance by performing acceptance and constancy methods as described by this standard, b) test houses, which can confirm performance of mr equipment using methods described in this standard, c) regulatory authorities, who can reference this standard, and d) responsible organisations who want to perform acceptance and constancy tests using methods described in this standard. The essential image quality parameters and measurement methodologies defined in this standard are: - signal-to-noise ratio, - uniformity, - slice thickness and slice profile, - geometric distortion, - spatial resolution, and - ghosting. This standard describes the preferred measurement procedures. It also describes alternative methods in Annex A. The preferred test methods may be substituted with the alternative methods. If necessary, other methods not described in this standard may be used, provided these other test methods are documented and validated against the methods described in the standard. Validation of other test methods requires an analysis of test sensitivity to the same parameter of interest and an analysis of the insensitivity of the test to other unrelated parameters and should demonstrate a similar, or better, level of sensitivity to the same parameter of interest and a similar, or better, level of robustness against unrelated parameters. All methods shall produce quantitative results. This standard also presents requirements for constancy tests suitable for MR equipment quality assurance programs concerning essential image quality parameters. There are no preferred constancy test methods, to provide flexibility in using existing automated procedures where available, but suggested examples of test methods are found in Annex A. If necessary, other constancy test methods not described in this standard may be used. Since the needs of responsible organisations' quality assurance programs may vary, responsible organisations are encouraged to determine the necessary scope of tests, quality of the tests, and the sensitivity of the data analysis etc. This standard places an emphasis on consistently repeatable, automated measuring tools that facilitate trend analysis and the frequent quick testing of a small set of important parameters which are sensitive to the overall operating characteristics of the mr equipment.