Guidance for Magnetic Resonance Diagnostic Devices - Criteria for Significant Risk Investigations




This document is intended to provide guidance in the preparation of a regulatory submission. It does not bind the FDA or the regulated industry in any manner.


Computed Imaging Devices Branch
Division of Reproductive, Abdominal,
Ear, Nose, Throat and Radiological Devices
Office of Device Evaluation





Document Issued on September 29, 1997




While this guidance document represents a final document, comments and suggestions may be submitted at any time for Agency consideration by writing Robert A. Phillips, Ph.D., Chief, Computed Imaging Devices Branch, Center for Devices and Radiological Health, HFZ-470, 9200 Corporate Blvd., Rockville, MD 20850. For questions regarding the use or interpretation of this guidance, contact Loren A. Zaremba, Ph.D., at 301-594-1212.




U.S. Department of Health and Human Services
Food and Drug Administration
Center for Devices and Radiological Health




Magnetic Resonance Diagnostic Devices

Criteria for Significant Risk Investigations

Patient studies utilizing magnetic resonance diagnostic devices which are conducted under any one of the following operating conditions are considered significant risk investigations, and require approval of an investigational device exemption (IDE) by the Food and Drug Administration (FDA) Center for Devices and Radiological Health (CDRH):

  1. Main static magnetic field greater than 4 tesla;

  2. Specific absorption rate (SAR) greater than

    1. 4 W/kg averaged over the whole body for any period of 15 minutes; or

    2. 3 W/kg averaged over the head for any period of 10 minutes; or

    3. 8 W/kg in any gram of tissue in the head or torso, or 12 W/kg in any gram of tissue in the extremities, for any period of 5 minutes;

  3. Time rate of change of gradient fields (dB/dt) sufficient to produce severe discomfort or painful nerve stimulation; or

  4. Peak unweighted sound pressure level greater than 140 dB or A-weighted r.m.s. sound pressure level greater than 99 dBA with hearing protection in place.

These criteria apply only to device operating conditions. Other aspects of the study may involve significant risks and the study may therefore require IDE approval.

(Updated October 3, 1997)