Contains Nonbinding Recommendations 
 
 
Criteria for Significant Risk 
Investigations of Magnetic Resonance 
Diagnostic Devices 
 
Guidance for Industry 
and Food and Drug Administration 
Staff 
Document issued on: June 20, 2014 
 
This document supersedes Guidance for Industry and FDA Staff  Criteria 
for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices 
issued on July 14, 2003. 
 
On June 20, 2014 this document was edited to amend a table on specific absorption 
rate (SAR) and make minor formatting and contact updates. 
 
For questions regarding this document, contact Jana Delfino, Ph.D., at 301-796-
6503, or by e-mail at jana.delfino@fda.hhs.gov. 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Devices and Radiological Health 
 
Magnetic Resonance and Electronic Products Branch 
Division of Radiological Health 
Office of In Vitro Diagnostics and Radiological Health 
    Contains Nonbinding Recommendations 
 
 
Preface 
Public Comment 
You may submit electronic comments and suggestions at any time for Agency consideration to 
http://www.regulations.gov. Submit written comments to the Division of Dockets Management, 
Food and Drug Administration, 5630 Fishers Lane, Room 1061, (HFA-305), Rockville, MD 
20852.  When submitting comments, please refer to the exact title of this guidance document.  
 
Comments may not be acted upon by the Agency until the document is next revised or updated. 
Additional Copies 
Additional copies are available from the Internet. You may also send an e-mail request to 
CDRH-Guidance@fda.hhs.gov to receive a copy of the guidance.  Please use the document 
number 793 to identify the guidance you are requesting.   
Criteria for Significant Risk 
Investigations of Magnetic Resonance 
Diagnostic Devices 
 
Guidance for Industry 
and Food and Drug Administration 
Staff 
This guidance represents the Food and Drug Administration's (FDA's) current thinking 
on this topic. It does not create or confer any rights for or on any person and does not 
operate to bind FDA or the public. You can use an alternative approach if the approach 
satisfies the requirements of the applicable statutes and regulations. If you want to 
discuss an alternative approach, contact the FDA staff responsible for implementing this 
guidance. If you cannot identify the appropriate FDA staff, call the appropriate number 
listed on the title page of this guidance. 
Introduction 
This guidance describes the device operation conditions for magnetic resonance diagnostic 
devices that FDA considers significant risk for the purposes of determining whether a clinical 
study requires Agency approval of an Investigation Device Exemption (IDE). Magnetic 
resonance diagnostic devices are class II devices described under 21 CFR 892.1000. The 
product codes for these devices are: 
 
LNH   Magnetic Resonance Imaging System 
LNI   Magnetic Resonance Spectroscopic System 
 
FDA's guidance documents, including this guidance, do not establish legally enforceable 
responsibilities. Instead, guidances describe the Agency's current thinking on a topic and 
should be viewed only as recommendations, unless specific regulatory or statutory 
requirements are cited. The use of the word should in Agency guidances means that 
something is suggested or recommended, but not required. 
1 
   
Studies of Magnetic Resonance Diagnostic Devices 
If a clinical study is needed to demonstrate substantial equivalence, i.e., conducted prior to 
obtaining 510(k) clearance of the device, the study must be conducted under the IDE 
regulation (21 CFR Part 812). FDA believes that a magnetic resonance diagnostic device used 
under any one of the operating conditions listed below is a significant risk device as defined 
in 21 CFR 812.3(m)(4) and, therefore, that studies involving such a device do not qualify for 
the abbreviated IDE requirements of 21 CFR 812.2(b). In addition to the requirement of 
having an FDA-approved IDE, sponsors of significant risk studies must comply with the 
regulations governing institutional review boards (21 CFR Part 56) and informed consent (21 
CFR Part 50). 
Significant Risk Magnetic Resonance Diagnostic 
Devices 
You should consider the following operating conditions when assessing whether a study may 
be considered significant risk: 
  main static magnetic field 
  specific absorption rate (SAR) 
  gradient fields rate of change 
  sound pressure level 
Generally, FDA deems magnetic resonance diagnostic devices significant risk when used 
under any of the operating conditions described below. 
 
Main Static Magnetic Field 
Main static magnetic 
Population 
field greater than (tesla) 
adults, children, and infants aged > 1 month  8 
neonates i.e., infants aged 1 month or less  4 
 
   
2 
   
Specific Absorption Rate (SAR) 
Time (min)  SAR 
Site  Dose 
equal to or greater than:  (W/kg) 
whole body  averaged over  15  >4 
head  averaged over  10  >3.2 
 
If you have questions about significant risk criteria related to local SAR, you may 
wish to contact FDA. 
 
Gradient Fields Rate of Change 
Any time rate of change of gradient fields (dB/dt) sufficient to produce severe 
discomfort or painful nerve stimulation 
 
Sound Pressure Level 
Peak unweighted sound pressure level greater than 140 dB. 
 
A-weighted root mean square (rms) 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, therefore, may require IDE approval regardless of 
operating conditions. See Blue Book Memorandum entitled Significant Risk and Non-
significant Risk Medical Device Studies 
(http://www.fda.gov/downloads/RegulatoryInformation/Guidances/ucm126418.pdf) for 
further discussion. 
 
After FDA determines that the device is substantially equivalent, clinical studies conducted in 
accordance with the indications reviewed in the 510(k), including clinical design validation 
studies conducted in accordance with the quality systems regulation, are exempt from the 
investigational device exemptions (IDE) requirements. However, such studies must be 
performed in conformance with 21 CFR 56 and 21 CFR 50. 
 
3