Table 3.

International Electrotechnical Commission’s SAR regulations ³ , ⁴⁷ and examples of how to reduce SAR. ¹¹ , ⁴⁹

Operating Mode	Whole‐Body SAR limit (W/kg)	Head SAR limit (W/kg)	Risk of physiological stress to subjects	Requirements
Normal	2	3.2	Unlikely to cause physiological stress	None – used for routine scanning
First‐level controlled	4	3.2	May cause physiological stress	Needs to be controlled by medical supervision
Second‐level controlled			Significant risk	Explicit ethical approval is required according to local requirements

SAR reduction method	Trade‐offs
Change patient into light gown/scrubs	Some patients may object
Control room temperature to keep cool	Patient may feel the cold more
Reduce the slice number per acquisition	Longer scanning time
Reduce the flip angle	Could alter contrast and signal to noise ratio
Alternate high and low SAR sequences/have breaks between high SAR sequences	Possible longer scanning time
Reduce pulse frequency (use normal or low SAR options)	Longer scanning time
Increase TR	Longer scanning time
Remove saturation bands	Increase in image artefact
Remove Restore pulse	Increase in TR increases scanning time
Reduce echo train length in (turbo factor)	Longer scanning time