A closer look into the Partial Body SAR definition in IEC 60601-2-33

Motivation: IEC 60601-2-33 does not provide any details on the "homogeneous cylinder" used to determine the effective volume of the RF transmit coil, upon which Partial Body SAR is derived. Goal(s): This study investigated whether the detailed specifications of the "homogeneous cylinder" have any significant impact on the effective volume of the RF transmit coil and the resultant SAR exposure limit. Approach: Numerical electromagnetic simulations were performed to determine the effective volume of typical whole body transmit coils with a variety of coil-filling cylinders. Results: Various coil-filling cylinders resulted in up to 8.1% difference of whole-body SAR exposure limit. Impact: The lack of specifications in IEC 60601-2-33 regarding RF transmit coil's effective volume can cause uncertainties in SAR exposure limit assessment. We propose the standard adding more specifications on this subject.