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RF Safety of Wires in Interventional MRI: Using a Safety Index

Summary: RF Safety of Wires in Interventional MRI:
Using a Safety Index
Christopher J. Yeung,1
Robert C. Susil,1
and Ergin Atalar1,2*
With the rapid growth of interventional MRI, radiofrequency (RF)
heating at the tips of guidewires, catheters, and other wire-
shaped devices has become an important safety issue. Previ-
ous studies have identified some of the variables that affect the
relative magnitude of this heating but none could predict the
absolute amount of heating to formulate safety margins. This
study presents the first theoretical model of wire tip heating
that can accurately predict its absolute value, assuming a
straight wire, a homogeneous RF coil, and a wire that does not
extend out of the tissue. The local specific absorption rate
(SAR) amplification from induced currents on insulated and
bare wires was calculated using the method of moments. This
SAR gain was combined with a semianalytic solution to the
bioheat transfer equation to generate a safety index. The safety
index (C/(W/kg)) is a measure of the in vivo temperature


Source: Atalar, Ergin - Department of Electrical and Electronics Engineering, Bilkent University


Collections: Engineering; Biology and Medicine