Changes in the specific absorption rate (SAR) of radiofrequency energy in patients with retained cardiac leads during MRI at 1.5T and 3T.

For the models based on 6 patients studied, simulations suggest that MRI could be performed safely using a local head coil at both 1.5T and 3T, and with a body coil at 1.5T with pulses that produced <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>4</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> . MRI at 3T could be performed safely in these patients using pulses with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mrow><mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo> <mml:mrow><mml:msubsup><mml:mi>B</mml:mi> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo></mml:msubsup> </mml:mrow> <mml:mo>‖</mml:mo> <mml:mo>‖</mml:mo></mml:mrow> <mml:mo>≤</mml:mo> <mml:mn>2</mml:mn> <mml:mo> </mml:mo> <mml:mo>μ</mml:mo> <mml:mi>T</mml:mi></mml:mrow> </mml:math> .