Purpose: To evaluate the local specific absorption rate (SAR) and heating around retained cardiac leads during MRI at 64 MHz (1.5T) and 127 MHz (3T) as a function of RF coil type and imaging landmark.
Methods: Numerical models of retained cardiac leads were built from CT and X-ray images of 6 patients with retained cardiac leads. Electromagnetic simulations and bio-heat modeling were performed with MRI RF body and head coils tuned to 64 MHz and 127 MHz and positioned at 9 different imaging landmarks covering an area from the head to the lower limbs.
Results: For all patients and at both 1.5T and 3T, local transmit head coils produced negligible temperature rise ( ) for . For body imaging with quadrature-driven coils at 1.5T, during a 10-min scan remained < 3°C at all imaging landmarks for and <6°C for . For body imaging at 3T, during a 10-min scan remained < 6°C at all imaging landmarks for . For shorter pulse sequences up to 2 min, remained < 6°C for .
Conclusion: 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 . MRI at 3T could be performed safely in these patients using pulses with .
Keywords: RF heating; SAR; abandoned lead; anatomical models; cardiac implanted electronic device; computational modeling; defibrillator; finite element method; pacemaker; retained lead; safety.
© 2018 International Society for Magnetic Resonance in Medicine.