Practical aspects of MR imaging in the presence of conductive guide wires.

Various aspects of RF-induced heating of guide wires during their MRI guidance have been investigated in the past. However, the previous works focused on inducing tip heating in either fully immersed or tip-immersed (and otherwise free) wires of impractical lengths in small phantoms. This study simulates real clinical conditions using a product guide wire and a same-length conductive wire partially inserted into a torso-size phantom filled with saline solution. The purpose was to identify potential safety concerns relevant to real clinical applications, as opposed to identifying the worst-case heating scenario. Significant heating occurred at the insertion point, independent of tip heating, with a strong correlation with excitation frequency-dependent imaging parameters. Heat transfer through the wire was also demonstrated to be a safety concern. From these experiments, we have been able to demonstrate additional impacting factors that increase the complexity of safety considerations for the use of conductive guide wires during MR imaging. Safety under a particular set of conditions does not imply safety in all possible conditions that can be encountered during real MRI-guided interventions.