Assessment of the potential for catheter heating during MR imaging

摘要

There is an increasing interest in using MR imaging as a means of guiding endovascular procedures due to MR's unparalleled soft tissue characterization capabilities and its ability to assess functional parameters such as blood flow and tissue perfusion. In order to evaluate the potential safety risk of catheter heating, we performed in vitro testing where we measured heat deposition in sample non-ferrous 5F catheters ranging in length from 80cm - 110cm within a gel phantom. To identify the conditions for maximum heat deposition adjacent to catheters, we measured (1) the effect of variable immersed lengths, (2) the effect of variable SAR, and (3) whether heating varied along the catheter shaft. Net temperature rise per scan and initial rate of temperature rise were determined for all configurations. The temperature recordings clearly and consistently demonstrated the correlations between MR scanning under the three variable conditions and heat deposition. Our overall maximum heating condition, which combined the maximum heating conditions of all three variables, was modest (<2℃/min), but well above the temperature response of the gel well away from the catheter. Reduced SAR acquisitions effectively limited these temperature rises, and RF exposure levels of 0.2W/kg produced little detectible temperature change over the 2 minute MR acquisitions studied here. A combination of SAR limits and imaging duty cycle restrictions appear to be sufficient to permit MR imaging in catheterized patients without concern for thermal injury.