Abstract 13022: Phase Contrast Velocity Mapping is Accurate Just Proximal and Distal to Stent Artifact During Cardiac Magnetic Resonance Imaging
Background: Cardiac magnetic resonance (CMR) is frequently used to evaluate and follow post-operative congenital heart disease. Phase contrast velocity mapping (PC-MRI) is increasingly relied upon for evaluation of physiology, often requiring measurements in the vicinity of various metal stents. Little data are available on the accuracy of PC-MRI flow measurements in the vicinity of stents. We therefore sought to determine this accuracy using in vitro experiments.
Methods: An in vitro flow phantom was used with three stent types: 1) 316L stainless steel, 2) nitinol self-expanding and 3) platinum-iridium. Steady and pulsatile flow was delivered with a CMR-compatible pump (CardioFlow 5000, Shelley Medical). Mean flows ranged from 0.5 to 7 L/min. Flows were measured using a transit time flow meter (ME19PSN, Transonic, Inc.). For each condition, 5 PC-MRI acquisitions were made: within the stent, immediately adjacent to both edges of stent artifact, and 1 cm upstream and downstream of the artifact. Mean PC-MRI flows were calculated by segmenting the tube lumen using clinical software (ARGUS, Siemens, Inc.). Locations and stent type were compared using linear regression, Bland-Altman and intraclass correlation.
Results: PC-MRI flows within the stent artifact were inaccurate for all stents studied, generally underestimating flow meter measured flow. Agreement between PC-MRI and flow meter measured flows was excellent for all stent types, both immediately adjacent to and 1cm away from the edge of the stent artifact. (See Table) Agreement was highest for the platinum-iridium stent and lowest for the nitinol stent.
Conclusions: PC-MRI flows are highly accurate just upstream and downstream of a variety of stents used clinically, including stainless steel. Nitinol had the greatest influence on PC-MRI flows. These findings support the use of PC-MRI to directly measure flows in stented vessels, which supports our previously reported clinical experience.
- © 2013 by American Heart Association, Inc.