Abstract
BACKGROUND: Low-field (0.55T) magnetic resonance imaging (MRI) may allow MRI-guided interventions using available catheterization equipment, as radiofrequency-induced heating of interventional devices is reduced at low field. The purpose of this study was to test the feasibility of real-time MRI-guided right and left heart catheterization (R&LHC) as well as angioplasty and stenting of the inferior vena cava using a commercially available 0.55T MRI system (MAGNETOM Free.Max, Siemens Healthineers AG, Erlangen, Germany) with 80 cm patient bore and maximum gradient amplitude and slew rate of 26 mT/m and 45 mT/m/ms, respectively. A secondary aim was to evaluate three different sizes of magnetic resonance (MR)-visible markers. METHODS: Sheaths were placed in the femoral vein and artery of juvenile Yorkshire pigs under general anesthesia. Air-filled balloon wedge catheters and Judkins right catheters were used for R&LHC, respectively, aided by an MR-compatible guidewire. Ferumoxytol was administered as a T1-shortening contrast agent and real-time visualization was carried out with a research interactive sequence using different spatiotemporal resolution settings. IVC angioplasty was performed using balloons filled with 1% gadolinium, and IVC stenting was performed with stainless-steel stents and one platinum-iridium-covered sten. RESULTS: RHC was successful in all eight attempts with balloon tip visibility in all real-time protocols. One pig expired with ferumoxytol infusion, but the catheterization was completed post-mortem. LHC and IVC angioplasty were attempted and successful in two and four pigs, respectively. For stenting, higher resolution, lower frame rate imaging was used. All six attempted stent implantations were successful. The MR markers on the angioplasty balloon with widths of 0.5 and 1 mm were more visible than the 0.25 mm markers. Marker placement affected distinguishability from the crimped stent. Stainless-steel stents created only minimal signal voids pre- and post-deployment; however, the platinum-iridium stent caused significant artifact obscuring wall apposition assessment. CONCLUSION: This study is the first to demonstrate the technical feasibility of R&LHC, IVC angioplasty, and IVC stenting using real-time MRI on a commercially available low-field scanner.