3:18 PM Abstract No. 314 ■ FEATURED ABSTRACT In vitro feasibility study of magnetic resonance navigation in realistic physiological settings

To demonstrate feasibility of Magnetic Resonance Navigation (MRN) as a treatment for non-resectable HCC, which consists in steering magnetic drug-eluting microbeads (MDEBs) in hepatic arteries towards diseased liver lobes using a clinical MRI machine, with regards to physiological, anatomical and technological limitations. In the first phase, in vivo experiments were performed on pig models to characterize the efficiency of arterial flow reduction using a balloon catheter and the reliability of flow measurement methods. Cine phase-contrast imaging was performed on the proper hepatic artery of eight pigs, with a balloon catheter, positioned upstream, both inflated and deflated. Four pigs had a liver lobe embolized using radio-opaque microbeads. In the second phase, in vitro proof-of-concept MRN experiments were performed to demonstrate the feasibility of using a custom gradient sequence on an unmodified MRI machine (Siemens, Germany) to selectively steer MDEB boluses of controlled size in a one-bifurcation arterial system. In the first phase, cine phase-contrast imaging on one-lobe embolized pigs revealed that the use of a balloon catheter, combined with a 0.5 ml/s saline injection, decreased the average flow velocity from 13.6 ± 2.0 cm/s to 5.4 ± 3.0 cm/s. For unembolized pigs [respectively one-lobe embolized], the systolic-diastolic flow variation was decreased from 24.0 ± 14 cm/s to 4.9 ± 2.3 cm/s [from 14.9 ± 1.4 cm/s to 3.3 ± 2.2 cm/s] (p<0.05 in all cases). In the second phase, we obtain different (p<0.0001) right/total bolus steering ratios of 22.5% when applying a 20 mT/m gradient towards the left and 67.5% when applying a 20 mT/m gradient towards the right, resulting in an overall steering efficiency of 72.5% (different from the 50% baseline, p<0.0001). This study shows that the use of a balloon catheter reduces arterial hepatic flow magnitude and variation. In reduced-flow conditions, satisfactory MDEBs steering efficiency is achieved in one-bifurcation in vitro settings. This demonstrates feasibility of MRN under realistic physiological and anatomical settings and with an unmodified clinical MRI machine.