Off-resonance positive contrast imaging of a passive endomyocardial catheter in swine.

The use of off-resonance methods in interventional MRI may be valuable since active devices that provide positive signal enhancements are currently not approved for human use. This study investigated the capacity of a low flip angle steady-state free precession (FLAPS) method for generating off-resonance positive contrast surrounding a susceptibility-shifted endomyocardial Stiletto catheter in excised swine hearts and in live swine. Consistent with theory, discernable positive contrast surrounding the interventional device was visualized under ex-vivo (CNR of 24 +/- 2.1 in the left ventricular (LV) chamber and 18 +/- 2.7 in LV myocardium) and in-vivo conditions (CNR of 22 +/- 3.9 in aorta, 16 +/- 4.1 in the LV chamber and 13 +/- 0.9 in LV myocardium). The findings show that off-resonance imaging with the FLAPS method may be used for passive device visualization with positive contrast. Further studies are necessary prior to clinical translation.