Accelerated passive MR catheter tracking into the carotid artery of canines.
BACKGROUND
Using magnetic resonance (MR) imaging for navigating catheters has several advantages when compared with the current "gold standard" modality of X-ray imaging. A significant drawback to interventional MR is inferior temporal and spatial resolutions, as high spatial resolution images cannot be collected and displayed at rates equal to X-ray imaging. In particular, passive MR catheter tracking experiments that use positive contrast mechanisms have poor temporal imaging rates and signal-to-noise ratio. As a result, with passive methods, it is often difficult to reconstruct motion artifact-free tracking images from areas with motion, such as the thoracic cavity.


METHODS
In this study, several accelerated MR acquisition strategies, including parallel imaging and compressed sensing (CS), were evaluated to determine which method is most effective at improving the frame rate and passive detection of catheters in regions of physiological motion. Device navigation was performed both in vitro, through the aortic arch of an anthropomorphic chest phantom, and in vivo from the femoral artery, up the descending aorta into the supra-aortic branching vessels in canines.


CONCLUSIONS
The different parallel imaging methods produced images of low quality. CS with a two-fold acceleration was found to be the most effective method for generating tracking images, improving the image frame rate to 5.2 Hz, while maintaining a relatively high in-plane resolution. Using CS, motion artifact was decreased and the catheters were visualized with good conspicuity near the heart.


CONCLUSIONS
The improvement in the imaging frame rate by image acceleration was sufficient to overcome motion artifacts and to better visualize catheters in the thoracic cavity with passive tracking. CS preformed best at tracking. Navigation with passive MR catheter tracking was demonstrated from the femoral artery to the carotid artery in canines.
Biomedical Engineering, University of Calgary, Calgary, AB, Canada. memacdon@ucalgary.ca
Matthew Ethan
ME
Macdonald
Randall B
RB
Stafford
Jérôme
J
Yerly
Linda B
LB
Andersen
Cheryl R
CR
McCreary
Richard
R
Frayne
D000818:Animals; D002406:Catheterization, Peripheral / Q000379:methods*; D003287:Contrast Media; D004285:Dogs; D005263:Femoral Artery / Q000033:anatomy & histology* / Q000601:surgery*; D019786:Gadolinium DTPA; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media; D019786:Gadolinium DTPA