Positive contrast spiral imaging for visualization of commercial nitinol guidewires with reduced heating

Background: cmr-guidance has the potential to improve tissue visualization during cardiovascular catheterization procedures and to reduce ionizing radiation exposure,but a lack of commercially available cmr guidewires limits widespread adoption. standard metallic guidewires are considered to be unsafe in cmr due to risks of rf-induced heating. here,we propose the use of rf-efficient gradient echo (gre) spiral imaging for reduced guidewire heating (low flip angle,long readout),in combination with positive contrast for guidewire visualization. methods: a gre spiral sequence with 8 interleaves was used for imaging. positive contrast was achieved using through-slice dephasing such that the guidewire appeared bright and the background signal suppressed. positive contrast images were interleaved with anatomical images,and real-time image processing was used to produce a color overlay of the guidewire on the anatomy. temperature was measured with a fiber-optic probe attached to the guidewire in an acrylic gel phantom and in vivo. results: left heart catheterization was performed on swine using the real-time color overlay for procedural guidance with a frame rate of 6.25 frames/second. using our standard cartesian real-time imaging (flip angle 60°),temperature increases up to 50 °c (phantom) and 4 °c (in vivo) were observed. in comparison,spiral gre images (8 interleaves,flip angle 10°) generated negligible heating measuring 0.37 °c (phantom) and 0.06 °c (in vivo). conclusions: the ability to use commercial metallic guidewires safely during cmr-guided catheterization could potentially expedite clinical translation of these methods. © 2015 campbell-washburn et al.