- Poster presentation
- Open Access
Two channel passive visualization of a nitinol guidewire with iron markers
© Campbell-Washburn et al; licensee BioMed Central Ltd. 2015
- Published: 3 February 2015
- Flip Angle
- Anatomical Image
- Marker Signal
- Convolution Kernel
- Positive Contrast
MRI-guidance for cardiovascular catheterization is appealing to reduce ionizing radiation exposure and to enable novel procedures. "Active" guidewire-antennas for MRI-guided procedures are often designed such that the tip and shaft have distinct signals  to improve navigation and to make it obvious when the tip moves out of plane. Here we present a method to isolate the signal from iron markers, and produce a two channel color overlay for visualizing the shaft and tip of a nitinol guidewire.
Three iron-oxide markers were added to a commercially available 0.035" nitinol guidewire (Nitrex, Covidien, Plymouth, MN). Gradient echo spiral imaging (8 interleaves, TE/TR=0.86/10ms, flip angle = 10°) was performed on a 1.5T MRI scanner (Aera, Siemens, Erlangen, Germany). Image processing was performed in MATLAB (R2013a, Mathworks, Natick, MA).
Channel 1 - Iron markers
Off-resonance spins, such as those created by the iron markers, cause blurring in spiral images . Images were reconstructed at two frequencies, on-resonance and 200Hz off-resonance. A subtraction of the two image reconstructions [(on-off)/on] generated a characteristic dark-bright-dark pattern from the iron markers, which was detected by a specifically designed convolution kernel.
Channel 2 - Nitinol guidewire
Through-slice dephasing  was applied to alternating frames to generate a positive contrast image, where the nitinol guidewire appears bright with background signal suppressed, from which the guidewire signal was isolated.
Here, we have presented a proof-of-concept experiment demonstrating two channel color overlay of a passive nitinol guidewire with iron markers. A new method utilizing off-resonance reconstruction of spiral images was applied to isolate the iron markers and depict them with a unique imaging signature to enhance usability. Future work will optimize the method to ensure robust detection of the marker signal.
This work was supported by the NHLBI DIR (Z01-HL006039-01, Z01-HL005062-08).
- Kocaturk O, et al: An Active two Channel 0.035" Guidewire for Interventional Cardiovascular MRI. JMRI. 2009, 30: 461-465. 10.1002/jmri.21844.PubMed CentralView ArticlePubMedGoogle Scholar
- Man LC, et al: Multifrequency interpolation for fast off-resonance correction. MRM. 1997, 37: 785-792. 10.1002/mrm.1910370523.View ArticlePubMedGoogle Scholar
- Seppenwoolde JH, et al: Passive Tracking Exploiting Local Signal Conservation: The White Marker Phenomenon. MRM. 2003, 50: 784-790. 10.1002/mrm.10574.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.