- Poster presentation
- Open Access
Two channel passive visualization of a nitinol guidewire with iron markers
https://doi.org/10.1186/1532-429X-17-S1-P236
© Campbell-Washburn et al; licensee BioMed Central Ltd. 2015
- Published: 3 February 2015
Keywords
- Flip Angle
- Anatomical Image
- Marker Signal
- Convolution Kernel
- Positive Contrast
Background
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 [1] 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.
Methods
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 [2]. 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 [3] 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.
Results
Phantom images of the nitinol guidewire with three iron-oxide markers (one large, two small) demonstrating reconstruction at -200Hz off-resonance (a), on-resonance (b) and +200Hz off-resonance (c). Image subtraction (d) creates a characteristic dark-bright-dark pattern from the iron markers.
Two channel passive visualization using isolated signal from the iron markers (red) and nitinol guidewire (green).
Conclusions
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.
Funding
This work was supported by the NHLBI DIR (Z01-HL006039-01, Z01-HL005062-08).
Authors’ Affiliations
References
- 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
Copyright
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.
