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Volume 18 Supplement 1

19th Annual SCMR Scientific Sessions

  • Poster presentation
  • Open Access

Spiral imaging with off-resonance reconstruction for MRI-guided cardiovascular catheterizations using commercial off-the-shelf nitinol guidewires

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Journal of Cardiovascular Magnetic Resonance201618 (Suppl 1) :P216

https://doi.org/10.1186/1532-429X-18-S1-P216

  • Published:

Keywords

  • Spiral Imaging
  • Spiral Sequence
  • bSSFP Sequence
  • Anatomical Imaging Data
  • Nitinol Guidewires

Background

MRI-guidance of cardiovascular catheterization offers improved soft-tissue contrast and reduced ionizing radiation exposure. The application of MRI-guidance to complex catheterization procedures has been limited by the unavailability of guidewires that are safe and visible under MRI. Here, we use RF-efficient spiral imaging for MR-guided cardiovascular catheterization, with real-time off-resonance reconstruction for improved visualization of off-the-shelf nitinol guidewires.

Methods

MRI-guided left and right heart catheterizations were performed on a swine using a commercial nitinol guidewire (0.035"/145 cm Nitrex, Covidien, Plymouth, MN) and balloon-tipped catheter (7 Fr, Arrow-Teleflex, Limerick, PA) with spiral imaging (gradient echo, 16 interleaves, TE/TR =0.86/11 ms, flip = 10°, FOV = 300 mm x 300 mm, matrix = 192 x 192, slice thickness = 6 mm). To enhance guidewire visualization, we exploited the off-resonance signal near the guidewire. Using a custom reconstruction framework (Gadgetron [1]), the imaging data was reconstructed at two different off-resonance frequencies (± 100 Hz) and the images were subtracted to produce guidewire-enhanced images. The method was implemented such that operators could rapidly toggle between anatomical imaging, saturation pre-pulses for visualization of gadolinium-filled balloon [2] and guidewire-enhanced imaging, as-needed throughout the procedure.

RF-induced heating of the guidewire/catheter configuration was evaluated in an ASTM 2182 phantom. A fiber-optic temperature probe (0.007" OpSens, Quebec, Canada) affixed to the guidewire tip measured temperature during 2 minutes of continuous scanning with the spiral sequence and our standard real-time imaging sequence (Cartesian bSSFP, TE/TR = 1.31/2.62 ms, flip angle = 45°).

Results

The spiral sequence generated 6 frames/s. Guidewire-enhanced images offered improved delineation of the guidewire shaft, compared to standard signal void visualization (Figure 1A), and a unique guidewire tip artifact when in-plane (Figure 1B). These images also preserve tissue boundaries, which is valuable to provide anatomical context for guidewire navigation.
Figure 1
Figure 1

Images from right heart (A) and left heart (B) catheterizations, comparing standard anatomical imaging (top) to guidewire-enhanced images (bottom). Improved guidewire visualization compared to signal-void imaging (A, red arrowheads) and a unique in-plane guidewire tip signal (B, red arrow) are demonstrated. Tissue boundaries are also visible in the guidewire-enhanced images which provides anatomical context for navigation.

Substantial heating (ΔT = 80.5°C) was observed using our standard real-time Cartesian bSSFP sequence. Heating was reduced to below allowable limits using spiral gradient echo imaging (ΔT = 1.63°C) (Figure 2).
Figure 2
Figure 2

Temperature at the tip of the nitinol guidewire measured during 2 minutes of continuous scanning using Cartesian bSSFP (TE/TR = 1.31/2.62 ms, flip angle = 45°) (A) and spiral gradient echo (TE/TR = 0.86/8.16 ms, flip angle = 10°) (B). Signal oscillation is observed in the non-linear range of the temperature probe (>85°C).

Conclusions

This visualization method is particularly flexible because it uses a targeted reconstruction of standard anatomical imaging data. This method may enable safe MRI-guided cardiovascular catheterizations using commercially available nitinol guidewires.

Authors’ Affiliations

(1)
Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
(2)
Department of Cardiology, Children's National Medical Center, Washington, DC, USA
(3)
Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey, USA

References

  1. Hansen MS, Sørensen TS: Gadgetron: an open source framework for medical image reconstruction. Magn Reson Med. 2013, 69 (6): 1768-1776.View ArticlePubMedGoogle Scholar
  2. Ratnayaka K, Faranesh AZ, Hansen MS, Stine AM, Halabi M, Barbash IM, Schenke WH, Wright VJ, Grant LP, Kellman P, Kocaturk O, Lederman RJ: Real-time MRI-guided right heart catheterization in adults using passive catheters. Eur Heart J. 2013, 34 (5): 380-389.PubMed CentralView ArticlePubMedGoogle Scholar

Copyright

© Campbell-Washburn et al. 2016

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.

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