title: Positive contrast spiral imaging for visualization of commercial nitinol guidewires with reduced heating.
abstract: 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.
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. adrienne.campbell@nih.gov.
authors.forename: Adrienne E
authors.initials: AE
authors.lastname: Campbell-Washburn
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. toby.rogers@nih.gov.
authors.forename: Toby
authors.initials: T
authors.lastname: Rogers
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. burcu.basar@nih.gov.|Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey. burcu.basar@nih.gov.
authors.forename: Burcu
authors.initials: B
authors.lastname: Basar
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. merdim.sonmez@nih.gov.
authors.forename: Merdim
authors.initials: M
authors.lastname: Sonmez
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. kocaturko@nhlbi.nih.gov.|Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey. kocaturko@nhlbi.nih.gov.
authors.forename: Ozgur
authors.initials: O
authors.lastname: Kocaturk
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. ledermar@nhlbi.nih.gov.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lederman
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. michael.hansen@nih.gov.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hansen
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA. faranesa@nhlbi.nih.gov.
authors.forename: Anthony Z
authors.initials: AZ
authors.lastname: Faranesh
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000818:Animals; D006328:Cardiac Catheterization / Q000295:instrumentation* / Q000379:methods; D062906:Cardiac Catheters; D004867:Equipment Design; D004868:Equipment Failure; D005336:Fiber Optic Technology; D006358:Hot Temperature; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation* / Q000379:methods; D008422:Materials Testing; D023421:Models, Animal; D019047:Phantoms, Imaging; D013552:Swine; D013997:Time Factors
chemical_list: D000497:Alloys; C013616:nitinol