title: Dual echo positive contrast bSSFP for real-time visualization of passive devices during magnetic resonance guided cardiovascular catheterization.
abstract: BACKGROUND
  Cardiovascular magnetic resonance (CMR) guided cardiovascular catheterizations can potentially reduce ionizing radiation exposure and enable new interventions. Commercially available paramagnetic X-Ray devices create a small signal void in CMR images, which is ambiguous and insufficient to guide catheterization procedures. This work aims to improve real-time CMR of off-the-shelf X-Ray devices by developing a real-time positive contrast sequence with color overlay of the device onto anatomy.
  
  
  METHODS
  A dual-echo bSSFP sequence was used to generate both a dephased positive contrast image and bSSFP image simultaneously. A variable flip angle scheme was implemented to reduce the specific absorption rate (SAR) and hence device heating. Image processing was used to isolate the device from background signal, and the device was overlaid in color on the anatomy, mimicking active device visualization. Proof-of-concept experiments were performed using a commercially available nitinol guidewire for left heart catheterization in Yorkshire swine.
  
  
  RESULTS
  The dual echo pulse sequence generated a temporal resolution of 175 ms (5.7 frames/second) with GRAPPA acceleration factor 4. Image processing was performed in real-time and color overlay of the device on the anatomy was displayed to the operator with no latency. The color overlay accurately depicted the guidewire location, with minimal background contamination, during left heart catheterization.
  
  
  CONCLUSIONS
  The ability to effectively visualize commercially available X-Ray devices during CMR-guided cardiovascular catheterizations, combined with safe low-SAR pulse sequences, could potentially expedite the clinical translation of interventional CMR.
authors.affiliation: Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda 20892, MD, USA. adrienne.campbell@nih.gov.
authors.forename: Adrienne E
authors.initials: AE
authors.lastname: Campbell-Washburn
authors.forename: Toby
authors.initials: T
authors.lastname: Rogers
authors.forename: Hui
authors.initials: H
authors.lastname: Xue
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hansen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lederman
authors.forename: Anthony Z
authors.initials: AZ
authors.lastname: Faranesh
mesh_terms: D000497:Alloys; D000818:Animals; D006328:Cardiac Catheterization / Q000295:instrumentation / Q000379:methods*; D062906:Cardiac Catheters; D004867:Equipment Design; D007090:Image Interpretation, Computer-Assisted; D053783:Magnetic Resonance Imaging, Interventional; D023421:Models, Animal; D011237:Predictive Value of Tests; D013552:Swine; D013997:Time Factors
chemical_list: D000497:Alloys; C013616:nitinol