title: Analysis of temperature dependence of background phase errors in phase-contrast cardiovascular magnetic resonance.
abstract: BACKGROUND
  The accuracy of phase-contrast cardiovascular magnetic resonance (PC-CMR) can be compromised by background phase errors. It is the objective of the present work to provide an analysis of the temperature dependence of background phase errors in PC-CMR by means of gradient mount temperature sensing and magnetic field monitoring.
  
  
  METHODS
  Background phase errors were measured for various temperatures of the gradient mount using magnetic field monitoring and validated in a static phantom. The effect of thermal changes during k-space acquisition was simulated and confirmed with measurements in a stationary phantom.
  
  
  RESULTS
  The temperature of the gradient mount was found to increase by 20-30 K during PC-CMR measurements of 6-12 min duration. Associated changes in background phase errors of up to 11% or 0.35 radian were measured at 10 cm from the magnet's iso-center as a result of first order offsets. Zeroth order phase errors exhibited little thermal dependence.
  
  
  CONCLUSIONS
  It is concluded that changes in gradient mount temperature significantly modify background phase errors during PC-CMR with high gradient duty cycle. Since temperature increases significantly during the first minutes of scanning the results presented are also of relevance for single-slice or multi-slice PC-CMR scans. The findings prompt for further studies to investigate advanced correction methods taking into account gradient temperature and/or the use of concurrent field-monitoring to map gradient-induced fields throughout the scan.
authors.forename: Julia
authors.initials: J
authors.lastname: Busch
authors.forename: S Johanna
authors.initials: SJ
authors.lastname: Vannesjo
authors.forename: Christoph
authors.initials: C
authors.lastname: Barmet
authors.forename: Klaas P
authors.initials: KP
authors.lastname: Pruessmann
authors.affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland. kozerke@biomed.ee.ethz.ch.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kozerke
mesh_terms: D003198:Computer Simulation; D003287:Contrast Media; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D009942:Organometallic Compounds; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013696:Temperature; D013997:Time Factors
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol