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Analysis of temperature dependence of background phase errors in phase-contrast cardiovascular magnetic resonance.

Busch J, Vannesjo SJ, Barmet C, Pruessmann KP, Kozerke S - J Cardiovasc Magn Reson (2014)

Bottom Line: The temperature of the gradient mount was found to increase by 20-30 K during PC-CMR measurements of 6-12 min duration.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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland. kozerke@biomed.ee.ethz.ch.

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.

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Related in: MedlinePlus

Experimental setup. Positioning of thermo-sensors on gradient mount (A); schematics of third order dynamic field camera (B) and three-directional PC-CMR sequence used for flow encoding (C). The acquisition window (AQ) during which field-monitoring data were acquired is indicated.
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Fig1: Experimental setup. Positioning of thermo-sensors on gradient mount (A); schematics of third order dynamic field camera (B) and three-directional PC-CMR sequence used for flow encoding (C). The acquisition window (AQ) during which field-monitoring data were acquired is indicated.

Mentions: Four fibre-optic thermo sensors were installed on the gradient mount of a 3 T Philips Achieva System (Philips Healthcare, Best, The Netherlands) as demonstrated in FigureĀ 1A. Using a Luxtron 790 fibre optic temperature measurement setup (LumaSense Technology, Santa Clara, CA, USA) the temperature was monitored and recorded during all scans.Figure 1


Analysis of temperature dependence of background phase errors in phase-contrast cardiovascular magnetic resonance.

Busch J, Vannesjo SJ, Barmet C, Pruessmann KP, Kozerke S - J Cardiovasc Magn Reson (2014)

Experimental setup. Positioning of thermo-sensors on gradient mount (A); schematics of third order dynamic field camera (B) and three-directional PC-CMR sequence used for flow encoding (C). The acquisition window (AQ) during which field-monitoring data were acquired is indicated.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4263200&req=5

Fig1: Experimental setup. Positioning of thermo-sensors on gradient mount (A); schematics of third order dynamic field camera (B) and three-directional PC-CMR sequence used for flow encoding (C). The acquisition window (AQ) during which field-monitoring data were acquired is indicated.
Mentions: Four fibre-optic thermo sensors were installed on the gradient mount of a 3 T Philips Achieva System (Philips Healthcare, Best, The Netherlands) as demonstrated in FigureĀ 1A. Using a Luxtron 790 fibre optic temperature measurement setup (LumaSense Technology, Santa Clara, CA, USA) the temperature was monitored and recorded during all scans.Figure 1

Bottom Line: The temperature of the gradient mount was found to increase by 20-30 K during PC-CMR measurements of 6-12 min duration.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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland. kozerke@biomed.ee.ethz.ch.

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.

Show MeSH
Related in: MedlinePlus