Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification - A multi-vendor study

Journal of Cardiovascular Magnetic Resonance

Research

Philip J Kilner¹  Peter D Gatehouse¹  Albert C van Rossum²  Beat Werner³  Martijn W Heymans⁴  Tino Ebbers⁵  Marijn P Rolf⁶  Rob M Heethaar⁶  Mark BM Hofman⁶  Martin J Graves⁷  John J Totman⁸  Karin Markenroth-Bloch⁹ 

[1] Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, London, UK;Department of Cardiology, ICaR-VU, VU University Medical Center, Amsterdam, the Netherlands;Department of Diagnostic Imaging, University Children's Hospital, Zürich, Switzerland;Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, the Netherlands;Department of Medical and Health Sciences, Linköping University, Linköping, Sweden;Department of Physics and Medical Technology, ICaR-VU, VU University Medical Center, Amsterdam, the Netherlands;Department of Radiology, Cambridge University Hospitals, Cambridge, UK;Division of Imaging Sciences, King's College, London, UK;Philips Healthcare, Skåne University Hospital, Lund, Sweden;

关键词: Cardiovascular Magnetic Resonance;    Eddy Current;    Slew Rate;    Symmetric Encode;    Scanner Type;   

DOI  :  10.1186/1532-429X-13-18

 received in 2010-10-07, accepted in 2011-03-09,  发布年份 2011

来源: Springer

【 摘 要 】

PurposeEddy current induced velocity offsets are of concern for accuracy in cardiovascular magnetic resonance (CMR) volume flow quantification. However, currently known theoretical aspects of eddy current behavior have not led to effective guidelines for the optimization of flow quantification sequences. This study is aimed at identifying correlations between protocol parameters and the resulting velocity error in clinical CMR flow measurements in a multi-vendor study.MethodsNine 1.5T scanners of three different types/vendors were studied. Measurements were performed on a large stationary phantom. Starting from a clinical breath-hold flow protocol, several protocol parameters were varied. Acquisitions were made in three clinically relevant orientations. Additionally, a time delay between the bipolar gradient and read-out, asymmetric versus symmetric velocity encoding, and gradient amplitude and slew rate were studied in adapted sequences as exploratory measurements beyond the protocol. Image analysis determined the worst-case offset for a typical great-vessel flow measurement.ResultsThe results showed a great variation in offset behavior among scanners (standard deviation among samples of 0.3, 0.4, and 0.9 cm/s for the three different scanner types), even for small changes in the protocol. Considering the absolute values, none of the tested protocol settings consistently reduced the velocity offsets below the critical level of 0.6 cm/s neither for all three orientations nor for all three scanner types. Using multilevel linear model analysis, oblique aortic and pulmonary slices showed systematic higher offsets than the transverse aortic slices (oblique aortic 0.6 cm/s, and pulmonary 1.8 cm/s higher than transverse aortic). The exploratory measurements beyond the protocol yielded some new leads for further sequence development towards reduction of velocity offsets; however those protocols were not always compatible with the time-constraints of breath-hold imaging and flow-related artefacts.ConclusionsThis study showed that with current systems there was no generic protocol which resulted into acceptable flow offset values. Protocol optimization would have to be performed on a per scanner and per protocol basis. Proper optimization might make accurate (transverse) aortic flow quantification possible for most scanners. Pulmonary flow quantification would still need further (offline) correction.

【 授权许可】

CC BY   
© Rolf et al; licensee BioMed Central Ltd. 2011