Research

Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements

Peter D Gatehouse¹ , Marijn P Rolf² , Martin J Graves³ , Mark BM Hofman² , John Totman⁴ , Beat Werner⁵ , Rebecca A Quest⁶ , Yingmin Liu⁷ , Jochen von Spiczak⁸ , Matthias Dieringer⁹ , David N Firmin¹ , Albert van Rossum¹⁰ , Massimo Lombardi¹¹ , Juerg Schwitter¹² , Jeanette Schulz-Menger¹³ and Philip J Kilner¹

¹  CMR Unit, Royal Brompton Hospital, London, UK

²  Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, the Netherlands

³  University Department of Radiology, Addenbrooke's Hospital, Cambridge, UK

⁴  Division of Imaging Sciences, King's College, London, UK

⁵  Division of Neuroradiology and Magnetic Resonance, University Children's Hospital, Zurich, Switzerland

⁶  Radiological Sciences Unit, The Hammersmith Hospitals NHS Trust, London, UK

⁷  Auckland MRI Research Group, University of Auckland, Auckland, New Zealand

⁸  Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

⁹  Franz-Volhard-Klinik, Charité Universitätsmedizin, Berlin, Germany

¹⁰  Department of Cardiology, VU University Medical Center, Amsterdam, the Netherlands

¹¹  Magnetic Resonance Laboratory, Italian National Research Council (CNR), Pisa, Italy

¹²  Cardiac MRI Center, University Hospital Zurich, Zurich, Switzerland

¹³  Franz-Volhard-Klinik, Charité Universitätsmedizin, Berlin, Germany

author email corresponding author email

Journal of Cardiovascular Magnetic Resonance 2010, 12:5doi:10.1186/1532-429X-12-5

Published:	14 January 2010

Abstract

Aims

Cardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems.

Methods and Results

In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement.

Conclusion

In the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions.