Journal Article

A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors

Gatehouse, Peter D, Kilner, Philip J, Bloch, Karin Markenroth, Rolf, Marijn P, Hofman, Mark BM, Graves, Martin J, Firmin, David N

2012

Overview

Phase-contrast velocity images often contain a background or baseline offset error, which adds an unknown offset to the measured velocities. For accurate flow measurements, this offset must be shown negligible or corrected. Some correction techniques depend on replicating the clinical flow acquisition using a uniform stationary phantom, in order to measure the baseline offset at the region of interest and subtract it from the clinical study. Such techniques assume that the background offset is stable over the time of a patient scan, or even longer if the phantom scans are acquired later, or derived from pre-stored background correction images. There is no published evidence regarding temporal stability of the background offset. This study assessed the temporal stability of the background offset on 3 different manufacturers' scanners over 8 weeks, using a retrospectively-gated phase-contrast cine acquisition with fixed parameters and at a fixed location, repeated 5 times in rapid succession each week. A significant offset was defined as 0.6 cm/s within 50 mm of isocenter, based upon an accuracy of 10% in a typical cardiac shunt measurement. Over the 5 repeated cine acquisitions, temporal drift in the baseline offset was insignificant on two machines (0.3 cm/s, 0.2 cm/s), and marginally insignificant on the third machine (0.5 cm/s) due to an apparent heating effect. Over a longer timescale of 8 weeks, insignificant drift (0.4 cm/s) occurred on one, with larger drifts (0.9 cm/s, 0.6 cm/s) on the other machines. During a typical patient study, background drift was insignificant. Extended high gradient power scanning with work requires care to avoid drift on some machines. Over the longer term of 8 weeks, significant drift is likely, preventing accurate correction by delayed phantom corrections or derivation from pre-stored background offset data.

• Publisher: Elsevier Inc,BioMed Central,BioMed Central Ltd,Elsevier
• Subject: Acquisitions / Algorithms / Analysis / Angiology / Background velocity offset error / Blood flow / Cardiac output / Cardiology / Cardiology and Cardiovascular Disease / Clinical Medicine / Clinical trials / Drift / Equipment Design / Europe / Humans / Image Interpretation, Computer-Assisted / Imaging / Kardiologi och kardiovaskulära sjukdomar / Klinisk medicin / Machinery / Magnetic resonance imaging / Magnetic Resonance Imaging, Cine - instrumentation / Magneto-electric machines / Marketing / Mechanical properties / Medical and Health Sciences / Medical research / Medicin och hälsovetenskap / Medicine / Medicine & Public Health / Medicine, Experimental / Offsets / Patients / Phantoms, Imaging / Phase-contrast velocity mapping / Physiological aspects / Predictive Value of Tests / Radiology / Regurgitation / Reproducibility of Results / Shunt flow / Speed / Stability / Technical Notes / Temporal logic / Time Factors / Whole Body Imaging - instrumentation