Adjustment of the velocity encoding parameter to the blood flow velocity is not necessary for accurate and precise quantification of aortic regurgitation severity with phase contrast magnetic resonance imaging
Journal of Cardiovascular Magnetic Resonance volume 17, Article number: P329 (2015)
Accurate and precise quantification of aortic regurgitation (AVR) severity by cardiovascular magnetic resonance is essential for the clinical decission-making and timing of surgery. The regurgitant flow volume (RV) can be measured directly by 2D phase contrast (PC) velocity measurements. The velocity encoding parameter, venc, has been identified by others as an important factor for accurate and precise determination of RV. For large vessel and high signal to noise measurements, though, integration of the measured blood flow velocities over the vessel lumen and over the cardiac phases for calculation of RV should average out variations in the measured velocities and enable high precision estimates of RV independently of venc. Furthermore, application of a correction method that effectively reduces the background velocity offset in the PC image to a sufficiently low value should enable accurate estimation of RV and remove the venc dependency. The aim of the study was to demonstrate venc insensitivity in the estimated RV with effectively background offset corrected PC velocity measurements.
Measurements with high and low venc (~150 and 50 cm/s, respectively) were performed at the sinotubular junction on patients (n=28; 27-83y) and volunteers (n=26; 24-58y) using a 1.5 T scanner. Corrections for background offsets were automatically performed by the scanner and post-acquisition by means of adaptive image filtering. The mean background offset, standard deviation (sd) and coefficient of variation (cv) of repeated measurements were determined for the whole cohort. The mean RV, and sd and cv of RV were determined for patients and volunteers separately. For comparison, Wilcoxon signed-rank test was performed at a significance level of p<0.05.
We have demonstrated venc insensitivity in both the accuracy and precision of RV using background offset corrected PC velocity measurements. Without the need for adjustment of venc to the blood flow velocity, the time for the examination will be substantially reduced.
This study was funded by a project grant from the Health & Medical Care Committee of the Regional Executive Board, Västra Götaland Region, Sweden.
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Svensson, F., Polte, C.L., Johnsson, Å.A. et al. Adjustment of the velocity encoding parameter to the blood flow velocity is not necessary for accurate and precise quantification of aortic regurgitation severity with phase contrast magnetic resonance imaging. J Cardiovasc Magn Reson 17 (Suppl 1), P329 (2015). https://doi.org/10.1186/1532-429X-17-S1-P329