Fabian Kording, Presenter: Nothing to Disclose

Bjoern Schoennagel MD, Abstract Co-Author: Nothing to Disclose

Friedrich Uberle, Abstract Co-Author: Nothing to Disclose

Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose

Jin Yamamura MD, Abstract Co-Author: Nothing to Disclose

Accurate synchronization of the cardiac cycle is one of the main challenges in cardiac magnetic resonance imaging. Ultrasound is not objected to magneto-hydro-dynamic effects, does not interact with the electromagnetic field of the MRI and measures the physiological motion of the heart rather than electrical activation. The purpose of this work was to evaluate Doppler ultrasound (DUS) as an alternative gating method in cardiac MRI.

Steady-state free precession (SSFP) 2D CINE MRI in 12 healthy subjects (8 male, 4 female) was performed at 1.5 T with DUS, electrocardiogram (ECG) and pulse oximetry (POX) gating signals. Trigger reliability and variance of detected trigger time points during acquisition were computed from signals stored by the internal log function of the physiologic unit of the MRI. Quantitative analysis of image quality was assessed by calculating endocardial border sharpness (EBS), signal-to-noise (left ventricular blood) and contrast-to-noise (blood-myocardium) ratios and left ventricular (LV) function parameters.

No interference with the MRI electromagnetic field was observed for DUS and POX signals whereas ECG showed small T-wave elevations due to magneto-hydro-dynamic effects. Trigger variances, displaying trigger accuracy, were 48 ± 11 ms (ECG), 41 ± 12 ms (DUS) and 81 ± 35 ms (POX). Mean stroke volume for ECG, DUS and POX was 82 ± 24 ml, 83 ± 22 ml and 81 ± 27 ml yielding an ejection fraction of 59 ± 6 %, 61 ± 7 % and 59 ± 6 %, respectively. EBS for systole, diastole and as temporal mean over the cardiac cycle was 3.1 ± 0.2 / 2.6 ± 0.1 / 2.9 ± 0.2 pixel (ECG), 3.1 ± 0.2 / 2.6 ± 0.2 / 2.9 ± 0.2 pixel (DUS) and for POX gated images 3.3 ± 0.1 / 2.9 ± 0.1 / 3.1 ± 0.2 pixel. Signal-to-noise ratios for ECG and DUS were 52 ±13 and 45 ± 16 with a contrast-to-noise ratio of 39 ±10 and 34 ±12.

Synchronization of 2D CINE SSFP cardiac MRI was successfully demonstrated using DUS at 1.5 T. Quantitative analysis revealed high agreement between ECG and DUS whereas trigger accuracy and EBS were smaller for POX gating. In conclusion, DUS gating is a promising alternative gating method for cardiac MRI.

Doppler ultrasound measures physiological motion of the heart rather than electrical activation and, hence, enables a more accurate gating, especially for higher field strength.

Kording, F, Schoennagel, B, Uberle, F, Adam, G, Yamamura, J, Doppler Ultrasound as an Alternative Gating Method in Cardiac Cine MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012793.html