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Evaluation and comparison of ECG-gated techniques at 1.5 T for contrast enhanced MR angiography of the thoracic aorta


3D T1-weighted contrast-enhanced MRA (CE-MRA) is routinely used for non-invasive evaluation of the thoracic aorta. However, competing demands of high spatial resolution and fast (breath-hold) acquisition often preclude ECG-gating, leading to motion artifact at the aortic root. Standard Cartesian-sampled ECG-gated CE-MRA acquires 1 partition per heartbeat resulting in long scan times, often exceeding breath-hold capabilities. We evaluated image quality and diagnostic capabilities of a novel ECG-gated CE-MRA utilizing alternative Cartesian k-space sampling whereby adjacent ky and kz points are acquired in a zigzag pattern (Z-MRA) to improve scanning efficiency and co-ordinate contrast timing with optimal cardiac phase acquisition.


42 patients (12 females, mean 52y) were enrolled and underwent CE-MRA at 1.5T (Avanto, Siemens Healthcare) using a two-injection protocol with standard ECG-triggered CE-MRA (S-MRA) and zigzag (Z-MRA) ECG-gated CE-MRA (IPR #573: Siemens Healthcare, Germany) performed in a randomized order following 0.15mmol/kg gadolinium contrast. S-MRA parameters were: TR 2.7/TE 0.9, FA 17°, FOV 400mm. Z-MRA parameters had matched spatial resolution and FOV with other parameters: TR 2.6ms/TE 0.9ms, FA 20°, time to center (TTC) approximately 4.5s, TTC per heartbeat (ky=0) acquired on average 566ms post-trigger, 2-3 kz loops per heartbeat (heart-rate dependent). A parallel imaging factor of 2 was used for both. Two physicians independently reviewed the images. Ten arterial segments were graded for image quality (IQ), artifacts, vascular contrast, pathology and diagnostic confidence.


1680 segments (840 x 2 readers) were evaluated. No scans were considered non-diagnostic. Average scan time was significantly longer with S-MRA compared to Z-MRA (52.4 vs. 17.9 sec, p<0.001). Overall image quality was similar for S-MRA compared to Z-MRA (Table 1). Sinus and sinotubular junction IQ and artifact scores were significantly superior for S-MRA, but beyond the ascending aorta, IQ and artifacts scores were significantly superior for Z-MRA. Vascular contrast was significantly superior at all segments for Z-MRA. Overall diagnostic confidence was significantly better for S-MRA, mainly due to difficulty discerning pathology at the aortic root.

Table 1 Overall comparison scores for both sequences.


ECG-gated Z-MRA is feasible for diagnostic evaluation of the thoracic aorta with significantly superior vascular contrast and comparably lower breath-hold times. However, motion artifact at the aortic root led to decreased diagnostic confidence at these segments for Z-MRA. Z-MRA provides a reasonable alternative to S-MRA, particularly for patients with limited breath-hold capabilities or in whom we want to limit contrast dose. Further optimization of Z-MRA k-space sampling strategies are needed to improve overall diagnostic performance.



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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Timoh, T., Lim, R.P., Bruno, M. et al. Evaluation and comparison of ECG-gated techniques at 1.5 T for contrast enhanced MR angiography of the thoracic aorta. J Cardiovasc Magn Reson 17 (Suppl 1), P397 (2015).

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