MR Angiography of the Thoracic Aorta with an Electrocardiographically Triggered Breath-Hold Contrast-enhanced Sequence

Abstract

An electrocardiographically (ECG) triggered breath-hold contrast material-enhanced magnetic resonance (MR) angiography sequence has been developed for imaging the thoracic aorta. A three-dimensional (3D) gradient-echo sequence is used with a contrast material bolus. Forty-nine patients with various aortic abnormalities and five healthy volunteers underwent imaging with the sequence. All studies were performed in a single breath hold. ECG-triggered breath-hold contrastenhanced MR angiography was tolerated in 48 of the 49 patients. The images demonstrated no respiratory motion artifacts and diminished pulsation artifacts. The cardiac chambers, aortic root, ascending and descending aorta, aortic arch, proximal arch vessels, and proximal coronary arteries were clearly demonstrated and not obscured by ghost artifacts. The 3D data set allowed excellent multiplanar reformation, permitting orthogonal or oblique views of the vascular anatomy. A variety of congenital and acquired abnormalities were clearly identified. When this sequence is used, it is important to evaluate both the maximum-intensity projection and source images. Delayed imaging should be performed to detect late filling. In conjunction with cine MR and T1-weighted spin-echo imaging, ECG-triggered breath-hold contrastenhanced MR angiography should be considered the technique of choice for imaging the thoracic aorta.Abbreviations: ECG = electrocardiography, MIP = maximum-intensity projection, 3D = three-dimensional

Imaging of the thoracic aorta

“…Limitation of this testbolus technique is the potential for diminished artery-to-vein contrast, associated additional cost of test-bolus contrast and the potential difficulty to observe the test-bolus in distal vessels or in cases with slow flow [25]. To further reduce respiratory motion artifacts and artifacts related to cardiac motion and pulsatile flow, electrocardiographic triggering techniques can be used [17,26]. The thus obtained images can either be viewed on a slice-to-slice basis, or can be reconstructed on a computer workstation into a maximum intensity projection (MIP-image).…”

“…It is of importance to evaluate both source images and reconstructed images, in order to optimize diagnostic yield (e.g. a dissection can be easily overlooked evaluating MIP images alone) [26]. The lack of clinically significant nephrotoxic effects (also at higher intravenous dosage of Gadolineum) makes contrastenhanced MRA the modality of choice for vascular imaging in patients suffering from renal insufficiency.…”

“…Right coronary aneurysms (either congenital or acquired) can be clearly depicted using three-dimensional techniques, thus aiding surgeons in preoperative planning [48,56]. The aortic sinus itself can also demonstrate aneurysmal degeneration, that can be depicted using three-dimensional imaging techniques [26]. Finally, three-dimensional techniques can be used to demonstrate aorto-coronary bypass grafts.…”

MRI assessment of thoracic stent grafts after emergency implantation in multi trauma patients: a feasibility study

“…The versatility of MRI enables a variety of imaging protocols comprising contrast agent-enhanced [10] and unenhanced angiography [11,12], black-blood techniques for vessel wall assessment [13], and especially the ability to visualise and quantify functional parameters such as vessel wall compliance [14] and blood flow [15,16]. The application of MRI in patients with endovascular stent grafts is not commonly performed.…”

Contrast-enhanced three-dimensional MR angiography of the thoracic aorta: experiences after 118 examinations with a standard dose contrast administration and different injection protocols

“…Several investigations have demonstrated the usefulness of contrast-enhanced three-dimensional (3D) MR angiography (MRA) for evaluation of both acquired and congenital diseases of the thoracic aorta and its branches. The contrast mechanism for gadolinium-enhanced MRA relies on the T1 shortening of blood which occurs in response to the administration of gadolinium chelates [2,3,4,5,6,7].…”