Acquired diseases of the thoracic aorta: role of MRI and MRA

Abstract

Diseases of the thoracic aorta can present with a broad clinical spectrum of symptoms and signs. Their prevalence appears to be increasing in western populations, most likely corresponding to aging and heightened clinical awareness but also influenced by the progress of high-resolution, noninvasive imaging modalities. Among them, MRI provides an excellent visualization of vascular structures and is well suited for evaluation of thoracic aorta disease. Currently, in many centers, noninvasive imaging modalities are the first choice in the cardiovascular system evaluation and diagnosis, reserving conventional angiography for use only before therapeutic intervention. Understanding the principle MRA techniques is essential for acquiring consistent diagnostic images. Basic technical considerations, which include fast spin-echo, fast gradient-echo, and MRA techniques with phase contrast and contrast-enhanced methods, are discussed and applied in the evaluation of acquired thoracic aorta diseases.

Magnetic Resonance Imaging of the Thoracic Aorta: A Review of Technical and Clinical Aspects, Including Its Use in the Evaluation of Aneurysms and Acute Vascular Conditions

“…Standard spin echo images and precontrast 3D-GRE also are helpful in evaluating changes in the aortic wall and periaortic structures. Areas of high signal intensity on spin echo images within the thrombus and aortic wall may indicate instability of the aneurysm (Sakamoto, 2010;Russo, 2006b emphasized by using fat suppressed T1-weighted sequences. Also, contrast enhanced MRA, using time resolved techniques, allows visualization of the Adamkiewicz artery (Bley, 2010), providing information that is important in planning the surgical repair of an aneurysm, thus avoiding postoperative neurologic deficit secondary to spinal cord ischemia (Nijenhuis, 2006;Yoshioka, 2006).…”

Noninvasive Imaging Approaches to Evaluate the Patient With Known or Suspected Aortic Disease

“…Whereas MRA methods without contrast enhancement have been available for some time, gadolinium-enhanced MRA has dramatically shortened examination time and emerged as preferred MR modality for aortic disease; adequate images result from only 15 mL of gadolinium. 13 Although MRA was considered ideal in renal failure, discovery of nephrogenic systemic fibrosis in patients with renal dysfunction receiving gadolinium has tempered enthusiasm 14 and contributed to a renaissance of nonenhanced MRA. 15 Among established nonenhanced sequences beyond ECG-gated partial Fourier fast spin-echo, balanced steady-state free precession (SSFP) 16 has emerged as a central technique to provide vivid imaging of flowing blood.…”

“…13,[23][24][25][26] Thus, speed and immediate access is not an issue when following the evolution of chronic dissection or aneurysm. Conversely, longitudinal changes over time and critical expansion are key issues and need to be addressed in the chronic setting; when repeat imaging is needed, MRI is most suitable, offering 3D reconstruction, exact dimensional quantification, and no radiation exposure.…”

“…Conversely, longitudinal changes over time and critical expansion are key issues and need to be addressed in the chronic setting; when repeat imaging is needed, MRI is most suitable, offering 3D reconstruction, exact dimensional quantification, and no radiation exposure. Flow-sensitive MR sequences even provide functional information (without gadolinium) on false lumen flow pattern in chronic dissection or aneurysm 13,15,17 ; MD-CT with or without contrast enhancement should be given preference only if MR techniques are not available.…”

Basic Design and Synthesis of Sulfonated Contrast Agents for Magnetic Resonance Imaging Based on Gadolinium Complexes

“…Magnetic resonance angiography (MRA) is a specialized MRI technique of gradually increasing importance that can provide angiography and can assess angiogenesis, blood volume and blood flow. [1][2][3][4] Various contrast agents based on gadolinium ion (Gd 3+ ) complexes have been developed to enhance the MRI signal intensity and to improve the contrast-to-noise ratio in regions of interest by shortening the longitudinal relaxation time (T1) of water protons. However, the presently clinically-used contrast agents, such as Gd(DTPA) (gadolinium-diethylenetriaminepentaacetic acid: Magnevist ® ) and Gd(EOB-DTPA) (gadolinium-(4S)-4-(4-ethoxybenzyl)-3,6,9-tris(carboxylatomethyl)-3,6,9-triazaundecanedioic aciddisodium salt: Eovist ® ), are not suitable as blood pool contrast agents for the MRA technique due to their short plasma halflives caused by rapid elimination from the kidney and the liver, respectively, [5][6][7][8][9] and/or the characteristic of free extravasation into background muscles, 10 resulting in a rapid decrease of the contrast-to-noise ratio in blood vessels.…”