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Overview of Imaging Atherosclerosis
Published in Robert J. Gropler, David K. Glover, Albert J. Sinusas, Heinrich Taegtmeyer, Cardiovascular Molecular Imaging, 2007
Vardan Amirbekian, Smbat Amirbekian, Juan Gilberto S. Aguinaldo, Valentin Fuster, Zahi A. Fayad
A powerful and complimentary tool that MRI offers is magnetic resonance angiography (MRA). MRA has the capability to delineate the distribution of stenotic atheromatous lesions as well as accurately assess the severity of stenosis. It is possible to combine high-resolution black-blood techniques and MRA whereby the former will provide characterization of plaque composition and vessel wall. New phased-array coils designed for cardiac and coronary imaging have also recently been applied to carotid artery imaging allowing for improved resolution all around (34–36). In addition, there are sequences that have been developed that further improve resolution along with providing black-blood imaging (34,36).
Introduction to medical imaging
Published in David A Lisle, Imaging for Students, 2012
Flowing blood can be shown with different sequences as either signal void (black) or increased signal (white). Magnetic resonance angiography (MRA) refers to the use of these sequences to display arterial anatomy and pathology. Computer reconstruction techniques allow the display of blood vessels in 3D as well as rotation and viewing of these blood vessels from multiple angles. MRA is most commonly used to image the arteries of the brain, although is also finding wider application in the imaging of renal and peripheral arteries.
An Unsupervised Parametric Mixture Model for Automatic Cerebrovascular Segmentation
Published in Ayman El-Baz, Jasjit S. Suri, Cardiovascular Imaging and Image Analysis, 2018
Mohammed Ghazal, Yasmina Al Khalil, Ayman El-Baz
Magnetic resonance imaging (MRI) has become one of the most versatile and widely used tools for clinical diagnosis of diseases over the last few decades. It has been considered essential for diagnosis of acute injuries, musculoskeletal diseases, brain pathologies, cancer detection, and cardiac imaging [16]. Being a noninvasive imaging modality, it is preferred over CT, especially in children and patients requiring multiple imaging examinations. Further advantages include superior intrinsic soft tissue contrast, unrestricted penetration depth, and high anatomical resolution [17]. Thus, MRI characterizes anatomy in greater detail, and is more sensitive to abnormalities within the studied tissues, compared to CT methods. Moreover, it allows for the evaluation of structures that may be ambiguous due to remaining artifacts from bone tissues in CT images [18]. However, for accurate estimation of intracranial vascular diseases through cerebrovascular segmentation, we require functional information about organ impairment during the infection, which is not available through structural MRI. Noninvasive magnetic resonance angiography (MRA) can accurately represent high-level information of the anatomy, function, and metabolism of the studied tissue. MRA is useful for detecting aneurysm, occlusions, and stenoses. Moreover, it has been extensively utilized in cases when the injection of contrast agents introduces high risk. As such, MRA allows for an accurate and noninvasive evaluation of blood flow and blood vessel morphology [19]. Two main MRA techniques commonly used for observing vascular structures are contrast-enhanced and non-contrast-enhanced MRA. While contrast-enhanced MRA utilizes a contrasting substance, such as intravenous gadolinium injection for blood flow detection, non-contrast-enhanced MRA methods rely on the effects of vascular flow as a fundamental contrast. The latter exploit mechanisms such as time-of-flight (TOF) and phase contrast angiography (PCA) [20].
Identifying and addressing the limitations of EVAR technology
Published in Expert Review of Medical Devices, 2018
Viony M Belvroy, Ignas B Houben, Santi Trimarchi, Himanshu J Patel, Frans L Moll, Joost A. Van Herwaarden
Magnetic Resonance Imaging (MRI, Figure 1F) does not involve ionizing radiation and MR Angiography (MRA) uses less nephrotoxic contrast agents than CTA, making it the preferred imaging modality for patients with severe renal dysfunction (glomerular filtration rate < 30)[22]. Nevertheless, CTA remains the gold standard and MRA is exceptionally used in pregnant, very young or chronic kidney disease patients. The commonly used intraoperative techniques are fluoroscopy and angiography, providing2D plain radiographic images after intravascular admission of contrast agent. The disadvantage of angiography is the use of a nephrotoxic contrast agent and the exposal to radiation damage. A new development is CTA with fluoroscopy fusion technology. This technique uses a 3D CTA image from a cone beam CT, a preoperative CTA or a preoperative MRA and combines this with another dynamic imaging modality, usually fluoroscopy. This produces an overlay, giving a real-time 3D road-map for catheterization and guide wire movements. It limits both operation time and the nephrotoxic ionized contrast dose [23]*.