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Cine sequences used in cardiovascular MRI are collection of images (usually at the same spatial location) covering of one full period of cardiac cycle or over several periods in order to obt ain complete coverage.
The pulse sequence used, is either a standard gradient echo pulse sequence, a segmented data acquisition, a gradient echo EPI sequence or a gradient echo with balanced gradient waveform.
In cardiac gating studies it is possible to assign consecutive lines either to different images, yielding a multiphase sequence with as many images as lines, or the lines are grouped together into segments and assigned to the same image. The overall time to acquire such a segment has to be small compared to the RR-interval of the cardiac cycle, i. e. 50 ms, and hence cont ains typically 8 to 16 image lines.
This strategy is called segmented data acquisition, and has the advantage of reducing overall imaging time for cardiac images so that they can be acquired within a breath hold, but obviously decreasing the temporal resolution of each individual image.
This method shows dynamic processes, such as the ejection of blood out of the heart into the aorta, by means of fast imaging and displaying the resulting images in a sequential-loop, the impression of a real-time movie is generated. Ejection fractions and stroke volumes calculated from these cine MRI images in different cardiac axes have been shown to be more accurate than any other imaging modality. See also Cardiac Gating. | | | | | | | Further Reading: | News & More:
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A large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle, the arteries effectively act as anastomoses for each other. This means that if any one of the communicating arteries becomes blocked, blood can flow from another part of the circle to ensure that blood flow is not compromised.
The circle of Willis is formed by both the internal carotid arteries, entering the brain from each side and the basilar artery, entering posteriorly. The connection of the vertebral arteries forms the basilar artery. The basilar artery divides into the right and left posterior cerebral arteries.
The internal carotid arteries trifurcate into the anterior cerebral artery, middle cerebral artery, and posterior communicating artery.
The two anterior cerebral arteries are joined together anteriorly by the anterior communicating artery. The posterior communicating arteries join the posterior cerebral arteries, completing the circle of Willis. The time of flight angiography MRI technique allows imaging of the circle of Willis without the need of a contrast medium (best results with high field MRI). A cerebrovasular contrast enhanced magnetic resonance angiography ( MRA) depicts the circle of Willis in addition to the vessels of the neck (carotid and vertebral arteries) with one bolus injection of a contrast agent.
For Ultrasound Imaging (USI) see Cerebrovascular Ultrasonography at Medical-Ultrasound-Imaging.com. | | | | | | • View the DATABASE results for 'Circle of Willis' (5).
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The act of m aint aining a constant phase relationship between oscillating waves or rotating objects. | | | | • View the DATABASE results for 'Coherence' (19).
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| | | Searchterm 'AIN' was also found in the following services: | | | | |
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| | | | • View the DATABASE results for 'Coil' (193).
| | | • View the NEWS results for 'Coil' (11).
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3T MRI-Compatible Small Body Array Gets FDA Nod Monday, 15 January 2024 by www.diagnosticimaging.com | | |
High-field MRI Coils – that work, superbly, even at 750 MHz
by www.dotynmr.com | | |
New superconducting coil improves MRI performance Wednesday, 20 July 2016 by www.eurekalert.org | | |
First European fully superconductive coil reaching a magnetic field of 25 Tesla produced Wednesday, 8 June 2016 by www.news-medical.net | | |
ScanMed Introduces a Groundbreaking New Orbit and Mandible Array to the MRI Market Wednesday, 26 March 2014 by www.digitaljournal.com | | |
MRI coil optimized for imaging of infants gets FDA clearance Tuesday, 17 April 2012 by www.medcitynews.com | | |
Low-profile MRI coil company inching toward commercialization Wednesday, 21 December 2011 by www.medcitynews.com | | |
High-Resolution Uniform MR Imaging of Finger Joints Using a Dedicated RF Coil at 3 Tesla Sunday, 31 January 2010 by www.ncbi.nlm.nih.gov | | |
DOTmed Industry Sector Report: MRI Coil Sales & Service Companies Thursday, 13 December 2007 by www.dotmed.com |
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Contrast agents are chemical substances introduced to the anatomical or functional region being imaged, to increase the differences between different tissues or between normal and abnormal tissue, by altering the relaxation times. MRI contrast agents are classified by the different changes in relaxation times after their injection.
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Negative contrast agents (appearing predominantly dark on MRI) are small particulate aggregates often termed superparamagnetic iron oxide ( SPIO). These agents produce predominantly spin spin relaxation effects (local field inhomogeneities), which results in shorter T1 and T2 relaxation times.
SPIO's and ultrasmall superparamagnetic iron oxides ( USPIO) usually consist of a crystalline iron oxide core cont aining thousands of iron atoms and a shell of polymer, dextran, polyethyleneglycol, and produce very high T2 relaxivities. USPIOs smaller than 300 nm cause a substantial T1 relaxation. T2 weighted effects are predominant.
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A special group of negative contrast agents (appearing dark on MRI) are perfluorocarbons ( perfluorochemicals), because their presence excludes the hydrogen atoms responsible for the signal in MR imaging.
The design objectives for the next generation of MR contrast agents will likely focus on prolonging intravascular retention, improving tissue targeting, and accessing new contrast mechanisms. Macromolecular paramagnetic contrast agents are being tested worldwide. Preclinical data shows that these agents demonstrate great promise for improving the quality of MR angiography, and in quantificating capillary permeability and myocardial perfusion.
Ultrasmall superparamagnetic iron oxide ( USPIO) particles have been evaluated in multicenter clinical trials for lymph node MR imaging and MR angiography, with the clinical impact under discussion. In addition, a wide variety of vector and carrier molecules, including antibodies, peptides, proteins, polysaccharides, liposomes, and cells have been developed to deliver magnetic labels to specific sites. Technical advances in MR imaging will further increase the efficacy and necessity of tissue-specific MRI contrast agents.
See also Adverse Reaction and Nephrogenic Systemic Fibrosis.
See also the related poll result: ' The development of contrast agents in MRI is' | | | | | | | | | | | • View the DATABASE results for 'Contrast Agents' (122).
| | | • View the NEWS results for 'Contrast Agents' (25).
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Brain imaging method may aid mild traumatic brain injury diagnosis Tuesday, 16 January 2024 by parkinsonsnewstoday.com | | |
A Targeted Multi-Crystalline Manganese Oxide as a Tumor-Selective Nano-Sized MRI Contrast Agent for Early and Accurate Diagnosis of Tumors Thursday, 18 January 2024 by www.dovepress.com | | |
FDA Approves Gadopiclenol for Contrast-Enhanced Magnetic Resonance Imaging Tuesday, 27 September 2022 by www.pharmacytimes.com | | |
How to stop using gadolinium chelates for magnetic resonance imaging: clinical-translational experiences with ferumoxytol Saturday, 5 February 2022 by www.ncbi.nlm.nih.gov | | |
Estimation of Contrast Agent Concentration in DCE-MRI Using 2 Flip Angles Tuesday, 11 January 2022 by pubmed.ncbi.nlm.nih.gov | | |
Manganese enhanced MRI provides more accurate details of heart function after a heart attack Tuesday, 11 May 2021 by www.news-medical.net | | |
Gadopiclenol: positive results for Phase III clinical trials Monday, 29 March 2021 by www.pharmiweb.co | | |
Gadolinium-Based Contrast Agents Hypersensitivity: A Case Series Friday, 4 December 2020 by www.dovepress.com | | |
Polysaccharide-Core Contrast Agent as Gadolinium Alternative for Vascular MR Monday, 8 March 2021 by www.diagnosticimaging.com | | |
Water-based non-toxic MRI contrast agents Monday, 11 May 2020 by chemistrycommunity.nature.com | | |
New method to detect early-stage cancer identified by Georgia State, Emory research team Friday, 7 February 2020 by www.eurekalert.org | | |
Researchers Brighten Path for Creating New Type of MRI Contrast Agent Friday, 7 February 2020 by www.newswise.com | | |
Manganese-based MRI contrast agent may be safer alternative to gadolinium-based agents Wednesday, 15 November 2017 by www.eurekalert.org | | |
Sodium MRI May Show Biomarker for Migraine Friday, 1 December 2017 by psychcentral.com | | |
A natural boost for MRI scans Monday, 21 October 2013 by www.eurekalert.org | | |
For MRI, time is of the essence A new generation of contrast agents could make for faster and more accurate imaging Tuesday, 28 June 2011 by scienceline.org |
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