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Result : Searchterm 'Gadolinium' found in 4 terms [] and 62 definitions []
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Searchterm 'Gadolinium' was also found in the following services: 
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Nonionic Intravenous Contrast AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Radiographic low-osmolar nonionic contrast agents have less side effects and fewer nephrotoxicity than ionic, high-osmolar agents. Gadolinium-based MRI contrast agents have a different formulation from iodinated X-ray contrast media, and there is no known cross sensitivity between these two types of contrast agents. Intravenous MRI contrast agents, specifically the gadolinium chelates have a high safety and lack of nephrotoxicity compared with X-ray contrast media.
The used gadolinium chelates differ in following properties: linear (e.g., gadodiamide and gadoversetamide have nonionic linear structures) vs. macrocyclic cores, and ionic vs. nonionic types. The nonionic molecules have lower osmolality and viscosity, which increase digestibility at greater concentrations, and make faster bolus injections conceivable. The macrocyclic molecules (e.g., gadoteridol has a nonionic macrocyclic ring structure) are more stable and show fewer tendencies to dissociate free Gd.

See also ProHance®, Omniscan®, OptiMARK®, Ionic Intravenous Contrast Agents.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'
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    • Gadolinium
    • Lumbar Spine MRI
    • Breast MRI
    • Nephrogenic Systemic Fibrosis
    • Ionic Intravenous Contrast Agents
 
Further Reading:
  News & More:
Spurious Hypocalcemia After Omniscan- or OptiMARK-Enhanced Magnetic Resonance Imaging: An Algorithm for Minimizing a False-Positive Laboratory Value
   by arpa.allenpress.com    
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Radiology  (1) Open this link in a new window
Perfusion ImagingForum -
related threadsInfoSheet: - Sequences - 
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(PWI - Perfusion Weighted Imaging) Perfusion MRI techniques (e.g. PRESTO - Principles of Echo Shifting using a Train of Observations) are sensitive to microscopic levels of blood flow. Contrast enhanced relative cerebral blood volume (rCBV) is the most used perfusion imaging. Both, the ready availability and the T2* susceptibility effects of gadolinium, rather than the T1 shortening effects make gadolinium a suitable agent for use in perfusion imaging. Susceptibility here refers to the loss of MR signal, most marked on T2* (gradient echo)-weighted and T2 (spin echo)-weighted sequences, caused by the magnetic field-distorting effects of paramagnetic substances.
T2* perfusion uses dynamic sequences based on multi or single shot techniques. The T2* (T2) MRI signal drop within or across a brain region is caused by spin dephasing during the rapid passage of contrast agent through the capillary bed. The signal decrease is used to compute the relative perfusion to that region. The bolus through the tissue is only a few seconds, high temporal resolution imaging is required to obtain sequential images during the wash in and wash out of the contrast material and therefore, resolve the first pass of the tracer. Due to the high temporal resolution, processing and calculation of hemodynamic maps are available (including mean transit time (MTT), time to peak (TTP), time of arrival (T0), negative integral (N1) and index.
An important neuroradiological indication for MRI is the evaluation of incipient or acute stroke via perfusion and diffusion imaging. Diffusion imaging can demonstrate the central effect of a stroke on the brain, whereas perfusion imaging visualizes the larger 'second ring' delineating blood flow and blood volume. Qualitative and in some instances quantitative (e.g. quantitative imaging of perfusion using a single subtraction) maps of regional organ perfusion can thus be obtained.
Echo planar and potentially echo volume techniques together with appropriate computing power offer real time images of dynamic variations in water characteristics reflecting perfusion, diffusion, oxygenation (see also Oxygen Mapping) and flow.
Another type of perfusion MR imaging allows the evaluation of myocardial ischemia during pharmacologic stress. After e.g., adenosine infusion, multiple short axis views (see cardiac axes) of the heart are obtained during the administration of gadolinium contrast. Ischemic areas show up as areas of delayed and diminished enhancement. The MRI stress perfusion has been shown to be more accurate than nuclear SPECT exams. Myocardial late enhancement and stress perfusion imaging can also be performed during the same cardiac MRI examination.
 
Images, Movies, Sliders:
 Normal Lung Gd Perfusion MRI  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 Left Circumflex Ischemia First-pass Contrast Enhancement  Open this link in a new window
 
Radiology-tip.comradPerfusion Scintigraphy
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Medical-Ultrasound-Imaging.comBolus Injection
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• View the DATABASE results for 'Perfusion Imaging' (16).Open this link in a new window


• View the NEWS results for 'Perfusion Imaging' (3).Open this link in a new window.
 
Further Reading:
  Basics:
CHAPTER 55: Ischemia
2003
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
  News & More:
Non-invasive diagnostic procedures for suspected CHD: Search reveals informative evidence
Wednesday, 8 July 2020   by medicalxpress.co    
Implementation of Dual-Source RF Excitation in 3 T MR-Scanners Allows for Nearly Identical ADC Values Compared to 1.5 T MR Scanners in the Abdomen
Wednesday, 29 February 2012   by www.plosone.org    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by www.imm.dtu.dk    
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
Measuring Cerebral Blood Flow Using Magnetic Resonance Imaging Techniques
1999   by www.stanford.edu    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
MRI Resources 
Bioinformatics - Health - Calculation - General - Breast MRI - Safety Training
 
Reticuloendothelial Contrast AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Liver imaging with gadolinium contrast enhanced MRI is sometimes not sufficient for a reliable diagnosis of liver lesions. For this reasons, special liver Contrast agents that are targeted to the reticuloendothelial system (RES), have been developed to improve both detection and characterization of liver and spleen lesions. Reticuloendothelial Contrast Agents, as e.g. superparamagnetic iron oxides (SPIO), are taken up by healthy liver tissue but not tumors.
These RES targeted contrast agents provide a prolonged imaging window and enough time for high spatial resolution or multiple breath hold images. Reticuloendothelial contrast agents have an increased sensitivity for the detection of small liver lesions (e.g., metastases), compared with gadolinium enhanced MRI and spiral CT. At higher field strengths with an increased signal to noise ratio the susceptibility effect with iron oxide particles may be enhanced.
Other new agents (Gadobenate Dimeglumine, Gadoxetic Acid) have both an initial extracellular circulation and a delayed liver-specific uptake. Since a considerable part of these contrast agents is excreted in the bile, functional biliary imaging can diagnose biliary anomalies, postoperative bile leaks, and anastomotic strictures. Other agents, such as liposomes (with encapsulated Gd-DTPA) or DOTA complexes are in different development stages.

See also Hepatobiliary Contrast Agents, Gadolinium Oxide, Superparamagnetic Iron Oxide and Liposomes.
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• View the DATABASE results for 'Reticuloendothelial Contrast Agents' (3).Open this link in a new window

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Bolus Injection
 
A bolus is a rapid infusion of high dose contrast agent. Dynamic and accumulation phase imaging can be performed after bolus injection. Since the transit time of the bolus through the tissue is only a few seconds, high temporal resolution imaging can be required to obtain sequential images during the wash in and wash out of the contrast material and, therefore, resolve the first pass of the tracer.
For the same injected dose of contrast agent the injection rate (and, consequently, the total injected volume) modifies the bolus peak profile. Increasing the injection rate produces a sharpening of the peak (Cmax increase, Tmax decrease, peak length decrease). At a low injection rate, the first pass presents a plateau form. Substantial changes in the gadolinium concentrations during signal acquisition induce artifacts. Furthermore, the haemodynamic parameters (cardiac output, blood pressure) influence the bolus profile. The characteristics of gadolinium agents are favorable in the early bolus phase, whereas the advantages of large complexes (e.g. blood pool agents) and ultrasmall superparamagnetic iron oxide (USPIO) are most evident in the distribution phase.
 
Images, Movies, Sliders:
 Left Circumflex Ischemia First-pass Contrast Enhancement  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 Normal Lung Gd Perfusion MRI  Open this link in a new window
 
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• View the DATABASE results for 'Bolus Injection' (9).Open this link in a new window

 
Further Reading:
  News & More:
Contrast Bolus Timing and Scan Delay
2003   by www.med.nyu.edu    
Searchterm 'Gadolinium' was also found in the following service: 
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Radiology  (1) Open this link in a new window
Contrast Enhanced Magnetic Resonance AngiographyInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - MRA -
 
(CE MRA) Contrast enhanced MR angiography is based on the T1 values of blood, the surrounding tissue, and paramagnetic contrast agent.
T1-shortening contrast agents reduces the T1 value of the blood (approximately to 50 msec, shorter than that of the surrounding tissues) and allow the visualization of blood vessels, as the images are no longer dependent primarily on the inflow effect of the blood. Contrast enhanced MRA is performed with a short TR to have low signal (due to the longer T1) from the stationary tissue, short scan time to facilitate breath hold imaging, short TE to minimize T2* effects and a bolus injection of a sufficient dose of a gadolinium chelate.
Images of the region of interest are performed with 3D spoiled gradient echo pulse sequences. The enhancement is maximized by timing the contrast agent injection such that the period of maximum arterial concentration corresponds to the k-space acquisition. Different techniques are used to ensure optimal contrast of the arteries e.g., bolus timing, automatic bolus detection, bolus tracking, care bolus. A high resolution with near isotropic voxels and minimal pulsatility and misregistration artifacts should be striven for. The postprocessing with the maximum intensity projection (MIP) enables different views of the 3D data set.
Unlike conventional MRA techniques based on velocity dependent inflow or phase shift techniques, contrast enhanced MRA exploits the gadolinium induced T1-shortening effects. CE MRA reduces or eliminates most of the artifacts of time of flight angiography or phase contrast angiography. Advantages are the possibility of in plane imaging of the blood vessels, which allows to examine large parts in a short time and high resolution scans in one breath hold. CE MRA has found a wide acceptance in the clinical routine, caused by the advantages:
•
3D MRA can be acquired in any plane, which means that greater vessel coverage can be obtained at high resolution with fewer slices (aorta, peripheral vessels);
•
the possibility to perform a time resolved examination (similarly to conventional angiography);
•
no use of ionizing radiation; paramagnetic agents have a beneficial safety.
 
Images, Movies, Sliders:
 CE-MRA of the Carotid Arteries  Open this link in a new window
    
SlidersSliders Overview

 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

 
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• View the DATABASE results for 'Contrast Enhanced Magnetic Resonance Angiography' (14).Open this link in a new window


• View the NEWS results for 'Contrast Enhanced Magnetic Resonance Angiography' (2).Open this link in a new window.
 
Further Reading:
  Basics:
Contrast-Enhanced MR Angiography(.pdf)
   by ric.uthscsa.edu    
CONTRAST ENHANCED MR ANGIOGRAPHY – PRINCIPLES, APPLICATIONS, TIPS AND PITFALLS(.pdf)
  News & More:
CONTRAST-ENHANCED MRA OF THE CAROTIDS(.pdf)
PERIPHERAL VASCULAR MAGNETIC RESONANCE ANGIOGRAPHY(.pdf)
CONTRAST ENHANCED MRI OF THE LIVER STATE-OF-THE-ART(.pdf)
MRI Resources 
Safety pool - Chemistry - - Developers - Supplies - Diffusion Weighted Imaging
 
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