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ContrastForum -
related threads
 
Contrast is the relative difference of signal intensities in two adjacent regions of an image.
Due to the T1 and T2 relaxation properties in magnetic resonance imaging, differentiation between various tissues in the body is possible. Tissue contrast is affected by not only the T1 and T2 values of specific tissues, but also the differences in the magnetic field strength, temperature changes, and many other factors. Good tissue contrast relies on optimal selection of appropriate pulse sequences (spin echo, inversion recovery, gradient echo, turbo sequences and slice profile).
Important pulse sequence parameters are TR (repetition time), TE (time to echo or echo time), TI (time for inversion or inversion time) and flip angle. They are associated with such parameters as proton density and T1 or T2 relaxation times. The values of these parameters are influenced differently by different tissues and by healthy and diseased sections of the same tissue.
For the T1 weighting it is important to select a correct TR or TI. T2 weighted images depend on a correct choice of the TE. Tissues vary in their T1 and T2 times, which are manipulated in MRI by selection of TR, TI, and TE, respectively. Flip angles mainly affect the strength of the signal measured, but also affect the TR/TI/TE parameters.
Conditions necessary to produce different weighted images:
T1 Weighted Image: TR value equal or less than the tissue specific T1 time - TE value less than the tissue specific T2 time.
T2 Weighted Image: TR value much greater than the tissue specific T1 time - TE value greater or equal than the tissue specific T2 time.
Proton Density Weighted Image: TR value much greater than the tissue specific T1 time - TE value less than the tissue specific T2 time.
See also Image Contrast Characteristics, Contrast Reversal, Contrast Resolution, and Contrast to Noise Ratio.

 
Images, Movies, Sliders:
 Fetus (Brain) and Dermoid in Mother  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 Anatomic MRI of the Knee 1  Open this link in a new window
    
SlidersSliders Overview

 Anatomic Imaging of the Liver  Open this link in a new window
      

 Brain MRI Inversion Recovery  Open this link in a new window
    
 
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• Related Searches:
    • Contrast Agents
    • Inversion Time
    • Breast MRI
    • Signal Intensity
    • Image Contrast Characteristics
 
Further Reading:
  Basics:
Magnetic resonance imaging
   by www.scholarpedia.org    
MRI's inside story
Thursday, 4 December 2003   by www.economist.com    
Image Characteristics and Quality
   by www.sprawls.org    
  News & More:
Sharpening MRI Images
Sunday, 1 December 2013   by www.onlinetmd.com    
A natural boost for MRI scans
Monday, 21 October 2013   by www.eurekalert.org    
A groundbreaking new graphene-based MRI contrast agent
Friday, 8 June 2012   by www.nanowerk.com    
New MRI Chemical Offers Amazing Contrast
Friday, 22 January 2010   by news.softpedia.com    
Searchterm 'Contrast' was also found in the following services: 
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Radiology  (106) Open this link in a new windowUltrasound  (149) Open this link in a new window
CMC Contrast AB
 
www.amersham.com

'CMC Contrast AB (Copenhagen Malmö Contrast AB) was established in April 2000. CMC Contrast AB was founded by professor Henrik Thomsen and the two main owners Malmöhus Invest AB and Øresund - Healthcare Capital KS.'
'The purpose of CMC Contrast AB is to develop the product CMC 001 to a registered medicinal product with market authorisation in the international pharmaceutical markets. CMC Contrast AB holds all the rights to CMC 001, and the company aims to develop CMC 001 to a registered medicinal product on a worldwide basis.'

Contact Information
MAIL CMC Contrast AB
Birger Jarlsgatan 26
SE-114 34 Stockholm
Sweden
PHONE +46 8 678 12 13
FAX +46 8 545 945 99
E-MAIL info@cmc-contrast.se
ONLINE www.amersham.com


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MRI Resources 
Used and Refurbished MRI Equipment - MRI Technician and Technologist Career - Patient Information - Safety Training - Homepages - Stimulator pool
 
Contrast AgentsForum -
related threadsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
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.
Positive contrast agents cause a reduction in the T1 relaxation time (increased signal intensity on T1 weighted images). They (appearing bright on MRI) are typically small molecular weight compounds containing as their active element Gadolinium, Manganese, or Iron. All of these elements have unpaired electron spins in their outer shells and long relaxivities.
Some typical contrast agents as gadopentetate dimeglumine, gadoteridol, and gadoterate meglumine are utilized for the central nervous system and the complete body; mangafodipir trisodium is specially used for lesions of the liver and gadodiamide for the central nervous system.
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 containing 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.
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'
 
Images, Movies, Sliders:
 Delayed Myocardial Contrast Enhancement from Infarct  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
 MR Colonography Gadolinium per Rectum  Open this link in a new window
      

Courtesy of  Robert R. Edelman
 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 
Radiology-tip.comContrast Agents,  Safety of Contrast Agents
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Radiology-tip.comUltrasound Contrast Agents,  Ultrasound Contrast Agent Safety
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• View the NEWS results for 'Contrast Agents' (25).Open this link in a new window.
 
Further Reading:
  Basics:
A safer approach for diagnostic medical imaging
Monday, 29 September 2014   by www.eurekalert.org    
Contrast Agents in Magnetic Resonance Imaging
1997
MR contrast agents: Applications in hepatobiliary imaging
Thursday, 11 November 2010   by www.appliedradiology.com    
  News & More:
3D 'bone maps' could spot early signs of osteoporosis
Monday, 27 February 2017   by www.gmanetwork.com    
A natural boost for MRI scans
Monday, 21 October 2013   by www.eurekalert.org    
Drastic market changes with MRI contrast media and PET radiopharmaceuticals emerging as most promising segments
Thursday, 21 October 2004   by www.news-medical.net    
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    
Searchterm 'Contrast' was also found in the following services: 
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News  (140)  Resources  (28)  Forum  (72)  
 
Contrast MediumForum -
related threadsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
A contrast medium (or contrast agent) is a chemical substance 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.
The chemical composition of the contrast media determines the specific usage. Similar to nuclear imaging is the intention in development of MR contrast media a high affinity to different organs or even tumors (e.g. necrosis avid contrast agent).
In 'contrast' to nuclear imaging contrast agents MR contrast media do not contain radiopharmaceuticals and the concentrations are about 100 times higher. Nuclear imaging contrast agents are direct contrast agents;; they are directly visible caused by their radioactivity. MR contrast agents affect the targeted tissue; they are indirect contrast agents.
See also Contrast Agents, the info sheet gives an overview and more in-depth information about different types of MRI contrast medium.
 
Images, Movies, Sliders:
 Breast MRI Images T1 Pre - Post Contrast  Open this link in a new window
      
 MRI of the Brain Stem with Temoral Bone and Auditory System  Open this link in a new window
    
SlidersSliders Overview

 
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• View the NEWS results for 'Contrast Medium' (2).Open this link in a new window.
 
Further Reading:
  Basics:
Questions and Answers on Gadolinium-Based Contrast Agents
Friday, 9 January 2009   by www.fda.gov    
Contrast Agents: Safety Profile
   by www.clinical-mri.com    
  News & More:
PRAC concludes assessment of gadolinium agents used in body scans and recommends regulatory actions, including suspension for some marketing authorisations
Friday, 10 March 2017   by www.satprnews.com    
GE Healthcare expands MRI contrast media product range in Europe with launch of macrocyclic agent ClariscanTM
Wednesday, 1 March 2017   by www.businesswire.com    
Lawson scientists develop commercial imaging product for PET/MRI scanners
Wednesday, 9 December 2015   by www.news-medical.net    
New oxygen-enhanced MRI scan 'helps identify most dangerous tumours'
Thursday, 10 December 2015   by www.dailymail.co.uk    
Contrast MRIs cause claims, concern, over residual metal in brain
Tuesday, 8 December 2015   by www.afr.com    
A Manganese Alternative to Gadolinium for MRI Contrast.
Friday, 4 December 2015   by www.ncbi.nlm.nih.gov    
Searchterm 'Contrast' was also found in the following services: 
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Radiology  (106) Open this link in a new windowUltrasound  (149) Open this link in a new window
Contrast Reversal
 
Contrast reversal is an MR image phenomenon where the dark parts become bright, and the bright parts become dark. This is usually most prevalent in sequences utilizing an extended TR.
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Further Reading:
  Basics:
MICRO-STRUCTURAL QUANTITIES - DIFFUSION, MAGNETISATION DECAY, MAGNETISATION TRANSFER AND PERMEABILITY(.pdf)
   by www.dundee.ac.uk    
  News & More:
Sharpening MRI Images
Sunday, 1 December 2013   by www.onlinetmd.com    
MRI Resources 
Nerve Stimulator - Health - Spine MRI - - Safety Products - Pacemaker
 
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