Magnetic Resonance - Technology Information Portal Welcome to MRI Technology••
Info
  Sheets


Out-
      side
 



 
 'positive contrast' 
SEARCH FOR    
 
  2 3 5 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Result : Searchterm 'positive contrast' found in 0 term [] and 3 definitions [], (+ 17 Boolean[] results
1 - 5 (of 20)     next
Result Pages : [1]  [2 3 4]
Searchterm 'positive contrast' was also found in the following service: 
spacer
News  (2)  
 
Positive Oral Contrast AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Types of oral contrast agents with positive signal enhancement:
Paramagnetic contrast agents (e.g., Gd-DTPA solutions)
Short T1-relaxation gastrointestinal agents (e.g., mineral oil)
Combinations of these
Ideal oral contrast agents are immiscible with water, biologically inert, have a low viscosity and surface tension. Oral positive contrast agents may improve the separation of bowel loops, the detection of polyps in colon MRI or the assessment of inflammatory bowel in the small intestine. Several positive oral contrast agents are available and they are safe to use, for example gadolinium solution, ferric ammonium citrate, different oil emulsions and pediatric formula.
Unfavorably motion artifacts caused by respiration and peristalsis may be increased in MR imaging. In addition, the signal of the positive contrast medium may decrease caused by dilution in gastrointestinal (GI) secretions. With the use of contrast agents that are immiscible with water, no dilution and accompanying signal loss occur even when the contrast agent is in contact with the intraluminal contents of the GI tract. Another disadvantage may be residual substances in the bowel, resembling masses when enclosed by bright signal. In addition, positive contrast agents may have a similar signal as bright masses, which make their (e.g. lipoma) detection difficult.
See also Gastrointestinal Paramagnetic Contrast Agents, Combination Oral Contrast Agents, Gastrointestinal Diamagnetic Contrast Agents.
 
Images, Movies, Sliders:
 MR Colonography Gadolinium per Rectum  Open this link in a new window
      

Courtesy of  Robert R. Edelman
 
spacer
 
• Share the entry 'Positive Oral Contrast Agents':  Facebook  Twitter  LinkedIn  
 
Further Reading:
  Basics:
Components of Oral Contrast Agent for Magnetic Resonance Imaging(.pdf)
   by www.ffcr.or.jp    
Hydro-MRI of the Small Bowel: Effect of Contrast Volume, Timing of Contrast Administration, and Data Acquisition on Bowel Distention
Sunday, 1 October 2006   by www.ajronline.org    
MRI Resources 
Spectroscopy pool - MR Guided Interventions - Fluorescence - Musculoskeletal and Joint MRI - Contrast Agents - Artifacts
 
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
spacer
Radiology-tip.comUltrasound Contrast Agents,  Ultrasound Contrast Agent Safety
spacer

• View the DATABASE results for 'Contrast Agents' (122).Open this link in a new window


• View the NEWS results for 'Contrast Agents' (25).Open this link in a new window.
 
Further Reading:
  Basics:
New guidelines urge caution on use of contrast agents during MR scans
Tuesday, 8 August 2017   by www.dotmed.com    
Manganese-based MRI contrast agents: past, present and future
Friday, 4 November 2011   by www.ncbi.nlm.nih.gov    
A safer approach for diagnostic medical imaging
Monday, 29 September 2014   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    
  News & More:
Sodium MRI May Show Biomarker for Migraine
Friday, 1 December 2017   by psychcentral.com    
Manganese-based MRI contrast agent may be safer alternative to gadolinium-based agents
Wednesday, 15 November 2017   by www.eurekalert.org    
3D 'bone maps' could spot early signs of osteoporosis
Monday, 27 February 2017   by www.gmanetwork.com    
New Study Sheds Light on Safety of Gadolinium-Based Contrast Agents
Wednesday, 29 November 2017   by www.empr.com    
Engineered atherosclerosis-specific zinc ferrite nanocomplex-based MRI contrast agents
Monday, 18 January 2016   by 7thspace.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    
MRI Resources 
Manufacturers - Implant and Prosthesis - Process Analysis - MRI Technician and Technologist Jobs - Fluorescence - Used and Refurbished MRI Equipment
 
Flow Related Enhancement
 
(FRE) Flow related enhancement could be seen most for blood flow, but also for other liquids with some MR imaging techniques, as an increase in intensity due to the washout of saturated spins. FRE provides positive contrast ("bright blood") of vascular details in time of flight MRA as well as the physiologic characterization of blood flow.
If stationary spins within the scanned region experience only an incomplete T1 relaxation between the repeated radio frequency (RF) excitations, this results in fewer signal of the stationary tissue (compared to inflowing blood with completely relaxed spins). The degree of the flow related enhancement is proportional to the blood flow velocity and the used repetition time. The use of flow compensation (gradient moment nulling) improves the FRE especially in gradient echo sequences.
 
Images, Movies, Sliders:
 TOF-MRA Circle of Willis Inverted MIP  Open this link in a new window
    

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

 
spacer

• View the DATABASE results for 'Flow Related Enhancement' (10).Open this link in a new window

 
Further Reading:
  Basics:
Conventional MRI and MR Angiography of Stroke
2012   by www.mc.vanderbilt.edu    
Searchterm 'positive contrast' was also found in the following service: 
spacer
News  (2)  
 
Gadolinium ZeoliteInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.
 
(Gadolite® oral Suspension) An oral paramagnetic MRI contrast agent to enhance delineation of the bowel. Zeolites are hydrated aluminosilicates with large holes that can provide a temporary home for guest molecules like gadolinium. Zeolites modified with Gd (III) are effective positive MRI contrast agents for gastrointestinal application.

spacer

• View the DATABASE results for 'Gadolinium Zeolite' (3).Open this link in a new window

MRI Resources 
General - MRI Centers - MRI Technician and Technologist Career - Sequences - Developers - Non-English
 
Half Scan
 
(HS) A method in which approximately one half of the acquisition matrix in the phase encoding direction is acquired. Half scan is possible because of symmetry in acquired data. Since negative values of phase encoded measurements are identical to corresponding positive values, only a little over half (more than 62.5%) of a scan actually needs to be acquired to replicate an entire scan. This results in a reduction in scan time at the expense of signal to noise ratio. The time reduction can be nearly a factor of two, but full resolution is maintained.
Half scan can be used when scan times are long, the signal to noise ratio is not critical and where full spatial resolution is required. Half scan is particularly appropriate for scans with a large field of view and relatively thick slices; and, in 3D scans with many slices. In some fast scanning techniques the use of Half scan enables a shorter TE thus improving contrast. For this reason, the Half scan parameter is located in the contrast menu.
More information about scan time reduction; see also partial fourier technique.
spacer

• View the DATABASE results for 'Half Scan' (4).Open this link in a new window

MRI Resources 
Implant and Prosthesis pool - Process Analysis - MR Guided Interventions - Fluorescence - Safety Products - Quality Advice
 
     1 - 5 (of 20)     next
Result Pages : [1]  [2 3 4]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

MR-TIP    
Community   
User
Pass
Forgot your UserID/Password ?  



The impact of TTIP/TPP on the MRI scanner market will bring :
more variety 
better scanners 
more risk 
less regulation 
cheaper scanners 
Lost in Translation 
no change at all 

Look
      Ups





MR-TIP.com uses cookies! By browsing MR-TIP.com, you agree to our use of cookies.

Magnetic Resonance - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • US-TIP • 
Copyright © 2003 - 2018 SoftWays. All rights reserved. [ 26 March 2019]
Terms of Use | Privacy Policy | Advertising
 [last update: 2018-03-08 05:11:00]