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Result : Searchterm 'Apparent Diffusion Coefficient' found in 1 term [] and 3 definitions []
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Apparent Diffusion CoefficientInfoSheet: - Artifacts - 
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 - Diffusion Weighted Imaging -
 
(ADC) A diffusion coefficient to differentiate T2 shine through effects or artifacts from real ischemic lesions. In the human brain, water diffusion is a three-dimensional process that is not truly random because the diffusional motion of water is impeded by natural barriers. These barriers are cell membranes, myelin sheaths, white matter fiber tracts, and protein molecules.
The apparent water diffusion coefficients can be calculated by acquiring two or more images with a different gradient duration and amplitude (b-values). The contrast in the ADC map depends on the spatially distributed diffusion coefficient of the acquired tissues and does not contain T1 and T2* values.
The increased sensitivity of diffusion-weighted MRI in detecting acute ischemia is thought to be the result of the water shift intracellularly restricting motion of water protons (cytotoxic edema), whereas the conventional T2 weighted images show signal alteration mostly as a result of vasogenic edema.
The reduced ADC value also could be the result of decreased temperature in the nonperfused tissues, loss of brain pulsations leading to a decrease in apparent proton motion, increased tissue osmolality associated with ischemia, or a combination of these factors. The lower ADC measurements seen with early ischemia, have not been fully established, however, a lower apparent ADC is a sensitive indicator of early ischemic brain at a stage when ischemic tissue remains potentially salvageable.
See also Diffusion Weighted Imaging and Diffusion Tensor Tractography.
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Further Reading:
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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    
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
Diffusion Imaging: From Basic Physics to Practical Imaging
1999   by ej.rsna.org    
  News & More:
Novel MRI Technique Could Reduce Breast Biopsies, University of Washington Study
Tuesday, 2 October 2012   by www.eurekalert.org    
Combination of diffusion tensor and functional magnetic resonance imaging during recovery from the vegetative state.
Tuesday, 31 August 2010   by 7thspace.com    
Hopkins researchers use diffusion MRI technique to monitor ultrasound uterine fibroid treatment
Monday, 8 August 2005   by www.eurekalert.org    
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ADC MapMRI Resource Directory:
 - Diffusion Weighted Imaging -
 
An ADC map shows parametric images containing the apparent diffusion coefficients of diffusion weighted images. The term apparent refers to the dependence of these coefficients on factors other than prior molecular mobility. Also called diffusion map.
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Further Reading:
  Basics:
Diffusion Imaging: From Basic Physics to Practical Imaging
1999   by ej.rsna.org    
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Diffusion Weighted ImagingForum -
related threadsMRI Resource Directory:
 - Diffusion Weighted Imaging -
 
(DWI) Magnetic resonance imaging is sensitive to diffusion, because the diffusion of water molecules along a field gradient reduces the MR signal. In areas of lower diffusion the signal loss is less intense and the display from this areas is brighter. The use of a bipolar gradient pulse and suitable pulse sequences permits the acquisition of diffusion weighted images (images in which areas of rapid proton diffusion can be distinguished from areas with slow diffusion).
Based on echo planar imaging, multislice DWI is today a standard for imaging brain infarction. With enhanced gradients, the whole brain can be scanned within seconds. The degree of diffusion weighting correlates with the strength of the diffusion gradients, characterized by the b-value, which is a function of the gradient related parameters: strength, duration, and the period between diffusion gradients.
Certain illnesses show restrictions of diffusion, for example demyelinization and cytotoxic edema. Areas of cerebral infarction have decreased apparent diffusion, which results in increased signal intensity on diffusion weighted MRI scans. DWI has been demonstrated to be more sensitive for the early detection of stroke than standard pulse sequences and is closely related to temperature mapping.
DWIBS is a new diffusion weighted imaging technique for the whole body that produces PET-like images. The DWIBS sequence has been developed with the aim to detect lymph nodes and to differentiate normal and hyperplastic from metastatic lymph nodes. This may be possible caused by alterations in microcirculation and water diffusivity within cancer metastases in lymph nodes.
See also Diffusion Weighted Sequence, Perfusion Imaging, ADC Map, Apparent Diffusion Coefficient, and Diffusion Tensor Imaging.

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Further Reading:
  Basics:
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
Novel MRI Technique Could Reduce Breast Biopsies, University of Washington Study
Tuesday, 2 October 2012   by www.eurekalert.org    
  News & More:
Imaging technique sheds new light on the composition of the brain of moderate cannabis users
Sunday, 7 May 2006   by www.eurekalert.org    
Conductivity tensor mapping of the human brain using diffusion tensor MRI
   by www.pnas.org    
High-b-value Diffusion-weighted MR Imaging of Suspected Brain Infarction
2000   by www.ajnr.org    
French pioneer of Diffusion MRI to receive top Japanese scientific award
Thursday, 27 September 2012   by www.domain-b.com    
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Diffusion Weighted SequenceInfoSheet: - Sequences - 
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 - Diffusion Weighted Imaging -
 
Diffusion weighted imaging can be performed similar to the phase contrast angiography sequence. The gradients must be increased in amplitude to depict the much slower motions of molecular diffusion in the body.
While a T1 weighted MRI pulse sequence is diffusion sensitive, a quantitative diffusion pulse sequence was introduced by Steijskal and Tanner. Its characteristic features are two strong symmetrical gradient lobes placed on either side of the 180 refocusing pulse in a spin echo sequence. These symmetrical gradient lobes have the sole purpose of enhancing dephasing of spins, thereby accelerating intravoxel incoherent motion (IVIM) signal loss.
Dephasing is proportional to the square of the time (diffusion time) during which the gradients are switched on and the strength of the applied gradient field. Therefore, the use of high field gradient systems with faster and more sensitive sequences, make diffusion weighting more feasible.
Areas in which the protons diffuse rapidly (swollen cells in early stroke, less restriction to diffusion) will show an increased signal when the echo is measured relative to areas in which diffusion is restricted. For increased accuracy of diffusion measurement and image enhancement, useful motion correction techniques such as navigator echo and other methods should be used. In addition to this, applying the b-value calculated by the strength and duration of motion probing gradients with a high rate of accuracy is very important.
See also Apparent Diffusion Coefficient, ADC Map, Lattice Index Map.

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• View the DATABASE results for 'Diffusion Weighted Sequence' (6).Open this link in a new window

 
Further Reading:
  Basics:
Diffusion-Weighted Imaging
   by spinwarp.ucsd.edu    
Diffusion Imaging: From Basic Physics to Practical Imaging
1999   by ej.rsna.org    
EVALUATION OF HUMAN STROKE BY MR IMAGING
2000
  News & More:
Hopkins researchers use diffusion MRI technique to monitor ultrasound uterine fibroid treatment
Monday, 8 August 2005   by www.eurekalert.org    
DWI Best in Subacute Stroke Imaging
Tuesday, 1 June 2004   by www.hospimedica.com    
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NMR - Stent - Diffusion Weighted Imaging - Brain MRI - Pathology - Raman Spectroscopy
 
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