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 DWI            Diffusion Weighted Imaging 
Searchterm 'DWI' was found in the Abbreviation Register. 
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BandwidthForum -
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(BW) Bandwidth is a measure of frequency range, the range between the highest and lowest frequency allowed in the signal. For analog signals, which can be mathematically viewed as a function of time, bandwidth is the width, measured in Hertz of a frequency range in which the signal's Fourier transform is nonzero.
The receiver (or acquisition) bandwidth (rBW) is the range of frequencies accepted by the receiver to sample the MR signal. The receiver bandwidth is changeable (see also acronyms for 'bandwidth' from different manufacturers) and has a direct relationship to the signal to noise ratio (SNR) (SNR = 1/squareroot (rBW). The bandwidth depends on the readout (or frequency encoding) gradient strength and the data sampling rate (or dwell time).
Bandwidth is defined by BW = Sampling Rate/Number of Samples.
A smaller bandwidth improves SNR, but can cause spatial distortions, also increases the chemical shift. A larger bandwidth reduces SNR (more noise from the outskirts of the spectrum), but allows faster imaging.
The transmit bandwidth refers to the RF excitation pulse required for slice selection in a pulse sequence. The slice thickness is proportional to the bandwidth of the RF pulse (and inversely proportional to the applied gradient strength). Lowering the pulse bandwidth can reduce the slice thickness.
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Image Guidance
A higher bandwidth is used for the reduction of chemical shift artifacts (lower bandwidth - more chemical shift - longer dwell time - but better signal to noise ratio). Narrow receive bandwidths accentuate this water fat shift by assigning a smaller number of frequencies across the MRI image. This effect is much more significant on higher field strengths. At 1.5 T, fat and water precess 220 Hz apart, which results in a higher shift than in Low Field MRI.
Lower bandwidth (measured in Hz) = higher water fat shift (measured in pixel shift).

See also Aliasing, Aliasing Artifact, Frequency Encoding, and Chemical Shift Artifact.
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• Related Searches:
    • Water Fat Shift
    • Low Field MRI
    • Fat Saturation
    • Artifact
    • Signal to Noise Ratio
 
Further Reading:
  Basics:
Bandwidth
   by en.wikipedia.org    
  News & More:
Automated Quality Assurance for Magnetic Resonance Image with Extensions to Diffusion Tensor Imaging(.pdf)
   by scholar.lib.vt.edu    
A Real-Time Navigator Approach to Compensating for Motion Artifacts in Coronary Magnetic Resonance Angiography
   by www.cs.nyu.edu    
MRI Resources 
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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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• View the NEWS results for 'Diffusion Weighted Imaging' (4).Open this link in a new window.
 
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    
Quantitative Apparent Diffusion Coefficient Measurements Obtained by 3-Tesla MRI Are Correlated with Biomarkers of Bladder Cancer Proliferative Activity
   by www.plosone.org    
  News & More:
Stability and repeatability of diffusion-weighted imaging (DWI) of normal pancreas on 5.0 Tesla magnetic resonance imaging (MRI)
Monday, 24 July 2023   by www.nature.com    
MRI innovation makes cancerous tissue light up and easier to see
Monday, 21 March 2022   by www.sciencedaily.com    
Diffusion MRI and machine learning models classify childhood brain tumours
Saturday, 6 March 2021   by physicsworld.com    
Diffusion-weighted MRI in Advanced Epithelial Ovarian Cancer: Apparent Diffusion Coefficient as a Response Marker
Tuesday, 1 October 2019   by pubs.rsna.org    
Novel Imaging Technique Improves Prostate Cancer Detection
Tuesday, 6 January 2015   by health.ucsd.edu    
High-b-value Diffusion-weighted MR Imaging of Suspected Brain Infarction
2000   by www.ajnr.org    
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Sample Imperfection (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Sample imperfection
DESCRIPTION
Shifts of the signal in the phase encoding direction
REASON
Distorting the k-space trajectory, reduced bandwidth
HELP
Fat suppression, more excitations
Artifacts either by distorting the k-space trajectory (i.e. due to imperfect shimming) or as a consequence of the reduced bandwidth in the phase encode direction, commonly with EPI sequences.
While a standard spin warp-based sequence has an infinitely large bandwidth in the phase encode direction (about 1 or 2 kH), the bandwidth in EPI is related to the time between the gradient echoes (about a millisecond).
Hence even small frequency offsets can result in significant shifts of the signal in the phase encoding direction. Segmentation can introduce ghosting if there are significant difference in the amplitude and phase of the signal. This can be a particular problem when trying to acquire the segments in rapid succession.
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Image Guidance
Suitable choices of excitation schemes and/or subsequent correction can help to reduce this artifact. The signal from fat can easily be offset by a large fraction of the FOV, and must be suppressed. The effect of frequency offsets can be reduced by collecting data with more than one excitation, which effectively increases the bandwidth in the phase encoding direction.
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Searchterm 'DWI' was also found in the following services: 
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News  (47)  Resources  (15)  Forum  (27)  
 
Diffusion Weighted Whole Body Imaging
 
(DWIBS) This diffusion weighted whole body imaging with background signal suppression provides diffusion weighted contrast throughout the body using a single or multi-station background-suppressed diffusion imaging. DWIBS images are comparable with PET images and provide applications from the visualization of nerve roots and brachial plexus to the detection of lesions throughout the body.

See also Diffusion Weighted Imaging (DWI).
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Further Reading:
  Basics:
Diffusion-Weighted MRI in the Body: Applications and Challenges in Oncology
Friday, 1 June 2007   by www.ajronline.org    
  News & More:
HSS Researchers Launch Study Using Novel MRI Techniques to Find a Biomarker for Parsonage-Turner Syndrome, A Nerve Disorder
Monday, 21 September 2020   by www.newswise.com    
Diffusion-weighted MRI shows promise as a radiation-free alternative for pediatric tumor staging
Wednesday, 19 February 2014   by www.2minutemedicine.com    
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Mallinckrodt, Inc.MRI Resource Directory:
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www.mallinckrodt.com Mallinckrodt, a Tyco Healthcare company makes and distributes products for respiratory care; bulk and dosage pharmaceuticals, primarily for pain relief and addiction therapy; and imaging agents for magnetic resonance, ultrasound, X-ray, and nuclear medicine applications. With worldwide manufacturing and distribution facilities, as well as worldwide sales offices, Mallinckrodt sells its products worldwide.
GastroMARK® is marketed in the United States by Mallinckrodt, Inc.

In June 2007 Tyco International Ltd. completed the separation of its healthcare business, which is named Covidien. Mallinckrodt, Inc. is now part of Covidien Ltd.

MRI Contrast Agents:
Contact Information
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Mallinckrodt, Inc.
675 McDonnell Blvd.
Hazelwood, MO 63042
USA
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International: +1-314-654-3177
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International: icsstl@mkg.com
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Further Reading:
  Basics:
Guerbet Completes Acquisition of Mallinckrodt’s Contrast Media and Delivery Systems Business
Sunday, 29 November 2015   by www.itnonline.com    
  News & More:
Covidien Completes Spin Off, Mallinckrodt Starts Trading On NYSE
Monday, 1 July 2013   by www.rttnews.com    
MRI Resources 
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