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

Out-
      side
 



 
 'Pixel' 
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 'Pixel' found in 1 term [] and 66 definitions []
previous     16 - 20 (of 67)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10 11 12 13 14]
Searchterm 'Pixel' was also found in the following services: 
spacer
Forum  (5)  
 
BandwidthForum -
related threads
 
(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.
mri safety guidance
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.
spacer
 
• Related Searches:
    • Spin
    • High Field MRI
    • Fat Saturation
    • Low Field MRI
    • Field Strength
 
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    
Searchterm 'Pixel' was also found in the following services: 
spacer
Radiology  (15) Open this link in a new windowUltrasound  (8) Open this link in a new window
C-SCAN™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.gehealthcare.com/usen/mr/cscan/index.html Manufactured by Esaote S.p.A.; compact in-office MRI system, fits in a 90 ft2 (8.4 m2) space and requires no shielding or special power. This low field MRI magnet is optimized for orthopedic use and imaging of the extremities.
The C-SCAN™ is developed from the ARTOSCAN™ - M with a new computer platform, and is also known as Artoscan C.
Esaote North America and Hologic Inc. are the U.S. distributors of this MRI device.
Device Information and Specification
CLINICAL APPLICATION
Dedicated extremity
CONFIGURATION
Closed
Linear and dual phased array, knee, ankle, wrist (6 total) coils
PULSE SEQUENCES
SE, GE, IR, STIR, FSE, 3D CE, GE-STIR, 3D GE, ME, TME, HSE
IMAGING MODES
Single, multislice, volume study, fast scan, multi slab
TR
12 - 5,000 msec
TE
5 - 220 msec
SINGLE SLICE
0.8 sec/image
MULTISLICE
0.8 sec/image
FOV
10 - 20 cm
2D: 2 mm - 10 mm;
3D: 0.6 mm - 10 mm
512 x 512
MEASURING MATRIX
256 x 256 maximum
PIXEL INTENSITY
4,096 gray lvls, 256 lvls in 3D
MAGNET TYPE
Permanent
BORE DIAMETER
or W x H
33.6 x 16 cm
MAGNET WEIGHT
960 kg
H*W*D
124 x 76 x 60 cm
POWER REQUIREMENTS
100/110/200/220/230/240
STRENGTH
10 mT/m
5-GAUSS FRINGE FIELD, radial/axial
28 cm/60 cm
Passive
spacer

• View the DATABASE results for 'C-SCAN™' (4).Open this link in a new window

MRI Resources 
Movies - Mobile MRI Rental - Guidance - Process Analysis - Jobs - RIS
 
Cardiac Gating
 
This method synchronize the heartbeat with the beginning of the TR, whereat the r wave is used as the trigger. Cardiac gating times the acquisition of MR data to physiological motion in order to minimize motion artifacts. ECG gating techniques are useful whenever data acquisition is too slow to occur during a short fraction of the cardiac cycle.
Image blurring due to cardiac-induced motion occurs for imaging times of above approximately 50 ms in systole, while for imaging during diastole the critical time is of the order of 200-300 ms. The acquisition of an entire image in this time is only possible with using ultrafast MR imaging techniques. If a series of images using cardiac gating or real-time echo planar imaging EPI are acquired over the entire cardiac cycle, pixel-wise velocity and vascular flow can be obtained.
In simple cardiac gating, a single image line is acquired in each cardiac cycle. Lines for multiple images can then be acquired successively in consecutive gate intervals. By using the standard multiple slice imaging and a spin echo pulse sequence, a number of slices at different anatomical levels is obtained. The repetition time (TR) during a ECG-gated acquisition equals the RR interval, and the RR interval defines the minimum possible repetition time (TR). If longer TRs are required, multiple integers of the RR interval can be selected. When using a gradient echo pulse sequence, multiple phases of a single anatomical level or multiple slices at different anatomical levels can be acquired over the cardiac cycle.
Also called cardiac triggering.
 
Images, Movies, Sliders:
 Cardiac Infarct Short Axis Cine Overview  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 Infarct 4 Chamber Cine  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 
spacer

• View the DATABASE results for 'Cardiac Gating' (15).Open this link in a new window

 
Further Reading:
  Basics:
Cardiac MRI - Technical Aspects Primer
Wednesday, 7 August 2002
Electrocardiogram in an MRI Environment: Clinical Needs, Practical Considerations, Safety Implications, Technical Solutions and Future Directions
Wednesday, 25 January 2012   by cdn.intechopen.com    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by www.imm.dtu.dk    
Searchterm 'Pixel' was also found in the following services: 
spacer
Forum  (5)  
 
Corrupted Data (Artifact)InfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Quick Overview
Artifact Information
NAME
Corrupted data
DESCRIPTION
Incorrectly interpretation or display
REASON
Corrupted data
HELP
Save to a new or different media
An artifact on a MR image can appear when data read off an optical disc became corrupted. There two effects can be seen.
Firstly, Bands where the intensity has been incorrectly interpreted or secondly areas, where the horizontal position of the pixels has been incorrectly displayed. It is important to be able to differentiate between artifacts caused during a MRI scan, from those caused by the associated hardware of an imaging system.
mri safety guidance
Image Guidance
Review the hardware and store the images on a new disc.
spacer
 
Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
Searchterm 'Pixel' was also found in the following services: 
spacer
Radiology  (15) Open this link in a new windowUltrasound  (8) Open this link in a new window
DC Offset ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
This artifact looks like a pixel at the exact center, which is brighter or darker than the surroundings by the Fourier transformation of a constant raw data offset.

See Central Point Artifact.
spacer
 
Further Reading:
  Basics:
Image Artefacts
   by www.fmrib.ox.ac.uk    
MRI Resources 
Knee MRI - Homepages - Equipment - Safety Products - Directories - Stimulator pool
 
previous      16 - 20 (of 67)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10 11 12 13 14]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

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



How AI will impact MRI :
only diagnostics 
saving time 
reducing cost 
makes planning obsolete 
reduce human knowledge 
not 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 • Medical-Ultrasound-Imaging • 
Copyright © 2003 - 2024 SoftWays. All rights reserved. [ 28 March 2024]
Terms of Use | Privacy Policy | Advertising
 [last update: 2024-02-26 03:41:00]