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Volume of Interest
 
(VOI) The selected volume for spectroscopic measurement or evaluation. For SVS, VOI and voxel are identical, but for hybrid CSI the VOI is divided into voxels.
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• View the DATABASE results for 'Volume of Interest' (3).Open this link in a new window

Volume Rendering
 
Volume rendering is a technique that incorporates data from all pixels in an image to provide a 3D representation. By incorporating cut planes to eliminate unwanted structures and by varying the degree of opacity of structures, image viewing may be optimized. This technique can be effective at depicting arteries and veins even when these structures are adjacent.
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• View the DATABASE results for 'Volume Rendering' (4).Open this link in a new window

 
Further Reading:
  Basics:
3D-DOCTOR Tutorial
   by www.ablesw.com    
MRI Resources 
MRI Training Courses - Spine MRI - Collections - Liver Imaging - Implant and Prosthesis - PACS
 
Volume Selective Excitation
 
The selective excitation of spins in only a limited region of space. This can be particularly useful for spectroscopy as well as imaging. Spatial localization of the signal source may be achieved through spatially selective excitation and the resulting signal may be analyzed directly for the spectrum corresponding to the excited region. It is usually achieved with selective excitation.
Typically, a single dimension of localization can be achieved with one selective RF excitation pulse (and a magnetic field gradient along a desired direction), while a localized volume (3D) can be excited with a stimulated echo produced with three selective RF pulses whose selective magnetic field gradients are mutually orthogonal, having a common intersection in the desired region. Similar 'crossed plane' excitation can be used with selective 180° refocusing pulses and conventional spin echoes.
A degree of spatial localization of excitation can alternatively be achieved with depth pulses, e.g. when using surface coils for excitation as well as signal detection. An indirect application of selective excitation for volume-selected spectroscopy is to use appropriate combinations of signals acquired after selective inversion of different regions, in order to subtract away the signal from undesired regions.
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• View the DATABASE results for 'Volume Selective Excitation' (3).Open this link in a new window

Volume ShimForum -
there are related threads
 
Shimming corrects local magnetic field inhomogeneities by adjusting the static gradients. A volume shim enables the shim volume to be limited. This local 3D shim provides a more precise result and therefore a better fat saturation. For spectroscopy, it provides a better starting value for an interactive shim.
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• View the DATABASE results for 'Volume Shim' (2).Open this link in a new window

 
Further Reading:
  Basics:
Improved shim method based on the minimization of the maximum off-resonance frequency for balanced SSFP
Monday, 1 June 2009   by www.ncbi.nlm.nih.gov    
  News & More:
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    
Volumetric Imaging
 
Volumetric imaging is a 3D technique where all the MRI signals are collected from the entire tissue sample and imaged as a whole entity, therefore providing a high signal to noise ratio. The acquisition of isotropic voxels or thin slices with high spatial resolution allows to create multiplanar reconstructions in all planes; a compensation for the usually longer scan time. The acquisition time can be reduced by parallel imaging technique.
New T2 weighted variants of 3D sequences (FSE-XETA, T2-SPACE, VISTA) have been introduced that differ from conventional FSE sequences. An echo train containing up to 200 echoes obtained at a minimum echo spacing allows very fast acquisition. A flip angle modulation (flip angle sweep - FAS) during the FSE readout carries magnetization as long as possible to avoid blurring and provide optimal signal at the effective echo time. This type of imaging is well suited for brain and spine MRI procedures.
Newer T1 weighted variants include Liver Acquisition with Volume Acquisition (LAVA) and T1W High Resolution Isotropic Volume Examination (THRIVE), which have advantages for dynamic breath hold imaging in liver and abdominal examinations.

See also Volume Imaging, 3 Dimensional Imaging.
 
Images, Movies, Sliders:
 Brain MRI Sagittal T1 001  Open this link in a new window
    
 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
SlidersSliders Overview

 MRI of the Skull Base  Open this link in a new window
    
SlidersSliders Overview

 
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• View the NEWS results for 'Volumetric Imaging' (1).Open this link in a new window.

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

 
Further Reading:
  Basics:
Cutting Edge Imaging of THE Spine
February 2007   by www.pubmedcentral.nih.gov    
3-D VOLUMETRIC IMAGING FOR STEREOTACTIC LESIONAL AND DEEP BRAIN STIMULATION SURGERY
MRI Resources 
General - MRI Reimbursement - DICOM - Calculation - Spectroscopy - Resources
 
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