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Result : Searchterm 'Temporal Resolution' found in 1 term [] and 18 definitions [], (+ 1 Boolean[] results
| previous 11 - 15 (of 20) nextResult Pages : [1] [2 3 4] | | | | Searchterm 'Temporal Resolution' was also found in the following services: | | | | |
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The principal advantage of MRI at high field is the increase in signal to noise ratio. This can be used to improve anatomic and/or temporal resolution and reduce scan time while preserving image quality. MRI devices for whole body imaging for human use are available up to 3 tesla (3T). Functional MRI ( fMRI) and MR spectroscopy ( MRS) benefit significantly. In addition, 3T machines have a great utility in applications such as TOF MRA and DTI. Higher field strengths are used for imaging of small parts of the body or scientific animal experiments. Higher contrast may permit reduction of gadolinium doses and, in some cases, earlier detection of disease.
Using high field MRI//MRS, the RF-wavelength and the dimension of the human body complicating the development of MR coils. The absorption of RF power causes heating of the tissue. The energy deposited in the patient's tissues is fourfold higher at 3T than at 1.5T. The specific absorption rate (SAR) induced temperature changes of the human body are the most important safety issue of high field MRI//MRS.
Susceptibility and chemical shift dispersion increase like T1, therefore high field MRI occasionally exhibits imaging artifacts. Most are obvious and easily recognized but some are subtle and mimic diseases. A thorough understanding of these artifacts is important to avoid potential pitfalls. Some imaging techniques or procedures can be utilized to remove or identify artifacts. See also Diffusion Tensor Imaging.
See also the related poll result: ' In 2010 your scanner will probably work with a field strength of' | | | | | | | | | | | Further Reading: | | Basics:
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Keyhole imaging is used for dynamic imaging with contrast medium. The advantage is that the keyhole technique increases temporal resolution without a loss of spatial resolution by limited data acquisition. Keyhole Fourier imaging updates the low spatial frequencies of the original full, high-resolution data set. The high spatial frequency content of the image is constant in time so that its updating would be unnecessary. The high spatial frequency data is acquired from a baseline image, for example, before injection of a contrast agent.
After contrast injection, only the lower spatial frequency data is acquired because, there is no change in the tissue that is responsible for the higher frequency spatial variation in the image. | | | | • View the DATABASE results for 'Keyhole' (8).
| | | • View the NEWS results for 'Keyhole' (1).
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| | | | • View the DATABASE results for 'PRinciples of Echo Shifting using a Train of Observations' (2).
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In parallel MR imaging, a reduced data set in the phase encoding direction(s) of k-space is acquired to shorten acquisition time, combining the signal of several coil arrays. The spatial information related to the phased array coil elements is utilized for reducing the amount of conventional Fourier encoding.
First, low-resolution, fully Fourier-encoded reference images are required for sensitivity assessment. Parallel imaging reconstruction in the Cartesian case is efficiently performed by creating one aliased image for each array element using discrete Fourier transformation. The next step then is to create an full FOV image from the set of intermediate images.
Parallel reconstruction techniques can be used to improve the image quality with increased signal to noise ratio, spatial resolution, reduced artifacts, and the temporal resolution in dynamic MRI scans.
Parallel imaging algorithms can be divided into 2 main groups:
Image reconstruction produced by each coil ( reconstruction in the image domain, after Fourier transform): SENSE ( Sensitivity Encoding), PILS (Partially Parallel Imaging with Localized Sensitivity),
ASSET.
Reconstruction of the Fourier plane of images from the frequency signals of each coil ( reconstruction in the frequency domain, before Fourier transform): GRAPPA. Additional techniques include SMASH, SPEEDER™,
IPAT (Integrated Parallel Acquisition Techniques - derived of GRAPPA a k-space based technique) and mSENSE (an image based enhanced version of SENSE).
| | | | | | • View the DATABASE results for 'Parallel Imaging Technique' (12).
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| | | | • View the DATABASE results for 'Phased Array Coil' (9).
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