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Result : Searchterm 'Fat Suppression' found in 2 terms [ ] and 26 definitions [ ]
| | 1 - 5 (of 28) nextResult Pages : [1] [2 3 4 5 6] |  | |  | Searchterm 'Fat Suppression' was also found in the following services: | | | | |
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| Fat Suppression |  |
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Fat suppression is the process of utilizing specific MRI parameters to remove the deleterious effects of fat from the resulting images , e.g. with STIR, FAT SAT sequences, or water selective (PROSET WATS - water only selection, also FATS - fat only selection possible) excitation techniques.
Spin magnetization can be modulated by using special RF pulses. CHESS or its variations like SPIR, SPAIR (Spectral Selection Attenuated Inversion Recovery) and FAT SAT use frequency selective excitation pulses, which produce fat saturation.
Fat suppression techniques are nearly used in all body parts and belong to every standard MRI protocol of joints like knee, shoulder, hips, etc.
Image Guidance
Imaging of, e.g. the foot can induce bad fat suppression with SPIR/FAT SAT due to the asymmetric volume of this body part. The volume of the foot alters the magnetic field to a different degree than the smaller volume of the lower leg affecting the protons there. There is only a small band of tissue where the fat protons are precessing at the frequency expected, resulting in frequency selective fat saturation working only in that area. This can be corrected by volume shimming or creating a more symmetrical volume being imaged with water bags.
Even with their longer scan time and motion sensitivity, STIR (short T1//tau inversion recovery) sequences are often the better choice to suppress fat. STIR images are also preferred because of the decreased sensitivity to field inhomogeneities, permitting larger fields of views when compared to fat suppressed images and the ability to image away from the isocenter.
See also Knee MRI.
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| | | | | | | | • Share the entry 'Fat Suppression':    | | | | | | | | | |  Further Reading: | | Basics:
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• View the DATABASE results for 'Chemical Shift Artifact' (7).
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Quick Overview
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A disturbance of the field homogeneity, because of magnetic material (inside or outside the patient), technical problems or scanning at the edge of the field.
When images were obtained in a progression from the center to the edge of the coil, the homogeneity of the field observed by the imaged volume, changes when the distance from the center of the volume increase.
The same problem appears by scanning at a distance from the isocenter in left-right direction or too large field of view.
There are different types of bad image quality, the images are noisy, distorted or the fat suppression doesn't work because of badly set shim currents.
E.g. by using an IR sequence, changes in the T1 recovery rates of the tissues are involved. The inversion time at the center of the imaged volume is appropriate to suppress fat, but at the edge of the coil the same inversion time is sufficient to suppress water. Since the inversion time is not changed, the T1 recovery rates will increase.
Image Guidance
Take a smaller imaging volume (and for fat suppression a volume shimming), take care that the imaged region is at the center of the coil and that no magnetic material is inside the imaging volume. |
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• View the DATABASE results for 'Field Inhomogeneity Artifact' (3).
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