fat suppression techniques in MRI

1. In the name
of God

2. Fat Suppression in
MR Imaging
By S.Shokoofeh Mousavi

3.  Introduction
 Indication
 Physics for fat suppression
 Methods • STIR
• CHESS
• SPIR
• SPAIR
• Water Excitation
• DIXON-based

4. Introduction
 A technique to suppress signal from normal adipose tissue
 Typically inserted at the beginning of a normal sequence
Mousavi. M.Sc graduated in medical physics
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5. Indication
 To reduce chemical shift artifact or improve
visualization
 To improve tissue characterization
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Mousavi. M.Sc graduated in medical physics

6. Physics for fat suppression
 Protons are saturated selectively
 It requires homogeneity
 Fat is different in terms of frequencies and relaxation
time
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Mousavi. M.Sc graduated in medical physics

7. Pros. & Cons.
Advantage
Contrast-enhanced T1w
imaging
Tissue characterization
Avoiding artifacts
Small details visualization
Disadvantage
Inhomogeneity of magnetic field
Inhomogeneity of frequency field
Inhomogeneity in tissue volume
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Mousavi. M.Sc graduated in medical physics

8. Fat Suppression Methods
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Mousavi. M.Sc graduated in medical physics

9. STIR (short time inversion recovery)
 An IR pulse sequence with specific timing
 Works in magnetic field inhomogeneities
 Can be used with low magnetic field
strength
 Long acquisition time and reduced SNR
 Can not be used post Gd
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Mousavi. M.Sc graduated in medical physics

10. STIR (cont.)
 Fluid appear bright and fat appear very
dark
 Pathological process are usually bright
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Mousavi. M.Sc graduated in medical physics

11. CHESS (chemical shift selective)
 Based on the chemical shift between fat & water
 RF pulses tuned to the resonance frequency of fat
 Fat protons were dephased
 Can be used for post contrast imaging
 Can not be used at low field strength or in inhomogeneity 11
Mousavi. M.Sc graduated in medical physics

12. Water Excitation
 Based on chemical shift
 Short series of RF pulses were used
 Reduced sensitivity to inhomogeneous
field
 Longer time and lower slice numbers
 Used in musculoskeletal system
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Mousavi. M.Sc graduated in medical physics

13. DIXON-based
 Based on chemical shift
 Uses “in phase” & “out phase” cycling
 “water only” & “fat only” images can be extracted
 Insensitive to magnetic field inhomogeneties
 Widely used in abdominal imaging
 Useful for detection of small amount of fat
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Mousavi. M.Sc graduated in medical physics

14. SPIR (spectral pre saturation with inversion recovery)
 A combination of STIR &
spectral saturation
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Mousavi. M.Sc graduated in medical physics

15. SPAIR (spectral attenuated inversion recovery)
 A combination of STIR & CHESS
 Uses adiabatic pulses
 Tissue contrast is not affected
 Longer inversion time
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Mousavi. M.Sc graduated in medical physics

16. Thanks for