MR for quantitative fat imaging
Transcript of MR for quantitative fat imaging
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MR for quantitative fat imaging
Pernilla Peterson1, Sven Månsson1
1Medical Radiation Physics, Lund University, Malmö, Sweden
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WHY FAT QUANTIFICATION?
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 2
• Obesity and diabetes
• Fat accumulation
– Liver, pancreas, myocardium
MR-image based fat quantification
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THE BASIC PRINCIPLE
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 3
1. Separation of MR-signals from fat and
water
2. Quantification of the amount of fat relative
the amount of water
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SUMMARY
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 4
• Fat / water separation
• Fat quantification
– T1-relaxation
– T2-relaxation
– Proton density
• Simple strategies
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SUMMARY
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 5
• Fat / water separation
• Fat quantification
– T1-relaxation
– T2-relaxation
– Proton density
• Simple strategies
![Page 6: MR for quantitative fat imaging](https://reader031.fdocuments.us/reader031/viewer/2022020705/61fb97fa2e268c58cd6005ad/html5/thumbnails/6.jpg)
FAT / WATER SEPARATION
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 6
W F
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FAT / WATER SEPARATION
Chemical shift
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 7
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FAT / WATER SEPARATION
Chemical shift
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 8
Total signal
Water
Fat
Time after excitation (ms)
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FAT / WATER SEPARATION
2-point Dixon
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 9
FWSIP
FWSIP
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SUMMARY
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 10
• Fat / water separation
• Fat quantification
– T1-relaxation
– T2-relaxation
– Proton density
• Simple strategies
![Page 11: MR for quantitative fat imaging](https://reader031.fdocuments.us/reader031/viewer/2022020705/61fb97fa2e268c58cd6005ad/html5/thumbnails/11.jpg)
FAT QUANTIFICATION
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 11
=
0
50
100
W F
F
+
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SOURCES OF IMAGE CONTRAST IN MR
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 12
T1-relaxation T2*-relaxation Proton density
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SOURCES OF IMAGE CONTRAST IN MR
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 13
T1-relaxation T2*-relaxation Proton density
Resonance
frequency
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FAT QUANTIFICATION
T1-relaxation
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 14
0 0.5 1 1.5 2Repetition time (s)
|Sig
nal|
Water
Fat
0 50 1000
20
40
60
80
100
Actual FF (%)
Estim
ate
d F
F (
%)
Identity line
Esimated FF
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FAT QUANTIFICATION
T2*-relaxation
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 15
Time after excitation
Ma
gn
itu
de
sig
na
l
0 0.05 0.1 0.15 0.2Echo time
Ma
gn
itu
de
sig
na
l
Water
Fat
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FAT QUANTIFICATION
Proton density
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 16
Water voxel Fat voxel
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SUMMARY
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 17
• Fat / water separation
• Fat quantification
– T1-relaxation
– T2-relaxation
– Proton density
• Simple strategies
![Page 18: MR for quantitative fat imaging](https://reader031.fdocuments.us/reader031/viewer/2022020705/61fb97fa2e268c58cd6005ad/html5/thumbnails/18.jpg)
SUMMARY
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 18
• Simple strategies to avoid bias
– Small flip angle or long repetition time
– A priori T2-values for fat and water
– Estimate proton density for water and
vegetable oils