mr for quantitative fat imaging
TRANSCRIPT
MR for quantitative fat imaging
Pernilla Peterson1, Sven Månsson1
1Medical Radiation Physics, Lund University, Malmö, Sweden
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
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
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
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
FAT / WATER SEPARATION
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 6
W F
FAT / WATER SEPARATION
Chemical shift
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 7
FAT / WATER SEPARATION
Chemical shift
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 8
Total signal
Water
Fat
Time after excitation (ms)
FAT / WATER SEPARATION
2-point Dixon
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 9
FWSIP
FWSIP
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
FAT QUANTIFICATION
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 11
=
0
50
100
W F
F
+
SOURCES OF IMAGE CONTRAST IN MR
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 12
T1-relaxation T2*-relaxation Proton density
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
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
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
FAT QUANTIFICATION
Proton density
Pernilla Peterson, [email protected]
Medical Radiation Physics, Lund University, Malmö 16
Water voxel Fat voxel
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
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
