Signal and Contrast of CSE T1 Weighted Imagingmri/CE/slides/Spin-echo Sequences... · Stimulated...
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3/10/2009 1 Lecture 5 Spin Echo Sequences and Applications Chen Lin, PhD Indiana University School of Medicine & Clarian Health Partners Conventional Spin Echo (CSE) Sequence TE/2 TE/2 Excitation Refocusing Phase Encoding Frequency Encoding TR Next Excitation Chen Lin, PhD 3/09 Signal and Contrast of CSE Max. signal when: Excitation = 90 0 Refocusing = 180 0 When TR>>TE: Chen Lin, PhD 3/09 Short TR Long TE PD T1 ? T2 Low SNR / 1 / 2 0 (1 ) TR T TE T S M e e T1 Weighted Imaging • Short TE to reduce T2 weighting and maximize signal. • Intermediate TR (~T1) for T1w contrast. Chen Lin, PhD 3/09 T2 Weighted Imaging • Long TR ( >> T1) to reduce T1 weighting and maximize signal. • Intermediate TE ( ~T2) for T2w contrast. Chen Lin, PhD 3/09 Short TE, Long TR PD Weighted Imaging Chen Lin, PhD 3/09
Transcript of Signal and Contrast of CSE T1 Weighted Imagingmri/CE/slides/Spin-echo Sequences... · Stimulated...
3/10/2009
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Lecture 5Spin Echo Sequences and
Applications
Chen Lin, PhD
Indiana University School of Medicine & Clarian Health Partners
Conventional Spin Echo (CSE) Sequence
TE/2TE/2
Excitation Refocusing
Phase Encoding
Frequency Encoding
TR
Next Excitation
Chen Lin, PhD 3/09
Signal and Contrast of CSE
Max. signal when:
Excitation = 900
Refocusing = 1800
When TR>>TE:
Chen Lin, PhD 3/09
Short TR
Long TE
PD
T1 ?
T2
Low SNR
/ 1 / 2
0(1 )
TR T TE TS M e e
T1 Weighted Imaging
• Short TE to reduce T2 weighting and maximize signal.
• Intermediate TR (~T1) for T1w contrast.Chen Lin, PhD 3/09
T2 Weighted Imaging
• Long TR ( >> T1) to reduce T1 weighting and maximize signal.
• Intermediate TE ( ~T2) for T2w contrast. Chen Lin, PhD 3/09
Short TE, Long TR
PD Weighted Imaging
Chen Lin, PhD 3/09
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Spin Echo Train
Rewind
Echo Spacing
Echo Train Length (Turbo Factor)Chen Lin, PhD 3/09
CPMG Condition
1. Refocusing RF pulses are 90 deg out of phase with respect to excitation RF pulse.
2. Identical spacing between refocusing RF pulses.
3. Identical phase accumulation between refocusing RF pulses.
Chen Lin, PhD 3/09
t
900 x
1800 +y 1800 -y 1800 +y
SE SE SE
B1 / Mxy
t 2t 2t
Multi Contrast Spin Echo Sequence
t
Mxy (TEn) = M0 exp(-TEn/T2)
Chen Lin, PhD 3/09
TE3TE2TE1
B1 / Mxy
T2 Mapping with MCSE
Chen Lin, PhD 3/09
11.5ms 23ms 34.5ms 46ms
57.5ms 69ms 80.5ms T2 Map
Cell
Water/
mobile
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GAG
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Morphology
Collagen
Biochemical Composure
Cartilage T2 Mapping
Chen Lin, PhD 3/09
RARE, FSE/TSE Sequence
t
Chen Lin, PhD 3/09
Short TEEffective Long TEEffective
B1 / Mxy
t 2t 2t
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Available TEeff in FSE/TSE
Echo Train Length = ? & Echo Spacing = ?Chen Lin, PhD 3/09
CSE FSE CSE FSE
FSE/TSE versus CSE
MT Effect
PD T2
Contrast
DifferenceBright FatChen Lin, PhD 3/09
T2 Blurring and Edge Ringing
ky
kx
ky Y
II
Multi-shot FSE/TSE
I-space Point Spread Function
FT
Chen Lin, PhD 3/09
K-space Intensity Profile
Blurring
Ringing/Ghosting
FSE/TSE Artifact with respect to TE
Chen Lin, PhD 3/09
CSE TE=30ms TSE TE=30ms EL=30 EP=10ms TSE TE=130ms EL=30 EP=10ms
ky
I
ky
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Bright Fat due to J-coupling
Lipid Mxy
TE(ms)
FSE/TSE
CSE
CC
H
H
H
80 160
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2D FSE/TSE Applications
TSE-RST, 3 mm
448 matrix, 28cm
T1 TSE, 3 mm, 448
matrix, PAT 2, 2:56
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Pelvic Applications
TSE T2 , 4mm, 24 x 29cm,
179 x 448, 4:41. TSE T2 , 3mm, 24 x 30cm,
198 x 448, 4:27.
Chen Lin, PhD 3/09
MSK Applications
SE, TE 14, 14cm, 3mm,
208 x 320, 3:04
TSE, Fat Sat, TE 14, 14cm,3mm,
208 x 320, 3:55
Courtesy University of Pittsburgh Medical Center
Chen Lin, PhD 3/09
Cardiac Applications
TSE DB T2 TSE DB T2 FS
Chen Lin, PhD 3/09
3D FSE Applications
3D TSE w. PACE 3D SPACE w. PACE
Chen Lin, PhD 3/09
Stimulated Echo
Mxy
t
Chen Lin, PhD 3/09
900 x
a10 y
SE SE + STE SE + STE
a20 y a30 y
Hyper Echo
B1 / Mxy
t900
a0
1800 1800
a0
Chen Lin, PhD 3/09
Prof. Jurgen HennigUniversity Hospital
Freiburg
3/10/2009
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3D SPACE / CUBESamplingPerfection withApplication optimizedContrast using different flip angleEvolutions
3D TSE with variable refocusing flip angle schedules:
• Constant: same as 3D TSE
• PD Variant: optimized for short TE
• T2 Variant: optimized for long TE
Constant Refocusing Flip Angles
Chen Lin, PhD 3/09
Variable Refocusing Flip Angles
Chen Lin, PhD 3/09
Isotropic Hires T2 with SPACE
3D SPACE, GRAPPA 2, 0.9 x 0.9 x 0.9 mm3 4:27 min
sCourtesy University of Tuebingen, Germany
Chen Lin, PhD 3/09
High Resolution 3D SPACE for IAC
Acoustic Nerve
3D SPACE with 0.3 mm
isotropic resolution in 6 min
Chen Lin, PhD 3/09
Reducing Susceptibility Artifact w. SPACE
2D TSE T2 MPR of 3D
SPACE T2
Chen Lin, PhD 3/09
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Variations of SPACE
Courtesy of Olga Hospital, Stuttgart; Germany
T1 SPACE1 x 1 x 3 mm³
Dark Fluid SPACE 1 x 1 x 1 mm³
T2 SPACE 1 x 1 x 1 mm³
Chen Lin, PhD 3/09
SSFSE/HASTE Sequence
k
Half Fourier Acquired Single Shot Turbo Spin Echo
Chen Lin, PhD 3/09
SSFSE/HASTE Applications
• Single-shot Technique:
– Fast scan -> Localizer
– Freeze motion -> Abdominal and cardiac imaging
• Long SE Train:
– T2 weighted imaging
– MRCP
Chen Lin, PhD 3/09
Courtesy of Laurel Highlands Advanced Imaging
HASTE T2, 40 x 40cm,5mm,
206 x 512
HASTE, MPCP Thick Slab, 23 x 35cm,
205 x 384, 1.35s
Abdominal T2w & MCP w. HASTE
Chen Lin, PhD 3/09
Summary
1. Convention SE
2. Multi-contrast SE
3. 2D/3D FSE/TSE
4. 3D CUBE/SPACE
5. 2D SSFSE/HASTE
Chen Lin, PhD 3/09
Thank You !
www.indiana.edu/~mri
