Transcript Diffusion - University of Oxford

Navigated Steady-State
Diffusion Imaging of Knee
Cartilage
Karla L. Miller, Garry E. Gold† and John M. Pauly
Department of Electrical Engineering
†Department of Radiology and Palo Alto VA Medical Center
Magnetic Resonance Systems Research Laboratory
Stanford University
DWI of cartilage
• in vitro studies
Burstein 1993, Henkelman 1994, Xia 1994,
Torzilli 1998, Frank 1999, Knauss 1999
• in vivo studies
Gold 1998, Eustace 2000
• evidence for correlation to damage
Xia 1995, Frank 1999
DWI of cartilage: challenges
• large gradient area
• small motions cause severe artifacts
• short T2 necessitates short TE
Navigated Steady-State DWI
• large gradient area
 strong diffusion weighting per unit area
• small motions cause severe artifacts
 navigated motion correction
• short T2 necessitates short TE
 short TE, TR
Outline
• Navigated SS-DWI
• In Vivo Results
• Discussion
Diffusion weighted imaging
90°
(1)
(2)
ACQ
(3)
(1) encode position
(2) spins diffuse
(3) decode position
SS-DWI diffusion sensitivity
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SS-DWI diffusion sensitivity
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90º
90º
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SS-DWI diffusion sensitivity
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D = nTR
n=1,2,3 …
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Steady-state diffusion
TR < T1,T2
Navigated steady-state diffusion
TR < T1,T2
Navigated phase correction
kx
ky
high resolution
kx
ky
navigator
• navigator measures motion-induced phase
• phase-correct high resolution data
(Poster #1112)
In vivo experiments
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5 subjects
FOV = 18 cm, 0.75 x 0.75 mm2, 5 mm thick
TR = 25 ms, = 25, nex = 64
G = {1, 2.75, 4} G/cm, t = 5 ms
beff = 40, 275, 500 s/mm2
imaging time: 7 minutes
In vivo results
40 s/mm2
275 s/mm2
500 s/mm2
Navigator correction
uncorrected
navigator
corrected
Conclusions
• diffusion has potential as contrast
mechanism in cartilage
• SS-DWI enables in vivo knee cartilage
diffusion imaging
• navigated motion-correction allows high
resolution