Presentation: Tuesday @ 1:30pm
# 3248
Ultra-High-Resolution Skin Imaging at 7 T
with Motion Correction and Fat/Water Separation
1Electrical
Engineering, 3Radiology
Stanford University
J.K. Barral1
M.M. Khalighi2
R.D. Watkins3
2Applied
Science Laboratory
GE Healthcare
4Electrical
M. Lustig1,4
B.S.
Hu1,5
Engineering & Computer Sciences
UC Berkeley
5Palo
D.G. Nishimura1
Alto Medical Foundation
In a Nutshell
High-resolution skin imaging requires:
(1) a short TE (dermis has short T2s)  GRE
(2) fat/water separation (hypodermis is fat)  IDEAL
(3) motion correction  navigators
Our sequence satisfies these requirements.
We imaged the calves of healthy volunteers at 1.5 T and 7 T
and demonstrate up to 100 µm isotropic resolution.
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The Skin
MUSCLE
Hypodermis (fat) ~ 10 mm
Dermis ~ 1 mm
Epidermis ~ 0.1 mm
SURFACE COIL
http://www.nlm.nih.gov
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Previous Work @ 3 T and 7 T
 Short TE:
GRE
 Fat/water separation:
Saturation
Dixon/IDEAL methods
Chemical shift used for segmentation
Barral, ISMRM 2009, p.1993
Laistler, ISMRM 2009, p. 828
Maderwald, ISMRM 2008, p. 1718
Maderwald, ISMRM 2009, p. 1994
 Immobilization to prevent motion:
Velcro ® fastener
Skin squeezed
Weight of subject
Methods limited to specific body areas
Aircast® plastic boot
 Image realignment before averaging  Intrascan motion not corrected
 Resolution limited or contrast agent used
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Hardware
Gradients:
– 40 mT/m
– 150 mT/m/ms
1.5 T and 7 T
Receive-only @ 1.5 T
Transmit-receive @ 7 T
1 inch Ø
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0.5 inch Ø
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Pulse Sequence
Fractional
echo readout
Navigator
Spoiler
Short TR (~20-100 ms)
Song, MRM 41:947-953, 1999 -- Barral, MRM 63:790-796, 2010
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Pulse Sequence
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
• Navigator interleaved (SNR; gradient duty cycle)
• Three TEs interleaved (fat/water separation)
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Reconstruction
Echo 1
Echo 2
Echo 3
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M
O
T
I
O
N
C
O
R
R
E
C
T
I
O
N
1.5 T, slice 8/16
Echo 1
Echo 2
Fat
I
D
E
A
L
Water
Echo 3
Skin Imaging - J.K. Barral et al.
Song, MRM 41:947-953, 1999
Barral, Motion Workshop 2010, p. 18
Reeder, MRM 54:586-593, 2005
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Experiment Parameters
Field strength [T]
TR [ms]
TE [ms]
1.5
28
5
7
50
6
FA [°]
BW [kHz]
FOV [cm3]
Matrix size
20
20
±32
6x3x1.6
512x256x16
±32
4x1.5x0.8
400x150x80
Scan time [min:sec]
5:44
Resolution [µm3]
Voxel volume [nL]
117x117x1000
14
30:00
100x100x100
1
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Results at 1.5 T
Motion estimates
A/P
L/R
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Results at 1.5 T
Slice 13/16, FOV cropped to 5.3 x 2.3 cm2
Fat
Motion-corrected fat
5 mm
Water
Motion-corrected water
Muscle
Hypodermis
Dermis
Epidermis
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Results at 1.5 T
16 slices, FOV cropped to 5.3 x 2.3 cm2
Fat
Motion-corrected fat
QuickTime™ and a
decompressor
are needed to see this picture.
Water
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Motion-corrected water
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Results at 7 T
Motion estimates
A/P
L/R
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Results at 7 T
Water
Fat
Axial
Sagittal
Water
=
Motion-corrected
version of the
image to its left.
Coronal
Fat
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Conclusions
 IDEAL efficient at separating fat and water at 7 T
 Motion correction needed and effective
(rigid-body motion)
 High-resolution achieved without contrast agent
 Long scan time
 Skin deformable: non-rigid motion not accounted for
Mirrashed, Skin Research and Technology, 10:149-160, 2004
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Thank you!
Contact:
jbarral@stanford.edu
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