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Ultra-High-Resolution Skin Imaging at 7 T
with Motion Correction and Fat/Water Separation
Presentation: Tuesday @ 1:30pm # 3248
1Electrical Engineering, 3RadiologyStanford University
2Applied Science LaboratoryGE Healthcare
4Electrical Engineering & Computer Sciences
UC Berkeley
5Palo Alto Medical Foundation
J.K. Barral1 M.M. Khalighi2
R.D. Watkins3
M. Lustig1,4
B.S. Hu1,5D.G. Nishimura1
# 3248 Skin Imaging - J.K. Barral et al.
2/16
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.
# 3248 Skin Imaging - J.K. Barral et al.
3/16
The Skin
Epidermis ~ 0.1 mm
Dermis ~ 1 mm
Hypodermis (fat) ~ 10 mm
http://www.nlm.nih.gov
SURFACE COIL
MUSCLE
# 3248 Skin Imaging - J.K. Barral et al.
4/16
Previous Work @ 3 T and 7 T
Barral, ISMRM 2009, p.1993 Laistler, ISMRM 2009, p. 828 Maderwald, ISMRM 2008, p. 1718Maderwald, ISMRM 2009, p. 1994
Short TE: GRE
Fat/water separation:SaturationDixon/IDEAL methodsChemical shift used for segmentation
Skin squeezedMethods limited to specific body areas
Immobilization to prevent motion: Velcro® fastenerWeight of subjectAircast® plastic boot
Image realignment before averaging Intrascan motion not corrected Resolution limited or contrast agent used
# 3248 Skin Imaging - J.K. Barral et al.
5/16
Hardware
0.5 inch Ø1 inch Ø
Transmit-receive @ 7 TReceive-only @ 1.5 T
1.5 T and 7 T
Gradients: – 40 mT/m– 150 mT/m/ms
# 3248 Skin Imaging - J.K. Barral et al.
6/16
Pulse Sequence
Song, MRM 41:947-953, 1999 -- Barral, MRM 63:790-796, 2010
Navigator
Spoiler
Fractional echo
readout
Short TR (~20-100 ms)
# 3248 Skin Imaging - J.K. Barral et al.
7/16
Pulse Sequence
• Navigator interleaved (SNR; gradient duty cycle)
• Three TEs interleaved (fat/water separation)
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
# 3248 Skin Imaging - J.K. Barral et al.
8/16
Reconstruction
MOTION
CORRECTION
Song, MRM 41:947-953, 1999
Barral, Motion Workshop 2010, p. 18
1.5 T, slice 8/16
Echo 1
Echo 2
Echo 3
Echo 1
Echo 2
Echo 3
IDEAL
Fat
Water
Reeder, MRM 54:586-593, 2005
# 3248 Skin Imaging - J.K. Barral et al.
9/16
Experiment Parameters
Field strength [T]
1.5 7
TR [ms] 28 50
TE [ms] 5 6
FA [°] 20 20
BW [kHz] ±32 ±32
FOV [cm3] 6x3x1.6 4x1.5x0.8
Matrix size 512x256x16 400x150x80
Scan time [min:sec]
5:44 30:00
Resolution [µm3] 117x117x1000
100x100x100
Voxel volume [nL]
14 1
# 3248 Skin Imaging - J.K. Barral et al.
10/16
Results at 1.5 T
L/R
A/P
S/I
Motion estimates
# 3248 Skin Imaging - J.K. Barral et al.
11/16
Results at 1.5 T
Fat
Motion-corrected fat
Water Motion-corrected water
Slice 13/16, FOV cropped to 5.3 x 2.3 cm2
EpidermisDermis
Hypodermis
Muscle
5 mm
# 3248 Skin Imaging - J.K. Barral et al.
12/16
Results at 1.5 TFat
Motion-corrected fat
Water Motion-corrected water
16 slices, FOV cropped to 5.3 x 2.3 cm2
QuickTime™ and a decompressor
are needed to see this picture.
# 3248 Skin Imaging - J.K. Barral et al.
13/16
Results at 7 T
Motion estimates
L/R
A/P
S/I
# 3248 Skin Imaging - J.K. Barral et al.
14/16
Results at 7 T
Axial
SagittalWater
CoronalFat
Water Fat
= Motion-corrected version of the image to its left.
# 3248 Skin Imaging - J.K. Barral et al.
15/16
Conclusions
Mirrashed, Skin Research and Technology, 10:149-160, 2004
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