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

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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

Epidermis ~ 0.1 mm

Dermis ~ 1 mm

Hypodermis (fat) ~ 10 mm

http://www.nlm.nih.gov

SURFACE COIL

MUSCLE

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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

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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

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Pulse Sequence

Song, MRM 41:947-953, 1999 -- Barral, MRM 63:790-796, 2010

Navigator

Spoiler

Fractional echo

readout

Short TR (~20-100 ms)

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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.

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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

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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

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Results at 1.5 T

L/R

A/P

S/I

Motion estimates

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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

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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.

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Results at 7 T

Motion estimates

L/R

A/P

S/I

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Results at 7 T

Axial

SagittalWater

CoronalFat

Water Fat

= Motion-corrected version of the image to its left.

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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

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Thank you!

Contact:

jbarral@stanford.edu