1. Ultra-High-Resolution Skin Imaging at 7 T with Motion Correction and Fat/Water Separation Presentation: Tuesday @ 1:30pm # 3248 1 Electrical Engineering, 3 Radiology Stanford University 2 Applied Science Laboratory GE Healthcare 4 Electrical Engineering & Computer Sciences UC Berkeley 5 Palo Alto Medical Foundation J.K. Barral 1 M.M. Khalighi 2 R.D. Watkins 3 M. Lustig 1,4 B.S. Hu 1,5 D.G. Nishimura 1

2. # 3248Skin 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.

3. # 3248Skin Imaging - J.K. Barral et al.3/16 The Skin Epidermis ~ 0.1 m m Dermis ~ 1 mm Hypodermis (fat) ~ 10 mm http://www.nlm.nih.gov SURFACE COIL MUSCLE

4. # 3248Skin 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. 1718 Maderwald, ISMRM 2009, p. 1994 Short TE: GRE Fat/water separation: Saturation Dixon/IDEAL methods Chemical shift used for segmentation Skin squeezed Methods limited to specific body areas  Immobilization to prevent motion: Velcro® fastener Weight of subject Aircast® plastic boot  Image realignment before averaging  Intrascan motion not corrected  Resolution limited or contrast agent used

5. # 3248Skin Imaging - J.K. Barral et al.5/16 Hardware 0.5 inch Ø 1 inch Ø Transmit-receive @ 7 TReceive-only @ 1.5 T 1.5 T and 7 T Gradients: –40 mT/m –150 mT/m/ms

6. # 3248Skin 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)

7. # 3248Skin Imaging - J.K. Barral et al.7/16 Pulse Sequence Navigator interleaved (SNR; gradient duty cycle) Three TEs interleaved (fat/water separation)

8. # 3248Skin Imaging - J.K. Barral et al.8/16 Reconstruction MOTIONCORRECTIONMOTIONCORRECTION 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 IDEALIDEAL Fat Water Reeder, MRM 54:586-593, 2005

9. # 3248Skin Imaging - J.K. Barral et al.9/16 Experiment Parameters Field strength [T]1.57 TR [ms]2850 TE [ms]56 FA [°]20 BW [kHz]±32 FOV [cm 3 ]6x3x1.64x1.5x0.8 Matrix size512x256x16400x150x80 Scan time [min:sec]5:4430:00 Resolution [µm 3 ] 117x117x1000100x100x100 Voxel volume [nL]141

10. # 3248Skin Imaging - J.K. Barral et al.10/16 Results at 1.5 T L/R A/P S/I Motion estimates

11. # 3248Skin Imaging - J.K. Barral et al.11/16 Results at 1.5 T FatMotion-corrected fat WaterMotion-corrected water Slice 13/16, FOV cropped to 5.3 x 2.3 cm 2 Epidermis Dermis Hypodermis Muscle 5 mm

12. # 3248Skin Imaging - J.K. Barral et al.12/16 Results at 1.5 T FatMotion-corrected fat WaterMotion-corrected water 16 slices, FOV cropped to 5.3 x 2.3 cm 2

13. # 3248Skin Imaging - J.K. Barral et al.13/16 Results at 7 T Motion estimates L/R A/P S/I

14. # 3248Skin Imaging - J.K. Barral et al.14/16 Results at 7 T Axial Sagittal Water Coronal Fat WaterFat = Motion-corrected version of the image to its left.

15. # 3248Skin 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

16. # 3248Skin Imaging - J.K. Barral et al.16/16 Thank you! Contact: jbarral@stanford.edu