1

Voxel volume 2 x 2 x 2 mm3 = 8

2 x 2 x 2 mm3 1 x 1 x 1 mm3 8 x 8 x 8 mm3 4 x 4 x 4 mm3

Voxel volume 1 x 1 x 1 mm3 = 1

Why high-field MRI?

•  Signal-to-noise ratio (SNR)

•  Contrast (anatomical & functional)

Benefits of high-field MRI

2

Outline

•  High-resolution vascular imaging

•  High-resolution fMRI applications

•  Anatomical contrast @ 7T MRI

•  Clinical applications of @ 7T MRI

Veins are dark due to elevated concentration of deoxyhemoglobin (BOLD)

A T1-weighted 3D gradient echo acquisition.

TR/TE = 32.4/5.5 ms

readout bandwidth 20 kHz

FOV: 20 x 20 x 5mm

Matrix: 256 x 256 x 32

Image resolution: 0.078 x 0.078 x 0.156 mm

San time: acquisition time 4:25 min/scan,

total scan time 35:20 min (n=8).

axial

Cat, 9.4T

coronal

High Resolution Vascular Imaging

Bolan, et al. NeuroImage 2006

axial axial

Excitation slab

Fresh blood that flows into the slice is fully relaxed, and therefore bright

Cat, 9.4T

coronal

In a T1-weighted sequence, long T1 spins are saturated because they don't have time to recover

High Resolution Vascular Imaging (Time-of-flight / inflow effects)

Bolan, et al. NeuroImage 2006

3

axial sagittal Cat, 9.4T

coronal

In a T1-weighted sequence, long T1 spins are saturated because they don't have time to recover

High Resolution Vascular Imaging (Time-of-flight / inflow effects)

Veins are dark due to elevated concentration of deoxyhemoglobin (BOLD)

Arteries are bright due to unsaturated fresh blood fast inflow into slab

Bolan, et al. NeuroImage 2006

Arteries

Vessel Classification

High Resolution Vascular Imaging (Time-of-flight / inflow effects)

In a T1-weighted sequence, long T1 spins are saturated because they don't have time to recover

Cat, 9.4T

Veins are dark due to elevated concentration of deoxyhemoglobin (BOLD)

Arteries are bright due to unsaturated fresh blood fast inflow into slab

Veins

axial

Bolan, et al. NeuroImage 2006

Maximum Intensity Projections (MIP)

MIP of the 3D subtraction (Pre/Post MION) Cat, 9.4T

In-vivo High Resolution Vascular Imaging

Bolan et al., NeuroImage 2006

MIP (subtraction of Pre/Post MION)

4

3D Vessel Reconstruction

Cat, 9.4T

Vessel Classification

Veins Arteries

Bolan et al., NeuroImage 2006

In-vivo High Resolution Vascular Imaging

Weber et al., Cereb. Cortex 2008

Scanning electron micrographs of a vascular corrosion cast from monkey visual cortex (superior temporal gyrus)

Ex-vivo

High Resolution Vascular Imaging (SEM )

Cat, 9.4T Multi slice BOLD fMRI: Voxel size: 0.25 x 0.25 x 0.5 mm

Harel et al, Front Neuroenergetics 2010

BOLD signal and the underlying vascular system

5

Functional ImageAnatomical Image

Ogawa, Tank, Menon, Ellermann, Kim, Merkle, Ugurbil. PNAS.1992

7 Tesla 4 Tesla

Advantages of high-field for fMRI

Yacoub, 2003

Yacoub et al., 2003

SE-BOLD 7T; 1 x 1 x 2 mm

Spatial Specificity of fMRI Signals

Yacoub, 2003

6

Brodmann's "areas" Surface

White Matter

Brodmann, 1909

•  Cell size •  type •  density

Cortical Lamina

gray matter / “tissue”

I

II / III

IV

V

VI

Korbinian Brodmann (1868-1918)

SE-BOLD GE-BOLD

High Resolution BOLD fMRI

0.7

0.1

0.5

0.1

Cat Magnet: 9.4T In-plane Resolution: 150 x 150 µm2

1mm

Harel et al. 2006

Surface

White Matter

Harel et al, NeuroImage 2006

MRI Histology (Nissl)

Harel et al. 2006

7

Low magnification photographs

High magnification Histology (Nissl)

I II & III IV V VI

Harel et al, NeuroImage 2006

Harel et al. 2006 Cat, 9.4T

GE-BOLD

Layer Specificity of BOLD fMRI (Cat, 9.4T, ∆S)

Harel et al, NeuroImage 2006

coronal

axial

In-vivo High Resolution Vascular Imaging

MIP (subtraction of Pre/Post MION)

Cat, 9.4T Bolan et al, NeuroImage 2006

8

Harel et al. 2006 Cat, 9.4T

SE-BOLD GE-BOLD

Harel et al, NeuroImage 2006

Layer Specificity of BOLD fMRI (Cat, 9.4T, ∆S)

Functional ImageAnatomical Image

Functional-units (cortical columns) are believed to be the basic computational unit in the brain

Ogawa, Tank, Menon, Ellermann, Kim, Merkle, Ugurbil. PNAS.1992

Surface

White matter

Neurons with similar response properties tend to cluster together in ‘columns’ extending through the entire cortex

LGN

9

Optical Imaging - Monkey

Recording Chamber

Ts’o et al., 1990

LR LRLR

Optical Imaging - Monkey

Monocular stimulation

Ocular Dominance Columns – 2DG

(Sokoloff et al., 1976) radioactively labeled glucose

Dechent & Frahm, 2000 Menon et al., 1997 Cheng et al., 2001 Goodyear & Menon, 2001

Horton & Hedley-Whyte, 1984; Horton, 2006

Anatomical (post-mortem) ODC Spatial Organization

Cheng et al., 2001

Functional (fMRI)

10

SE-BOLD 7 T

1 mm

Monocular stimulation

Yacoub et al., 2007

Image resolution: 0.5 x 0.5 x 3 mm

ODC Spatial Organization

Cheng et al., 2001

3 cm EPI Image

Electrophysiological Recording

Hubel & Wiesel, 1968

Cell Discharge

“Ice cube” model

orientations ODC

Optical Imaging - Cat

Bonhoeffer & Grinvald, 1991; 1993; Blasdel 1992

“Pinwheels” “Ice cube” model

Hubel & Wiesel, 1968 orientations ODC

11

0°

Phase Map - fMRI

1 mm

2π

Pha

se

2π

0°

Does the fMRI-Phase Map Reveal Orientation Specific Activation

Zones?

Bonhoeffer & Grinvald, 1991; 1993

Orientation Map – Optical Imaging Phase Map - fMRI

1 mm

Pha

se

1 mm

2π

0°

Yacoub, Harel & Ugurbil, PNAS 2008

12

Pha

se

fMRI - human

Optical Imaging - cat

2π

0°

1 mm

Yacoub, Harel & Ugurbil, PNAS 2008

ODC Phase Map

1 mm 1 mm

Scalebar = 0.5 mm

Ipsi- C

ontra-

Phase 0° 2π

Phase Map ODC Map Phase Map + ODC borders

Yacoub, Harel & Ugurbil, PNAS 2008

13

Yacoub, Harel & Ugurbil, PNAS 2008 Obermayer & Blasdel, JNS 1993

~4 mm ~4 mm

Zimmermann et al., 2011

Anatomical Imaging at Ultra-high Field MRI

14

1.5 T (clinical) 7 T

Noam Harel, University of Minnesota / CMRR

Benefits of high-field (7 Tesla) MRI

7T, T2W, 0.4 x 0.4 x 2 mm3

Benefits of High-field MRI

Susceptibility-Weighted Imaging (SWI)

Duyn J et al. PNAS 2007;104:11796-11801

Phase contrast in the primary visual cortex

15

T2W T1W SWI

Anatomical contrast @ 7 Tesla

STN: subthalamic nucleus SN: substantia nigra RN: red nucleus

STN

SN RN

Abosch, et al., Neurosurgery 2010

STN = Subthalamic Nucleus SN = Substantia Nigra

Susceptibility-Weighted Imaging @ 7T

STN

SN

Magnet: 7T Resolution: 0.4 x 0.4 x 0.8 mm

SWI @ 7T (In-vivo)

Schaltenbrand and Wahren Atlas (Ex-vivo)

Lamina pallidi medialis

GPi GPe

GPi

GPe

GP = Globus pallidus

Susceptibility-Weighted Imaging @ 7T

Abosch, et al., Neurosurgery 2010

16

Detections of Brain Structures with 7 Tesla MRI

Patient-Specific Anatomical Model

SWI

T2W

Thalamus (Tha) Subthalamic nucleus (STN) Substantia nigra (SN) Red nucleus (RN) Globus Pallidus GPi GPe

Put GPe

IC

VIM

Ca

SN

ZI STN Successful DBS surgery is

critically dependent on precise placement of DBS electrodes into target structures

McIntyre et al., Brain Stimulation 2014

Limitation of Current Procedure

2D - Stereotactic atlas Microelectrode recording (MER)

Patient awake during surgery

Success of DBS surgery is critically dependent on the precise placement of the electrodes into the target structures

17

7T MRI Patient-Specific Model Shape and Size Variability of STN

PD 031 PD 032 PD 033

PD 034 PD 036 PD 037

STN

SN

RedN

Location, shape, size & orientation

one-size-fits-all does not apply!

PD 031

PD 032

PD 033

PD 034 PD 036

PD 037

STN

SN

RedN

7T MRI Patient-Specific Model Shape and Size Variability of STN

Duchin, Sapiro, Vitek, Harel

RedN SN

STN DBS

DBS lead

18

Summary

•  High-resolution vascular imaging

•  High-resolution fMRI applications

•  Anatomical contrast @ 7T MRI

•  Clinical applications of @ 7T MRI

U of Minnesota / CMRR Essa Yacoub Patrick Bolan Steen Moeller

Christophe Lenglet Yuval Duchin Remi Patriat Kamil Ugurbil

Neurosurgery Aviva Abosch Jon McIver

Michael Park

Duke University Guillermo Sapiro

Neurology Jerrold Vitek Scott Cooper

Work supported in part by the National Institutes of Health (R01NS085188, P41RR08079, P30 NS057091, R01 NS081118) the W.M. Keck Foundation, and MIND institute.