NMR of SCI

Using Nuclear Magnetic Resonance to Explore Spinal Cord Injury

Outline

Goals

Spinal Cord Injury (SCI) Nuclear Magnetic Resonance (NMR)

Methods Results to date

Summary Time line

Goals

Big Picture Goal Non-invasive assessment of

SCI Progression of SCI Treatment of SCI

Why NMR non-invasive assessment of

Gross physical changes Changes in water distribution Changes in metabolites

Repeatable

Progression of SCI

Primary Injury Severity Location

Secondary Injury Vascular Changes Cellular Changes Biochemical Changes

Incomplete tetraplegia

Complete paraplegia

Incomplete paraplegia

Complete tetraplegia

Interventions

Immobilization Prevents further damage

Drugs Methylpresnisolone

Surgery Remove damaged tissue

Physiotherapy Train

Functional Electronic Stimulation Intra Spinal Micro Stimulation

NMR Spin

Spin basic property of matter 1H, 13C, 31P all have an observable magnetic

moment This project deals with protons 1H The protons precess in a magnetic field at a frequency

proportional to the field strength B0

B0

Nucleus

M

ω0=−γ B0

NMR

An orthogonal field B1 at the same

frequency can tip the magnetic moment into the transverse plane

In the transverse plane the the motion of the magnetic moment create a radio frequency signal at a frequency proportional to the B

0 they are

experiencing

y'

z'

x'

M

B1

θ

refference frame rotating at ω0

NMR Relaxation

T1

Longitudinal relaxation Return to thermal

equilibrium T

2

Transverse relaxation Dipole dipole interactions

T2*

T2 plus Static

inhomogeneities y'

z'

x' M

refference frame rotating at ω0

Magnetic Resonance Imaging

Gradient Echo

B1 Excitation

Slice Defining Gradient

Phase Encoding Gradient

Frequency Encoding Gradient

Acquisition Signal

B (r)

B (p)

B (q)

Magnetic Resonance Spectroscopy

Chemical Shift J-coupling

ppm

C

C

O

H

HH

H

MRI Preoperative

Gradient Echo Sequence TE 25 ms, TR 850 ms Ernst angle 0.31 mm/pixel in plane 4 mm slice thickness

Custom Surface Coil

A Surface Coil

tuningcapacitor

matchingcapacitor Receiver

AndPulse

Generator

capacitor (C)inductance (L) variable capacitor

Key

TR

TE

MRI Micro Wires

Spin Echo TE 34 ms, TR 2000 ms 0.39 mm/pixel in plane 1.5 mm slice thickness

B1

SliceSelect Gradient

Phase Encode Gradient

FrequencyEncodeGradient

AcquisitionSignal

90o180o

Water Compartmentalization

Separates myelin water from other water TORO coils CPMG imaging TE 7-300 ms 10mm rostral 12mm, 21mm,35mm caudal

B1 Excitation

Phase Encoding Gradient

Frequency Encoding Gradients

Acquisition Signals

Slice Defining Gradients

180o90o 180o180o 180o

Transverse Image of the Lumbar Spine

White MatterGrey Matter

dorsal

ventral

Coronal Image of the Lumbar Spine

caudalrostral

Sagital Image of the Lumbar Spine

dorsal

ventral

caudalrostral

Implanted Pl/Ir Wires

Transverse

Coronal

Sagittal

T2 Distributions

1 ms 1 s 10 s10 ms 100 ms

35 mm caudal

10 mm rostral

1 ms 1 s 10 s10 ms 100 ms

1 s

21 mm caudal

1 ms 1 s10 ms 100 ms 10 s

12 mm caudal

1 ms 10 ms 100 ms 10 s

white mattergrey matter

white matter sample region

grey matter sample region

Sample In-Vitro Spectrum

Lesion and Removal

The 24 rats injured with clip Complete laminectomy and spinal cords extracted at

4h, 24h, 1 week, or 4 weeks 6 control cords also extracted

Cords are cut into approximately 3 equal sections centered at T8

Sections are frozen in isopentane then liquid N2 and stored

at -80oC 800MHz (18.8T) 25oC sweep width = 12kHz 180o-τ-90o pulse and acquire 32 averages

CaudalLesion

Rostral

Choline Difference From Control

4 hour 1 day 1 week 4 weeks-0.01

0

0.01

0.02

0.03

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

±S

EM

*

CaudalLesionRostral

Glutamate Difference From Control

4 hour 1 day 1 week 4 weeks-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

±S

EM *

CaudalLesionRostral

Glutamine Difference From Control

Row 1 Row 2 Row 3 Row 40

2

4

6

8

10

12

Column 1

Column 2

Column 3

4 hour 1 day 1 week 4 weeks-0.1

-0.05

0

0.05

0.1

0.15

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

±S

EM

*

CaudalLesionRostral

Myo-Inositol Normalized to Central Control Section

Control 4 hour 1 day 1 week 4 weeks0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

No

rma

lize

d C

on

cen

tra

tion

±S

EM

**

CaudalLesionRostral

Myo-Inositol Difference From Control

4 hour 1 day 1 week 4 weeks-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

±S

EM

**

*

*

CaudalLesionRostral

NAA Difference From Control

4 hour 1 day 1 week 4 weeks-0.15

0

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

±S

EM

*

**

*

*

CaudalLesionRostral

NAAG Normalized to Central Control Section

Control 4 hour 1 day 1 week 4 weeks0

0.2

0.4

0.6

0.8

1

1.2

No

rma

zed

Co

nce

ntr

atio

n ±

SE

MCaudalLesionRostral

**

NAAG Difference From Control CaudalLesionRostral

4 hour 1 day 1 week 4 weeks-0.06

-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

Diff

ere

nce

Fro

m C

on

tro

l (m

M)

± S

EM

*

*

*

**

*

*

In-Vivo MR Spectroscopy

Cr

Cho

ppm

NAA

3.5 3 2.5 3

Summary

Preoperative images with high detail can be obtained Distortion from Pl/Ir micro wires large enough to be

observed but small enough not to ruin the image. Water compartmentalization can separate mylin water from

other cellular water and this seems to change with injury Major changes are observable in-vitro in both Myline and

NAAG NAA, Creatine, and Choline can be observed in the spinal

cord in-vivo

Future Directions

Imaging of human spinal cord Imaging of Pl/Ir wires in a live cat Determining if water component ratios and times vary with

respect to time of injury Can Myo-Inositol or NAAG be observed in-vivo

Acknowledgments

Steve McGie Enid Pehowich Vivian Mushahwar Peter Allen Ryan McKay Chris Hanstock Brent McGrath