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

SCI C1-C8 T1-T12 L1-L5 S1-S5 Occurrence  32 per million  1/3 million in North America Causes  Vehicular accidents  Falls Progression  Initial physical damage  Secondary Biological changes Interventions  Immobilization to ISMS

Progression of SCI Primary Injury  Severity  Location Secondary Injury  Vascular Changes  Cellular Changes  Biochemical Changes

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  1 H, 13 C, 31 P all have an observable magnetic moment This project deals with protons 1 H The protons precess in a magnetic field at a frequency proportional to the field strength B0 B0B0 Nucleus M

NMR An orthogonal field B 1 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 B1B1 θ

NMR Relaxation T 1  Longitudinal relaxation  Return to thermal equilibrium T 2  Transverse relaxation  Dipole dipole interactions T 2 *  T 2 plus Static inhomogeneities y' z' x' M

Magnetic Resonance Imaging Gradient Echo B 1 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 H H 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 tuning capacitor matching capacitor Receiver And Pulse Generator capacitor (C) inductance (L) variable capacitor Key

MRI Micro Wires Spin Echo  TE 34 ms, TR 2000 ms  0.39 mm/pixel in plane  1.5 mm slice thickness B1B1 Slice Select Gradient Phase Encode Gradient Frequency Encode Gradient Acquisition Signal 90 o 180 o

Water Compartmentalization Separates myelin water from other water TORO coils CPMG imaging  TE ms  10mm rostral  12mm, 21mm, 35mm caudal B 1 Excitation Phase Encoding Gradient Frequency Encoding Gradients Acquisition Signals Slice Defining Gradients 180 o 90 o 180 o

Transverse Image of the Lumbar Spine Transverse image of the lumbar spine White MatterGrey Matter dorsal ventral

Coronal Image of the Lumbar Spine Coronal image of the lumbar spine caudal rostral

Sagital Image of the Lumbar Spine Sagittal image of the lumbar spine dorsal ventral caudal rostral

Implanted Pl/Ir Wires Transverse Coronal Sagittal

T2 Distributions T2 distributions white matter grey matter 1 ms 1 s 10 s 10 ms100 ms 35 mm caudal 10 mm rostral 1 ms 1 s 10 s 10 ms100 ms 1 s 21 mm caudal 1 ms 1 s 10 ms 100 ms 10 s 12 mm caudal 1 ms 10 ms 100 ms 10 s white matter grey 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 N 2 and stored at -80 o C 800MHz (18.8T) 25 o C sweep width = 12kHz 180 o -τ-90 o pulse and acquire 32 averages Caudal Lesion Rostral

Choline Difference From Control * Caudal Lesion Rostral

Creatine Difference From Control * * * * Caudal Lesion Rostral

Glutamate Difference From Control * Caudal Lesion Rostral

Glutamine Difference From Control * Caudal Lesion Rostral

Myo-Inositol Normalized to Central Control Section * * Caudal Lesion Rostral

Myo-Inositol Difference From Control * * * * Caudal Lesion Rostral

NAA Difference From Control * * * * * Caudal Lesion Rostral

NAAG Normalized to Central Control Section Caudal Lesion Rostral * *

NAAG Difference From Control Caudal Lesion Rostral * * * * * * *

In-Vivo MR Spectroscopy Cr Cho ppm NAA

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