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An Overview of MRS on mTBI

An Overview of MRS on mTBI. He (Henry) Zhu VUIIS Dept. of Radiology and Radiological Sciences, Vanderbilt Univ. Magnetic Resonance Spectroscopy. Glutamate ( Glu )&Glutamine ( Gln ): Glu is primary excitatory neurotransmitter; Glu-Gln cycle controls γ- Aminobutyric acid ( GABA ).

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An Overview of MRS on mTBI

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  1. An Overview of MRS on mTBI He (Henry) Zhu VUIIS Dept. of Radiology and Radiological Sciences, Vanderbilt Univ.

  2. Magnetic Resonance Spectroscopy Glutamate (Glu)&Glutamine (Gln): Glu is primary excitatory neurotransmitter; Glu-Gln cycle controls γ-Aminobutyric acid (GABA) Choline (Cho): marker of membrane turnover; tissue change leads to increase of Cho after injury Creatine and phosphocreatine (Cr & PCr): related to energy consumption; often used as an internal reference, i.e. NAA/Cr or Cho/Cr N-acetyl aspartate (NAA): marker of neuronal health and axon integrity; decrease after brain injury. Myo-Inositol (mI): marker of astrolyte (in glial cells); increase after injury Water (H20): source of MRI: structural, DTI, SWI, fMRI, etc

  3. Recovery: Cognitive vs. Metabolic Vagnozzi, Signoretti et al Neurosurgery 62: 1286-1296, 2008 Concussion initiates a period of neuron vulnerability, marked by reduced NAA content. Metabolic recovery does not coincide with, and usually occurs after functional recovery. “2nd hit” during this vulnerable period will result in more severe damage.

  4. The mTBI challenge: where do you look? MRI Cho Cr NAA 2 1 Whole-brain coverage is essential for clinical applications to mTBI.

  5. Volume Selective Spectroscopy TE/4 TE/2 TE/4 90˚ 180˚ 180˚ PRESS TE/2 TM TE/2 TE Semi-Laser STEAM 90˚ 180˚ 180˚ 90˚ 90˚ 90˚ MR Spectroscopy and Spectroscopic Imaging of the Brain, Magnetic Resonance Neuroimaging, Methods in Molecular Biology 711, Zhu & Barker 2011

  6. Interleaved Slice-selective MRSI OVS Dualband+ OVS Suppression 90˚ 180˚ RF OVS GX GY GZ TE Slice 1 Slice 2 Slice 3 Slice 4 Slice 5 Zhu, Ouwerkerk, Barker MRM63: 1486-1492, 2010

  7. 3D PRESS vs. Multi-Slice Spin Echo TR of PRESS TR of PRESS TR of PRESS • Specific ROI, easy to plan & shim • More Freedom with FOV, resolutions • In-plane Chemical Shift Displacement • More Pulses, Higher SAR, Longer TE • Can not be interleaved, Shorter TR • More T1 & T2 loss at 7T 90˚ 90˚ 90˚ 180˚ 180˚ 180˚ 180˚ 180˚ 180˚ TE of PRESS RF RF RF GX GX GX GY GY GY GZ GZ GZ • Multi-slice w/ whole slice coverage • Allows Dynamic Shimming • Allows Longer TR, less T1 loss • Less Pulses, Lower SAR, Shorter TE • Restrictions on FOV and resolution • Requires fast imaging technique TR of Spin Echo 180˚ 180˚ 180˚ 90˚ 90˚ 90˚ TE of Spin Echo RF RF RF GX GX GX GY GY GY GZ GZ GZ MR Spectroscopy and Spectroscopic Imaging of the Brain, Magnetic Resonance Neuroimaging, Methods in Molecular Biology 711, Zhu & Barker 2011

  8. MRI Cho Cr NAA Whole-brain MRSI • Scan parameters: • 5 slices of 13.2mm w/ 2.2mm gaps.; • FOV=188×240mm w/ matrix size 25×32; • Voxel size=0.74cm3 ; • TE/TR = 144ms/2.5s w/ dualband + OVS suppression; • SENSE = 4 (2 in AP and 2 in RL) w/ 32-channel phased array head coil; • Fieldmap based global B0 shimming • MRSI scantime: 15min 20sec.

  9. Center Slice Spectra of 3TMRSI

  10. Atlas-Based MRSI Reconstruction Template MNI #38: Right CingulateGyrus MP-RAGE

  11. Pro and Con of translating to 7T Zhu, Soher, Ouwerkerk, Schär, Barker MRM(2012 In Press) a) Slice Location b) MRI c) H20 d) B1 90⁰ 0⁰ e) Glx f) mI g) Cho h) Cr i) NAA 1 slice, FOV=190×210mm. Matrix size = 32×29 Res.=7mm×7mm. Slice thick.=15mm. Voxel Size=0.74cm3 TE/TR=29ms/4.5s. SAR=53%. SENSE=2×2. Scan Time = 12.5 min. Higher field strength allows more compounds to be mapped. However, more restrictive RF conditions limit spatial coverage to 1 slice.

  12. Only Slice Spectra of 7T MRSI

  13. MRI Cho Cr NAA Application to mTBI at 3T 1 2 NAA Cr Cho 2 1 • A retired football player (42 years old, in NFL '93-02); • Persistent headache and fatigue; • Imaging results all normal; • Not possible with a PRESS box (dashed).

  14. Juvenile Post Auto Accident MRI Cho Cr NAA

  15. Conclusions • MR spectroscopy is a natural modality to evaluate mTBI. • NAA mapping(s) post-injury can monitor metabolic recovery. • Whole-brain coverage is essential as structural MRI’s are expected to be normal. • Multi-slice MRSI is better suited for mTBI than 3D PRESS. • More improvements are needed such as dynamic shimming and spectral editing for GABA etc.

  16. Acknowledgements • VUIIS: • Victoria Morgan, SakaitSengupta, Megan Strother (MD), John Gore • Philips: • Michael Schär, Ryan Robison, Charles Nockowski • JHU: • Peter Barker, Ronald Owerkerk, Susumu Mori, Jinyuan Zhou, Jaishri Blakely(MD), Stacy Suskauer(MD)

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