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1 H Magnetic Resonance Spectroscopy (MRS)

1 H Magnetic Resonance Spectroscopy (MRS). Introduction commonly detectable metabolites commonly used 1 H MRS data acquisition methods examples of 1 H MRS applications in studies of neurodisorders and breast cancer. Introduction.

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1 H Magnetic Resonance Spectroscopy (MRS)

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  1. 1H Magnetic Resonance Spectroscopy (MRS) • Introduction • commonly detectable metabolites • commonly used 1H MRS data acquisition methods • examples of 1H MRS applications in studies of neurodisorders and breast cancer

  2. Introduction • useful and important as an additional evaluation tool for various neurodisorders, such as brain cancer, stroke, epilepsy, Alzheimer’s disease, multiple sclerosis, etc. • Neuro 1H MRS scans reimbursable. • Research beyond neuro-applications • breast cancer • prostate cancer, etc.

  3. Commonly detectable Brain Metabolites at low field strength ( 1.5T) • N-acetylaspartate (NAA) • neuronal marker • 2.02 ppm • Total creatine (Cr: creatine and phosphocreatine) • Energy storage molecules in tissue • Stable concentration, as internal reference in MRS studies • 3.03 ppm • Choline compounds (Cho: phosphocholine, glycero- phosphocholine) • cell membrane turnover • precursor of molecules for cellular signal transduction • 3.23 ppm • Lactate (Lac) • anaerobic glycolysis • 1.33 ppm

  4. Myo-inositol (mI) • glial marker • precursor of molecules for cellular signal transduction • 3.56 ppm • Higher filed strength ( 3 T) • improved S/N, spectral resolution • more detectable metabolites, such as Gaba • separating glutamate and glutamine • 13C MRS --- glucose metabolism • 31P MRS --- energy metabolism

  5. Common 1H MRS data acquisition • PRESS (Point RESolved Spectroscopy, 90o-180o-180o) • stronger signal, long TE application • STEAM (STimulated Echo Acquisition Mode, 90o-90o-90o) • weaker signal, short TE application • Water suppression (H2O ~ 50 M, metabolites ~ 1-10 mM) • CHESS (chemical shift selective) pulses for saturation • Single voxel • Multi-voxel (CSI, MRSI) • 2D, multi-slice • 3D

  6. PRESS sequence

  7. 90o 90o TE/2 TM TE/2 • STEAM sequence

  8. Single-Voxel MRS Studies of Alzheimer’s Disease(Neurology 2001; 57: 626-632)

  9. 1H MRSI Study inMultiple Sclerosis (TE/TR: 135/1500 ms)

  10. Common 1H MRS data quantitation • Metabolite ratio (ratio of peak areas): NAA/Cr, Cho/Cr • Absolute quantitation: mmol/tissue volume • Internal reference: Cr, H2O • Phantom replacement method --- correction for coil load • External reference --- correction for B1 inhomogeneity * MRS signals are both T1 and T2-weighted, corrections for differences in T1 and T2 between in vivo tissue and aqueous solution environments.

  11. Single-Voxel MRS Studies of Alzheimer’s Disease(Neurology 2001; 57: 626-632)

  12. Single-Voxel MRS Studies of Alzheimer’s Disease

  13. Single-Voxel MRS Studies of Alzheimer’s Disease

  14. Single-Voxel MRS Studies of Down Syndrome( Am J Psychiatry 1999; 156: 1879-1886)

  15. Single-Voxel MRS Studies of Ts65Dn Mouse---Down Syndrome Model (NeuroReport 2000; 11: 445-448)

  16. Single-Voxel MRS Studies of Ts65Dn Mouse---Down Syndrome Model Li • mI mI-1- phosphate

  17. 1H MRSI Study inMultiple Sclerosis (TE/TR: 135/1500 ms)

  18. Significant correlations between NAA/Cho, NAA/Cr, CCSF volume fraction (of the total brain and CSF volume), and BRB scores

  19. Relation between overall neuropsychological performance and standardized predicted score from a multiple regression model including: central cerebral atrophy, lesion volume, and RPPV NAA/Cho (R = - 0.785 p < .001)

  20. NAA quantification using CSF water as internal reference • Reference MRSI scan without water suppression, 1 scan average, other parameters kept the same • Water signal from CSF voxel as internal reference • NAA/H2Oratio corrected for CSF volume fraction in the MRS voxel.

  21. 1H MRS Study of Breast Cancer • High false positive rate (60-80%) in conventional mammography, resulting unnecessary biopsy. • Recently, dynamic contrast enhancement (DCE) T1-weighted MRI ---- an integral part of a standard breast cancer diagnostic protocol. • Excellent sensitivity (88-100%) • Specificity rather variable (37-97%)

  22. 1H MRS Study of Breast Cancer • Promising tools for improving specificity in detection of breast malignancy: • 1H MRS • Perfusion T2*-weighted MRI • 1H MRS measurement • detection of enhancing Cho signal, marker of active tumor

  23. 1H MRS Study of Breast Cancer

  24. 1H MRS Study of Breast Cancer Single-voxel MRS, PRESS (TE/TR 135/2000 ms)

  25. 1H MRS Study of Breast Cancer • DCE MRI: • 100% sensitivity, no false negative • 9 out of 39 positive turned out benign by biopsy ------ 77% specificity. • DCE MRI + MRS: • no false negative • 3 out of 26 MRS cases turned out false positive ------ 88% specificity

  26. 1H MRS Study of Brain Cancer • In recent years, in addition to conventional pre- and post-contrast MRI, several other MR techniques have been used for the diagnosis and evaluation of brain tumors. • 1H MRS: diagnosis, clinical evaluation of tumor response to therapy, differentiate tumor recurrence and radiation necrosis. • Elevated Cho signal is a marker of viable tumor • Diffusion Weighted Imaging (DWI): differentiate necrosis, edema, and viable tumor regions. • Perfusion Imaging: evaluate tumor vascularity, assess tumor grade.

  27. Monitoring tumor response to intracarotid therapy using MRS

  28. Post-contrast T1 Images and Proton Spectra of a Patient with CNS Lymphoma Pre - ICC Post - 1st ICC Post - 4th ICC

  29. ADC and rCBV Maps of a Patient with CNS Lymphoma Pre - ICC Post - 1st ICC Post - 4th ICC

  30. 1H MRS for Monitoring Head and Neck Cancer Response to Therapy Localization of Spectroscopic Voxel for a Patient with Metastatic Squamous Cell Carcinoma Pre-therapy Post-therapy

  31. Proton Spectra of a Patient with Metastatic Squamous Cell Carcinoma Pre-therapy Post-therapy

  32. Localization of Spectroscopic Voxel for a Patient with Squamous Cell Carcinoma Pre-therapy Post-therapy

  33. Proton Spectra of a Patient with Squamous Cell Carcinoma Pre-therapy Post-therapy

  34. Changes of Cho/Water Ratio for Head and Neck Tumor Patients

  35. Discriminating Neoplastic and Non-neoplastic Thyroid Lesions Using 1H MRS • 29 patients with thyroid lesion • 1H MRS examination • PRESS single-voxel (TE/TR 135/2000) • at lesion (n = 29) and at normal contralateral side (n=5) • from healthy control (n=2) • Resection of thyroid mass within one week

  36. Proton spectra from neoplastic thyroid lesion and normal-appearing contralateral region

  37. Non-neoplastic thyroid lesion Normal healthy control Lip/Lac Cho

  38. Significant difference in Cho/Water ratio between neoplastic (3.36  2.55, n=22) and non-neoplastic (0.16  0.11, n=7) thyroid lesions

  39. Results • Thyroid neoplasm Cho/water > 1.0 x 10-3 • Thyroid non-neoplasm Cho/water < 0.4 x 10-3

  40. Conclusion • Strong correlation between MRS and pathology results • It’s difficult to distinguish neoplastic from non-neoplastic thyroid lesions based on conventional post-contrast T1-weighted images, as both are usually enhanced. • 1H MRS can be a valuable screening tool with high sensitivity in detection of thyroid neoplasm. • Aid in treatment planning and evaluation of post-operation recurrence and node/metastasis.

  41. Proton MRS Studies of Pediatric Neurodisorder

  42. 1H MRS Study of a child with NKH(Non Ketotic Hyperglycinemia)(J Neuroimaging 2001; 11: 209-212)

  43. WM proton spectra at 10 and 13 months(TE/TR 270/2000)

  44. Correlation of plasma and brain glycine levels

  45. 1H MRS Study of a child with ADEM(Acute Disseminated Encephalomyelitis)

  46. Brain Metabolite Ratios in a Child with ADEM MRS Study NAA/Cr Cho/Cr Lac/Cr Voxel BG initial 0.71 0.76 0.51 BG follow-up 0.83 0.88 0.21 WM initial 1.62 0.91 0.00 WM follow-up 1.38 1.10 0.00

  47. In vivo1H MRS study of a rat model of autism(Physiol Behav 2002; 75: 403-410)

  48. PRESS (TE/TR 40/2000), 0.2 cc voxel size

  49. Significant decrease of NAA/Cr in autistic rats

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