1. Diffusion Tensor ImagingBiomarkers of BrainDevelopment and DiseaseEvan Calabrese

2. Outline1. Introduction and Background2. Optimization of DT-MRH for the rat brain3. DT-MRH of rat postnatal neurodevelopment4. Ontology-based segmentation of the postnatal ratbrain5. Analysis of regional volume changes6. Analysis of diffusion tensor changes7. Future directions: application to FASD 3. Introduction and Background 4. Postnatal neurodevelopmentChanges: Functional Behavioral Macrostructural Microstructural 5. Neurodevelopmental disorders Genetic Down syndrome Fragile X syndrome Infectious Congenital toxoplasmosis Congenital syphilis Metabolic Phenylketonuria Mucopolysaccharidoses Toxic/nutritional Neural tube defects Fetal Alcohol Spectrum Disorders (FASD) Traumatic Shaken baby syndrome Perinatal asphyxia Unknown/multifactorial Autism spectrum disorders Attention deficit hyperactivity disorder SchizophreniaAberrant postnatal neurodevelopment 6. Animal modelsChanges: Functional Behavioral Macrostructural Microstructural 7. Animal models 8. Magnetic Resonance HistologyThe use of high-resolution MRI tostudymicrostructure infixed tissues 9. Magnetic Resonance HistologyHistology:the microscopicstructure of tissuesMicroscopic:too small to beseen by theunaided eye 10. Magnetic Resonance HistologyPros Non-destructive Non-deforming 3D and isotropic Many H1 contrasts Quantitative contrast(Diffusion Tensor MRH)Cons Resolution (10 m?) Expensive equipment Contrasts mechanismsnot alwaysstraightforward 11. Developmental Brain Atlasing Neurodevelopmental diseases are difficult to studyin the dynamic background of neurodevelopment A well defined normal is necessary fordistinguishing normal from pathologic changes A quantitative normative atlas of ratneurodevelopment would be helpful for studyingrat models of neurodevelopmental diseases 12. Developmental Brain Atlasing1970 2008 2011 13. Developmental Brain Atlases 14. An MRH Atlas of Rat PostnatalNeurodevelopment Will reveal thespatiotemporal trajectory ofnormal postnatalneurodevelopment Will serve as a quantitativereference and database forstudying rat models ofneurodevelopmental disease 15. Diffusion Tensor MagneticResonance Histology DT-MRH is the combination of DiffusionTensor Imaging (DTI) with MagneticResonance Histology (MRH) DT-MRH provides quantitativemeasurements of water diffusionmagnitude and directionality at every voxel 16. Diffusion Weighted ContrastSdiff = Se-bDb = diffusion weighting factorD = diffusion coefficient of tissue 17. Diffusion Weighted ContrastNo diffusion gradient 18. Diffusion Tensor ImagingTensorEstimation 19. Diffusion Tensor Imaging 20. FractionAnisoColorFADiffusionCoefDiffusion Tensor Imaging 21. Diffusion Tensor Imaging 22. Barriers to High-Resolution DT-MRH Small voxel volume Large data matrices Long echo time from diffusionencoding Diffusion contrast = signal loss 23. Optimization Points Pulse sequence design Specimen preparation Radio frequency coil design 24. Diffusion Pulse Sequence Designb =g2d2G2 4D -dp2S = M0(1-e-TR /T1)e-TE /T 2e-bD 25. Specimen Preparation50 mM5 mM for 3-5 days 26. Specimen Preparation For stained brains T2 T1 Optimal T1 for our pulsesequence = 107 ms We achieved comparable T1sin rat brains throughoutpostnatal neurodevelopmentS = M0(1-e-100/T1)e-16.2/T 2Mean T1 110 ms 27. Radio Frequency Coil Design30 mm ID25 mm ID20 mm ID 28. Optimization Results 25 m anatomic (~1 billion voxels) 50 m DTI (~128 million voxels) SNR > 30 29. DT-MRH of rat postnatalneurodevelopment 30. 50 micron isotropic spatialresolution The atlas includes 9 differenttime points between birth (p0)and adulthood (p80) Each time point features 9distinct image contrasts, plustractographyGRE = gradient recalledechoFAC = FA colorAD = axial diffusivityDWI = diffusion-weightedimageX = magnetic susceptibilityRD = radial diffusivityT2 = T2-weighted contrastFA = Fractional anisotropyADC = apparent diffusioncoefficientAtlas Dimensionality 31. Paxinos & Watson Paxinos & Ashwell Data were oriented towards the relevant histology atlas p0-p12: Paxinos and Ashwell, Atlas of the Developing Rat Brain p18-p80: Paxinos and Watson, The Rat Brain in Stereotaxic CoordinatesAtlas Orientation 32. Atlas Orientation 33. An Ontology-Based Segmentation for thePostnatal Rat Brain 34. The Developmental Ontology 35. The Developmental Ontology 36. The Developmental Ontology 37. Regional Volume Changes ThroughoutPostnatal Neurodevelopment 38. Regional Postnatal Volume Changes 39. Regional Postnatal Volume Changes 40. Regional Postnatal Volume Changesa = estimated adult volumeb = days until inflection pointc = relative growth rate 41. Voxelwise Estimates of Variability 42. Diffusion Parameter Changes ThroughoutPostnatal Neurodevelopment 43. Postnatal Diffusion Tensor Changes 44. White Matter Diffusion Changes 45. White Matter Diffusion Changes 46. Gray Matter Diffusion Changes 47. Gray Matter Diffusion Changes 48. Quantifying Neurodevelopmental Changes in aRat Model of FASD 49. Fetal Alcohol Spectrum Disorders Caused by maternaldrinking during pregnancy Leading preventable causeof mental retardation andbirth defects Prevalence 1% in USA At its most severe (FAS)retardation and craniofacialabnormalities 50. Rodent Models of FASD 51. Rodent Models of FASD The spatiotemporal trajectory of FASDassociated brain injury is not known Understanding the time-course of the injurywill be important for planning interventions Specific Aim: Quantify the spatiotemporalcourse of brain injury in a rat model of FASD 52. Research Strategy Model of 3rd trimester maternal binge drinking Ethanol gavage on postnatal days 4-9(human 3rd trimester equivalent) Imaging time points: p12, p18, p24, p40, p80 8 ethanol exposed and 8 sham controls ateach time point 53. Research StrategyVoxelwise analysisROI analysis 54. Expected Results and Interpretation 55. Expected Results and Interpretation 56. Expected Results and Interpretation 57. Potential Problems and Alternative Approaches Model produces consistent injury Alcohol gavage is technically challenging(Sulik lab collaboration) Lots of scan time required Analysis will be computationally demanding Results may require conventional histologicvalidation 58. Acknowledgements Lab Al Johnson Alexandra Badea Yi Qi Gary Cofer James Cook Matt Sherrier Duke Chunlei Liu John Lee David Lee Neil Medvitz Sara Miller Committee Al Johnson Charles Watson Chunlei Liu Gregg Trahey James Provenzale External Charles Watson George Paxinos Kathleen Sulik Shonagh OLeary-Moore 59. Thanks!