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Curtis Johnson, PhD candidate Mechanical Science Engineering Dept. University of Illinois U-C

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Curtis Johnson, PhD candidate Mechanical Science Engineering Dept. University of Illinois U-C

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    1. ME/BIO 481 23 Sept 2009 Magnetic Resonance Imaging --Basics Curtis Johnson, PhD candidate Mechanical Science & Engineering Dept. University of Illinois U-C

    2. 2 Outline Background: MRI Physics Relaxation phenomena and kinetics Space encoding In Vivo Applications: Bone and muscle Human calf in dorsiflexion Brain elastography

    3. 3

    4. 4 MRI Today

    5. 5 MRI Guided-Coronary Balloon Angioplasty

    6. 6 NMR signal …predominantly from protons

    7. 7

    8. 8

    9. 9

    10. 10

    11. 11

    12. 12

    13. 13

    14. 14 Proton Relaxation in Solution

    15. 15

    16. 16

    17. 17

    18. 18

    19. 19

    20. 20 Nuclear spins in a B Gradient

    21. 21

    22. 22

    23. 23 2-D Images with MRI

    24. 24 MRI Guided-Coronary Balloon Angioplasty

    25. 25 MRI Scanner

    26. 26 Scanner Overview

    27. 27 Superconducting Magnet

    28. 28 Other Magnet Types

    29. 29 Shimming

    30. 30 Other Magnet Types

    31. 31

    32. 32 MRI Guided-Coronary Balloon Angioplasty

    33. 33 Knee

    34. 34 MRI Measures of Muscle & Bone

    35. 35 Orientation dependent diffusion

    36. 36 Displacement-Weighted MRI

    37. 37 Displacement-Weighted MRI

    38. 38 Displacement-Weighted MRI

    39. 39 Displacement-Weighted MRI

    40. 40 Calf Muscles

    41. 41 Soleus Anatomy

    42. 42 Fiber orientation maps

    43. 43 High Resolution (SOL, LG, MG)

    44. 44 6 Slices (SOL, LG, MG)

    45. 45 Muscle fiber superstructure: intramuscular connective tissue ? lateral force transmission We analyzed the structural features of the perimysium collagen network in bovine Flexor carpi radialis muscle using various sample preparation methods and microscopy techniques. We Wrst observed by scanning electron microscopy that perimysium formed a regular network of collagen Wbers with three hierarchical levels including (i) a loose lattice of large interwoven Wbers ramiWed in (ii) numerous collagen plexi attaching together adjacent myoWbers at the level of (iii) speciWc structures that we call perimysial junctional plates. Second, we looked more closely at the intracellular organization underneath each plate using transmission electron microscopy, immunohistochemistry, and a three-dimensional reconstruction from serial sections. We observed the accumulation of myonuclei arranged in clusters surrounded by a high density of subsarcolemmal mitochondria and the proximity of capillary branches. Third, we analyzed the distribution of these perimysial junctional plates, subsarcolemmal mitochondria, and myonuclei clusters along the myofibers using a statistical analysis of the distances between these structures. This revealed a global colocalization and the existence of adhesion domains between endomysium and perimysium. Taken together, our observations give a better description of the perimysium organization in skeletal muscle, and provide evidence that perimysial junctional plates with associated intracellular subdomains may participate in the lateral transmission of contractile forces as well as mechanosensing. The perimysium collagen network and junctional plates. Electron micrographs (SEM) of skeletal muscle Wbers prepared according to the NaOH digestion technique (6N at 18 °C) revealed (A) on lateral and (B) front views the overall lattice of collagen interwoven Wbers, (C) the distribution of plexi at the surface of myoWber (noted p), and (D) plexi adhering to the surface of adjacent myoWbers. Note the collagen Wbers crossing myoWbers at an angle of approximately 60°. Electron micrographs of skeletal muscle Wbers prepared according to the fracture technique show in greaster detail (E) the attachment of perimysium plexi to myoWbers at the level of a particular structure that we call “the perimysial junctional plate” (PJP). PJP are approximately 150– 200 m in length. High magniWcation (F) shows the merging of the perimysium with the endomysium (noted e) at the extremities of two branches of the same plexus, which seems to connect with the outer surface of the sarcolemma at and between costameric structures. Model of perimysium organization in skeletal bovine muscle. The top panel represents a longitudinal view of a skeletal muscle covering 1mm in length. We show the perimysium as a loose network of interwoven collagen Wbers as observed by SEM. At the angles of these interwoven Wbers, plexi branches originate and adhere to the surface of adjacent myo- Wbers. This illustration in the second panel shows its branches as well as its association with a myonuclei cluster and the accumulation of subsarcolemmal mitochondria in the intracellular subdomain. The bottom panel is a simpliWed drawing of the attachment region that we called the perimysial junctional plate (200 m long) with several adhesion points on and between the costameric structures, as well as associated membrane densiWcations as indicated in SEM and TEM views. A sarcomere has been depicted on the bottom left to give an idea of the scale. We analyzed the structural features of the perimysium collagen network in bovine Flexor carpi radialis muscle using various sample preparation methods and microscopy techniques. We Wrst observed by scanning electron microscopy that perimysium formed a regular network of collagen Wbers with three hierarchical levels including (i) a loose lattice of large interwoven Wbers ramiWed in (ii) numerous collagen plexi attaching together adjacent myoWbers at the level of (iii) speciWc structures that we call perimysial junctional plates. Second, we looked more closely at the intracellular organization underneath each plate using transmission electron microscopy, immunohistochemistry, and a three-dimensional reconstruction from serial sections. We observed the accumulation of myonuclei arranged in clusters surrounded by a high density of subsarcolemmal mitochondria and the proximity of capillary branches. Third, we analyzed the distribution of these perimysial junctional plates, subsarcolemmal mitochondria, and myonuclei clusters along the myofibers using a statistical analysis of the distances between these structures. This revealed a global colocalization and the existence of adhesion domains between endomysium and perimysium. Taken together, our observations give a better description of the perimysium organization in skeletal muscle, and provide evidence that perimysial junctional plates with associated intracellular subdomains may participate in the lateral transmission of contractile forces as well as mechanosensing. The perimysium collagen network and junctional plates. Electron micrographs (SEM) of skeletal muscle Wbers prepared according to the NaOH digestion technique (6N at 18 °C) revealed (A) on lateral and (B) front views the overall lattice of collagen interwoven Wbers, (C) the distribution of plexi at the surface of myoWber (noted p), and (D) plexi adhering to the surface of adjacent myoWbers. Note the collagen Wbers crossing myoWbers at an angle of approximately 60°. Electron micrographs of skeletal muscle Wbers prepared according to the fracture technique show in greaster detail (E) the attachment of perimysium plexi to myoWbers at the level of a particular structure that we call “the perimysial junctional plate” (PJP). PJP are approximately 150– 200 m in length. High magniWcation (F) shows the merging of the perimysium with the endomysium (noted e) at the extremities of two branches of the same plexus, which seems to connect with the outer surface of the sarcolemma at and between costameric structures. Model of perimysium organization in skeletal bovine muscle. The top panel represents a longitudinal view of a skeletal muscle covering 1mm in length. We show the perimysium as a loose network of interwoven collagen Wbers as observed by SEM. At the angles of these interwoven Wbers, plexi branches originate and adhere to the surface of adjacent myo- Wbers. This illustration in the second panel shows its branches as well as its association with a myonuclei cluster and the accumulation of subsarcolemmal mitochondria in the intracellular subdomain. The bottom panel is a simpliWed drawing of the attachment region that we called the perimysial junctional plate (200 m long) with several adhesion points on and between the costameric structures, as well as associated membrane densiWcations as indicated in SEM and TEM views. A sarcomere has been depicted on the bottom left to give an idea of the scale.

    46. 46 Biomechanical implications

    47. 47 Foot Dorsiflexion

    48. 48 Passive dorsiflexion: NIRS

    49. 49 Skeletal muscle microstructure: Composite medium model of myocytes Two main compartments contribute to the diffusion properties of the composite medium: the intracellular space (within the muscle fiber) and he extracellular space (endomysium) that surrounds the muscle fibers) Two main compartments contribute to the diffusion properties of the composite medium: the intracellular space (within the muscle fiber) and he extracellular space (endomysium) that surrounds the muscle fibers)

    50. 50 MRI Guided-Coronary Balloon Angioplasty

    51. 51 MR Elastography Setup

    52. 52 MR Elastography – Agar Gel

    53. 53 Incompressibility ?

    54. 54 Incompressibility ?

    55. 55 MRE in brain phantom

    56. 56 MRE in gel with brain tissue

    57. 57 MRE in Human Brain Add one of your brain videos here…

    58. 58 Sources RW Cox “(f)MRI Physics with Hardly Any Math” 2001 RR Ernst, G Bodenhausen, A. Wokaum “Principles of NMR in 1 & 2 Dimensions” 1987 A Abragam “The principles of Magnetic Resonance” 1980 F Wehrli, J MacFall, T Newton “Parameters determining the appearance of NMR images” GE 1984

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