Imaging of musculo skeletal system

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Imaging of musculo skeletal system

  1. 1. Imaging Of Musculo-Skeletal System
  2. 2. Introduction • “Imaging” excludes direct visualization of the body… for e.g. arthroscopy. • For all the right reasons Plain Roentgenography is termed the mother of imaging in medical science. • Roentgen’s discovery of X-rays in 1895.
  3. 3. Imaging modalities • Plain X ray • Computerized Axial Tomography • Magnetic Resonance Imaging • Others  PET, Bone scan.
  4. 4. • EM spectrum ranges from cosmic waves to radio waves. • Visible spectrum  VIBGYOR • Principle of vision  interpretation of chemical reaction induced by visible light on retina. • Possibility to expand the visible spectrum??? • “See” the effects of the non-visible spectrum.
  5. 5. R o e n g e n o g r a p h y
  6. 6. Plain X ray imaging • Principle based on a particular property of electromagnetic waves  Penetrance. • Penetration potential of EM waves α frequency. • Objects which absorb/reflect EMW are termed radio-dense objects. • Radio-density depends on the composition, and thickness a given object.
  7. 7. Pb BaSO4 Bone Muscle Blood Liver Butter Fat Air E M W
  8. 8. Object EMW
  9. 9. How is a X-ray image taken? F i l m X Ray source Object
  10. 10. X ray… • Summation of shadow layers. • Negative of the true image commonly used • Shows structures closest to the film with the best clarity. • Clear anatomical knowledge is essential to interpret a X ray. • Should be obtained prior to any other imaging techniques.
  11. 11. Tomography • Is basically glorified Roentgenography, which shows the anatomy much superiorly than a plain X ray with the drawback of increased radiation exposure. • Conventional Tomography is a technique by which an image is procured with the use of X rays  emphasizing a particular plane of interest and blurring the rest. (obsolete)
  12. 12. CAT • CAT focuses on multiple planes of pre- specified thickness around a particular pivot line, usually the Axis being the pivot.
  13. 13. Advantages of CAT Disadvantages of CAT • Excellent image resolution • Faster procuring time (v/s MRI) • 3D reformations are possible • Best imaging tech to detect cortical pathology • Radiation effectiveness (100- 200 times a plain X ray) • Cost effectiveness • Requires contrast to visualize vessels.
  14. 14. M R I
  15. 15. Introduction • Unlike the yet discussed techniques, it doesn’t use ionizing radiations. • As the name suggests, MRI incorporates two physical principles, Magnetism and resonance. • Magnets in discussion  H+ ions in our body and the external magnetic field source. • Resonance  b/w the magnetic moment of the H+ ions and the magnetic impulse produced by the external magnet.
  16. 16. The external magnetic field • Strengths range from 0.3 – 1.5 Tesla • 1 Tesla = 10,000 Gauss • Earth’s magnetic field = 0.5 Gauss
  17. 17. “Outline” of the technique • H+ ions in random rotation and alignment  external magnetic field aligns them to a vector. • Energy as radio wave pulse  applied to such a setting, certain number of H+ ions  knocked out of their alignment  eventually return back as the ext energy wades off. • Return phase  H+ ions emit energy  final phase, resonates together  pattern picked up by electronic devices and visualized.
  18. 18. T1 and T2???? • Time intervals pertaining MR scan include Time of echo ; TE Time of repetition ; TR • T1  short TE + Short TR • T2  short TE + Short TR • Still ????
  19. 19. Practical purpose • T1 weighted images depict Normal anatomy at its best. • T2 weighted images picks up “pathology” better than T1.
  20. 20. Other differences T1 T2 • Fat • Marrow • Brain WM • Liver, pancreas • Brain GM • Kidney • Spleen • CSF • Water, lung • Bone, air, flowing blood • CSF, water • IVD • Brain, GM • Spleen • Brain, WM • Liver • Fat • Iron in basal ganglia • Bone, air, flowing blood
  21. 21. MR in Orthopedics • THE BEST method to detect soft tissue pathology. • Not of much use in cortical bone studies, as bone cortex contains minimal H+ ions.
  22. 22. Pros and cons Pros Cons • Best soft tissue detailing, contrast • No ionizing rad: • Possibility of creating infinite no: of virtual planes • Virtual arthroscopy + • Cost • Procuring time is high resulting in more movement blur • Claustrophobia/ magnetic implants • Bone cortex poorly visualized
  23. 23. Other investigations • USG  useful in detecting joint pathology like effusion • New generation high frequency probes can detect hair line cracks which are not picked on X rays.
  24. 24. Summarize • X ray  absolute necessity in Ortho invest: • CT  currently the best modality for cortical studies. • MRI  best to detect soft tissue pathology. • None of these have a complete dominance over the other. • Cost  Pelvis Xray = Rs 135/- CT = Rs 2000/- MRI = Rs 6000/-
  25. 25. T h a n k Y o u

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