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PRINCIPLES OF CT

PRINCIPLES OF CT. Dr Mohamed El Safwany, MD. Intended learning outcome. The student should learn at the end of this lecture principles of CT. TOMOGRAPHY TOMOS ---SECTION. RADIOGRAPHY LIMITATIONS. SUPERIMPOSITION

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PRINCIPLES OF CT

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  1. PRINCIPLES OF CT Dr Mohamed El Safwany, MD

  2. Intended learning outcome The student should learn at the end of this lecture principles of CT.

  3. TOMOGRAPHYTOMOS---SECTION

  4. RADIOGRAPHY LIMITATIONS • SUPERIMPOSITION • DIFFICULTY IN DISTINGUISHING BETWEEN HOMOGENOUS OBJECTS OF NON-UNIFORM THICKNESS.

  5. SUPERIMPOSITION

  6. RADIOGRAPHY LIMITATIONTISUE DIFFERENCE SENSITIVITY>10%

  7. TOMOGRAPHY (CONVENTIONAL) • ELIMINATES TISSUE SUPERIMPOSITION • INCREASES CONTRAST OF LOW SUBJECT CONTRAST TISSUES

  8. TOMOGRAPHY

  9. TOMOGRAPHY

  10. TOMOGRAPHY LIMITATIONSMOTION BLURR

  11. CT ADVANTAGES

  12. LIMITATIONS OF CT • UNABLE TO DIFFERENTIATE BETWEEN TISSUES WITH SLIGHT CONTRAST DIFFERENCES < 1%.

  13. GOALS OF CT • MINIMAL SUPERIMPOSITION • IMAGE CONTRAST IMPROVEMENT • SMALL TISSUE DIFFERENCE RECORDING

  14. CT DATA AQUISITION

  15. TRANSMISSION RELATIVE TRANSMISSION=Io/I

  16. MODERN SCANNER

  17. CT MAIN SYSTEMS • IMAGING SYSTEM • COMPUTER SYSTEM • DISPLAY, RECORDING, STORAGE SYSTEM • DATA ACQUISITION SYSTEM

  18. IMAGING SYSTEM • PRODUCTION OF X-RAYS • SHAPING OF X-RAY BEAM ENERGY • FILTERING X-RAY BEAM

  19. SCANNER GANTRY TABLE/COUCH

  20. GANTRY INSIDE

  21. COMPUTER SYSTEM • RECONSTRUCTION AND POSTPROCESSING • CONTROL OF ALL SCANNER COMPONENTS • CONTROL OF DATA ACQUSITION, PROCESSING, DISPLAY. • DATA FLOW DIRECTION

  22. COMPUTER SYSTEM IN CT • MINICOMPUTERS

  23. IMAGE DISPLAY, RECORDING, STORAGE • DISPLAYS IMAGE ( OUTPUT FROM COMPUTER) • PROVIDES HARD COPY OF THE IMAGE • FACILITATES THE STORAGE AND RETRIEVAL OF DIGITAL DATA • COMMUNICATES IMAGES IN THE NETWORK

  24. DATA ACQUISITION SYSTEM (DAS) • SET OF ELECTRONICS BETWEEN DETECTORS AND HOST COMPUTER.

  25. COORDINATE SYSTEM IN CT X

  26. COORDINATE SYSTEM IN CT Y

  27. COORDINATE SYSTEM IN CT Z

  28. COORDINATE SYSTEM IN CT ISO-CENTER

  29. SCAN FOV SFOV DETECTORS

  30. DFOV – DISPLAYED FIELD OF VIEW • SIZE DISPLAYED ON THE MONITOR

  31. PIXEL SIZE PIXEL SIZE= DFOV (mm)/ MATRIX SIZE

  32. PIXEL vs VOXEL PIXEL VOXEL

  33. PIXEL SIZE DEPENDS ON: • MATRIX SIZE • FOV

  34. VOXEL SIZE DEPENDS • FOV • MATRIX SIZE • SLICE THICKNESS

  35. IMAGE DISPLAY

  36. IN CT DIGITAL RECONSTRUCTED IMAGE IS CONVERTED IMAGE IS CONVERTED INTO A GRAY SCALE IMAGE.

  37. CT # vs BRIGHTNESS LEVEL + 1000 -1000

  38. CT # 1000

  39. CT # - 500

  40. CT # OF CYST 5

  41. CT # OF LIPOMA ( FATTY TUMOR) -100

  42. SCANNING

  43. TECHNIQUE • kVp • mA • TIME • SLICE THICKNESS • SLICE INCREMENTATION

  44. PATIENT ORIENTATION • HEAD FIRST • FEET FIRST

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