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. TOMOGRAPHY TOMOS---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

10. TOMOGRAPHY LIMITATIONS MOTION BLURR

11. CT ADVANTAGES

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

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

15. CT DATA AQUISITION

17. TRANSMISSION RELATIVE TRANSMISSION=Io/I

18. MODERN SCANNER

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

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

21. SCANNER GANTRY TABLE/COUCH

22. GANTRY INSIDE

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

24. COMPUTER SYSTEM IN CT MINICOMPUTERS

25. 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

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

27. COORDINATE SYSTEM IN CT X

28. Y

29. Z

30. ISO-CENTER

32. SCAN FOV SFOV DETECTORS

33. DFOV – DISPLAYED FIELD OF VIEW SIZE DISPLAYED ON THE MONITOR

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

35. PIXEL vs VOXEL PIXEL VOXEL

36. PIXEL SIZE DEPENDS ON: MATRIX SIZE FOV

37. VOXEL SIZE DEPENDS FOV MATRIX SIZE SLICE THICKNESS

38. IMAGE DISPLAY

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

42. CT # vs BRIGHTNESS LEVEL + 1000 -1000

43. CT # 1000

44. CT # - 500

45. CT # OF CYST 5

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

48. SCANNING

49. TECHNIQUE kVp mA TIME SLICE THICKNESS SLICE INCREMENTATION

50. PATIENT ORIENTATION HEAD FIRST FEET FIRST

52. SCANNING TOPOGRAM REGULAR SCAN

53. TOPOGRAM (SCOUT) TUBE DOES NOT REVOLVE AROUND THE PATIENT

54. AP SCOUT TUBE SUSPENDED ABOVE PATIENT DURING SCOUT GENERATION TUBE

55. LAT SCOUT TUBE AT THE 90º ANGLE TO PATIENT

56. AXIAL SCAN TABLE STOPS AT THE SCANNING POSITION AND THE TUBE ROTATES AROUND A PATIENT.

57. SPIRAL PATIENT CONTINUOUSLY MOVES IN THE Z-AXIS DIRECTION WHILE THE TUBE ROTATES AROUND.

58. CONVENTIONAL AND SPIRAL/HELICAL CT

59. ADVANTAGE OF SPIRAL IMAGING OVER CONVENTIONAL SPEED

60. CT SPECIAL APPLICATIONS

61. CARDIAC ANGIOGRAPHY

62. VIRTUAL ENDOSCOPY

63. RADIATION TREATMENT

64. 3D IMAGING

66. Text Book David Sutton’s Radiology Clark’s Radiographic positioning and techniques

67. Assignment Two students will be selected for assignment.

68. Question Define topogram and tomogram?

69. Thank You