1. IMAGE QUALITY
NOISE
LINEARITY
CROSS-FIELD UNIFORMITY
IMAGE ARTIFACTS

2. NOISE IN CT
FLUCTUATION OF CT# BETWEEN POINTS IN THE IMAGE FOR A SCAN OF UNIFORM MATERIAL SUCH WATER.

3. NOISE IN CT

4. NOISE LEVEL %= STANDARD DEVIATION /CT # RANGE
PERCENTAGE OF CONTRAST OR IN CT NUMBERS
NOISE LEVEL %= STANDARD DEVIATION /CT # RANGE

5. NOISE CAN BE MEASURED BY SCANNING A WATER PHANTOM AND COMPUTING THE MEAN AND STANDARD DEVIATION FOR FOR A REGION OF INTEREST. (ROI)

10. THE NOISE LEVELS FOR CT SCANNERS VARY AND DEPEND ON:
MAS
SCAN TIME
KVP
SLICE THICKNESS
OBJECT SIZE
ALGORITHM

11. MAS KVP SCAN TIME SLICE T. NOISE

12. OBJECT SIZE NOISE

13. ALGORITHM vs NOISE
DETAIL
EDGE-ENHANCEMENT
STANDARD
SMOOTHING
NOISE

14. NOISE IN CT IS MAINLY RELATED TO
PHOTON FLUX ( # OF DETECTED PHOTONS)
MATRIX SIZE (PIXEL SIZE)
SLICE THICKNESS
ALGORITHM
ELECTRONIC NOISE ( DETECTOR ELECTRONICS)
SCATTER RADIATION

15. NOISE WIDTH OF PIXEL SLICE THICKNESS DOSE NOISE SPATIAL R.

16. LINEARITY
RELATIONSHIP OF CT# TO THE LINEAR ATTENUATION COEFFICIENT

17. CROSS-FIELD UNIFORMITY
THE UNIFORMITY OF CT # THROUGHOUT THE ENTIRE SCAN FIELD OF VIEW IS ONE INDICATION THAT CT SCANNER IS PERFORMANCE IS ACCEPTABLE.
IT REFERS TO THE VALUES OF THE PIXELS IN THE RECONSTRUCTED IMAGE
THEY SHOULD BE CONSTANT AT ANY POINT IN THE IMAGE OF PHANTOM

18. CROSS-FIELD UNIFORMITY

19. IMAGE ARTIFACTS
A DISTORTION OR ERROR IN AN IMAGE THAT IS UNRELATED TO THE SUBJECT BEING STUDIED

20. IMAGE ARTIFACTS
STREAKS
RING
CT# DISTORTION

21. SOURCES OF ARTIFACTS
PATIENT
IMAGING PROCESS
EQUIPMENT

22. TYPES AND CAUSES OF ARTIFACTS
STREAKS
IMPROPER SAMPLING OF DATA
PARTIAL VOLUME AVERAGING
PATIENT MOTION
METAL & BEAM HARDENING
NOISE
SPIRAL SCANNING
MECHANICAL FAILURE

23. TYPES AND CAUSES OF ARTIFACTS
SHADING
PART. VOLUME AVG.
BEAM HARDENING
SPIRAL SCANNING
SCATTER
OFF-FOCUS RADIATION
INCOMPLETE PROJECTION

24. TYPES AND CAUSES OF ARTIFACTS
RINGS AND BANDS
BAD DETECTOR IN III
GENERATION CT

25. MOTION ARTIFACT- VOLUNTARY & INVOLUNTARY
CORRECTION:
IMMOBILIZATION
PROPER EXPLANATION OF PROCEDURE
SHORT SCAN TIME
MOTION REDUCTION SOFTWARE (SHIMADZU –MAC) I

26. MOTION

29. INCOMPLETE PROJECTION PROFILES
METAL ARTIFACTS
INCOMPLETE PROJECTION PROFILES
STAR SHAPED ARTIFACTS

31. METAL ARTIFACTS

32. METAL ARTIFACT

34. MAR

35. BEAM HARDENING ARTIFACT-CUPPING ARTIFACT
INCREASE IN THE MEAN ENERGY OF THE X-RAY BEAM AS IT PASSES THROUGH THE PATIENT
IT CAN OCCUR WHEN RADIATION BEAMS HAVE DIFFERENT PATH LENGTHS

36. BEAM HARDENING

37. BEAM HARDENING ARTIFACT STREAKS OR BROAD DARK BANDS

38. REDUCTION OF BEAM HARDENING
BOW TIE FILTER UTILIZATION
SPECIAL CORRECTION SOFTWARE

39. CORRECTED

40. PARTIAL VOLUME ARTIFACT
AVERAGE CT NUMBERS IN SLICE

42. CORRECTING PARTIAL VOLUME ARTIFACT
THIN SLICES

43. NOISE – PHOTON STARVATION

44. OUT OF FIELD ARTIFACT

45. EQUIPMENT INDUCED ARTIFACTS STREAK ARTIFACTS
MECHANICAL FAILURE
POOR GANTRY RIGIDITY
MECHANICAL ASSIGNMENT
TUBE ROTOR WOBBLE
POOR SAMPLING OF THE DETECTOR
BAD DETECTOR-RING ARTIFACTS ( III GEN.)
TUBE ARCING

46. RING ARTIFACTS- III GENERATION

48. CORRECTION OF RING ARTIFACT
DETECTOR RECALIBRATION
BALANCING ALGORITHM UTILIZATION

49. ALIASING ARTIFACT
NOT ENOUGH SAMPLES

50. CORRECTION OF ALIASING ARTIFACT
INCREASE NUMBER OF VIEWS OR RAY SAMPLES PER VIEW.
CONVOLUTION FILTER (SOFTWARE METHOD)

51. ALIASING ARTIFACT

52. TUBE ARCING

53. SPIRAL ARTIFACTS
WINDMILL
MOTION
STAIRCASE
SHADING

54. WINDMILL

55. MOTION

56. MOTION

57. STAIRCASE