1. IMAGE RECONSTRUCTION

2. ALGORITHM-A SET OF RULES OR DIRECTIONS FOR GETTING SPECIFIC OUTPUT FROM SPECIFIC INPUT

4. ALGORITHM MUST TERMINATE AFTER FINATE NUMBER OF STEPS

5. PRE-PROCESING REFORMATTED RAW DATA CONVOLUTION WITH FILTER IMAGE RECONSTRUCTION ALGORITHM RECONSTRUCTED IMAGE IMAGE: STORAGE DISPLAY RECORDING ARCHIVING DETECTORS

6. HISTORY OF IMAGE RECONSTRUCTION 1917 RADON DEVELOPED MATHEMATICAL SOLUTIONS TO THE PROBLEM OF IMAGE RECONSTRUCTION FROM A SET OF PROJECTIONS. UTILIZED IN SOLVING PROBLEMS IN ASTRONOMY AND OPTICS. 1961 FINALLY THESE TECHNIQUES WERE USED IN MEDICINE.

7. HOUNSFIELD’S IMAGES—NOISY BECAUSE OF HIS RECONSTRUCTION METHOD. CONVOLUTION BACK PROJECTION USED TO IMPROVE IMAGE QUALITY AND SHORTEN PROCESSING TIME. ( USED BY Shepp & Logan)

8. ORIGINAL DATAFILTERED DATA

9. CONVOLUTION BACK PROJECTION DEVELOPED BY: RAMCHANDRAN LAKSHMINARAYANAN

10. BEAM GEOMETRIES AND DATA ACQUSITION PARALLEL –SLOW FAN -FASTER

12. Algorithms applicable to CT Back projectionIterative methodsAnalytic methods

13. BACK PROJECTION ALSO CALLED SUMMATION METHOD OR LINEAR SUPERPOSITION METHOD

18. Example image of how a cube generates different projections depending on the angle of projection

21. INCOMPLETE BACK- PROJECTION

22. ITERATIVE ALGORITHMS SIMULTANEOUS ITERATIVE RECONSTRUCTION TECHNIQUE ITERATIVE LEAST SQUARES TECHNIQUE ALGEBRAIC RECONSTRUCTION TECHNIQUE

24. ART USED BY HOUNSFIELD IN HIS FIRST EMI BRAIN SCANNER

25. ITERATIVE TECHNIQUES ARE NOT USED IN TODAY’S COMMERCIAL SCANNERS

26. ANALYTIC RECONSTRUCTION ALGORITHMS FOURIER RECONSTRUCTION FILTERED BACK PROJECTION USED IN MODERN CT SCANNERS

27. FILTERED BACK-PROJECTION CONVOLUTION METHOD PROJECTION PROFILE IS FILTERED OR CONVOLVED TO REMOVE THE TYPICAL STAR LIKE BLURRING THAT IS CHARACTERISTIC OF THE SIMPLE BACK PROJECTION.

31. STEPS IN FILTERED BACK PROJECTION ALL PROJECTION PROFILES ARE OBTAINED THE LOGARITHM OF DATA IS OBTAINED LOGARITHMIC VALUES ARE MULTIPLIED BY DIGITAL FILTER FILTERED PROFILES ARE BACKPROJECTED THE FILTERED PROJECTIONS ARE SUMMED AND THE NEGATIVE AND POSITIVE COMPONENTS ARE CANCELLED

32. FOURIER RECONSTRUCTION USED IN MRI NOT USED IN CT BECAUSE OF COMPLICATED MATHEMATICS

33. FOURIER TRANSFORM RADIOGRAPH –AN IMAGE IN SPATIAL DOMAIN IN FOURIER TRANSFORM IMAGE IN FREQUENCY DOMAIN CAN BE RETRANSFORMED BACK TO SPATIAL DOMAIN BY WITH THE INVERSE FOURIER

36. TYPES OF DATA MEASUREMENT DATA RAW DATA CONVOLVED DATA IMAGE DATA

37. MEASUREMENT DATA (SCAN DATA) DATA THAT ARISES FROM DETECTORS. IT NEEDS TO BE PREPROCESSED TO ELIMINATE ARTIFACTS.

38. RAW DATA IT’S THE RESULT OF SCAN DATA BEING PRE-PROCESSED

39. CONVOLVED DATA FILTERED BACKPROJECTION IS THE ALGORITHM USED BY MODERN CT. IT REQUIRES FILTERING AND THEN BACKPROJECTION. RAW DATA IS FILTERED USING MATHEMATICAL FILTER OR KERNEL (CONVOLUTION) IT REMOVES BLURR. CONVOLUTION CAN ONLY BE APPLIED TO RAW DATA.

40. IMAGE DATA (RECONSTRUCTED DATA) CONVOLVED DATA THAT HAVE BEEN BACKPROJECTED INTO THE IMAGE MATRIX TO CREATE CT IMAGES DISPLAYED ON THE MONITOR.

41. DETECTORS SCAN DATA PREPROCESSING RAW DATA CONVOLUTION CONVOLVED DATA DATA BACK PROJECTION

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

43. RECONSTRUCTION IN SPIRAL CT FILTERED BACK PROJECTION USED + INTERPOLATION BACAUSE OF THE CONTINUOUS MOVEMENT OF THE PATIENT IN THE Z-DIRECTION. ( TO ELIMINATE MOTION BLURR)

44. RECONSTRUCTION IN MULTISLICE SPIRAL CT INTERLACED SAMPLING LONGITUDINAL INTERPOLATION FAN BEAM RECONSTRUCTION

45. RECONSTRUCTION ALGORITHM COMPARISON ANALYTIC METHODS ARE FASTER THAN ITERATIVE ALGORITHMS. FILTERED BACK PROJECTION IS USED IN MODERN CT SCANNERS