1. CONVENTIONAL AND SPIRAL/HELICAL CT

2. CONVENTIONAL SLICE-BY SLICE DATA ACQUSITION

3. CONVENTIONAL CT
X-RAY TUBE ROTATES AROUND THE PATIENT TO COLLECT DATA FROM A SINGLE SLICE OF TISSUE-FOLLOWED BY TABLE INDEXING SO THE NEXT CONTIGUOUS SLICE CAN BE COLLECTED.

4. FOUR STEP PROCESS OF CONVENTIONAL CT1 2
START
TUBE AND DETECTORS ARE
ACCELERATED TO CONST. SPEED
X-RAYTUBE ENERGIZED
DATA COLLECTED
FOR 360DEG. 4 3
STOP
TABLE & PATIENT
INDEXED TO THE
NEXT SCANNING POSITION
TUBE & DETECTORS
SLOW DOWN & STOP

5. SECTION THICKNES vs INDEX
SCAN
INDEX
SCAN

6. INDEX vs SECTION THICKNESS- CONTIGUOUS SLICES
5MM
5MM
5MM
5MM
5 MM
5 MM
5 MM
5 MM

7. INDEX vs SECTION THICKNESS 100% GAP 5MM SLICE –5MM GAP

8. INDEX vs SECTION THICKNESS 50% OVERLAP SLICES 5MM SLICE 2.5 MM INDEX

9. DATA ACQUSITION CONVENTIONAL CT
BREATH
HOLD
BREATH
HOLD
BREATH
HOLD
TIME

10. DATA ACQUSITION CONVENTIONL CT CLUSTER METHOD
BREATH
HOLD
TIME

11. CONVENTIONAL CT INTERSCAN DELAY TUBE COOLS OFF
ISD
ISD
ISD
TIME

12. LIMITATIONS OF CONVENTIONAL CT
LONGER EXAM TIME
PERTINENTANATOMY OMISSION
(MISREGISTRATION)
INACCURATE GENERATIONOF 3-D IMAGES
DIFFICULTY IN MAINTAINING HIGH CONTRAST ENHANCEMENT

13. MISREGISTRATION CONVENTIONAL CT

14. SPIRAL CT

15. MPR IN CONVENTIONAL CT

16. MPR IN SPIRAL/HELICAL CT

17. SPIRAL

18. HISTORICAL BACKGROUND
DR.KALENDER ( GERMAN SCIENTIST)
1988 STARTED WORKING ON SPIRAL CT WITH PETER VOCK FROM SWITZERLAND.
1989 DR. KALENDER DESCRIBED TECHNICAL DETAILS AND CLINICAL APPLICATIONS TO RSNA

19. SPIRAL or HELICAL CT ?

20. HELIX-TYPE OF SPIRAL!!

21. SPIRAL ? HELIX ? SPIRAL - CURVE ON PLANE SURFACE
HELIX – CURVE IN 3-D SPACE

22. DR.KALENDER SUPPORTS SPIRAL CT TERM
BOTH TERMS USED!!
DR.KALENDER SUPPORTS SPIRAL CT TERM

24. SPIRAL/HELICAL SCANNI NG
SPIRAL VOLUME CT
HELICAL VOLUMETRIC CT

25. SPIRAL/HELICAL CT

26. REQUIREMENTS FOR VOLUME DATA ACQUSITION
CONTINUOUSLY ROTATING SCANNER BASED ON SLIP RING TECHNOLOGY
CONTINUOUS COUCH MOVEMENT
INCREASE IN TUBE HEAT LOADABILITY
INCREASED COOLING CAPACITY
CAPABILITY TO STORE LARGE VOLUME OF DATA

27. CT SCANNING IN SPIRAL-HELICAL GEOMETRY BASED ON SLIP RING TECHNOLOGY

29. SPIRAL CT MODES
SINGLE SLICE

30. SPIRAL CT MODES
MULTI - SLICE

31. SPIRAL CT MAJOR STEPS
DATA ACQUSITION-ENTIRE TISSUE IS BEING SCANNED DURING ONE BREATH HOLD
IMAGE RECONSTRUCTION-INTERPOLATION USED TO GENERATE SLICES. FILTERED BACK PROJECTION USED TO REDUCE BLURR.

32. DATA ACQUSITION
Z-AXIS

33. SPIRAL CT CONTINUOUS SCANNING IN SHORT TIME
IMAGE RECONSTRUCTION AT ANY POSITION ALONG Z-AXIS
SLICES CAN OVERLAP OR BE SPACED AWAY

34. COUCH MUST MOVE WITH CONSTANT SPEED!

35. DATA ACQUSITION SPIRAL CT
BREATHOLD
TIME

36. SOLVING PROBLEMS IN SPIRAL CT
SPECIAL POSTPROCESSING TECHNIQUES ( DEDICATED RECONSTRUCTION ALGORITHM)
INTERPOLATION ALGORITHM

37. INTERPOLATION & EXTRAPOLATION
KNOWN
DATA
INTERPOLATED
DATA
KNOWN
DATA

38. INTERPOLATION
INTERPOLATION

39. SCANNER POWER SUPPLY-SLIP RINGS

40. SLIP RINGS

41. LOW VOLTAGE
GANTRY
A/C
HIGH V GENERATOR
SLIP RINGS

42. HIGH VOLTAGE
GANTRY
A/C
HIGH V GENERATOR
SLIP RINGS

43. SPIRAL SCAN PARAMETERS
PITCH
VOLUME COVERAGE

44. PITCH
DISTANCE IN mm THAT CT TABLE MOVES DURING ONE REVOLUTION OF THE X-RAY TUBE AROUND THE PATIENT

45. PITCH= DISTANCE TABLE TRAVELS DURING ONE REV
SLICE THICKNESS

46. PITCH
SMALL PITCH
LARGE PITCH

47. PITCH x SLICETHICKNESS x SCAN TIME
VOLUME COVERAGE
VOL. COVERAGE =
PITCH x SLICETHICKNESS x SCAN TIME

48. RECONSTRUCTION INCREMENT
DETERMINES THE DEGREE OF SECTIONAL OVERLAP TO IMPROVE IMAGE QUALITY
RI IMAGE QUALITY

49. PITCH
PITCH SCAN TIME

50. PITCH
PITCH IMAGE QUALITY

51. MULTISLICE SPIRAL IMAGING

53. CT EVOLUTION

55. BEAM GEOMETRY
SINGLE SLICE SPIRAL
MULTISLICE
FAN
CONE

56. BEAM GEOMETRY
AS THE NUMBER OF DETECTORS IN A MULTIROW DETECTOR ARRAY INCREASES THE BEAM BECOMES WIDER TO COVER THE 2D DETECTOr ARRAY. LARGER # OF ROWS IN THE DETECTOR ARRAY WILL RESULT IN A WIDER BEAM IN Z-AXIS DIRECTION ( CONE BEAM)

57. POST DETECTOR COLLIMATION IN MULTISLICE CT
THE COLLIMATORS ARE POSITIONED BETWEEN DETECTOR COLUMNS.

58. DAS
ALMOST ALL MULTISLICE CT SCANNERS ARE BASED ON III GENERATION SYSTEM DESIGN
ROTATE-ROTATE