1. COMPUTED TOMOGRAPHY INSTRUMENTATION AND OPERATION

2. OUTLINE CT SYSTEM COMPONENTS – DEFINITION OF A SCANNER
SCANNER COORDINATE SYSTEM – XYZ, ISOCENTER
IMAGING SYSTEM
COMPUTER SYSTEM
DISPLAY, RECORDING, AND STORAGE SYSTEMS

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

4. CT SYSTEM GANTRY X-RAY TUBE GANTRY CONTROL DETECTORS HIGH VOLTAGE
GENERATOR
DAC
S/H
ADC
SCAN CONTROLLER
ARRAY PROCESSOR
HOST
COMPUTER
CONSOLE
STORAGE

5. SCANNER

6. SCANNER
GANTRY
PATIENT COUCH

7. GANTRY HOUSES: X-RAY TUBE GENERATOR (LOW VOLTAGE DESIGN) COLLIMATORS
DETECTORS

8. GANTRY CHARACTERISTICS
APERTURE
TILTING RANGE

9. MOST OF THE SCANNERS HAVE 70CM APERTURE

10. 70 CM

11. COORDINATE SYSTEM X

12. COORDINATE SYSTEM Y

13. COORDINATE SYSTEM Z

14. ISOCENTER

15. TILTING RANGE OF MOST SCANNERS- +30 TO -30 DEGREES

16. PATIENT COUCH : 450 LBS (204 KG) DISTRIBUTED WEIGHT LIMIT

17. SCANNABLE RANGE: COVERAGE FROM HEAD TO THIGH (162CM)

18. MAX. SCANNABLE RANGE

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

20. IMAGING SYSTEM COMPONENTS
X-RAY TUBE
GENERATOR –HIGH VOLTAGE
COLLIMATORS
FILTER
DETECTORS
DETECTOR ELECTRONICS

21. X-RAY TUBE AND X-RAY PRODUCTION

22. CATHODE -------- MADE OF TUNGSTEN
IN CT – STILL SMALL AND LARGE

23. THERMIONIC EMISSION CATHODE HEATED UP TO AT LEAST 2,200 DEG. CELSIUS
TO LIBERATE ELECTRONS FOR TRANSIT TO ANODE

24. FOCAL SPOT- CT UTILIZES DIFFERENT FOCAL SPOTS
THE FILAMENT SIZE – LENGTH – FOCAL SPOT
SMALLER FOCAL SPOT - Low mA
SMALLER FOCAL SPOT – sharper image

25. ANODE +++++ MADE OF TUNGSTEN AND MOLYBDENUM
TARGET
TARGET MADE OF TUNGSTEN
AND
RHENIUM

26. mA – tube current
The number of electrons flowing from cathode to anode

27. kVp
Potential difference between cathode and anode (Volts) kilo means 1,000 x.

28. S –time of exposure mAs tube current for certain length of time

29. X-RAY PRODUCTION RESULTS IN A LOT OF HEAT AND VERY LITTLE X-RAYS BEING GENERATED
HEAT UNITS CALCULATION
HU= kVp X mA x time
MOST CT TUBES HEAT CAPACITY
3-5 MILLION HU

30. REDUCTION OF HEAT UNITS – TECHNIQUE COMPENSATION
kVp mA
Time
INCREASED NOISE

31. TOO LOW OF kVp:
NOISE !!!!

32. X-RAY EMISSION

33. TUBE CURRENT CHANGE 2 * mA = 2 * number of photons
INTENSITY
ENERGY – NO CHANGE
CURRENT
2 * mA = 2 * number of photons
4 * mA = 4 * number of photons

34. Why changing mA or time Avoiding motion – mA time
Pediatric technique modification
Reducing noise - mAs
MOTION
NOISE

35. Tube voltage (kVp) CHANGE
INTENSITY -
ENERGY –
kVp
15% INCREASE OF KVP = 2 * mAs

36. kVp IN CT 80-140 TOO LOW – NOISE
(NOT ENOUGH PENETRATION OF THE PATIENT )
PHOTON STARVATION - NOISE!!!!!

37. HIGH VOLTAGE GENERATOR –(HVG)
GENERATES HIGH VOLTAGE POTENTIAL BETWEEN CATHODE AND ANODE OF AN X-RAY TUBE

38. CT GENERATOR 5-50 kHz 30-60 kW KVP SELECTION: 80, 100, 120, 130,140
mA selection:
30, 50, 65, 100, 125, 150, 175, 200, 400

39. PRE-PATIENT COLLIMATION POST-PATIENT COLLIMATION
COLLIMATION IN CT
PRE-PATIENT COLLIMATION
POST-PATIENT COLLIMATION
ADC

40. BASIC DATA AQUSITION SCHEME IN CT
FILTRATION
ADC

41. FILTRATION CHANGE
INTENSITY
ENERGY –
FILTRATION

42. TO MAKE THE BEAM HARDER AND
FILTRATION MATERIAL
ALUMINIUM ( SPECIAL FILTER IN CT)
BOWTIE
TO MAKE THE BEAM HARDER AND
MORE MONOENERGETIC

43. Filter Patient Detector DEFINES SLICE THICKNESS REDUCES SCATTER
RECHING THE PATIENT
Detector

44. CT DETECTORS

45. DETECTOR TYPES: SCINTILLATION
S. CRYSTAL
S. CRYSTAL
PHOTODIODE
PM TUBE

46. SCINTILLATION CRYSTALS USED WITH PM TUBES:
SODIUM IODIDE –AFTERGLOW + LOW DYNAMIC RANGE ( USED IN THE PAST)
CALCIUM FLUORIDE
BISMUTH GERMANATE

47. S. CRYSTAL USED WITH PHOTODIODE
CALCIUM TUNGSTATE
RARE EARTH OXIDES - CERAMIC

48. DETECTOR TYPE: GAS IONIZATION
XENON GAS
30 ATM

49. EFFICIENCY OF DETECTORS- QDE
SCINTILLATION – 95% - 100%- COMMONLY USED IN III & IV GENERATION SCANNERS
GAS – 50% - 60%

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

51. COMPUTER SYSTEM IN CT
MINICOMPUTERS

52. COMPUTER SYSTEM COMPOSED OF:
HARDWARE
SOFTWARE

53. COMPUTER PROCESSING IN CT
SEQUENTIAL PROCESSING
MULTITASKING
MULTIPROCESSING

54. SOFTWARE –PROGRAM (S) HELPING CT USER TO COMMUNICATE WITH THE CT SYSTEM

55. CT OPERATING SYSTEM-PROGRAMS THAT CONTROL THE HARDWARE COMPONENTS AND THE OVERALL OPERATION OF THE CT COMPUTER

56. CT OPERATING SYSTEM
UNIX
WINDOWS

57. HOST COMPUTER CONTROL OF ALL COMPONENTS
CONTROL OF DATA ACQUSITION, PROCESSING, DISPLAY.
DATA FLOW DIRECTION

58. ARRAY PROCESSOR
TAKES DETECTOR MEASUREMENTS FORM HUNDREDS OF PROJECTIONS. RESPONSIBLE FOR RETROSPECTIVE RECONSTRUCTION AND POSTPROCESSING OF DATA.
THE MORE PROCESSORS IN THE COMPUTER
THE SHORTER THE RECONSTRUCTION TIME

59. DATA ACQUISITION SYSTEM (DAS)
SET OF ELECTRONICS BETWEEN DETECTORS AND HOST COMPUTER.
IT CONTAINS: AMPLIFIER, ADC, DAC, GENERATOR, S/H.

60. AMPLIFIER
SIGNAL FROM DETECTORS GOES TO AMPLIFIERS FOR SIGNAL MAGNIFICATION AND THEN IS SENT TO SAMPLE/HOLD UNIT

61. ADC
CONVERTS ANALOG SIGNAL OUTPUT FROM THE SCANNING EQUIPMENT TO A DIGITAL SIGNAL SO IT CAN BE PROCESSED BY A COMPUTER.

62. SAMPLE/HOLD UNIT (S/H)
LOCATED BETWEEN AMPLIFIER AND ADC PERFORMS SAMPLING AND ASSIGNS SHADES OF GRAY TO THE PIXELS IN THE DIGITAL MATRIX CORRESPONDING TO THE STRUCTURES

63. DAS GANTRY X-RAY TUBE GANTRY CONTROL DETECTORS HIGH VOLTAGE GENERATOR
DAC
S/H
ADC
SCAN CONTROLLER
ARRAY PROCESSOR
HOST
COMPUTER
CONSOLE
STORAGE

64. 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

65. IMAGE DISPLAY

66. IMAGE RECORDING SYSTEMS (LASER PRINTERS)
SOLID STATE LASER PRINTERS
GAS LASER PRINTERS

67. HARD COPY

68. IMAGE STORAGE MEDIA
MAGNETIC TAPES
MAGNETO-OPTICAL DISK (MOD) CD

69. COMMUNICATION
PACS

70. OVERREAD NETWORK
While most teleradiology systems purchased over the last decade were intended for on-call purposes, the past two years have seen a rapid increase in the use of teleradiology to link hospitals and affiliated satellite facilities, other primary hospitals, and imaging centers. A number of the enabling technologies needed for effective overread networks, such as more affordable high-speed telecommunications networks and improved data compression techniques, have matured in recent years.

71. NightHawk Radiology Services has developed an innovative approach to the delivery of radiology services by operating centralized, state-of-the-art reading centers in Sydney, Australia and Zurich, Switzerland. Staffing U.S.-trained, board-certified radiologists specializing in emergency radiology, these locations are ideally situated for U.S. care because when it’s the middle of the night in Boston, it’s daytime “Down Under.” When it’s early morning in Los Angeles, it’s daytime in the Alps. From the centralized reading centers, NightHawk radiologists interpret exams and report the results to attending physicians in real-time, usually less than 20 minutes.

72. CT ROOM LAYOUT