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IMAGE GENERATION IN CT. CT EXAM PROTOCOL AND PARAMETERS SELECTION PATIENT POSITIONING SCANNING DATA RECONSTRUCTION IMAGE DISPLAY.

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Presentation on theme: "IMAGE GENERATION IN CT. CT EXAM PROTOCOL AND PARAMETERS SELECTION PATIENT POSITIONING SCANNING DATA RECONSTRUCTION IMAGE DISPLAY."— Presentation transcript:

1 IMAGE GENERATION IN CT

2 CT EXAM PROTOCOL AND PARAMETERS SELECTION PATIENT POSITIONING SCANNING DATA RECONSTRUCTION IMAGE DISPLAY

3 PROTOCOL AND TECHNIQUE SELECTION PROTOCOL PARAMETERS SCANNING MODE kVp mA Time RECONSTRUCTION PATIENT POSITION PATIENT ORIENTATION SFOV DFOV

4 PROTOCOL PEDIATRIC OR ADULT HEAD, ABDOMEN, EXTREMITIES VASCULAR OR REGULAR

5 SCANNING MODE AXIAL (SLICE BY SLICE) SPIRAL (HELICAL)

6 TECHNIQUE kVp mA time

7 RECONSTRUCTION SECTION THICKNESS SECTION INDEX ALGORITHM

8 PATIENT POSITION SUPINE OR PRONE BODY PART UNDER SCRUTINY MUST BE PLACED IN THE ISOCENTER OF THE SCANNER

9 PATIENT ORIENTATION HEAD FIRST FEET FIRST

10 SFOV SCANNING FIELD OF VIEW (CALLIBRATION FIELD OF VIEW) AREA WITHIN THE GANTRYS ISOCENTER FROM WHICH THE RAW DATA IS ACQUIRED DURING THE SCAN. IT DEPENDS ON THE NUMBER OF DETECTORS ACTIVATED TO COLLECT DATA.

11 LARGE SFOV

12 SMALL SFOV

13 SFOV

14 LARGE SFOV SFOV

15 CHOOSE THE SMALLEST SFOV THAT WOULD ACCOMMODATE BODY PART FOR BEST RESOLUTION

16 IF BODY PART LIES OUTSIDE SFOV NO DATA WILL BE COLLECTED FOR THAT PART THAT EXTEND BEYOND. IT ALSO CAUSES OUT OF FIELD ARTIFACT

17 OUT OF FIELD ARTIFACT

18 DFOV – DISPLAYED FIELD OF VIEW (ZOOM OR TARGET) DETRMINES HOW MUCH RAW DATA FROM WITHIN SFOV WILL BE UTILIZED TO CREATE AN IMAGE.

19 SFOV DFOV

20 DISPLAYED FOV vs SCANNING FOV DFOV CAN BE EQUAL OR LESS OF SFOV

21 DFOV VS PIXEL SIZE SMALL DFOV LARGE FOV SMALL PIXEL LARGE PIXEL LARGE DFOV LOW SPATIAL RESOLUTION LOW VISIBILITY OF DETAIL

22 LARGE DFOV

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24 SMALL DFOV

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32 DFOV

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37 PIXEL SIZE PIXEL SIZE= DFOV (mm)/ MATRIX SIZE

38 SAMPLE

39 SCANNING TOPOGRAM REGULAR SCAN

40 TOPOGRAM (SCOUT) TUBE DOES NOT REVOLVE AROUND THE PATIENT

41 AP SCOUT TUBE SUSPENDED ABOVE PATIENT DURING SCOUT GENERATION TUBE

42 LAT SCOUT TUBE AT THE 90º ANGLE TO PATIENT

43 REGULAR SCAN

44 I, II, AND III GENERATION CONTINUOUS DATA ACQUSITION GEOMETRY

45 IV GENERATION STATIONARY DATA ACQUSITION GEOMETRY

46 REGULAR SCAN AXIAL (CONVENTIONAL, SLICE-BY- SLICE) SPIRAL

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

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

49 TOTAL NUMBER OF TRANMISSION MEASUREMENT EQUALS NUMBER OF VIEWS X NUMBER OF RAYS IN EACH VIEW

50

51 ACQUSITION TERMINOLOGY RAY VIEW PROFILE

52 RAY PART OF THE X-RAY BEAM THAT FALLS ON ONE DETECTOR

53 VIEW COLLECTION OF THE RAYS FOR ONE TRANSLATION ACROSS THE OBJECT

54 PROFILE ANALOG SIGNAL GENERATED IN A VIEW

55 RAY PROFILE VIEW

56

57 RECONSTRUCTION DATA THAT HAVE BEEN BACKPROJECTED INTO THE IMAGE MATRIX TO CREATE CT IMAGES DISPLAYED ON THE MONITOR

58 RECONSTRUCTION TRANSMISSION MEASUREMENT (LINEAR ATTENUATION COEFFICIENT) IS CONVERTED INTO CT NUMBER (HOUNSFIELD UNIT) Ц CT # RECONSTRUCTION

59 LINEAR ATTENUATION COEFFICIENT ( cm -1 ) BONE BLOOD G. MATTER W. MATTER CSF WATER FAT AIR

60 CT NUMBER CALCULATION

61 CT NUMBER SCALE CORTICAL BONE +1,000 MUSCLE +50 WHITE MATTER+45 GRAY MATTER+40 BLOOD+20 CSF+15 FAT-100 LUNG-200 AIR -1,000 APPEARS WHITE GRAY LIGHT GRAY GRAY DARK GRAY TO BLACK WATER – 0 BASELINE

62 CT # vs BRIGHTNESS LEVEL

63 CT # +400

64 CT # +500

65 CT # +40

66 CT # +15

67 CT # - 200

68 CT # OF CYST 0

69 CT # OF LIPOMA ( FATTY TUMOR) -100

70 CT # -100


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