Basics of CT
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Transcript of Basics of CT
•Principle of Raw Data.
•Terms used in CT.
•Image processing.
The X-Ray Concept
• Electrons Gush.
• Object.
• Film/Screen.
The X-Ray Concept
2D Image
CT
• Stronger X-Ray.
• Rotating Tube.
• A Row of Detectors.
Tube
Object
Detectors
COMPUTERFilm
Raw Data
Field of View(FOV)
10 volt.75 HU
A6 + B6 + C6 + D6 + E6 + F6 + G6 = 75 HU
12 volt.90 HU
A7 + B7 + C7 + D7 + E7 + F7 + G7 = 90 HU
20 volt.102 HUA8 + B8 + C8 + D8 + E8 + F8 + G8 = 102 HU
30volt.
307 HUD1 + D2 + D3 + D4 + D5 + D6 + D7 = 307 HU
43 volt.
360 HU
E1 + E2 + E3 + E4 + E5 + E6 + E7 = 360 HU
X + Y = 8
X + Z = 10
Y + Z = 12
X = 3
Y = 5
Z = 7
A6 + B6 + C6 + D6 + E6 + F6 + G6 + ……...………………..…… = 75 HU A7 + B7 + C7 + D7 + E7 + F7 + G7 + ………………………..……= 90 HU A8 + B8 + C8 + D8 + E8 + F8 + G8 + ……………………………= 102 HU D1 + D2 + D3 + D4 + D5 + D6 + D7 + ………………..............…= 307 HU E1 + E2 + E3 + E4 + E5 + E6 + E7 + ………….…………………= 360 HU
A4 + B5 + F77 + H678 + K706 + F6 + G6 + ……….………….…= 555 HU S7 + R4557 + F47 + D7 + H57 + F57 + X475 + …..……………= -586 HU A83 + E58 + V667 + D6778 + M788 + G98 + R9008 + ………= -8898 HU D455 + F562 + H773 + Q54 + J75 + Y666 + K77 + …….…..…= 9002 HU W31 + C42 + Y53 + J674 + M665 + T66 + R557 + …………..…= 596 HU
A1 = 400 HUA2 = 599 HUA3 = 556 HU...
1. Attenuation Value (HU): White/Grey/Black.
2. Place: X-Y-Z.
X
Y Z
A-s-3-2037 HU
C-v- 261033 HU
Raw Data Image
Raw Data
Image Image
- 3000 30000
- 3000 30000
Center
20 HU
500 500Width
- 480 HU 520 HU
- 3000 3000
Center
20 HU
Width
- 480 HU 520 HU
- 30003000
Center
70 HU
Width
- 10 HU 150 HU
80
- 30003000
Center
-1000 HU
Width
- 1900 HU -100 HU
900
Field of View(FOV)
0.5 mm
19 10 20 -99 -19 -20 -88 -56 75 22 77 265 154 332143 31
5 mm
Volume Average Artifact
Voxel Pixel
Pixel
Collimation
Collimation
• 1 mm.→ 10 – 5 – 2 – 1 – 0.75 mm.
• 2 mm.→ 10 – 5 – 2 – 1 mm.
• 3 mm. → 10 – 5 – 2 mm.
Collimation
1 mm.
2 mm.
3 mm.
Collimation
▲Collimation ( Beam Width)→
▲ scan time
▲ exposure
▲ motion artifact
▲ thinnest possible slice thickness
Table Increment
Pitch
• T = table increment.• W = beam width (collimation).
Pitch = T/W
Pitch
• Table increment = 10 mm.• Width = 10 mm.
Pitch = 1
Pitch = T/W
Pitch = 1
• NO GAP
• NO OVERLAP
10 mm.
10 mm.
Pitch
• Table increment = 5 mm.• Width = 10 mm.
Pitch = 0.5
Pitch = T/W
Pitch = 0.5
• NO GAP
• OVERLAP
5 mm.
10 mm.
Pitch
• Table increment = 10 mm.• Width = 5 mm.
Pitch = 2
Pitch = T/W
Pitch = 2
• GAP
• NO OVERLAP
10 mm.
5 mm.
Pitch
▼ Pitch →
Overlap.
▲ scan time → motion artifact.
▲ exposure.
Break
• Reconstruction =
Raw Data Axial / Coronal / Sagittal images.→
• Reformatting =
(Axial) Images Coronal / Sagittal Images.→
Multi-Planar Reformatting
MPR
Multi-Planar ReformattingMPR
MPR
MPR
Curved Planar Reformatting
Curved Planar Reformatting
Curved Planar Reformatting
Curved Planar Reformatting
Curved Planar Reformatting
Curved Planar Reformatting
Maximum Intensity Projection
MIP
MIP
MIP
23 -10 38 103 232 -100 10 1 12 4 232
MIP
MIP
MIP
MIP
23 -10 38 103 232 -100 10 1 12 4 -100
MinIP
MinIP
MIP Min IP
Surface Shaded Display
SSD
Surface Shaded DisplaySSD
Surface Shaded DisplaySSD
Surface Shaded DisplaySSD
280
276
170
Surface Shaded DisplaySSD
Surface Shaded DisplaySSD
Volume Rendering Technique
VRT
Volume Rendering TechniqueVRT
Volume Rendering TechniqueVRT
Volume Rendering TechniqueVRT
Volume Rendering TechniqueVRT
Volume Rendering TechniqueVRT
VIRTUAL ENDOSCOPY
VIRTUAL ENDOSCOPY
The voxels located on the edge of a structure are identified, usually by intensity thresholding, and these voxels are displayed. The remaining voxels in the image are usually invisible.
VIRTUAL ENDOSCOPY
VIRTUAL ENDOSCOPY
VIRTUAL ANGIOSCOPY
VIRTUAL NEPHROSCOPY
Image Display
• MPR / Curved MPR.
• MIP / Min IP.
• SSD.
• VRT.
• Virtual Endoscopy.
THANK YOU
