CT Scan

1. By SIDRA IQBAL
Introduction to CT Scan

2. CT Scanner

3. Objectives
After this lecture students will be able to
• describe the need of CT scan
• identify components of CT scan machine
• describe the functioning of each component
• identify shades on image

4. • What do you know about CT Scans?
• Why CT scans are carried out?
• Which technology is used in CT scan to generate images?
• Have anyone of you go through a CT procedure?

5. Principle of CT Scan
In CT scan X ray beam move in a circular motion around the body
emitting the radiations, some radiations are absorbed by the body
structues and some pass through the body that falls on the detectors
array to generate images by producing shades of white, black and grey
diffrentiating bones, muscels and fluid.

6. Uses of CT Scans
• A CT scan is a diagnostic imaging modality that use X rays as ionizing
radiation to produce the images of internal structure of body.
• It is use to show details of bones, muscels, organs and blood vessels.
• It is also use for fluid and tissue biopsies.
• It provide ease to radiologists to find abnormalities by providing multislice
images by single exposure within seconds as compare to x ray that only
produce single static image for each exposure .

7. Components of CT scan machine
Gantry and Table
This circular part is called gantry
that contains
• High voltage generators
• X ray tube
• Collimators and filters
• X ray detectors

8. • Generators
High voltage generators are use to produce X ray
beams of same quality images every time by
maintaining the power supply.
• X ray Tube
It consist of a cathode filament that produce ions
that hits the rotating anode and produce high
energy X ray beam.

9. • Colimation
Then beam is collimated to creat a “dose slice”. Collimaters are use to
reduce the scattered beam resulting in reducing the patient dose by
restricting the beam to selected body part.
• Filteration
Beam filters are also use to creat a gradient in the intensity of X ray
beam to generate quality image.

10. • X ray Detectors
There are about 1000-1320 detectors are aling along the gantry to receive
the radiations for generation of image.
now a days solid state detectors are used that convert x ray photons to
generate light that may result to incease in image quality.
A moveable table/couch
Patient lies on the moveable table either head to feet or feet to head
position depending upon requirement of imaging.

11. Operating Console/Control
Pannel
• it contain input of all the pannels
that are use to conduct a
procedure.
• usually it contains
 computer
 keyboard
 multi monitors

12. • from operating console diffrent varriable of images can
also control that could be
thickness of imaged tissue slice
machenical movement of patient couch
other radiographic technical factors.

13. Appearance of structures on CT images
• Images of a CT scan consist of diffrent shades of grey, white and
black depnding upon the intensity of x ray beam received by the
detectors .
• High intensity x rays produce black shade , rays completly
blocked/absorbed by body generate white shade and diffrent
level of attenuated rays produce shades of grey.

14. Which of them appears white on CT scan images?
• bone
• muscel
• fluid

15. • areas with high level of calcium lie bones and teeth block the
radiations thus appears white on the image.
• soft tissues allows radiation to pass through them depending
upon their density so appear grey or black.

16. • How iamges of CT scan look like?

17. Multi Sclice Images of Brain by CT Scan

18. How many shades of grey are
found in CT scan image?

19. 12 - 16 bits/pixel image of
CT scan corresponds
between
4,096 - 65,536 shades
of grey.

20. Can you explain the picture?

21. For further citation
• Buzug TM. Computed Tomography: From Photon Statistics to Modern
Cone-Beam CT.ISBN 9783540394075. Springer. 2008
• Kalender W. Computed Tomography: Fundamentals,System Technology,
Image Quality, Applications. Publicis Corporate Publishing. 2005