Computed Tomography (CT) is a medical imaging technique that uses X-rays to create cross-sectional images of the body, allowing for detailed examination of structures like the brain. The CT process involves three main steps: data acquisition, image reconstruction, and image display, all facilitated by a sophisticated computer system. While CT scans are quick and effective for diagnosing various conditions, they carry certain risks, particularly due to radiation exposure.

1. CT SCAN (Computed
Tomography)
Presented by,
J.SAROJINI
MPT (NEUROLOGY)

2. Introduction
Computed use of computer Tomography:
Greek word tomos means “slice”, graphy means “Write”.
Computed Tomography is the process of generating a two-dimensional
image of a slice or section through a 3-dimensional object (a
tomogram).
• Computed tomography (or computerized axial tomography) is an
examination that uses X-ray and computer to obtain a cross-sectional
image of the human body.

3. Parts of a CT scan machine
1. Gantry (scanner system)
2. Patient's table
3. Computer(operation control)
Scanner system:
1. X ray tube
2. Detector system
3. Collimators
4. Filters

4. Parts of Gantry:
• X-ray tube: generates x-ray beams
• Detector: detects the x-rays passing through the patient's body.
• Collimator: narrows the beams of x-rays
• Filters: these are used to filter some rays from entering the patient's
body that may be harmful.

5. Principle:

6. 2 types:
• Conventional: scan is taken slice by slice and after slice the scan
stops.e.g.. from top of abdomen till the pelvis. This needs the patient
to hold their breath.
• Spiral scan: continuous scan taken in spiral fashion. It is quick.

7. Parameters:
• Scan range starting at base of the skull; ending at vertex of the skull
• Respiration: shallow breathing
• Positioning
• Supine
• Head immobilized
• Arms along the sides

8. Procedure:
• When X-rays pass through the human body, some of the rays are
absorbed and some pass through the body to produce an image.
• In plain X-ray imaging, the film directly absorbs penetrated X-rays.
• In CT scanning, an electronic device called a "detector array" absorbs
the penetrated X-rays, measures the X-ray amount, and transmits the
data to a computer system.
• A sophisticated computer system, in turn, calculates and analyzes data
from each detector in each level, and finally reconstructs multiple,
two- dimensional, cross-sectional images.

11. Process
• It involves 3 steps:
• Data Acquisition
• Image reconstruction
• Image display

12. Data Acquisition:
• The term data acquisition refers to the collection of x-ray
transmission measurements from the patient.
• Once x rays have passed through the patient, they fall onto special
electronic detectors that measure the transmission values.

13. Image Reconstruction:
• After enough transmission measurements have been collected by the
detectors, they are sent to the computer for processing.
• The computer uses special mathematical techniques to reconstruct
the CT image in a finite number of steps called image
reconstruction.

14. Image Display, Processing, Storage, computer can use Recording, and
Communications
• After the computer has performed the image reconstruction process,
the reconstructed image can be displayed and recorded for subsequent
view and stored for later analysis.
• The image is usually displayed on a cathode ray tube.

15. X-RAYS ARE ABSORBED TO DIFFERENT
DEGREES BY DIFFERENT TISSUES
• Always describe CT findings as densities- isodense/hypodense/hyperdense.
• Higher the density = whiter the appearance
• Lower the density = darker the appearance
• Higher density than brain-hyperdense ( skull is the best example)
• Anything darker (lower density) than brain= hypodense( CSF and air are
classical examples)

17. CT SCAN OF BRAIN:
• An imaging technique of the brain that reveal tumors, blood clots,
hemorrhages, or other abnormal anatomy.
• A series of computerized images of the brain at various levels are
taken to reveal normal anatomy or any abnormality.
• Routine scans of the brain usually begin at the base of the skull and
continue superiorly.

18. • Symmetry - Compare left and right side of the Midline
• Look for midline shift of cranium
• Cross-sectional anatomy - Review anatomical landmark for each
section.
• Brain tissue: gray matter, white matter, intracerebral lesions
• CSF space : ventricle (dilated or not)
• Skull and soft tissue: scalp swelling, fractures, sinuses, orbit
• Subdural windows: Look for blood collection adjacent to the skull
• Bone windows: Skull, orbit and sinuses, intracranial air

19. Normal scan:
• Ventricles are normal sized, the
grey versus white distinction is
clear.
• Midline is straight.
• Sulci are symmetrical on both sides.
• Skull is intact with no scalp edema.

22. USES:
• Evaluate acute cranial-facial trauma
• Determine acute stroke
• Evaluate suspected intracranial hemorrhage
• Evaluate headache
• Determine if there is abnormal development of the head and neck
• Tumors, clots

23. ADVANTAGES:
• Quick and painless
• Can detect the presence of more serious problems
• To Check if a previously treated disease has recurred
• No superimposition of images

24. DISADVANTAGES:
• Small risk of developing cancer in future from exposure to X-rays. Risk is greater for children
• Uses higher doses of radiation are used in chest, abdomen, so the risks are in general greater than other
imaging types
• Some procedures require anesthesia.
• Requires breath holding which some patients cannot manage.
• Ct scan of brain can affect nearby bone.
• There is also risk of childhood cancer and leukaemia in mothers who have imaging during pregnancy.
• Pregnant women are not allowed for this imaging

27. ISCHAEMIC STROKE

29. INTRACRANIAL HEMORRHAGE

30. Thank you...