computed tomography

1. 20

2. 1. CT image= matrix with thousand of pixels
A computerized tomography
(CT) scan combines a series of
X-ray images(multiple images
in succession) taken from
different angles around your
body and uses computer
processing to create cross-
sectional images (slices) of the
bones, blood vessels and soft
tissues inside your
body. CT scan images provide
more-detailed information than
plain X-rays do.

3. Pixels are measured in hounsfield units(hu) based on
how much the x-ray beam is absorbed ,
which reflects density

4. When CT Scans are used
• CT scans can produce detailed images of many structures inside the body, including the internal organs,
blood vessels and bones.
• CT scans can help determine the location, size and shape of a tumour before having radiotherapy, or allow a
doctor to take a needle biopsy (where a small tissue sample is removed using a needle) or drain an abscess.
• we can diagnose the conditions including damage to bones, injuries to internal organs, problems with
blood flow, stroke, and cancer.
• To evaluate a change in the density of organs and pathological areas in Hounsfield units in contrasting in
the arterial, parenchymatous and venous phases

5. Procedure
• During the scan, you'll usually lie on
your back on a flat bed that passes
into the CT scanner.
• The scanner consists of a gantry or
ring and the patient slowly moves
through it. The gantry has detectors
and while it rotates around the patient
it shoots narrow beams of X-rays
through the body.
• While each scan is taken, you'll need
to lie very still and breathe normally.
This ensures that the scan images
aren't blurred.

6. Contrast Materials
• A special dye called contrast material which contain either barium or
iodine are needed for some CT scans, to examine organs that do not
have natural inherent contrast with surrounding tissue , it helps to
improve resolution of the final images produced with the the scan for a
more exact diagnosis
• These are completely riskless and easily removed from the body
through urine.
• These contract materials can be given through mouth , by injection and
as well as by enema

8. CT images can be post processed into different planes
• Axial – looking at the patient from the feet up to the head
• Sagittal – looking at the patient from the side
• Coronal – looking the patient from the front

9. Advantages of CT scan
• CT scans can provide detailed information to diagnose,
plan treatment for, and evaluate many conditions in adults
and children.
• CT scans are quick(duration of 30mins for a full body
scan), painless and generally safe.

10. Disadvantages
• Exposure to ionising radiations
• There is a small risk you could have an allergic reaction
to the contrast dye used and you'll be exposed to X-ray.
• Use of a contrast material is problematic for patients
with significant kidney problems.