Computed tomography (CT) scanning uses X-rays and computer technology to create cross-sectional images of the body. Sir Godfrey Hounsfield invented the first commercially successful CT scanner in 1971. CT scanning provides clearer images than traditional X-rays and can detect many abnormalities, but does expose patients to small amounts of radiation.

2.  2D imaging was used – X-rays
 there was super imposition of structures.
 less clarity of images

3.  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.

4.  The first commercially CT scanner was invented by
Sir Godfrey Hounsfield in Hayes, United Kingdom,
at EMI Central Research Laboratories using X-rays
 The first EMI-Scanner was installed in Atkinson
Morley Hospital in Wimbledon, England
 The first patient brain-scan was done on 1 October
1971.
 Emi scanner is limited to scanning only brain.

6.  Hounsfield and Cormack got the 1979 Nobel
Prize for their contributions to CT.
 Allan McLeod Cormack 's theoretical
calculations on x-ray was used by Hounsfield.

10.  Gantry (scanner system)
 Patient's table
 Computer(operation control)

12.  Scanner system:
1. X ray tube
2. Detector system
3. Collimators
4. Filters

13.  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.

14.  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.

17.  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 CAT 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.

18. ◦ Displayed on screen
◦ Hounsfield scale( linear transformation
reference being distilled water)
◦ Range from +1000(bone) to -1000(air/gas)
◦ Ct number or Hounsfield scale is a measure
of radiodensity.
◦ Ct number measured in Hounsfield unit.

21.  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.

23.  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
 Tumours , clots

24. 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.

28.  Patient preparation:
 Fasting for 4 Hours before the examination.
 Starting at floor of the mouth Ending at
supraclavicular fossa .
 Respiration suspended in expiration with no
swallowing.

32.  Spine, airway ,carotid vessels, salivary and
thyroid glands are included.
• To evaluate parotid or submandibular gland
lesions or infections.
 Head and neck diseases
 Foreign bodies that are logged in the neck or
upper airway
 Tumours or infections of pharynx vocal cord.

34.  Show the size, shape, and position of lungs
and other structures in the chest.
 Follow up on abnormal findings from
standard chest x rays.
 Find the cause of lung symptoms, such as
shortness of breath or chest pain.
 Diagnose lung diseases such as a tumor,
excess fluid around the lungs, or a pulmonary
embolism. The test also is used to check for
tuberculosis , emphysema and pneumonia

41.  To test abdominal pain or swelling
 Masses and tumours including cancer
 Injury or infections
 Kidney stones
 Appendicitis
 Alcoholic liver diseases
 Cancer of pancreas, colon, renal pelvis.
 Peritoneal fibrosis

47.  Purpose of the Bone CT Scan
 To identify abnormalities in the spine,
such as spinal stenosis that may be
causing back pain
 To detect bone tumors and tumors in the
soft tissue surrounding bones

48.  To diagnose osteoporosis, which is common
in women after menopause and also may
occur in men
 To evaluate fracture
 To detect unusual formation of bone
 To diagnose joint abnormalities.

51.  Quick and painless
 Can help diagnose and guide treatment for a
wider range of conditions than plain X-rays
 Can detect the presence of more serious
problems
 check if a previously treated disease has
recurred
 No superimposition of images.

52.  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
 Injection of a contrast medium (dye) can
cause kidney problems or result in allergic or
injection-site reactions in some people
 Some procedures require anesthesia

53.  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 .