1. Senior Secondary or A-Level Physics
~Dr Lalit Kishore, The plenum School, HP
Computed Tomography or CT Scanning
in Medical Physics
2. Genesis of CT Scanning
CT scanning arose to overcome of
the following limitations of X-ray
imaging on films
Image being just a two-dimensional flat
shadow
Details in the image being unclear
Dense tissues went undetected
3. What is Computed Tomography
(CT)?
It is a technology that produces
three-dimensional image (slice) of
internal organ along with that of the
body
The CT device is called the CT
scanner
The CT scanner is operated by a
certified radiologist or medical
physicist
It can even scan through head of a
4. How does CT Scan work?
Image display and manipulation
Image of whole object viewed
directly
Rotation of image for viewing
from every angle
Repetition with with successive slices fed into high powerful computer
Images combined Three dimensional image created
Data of X-ray in two forms of two-dimensional slice collected and computed as
pixels
Individual X-ray image Angle of image
5. CT Scanner chamber
Visual Parts
Whole body can be
scanned three
dimensionally
The number labels
1. Radiologist /
medical physicist
2. Patient
3. CT scanner chamber
4. Stretcher
6. Arrangement of CT Scan
Diagram Part labels
1. X-ray beam
2. body of the person /
patient
3. X-ray detectors
(sensors and
transducers)
4. Direction of
rotation of X-ray
tube
5. Direction of rotation
of X-ray detectors
7. Versatility of CT scan
Visual showing cerebral
lymphoma Brain mapping through
the skull is possible
CT scan technology
has been refined with
better computing that
on can scan the head
This visual is showing
two spots indicating the
symptoms of cerebral
lymphoma
Image can be viewed
3-dimensionally to find
the extent and location
of malign portion
8. Basic principles of scanning
Slice and rays’ angle
variation and adding up
information Principality aspects
Slice / section is seen as made
of series of small cubes called
voxels
The intensity of X-rays
transmitted through each voxel
is given a number by the
computer called pixel
Once patter of pixels from one
section is obtained, the scanner
is rotated for next section
analysis
Computer stores all analysed
data and construct the final
image for viewing
Note: Radiation dose during CT
scan is higher than that of X-ray
film imaging , hence scanning
has be quick
9. Newer and better CT scanners get
marketed periodically
With the advancements in digital
technology and faster / smarter
computers, and material science. the
CT scan machines keep on getting
updated every now and then.
Also, radiologists / medical physicists
under go refresher courses along with
the surgeons to become proficient in
their professions to provide better
expert services
