This document provides background information on computed tomography (CT) scans. It discusses how CT scans work, the process a patient goes through during a scan, and how images are produced and analyzed. Key advantages of CT scans are its ability to show soft tissue and structural changes. However, risks include exposure to radiation, which can potentially increase cancer risks. The document serves to inform readers on the technical aspects and clinical applications of CT scans.

1. Computed
Tomography
(CT) Scans
Brandon Lau Edward L
4B IB Psychology

2. Background
information
X-Ray Computed Tomography is a medical imaging procedure
using computer processed x-rays to produce tomographic images
The produced cross-sectional images are used primarily for
diagnostic and therapeutic processes
Greek Foundation of the word: ‘Tomo’ = Slice
Invented by Hounsfield and Cormack in 1972, both won Nobel
prize for the invention
About 6,000 CT scanners in US and about 30,000 worldwide today

3. Background Info
(cont.)
Usage of CT scans has dramatically increased over the past two
decades
Estimated 72 million scans were performed in the United
States in 2007
Older versions of the scan were known as Computed Axial
Tomography or CAT Scans
Although previously images produced were in the axial plane
(limited to one angle), modern scanners allow data to be
reformatted as volumetric 3D representations of structures

4. How it works
Since the 1970s, CT scans have become an important tool in
medical imaging to supplement X-rays and medical
ultrasonography
Unlike simple X-ray scans, the combination of computed
technology allows soft tissue to be visible
A x-ray tube and detector are physically rotated behind a circular
shroud
Pixels in an image obtained by CT scanning are displayed in terms
of relative radio-density
Images can be acquired from any angle and at any depth

5. How it works (cont.)
- Patient lies flat on back on a flat
bed
- X-ray tube rotates around body of
patient
-Patient will be moved continuously
through this rotating beam
-Rays are analyzed by detector on
opposite side of body

6. Results of CT Scan
A visual representation of the raw data is
referred to as a sinogram (not yet sufficient
for interpretation)
Data must then be processed using a form
of tomographic reconstruction
This process produces a series of crosssectional images
Can show a full body CT scan or be
focused on just the brain/head
Images produced are called Tomograms
Individual scans can be combined to
create 3D images

7. Strengths
Has many advantages over traditional 2D medical radiography
Eliminates the superimposition of images of structures outside
the area of interests
Differences between tissues that differ in physical density by
less than 1% can be distinguished
Capable of showing soft tissue and structural changes
eg. Brain tumors, Brain damage, Liver, and other organs
Far more useful than an MRI in terms of skull fractures
Cheaper than a MRI but equally as fast
Can be performed on patients with implanted medical devices

8. Weaknesses
Can only produce structural images
Unable to provide any information on brain
activity
Inferior to MRIs when it comes to soft
tissue contrast
Potentially Dangerous (see next slide)

9. Dangers
Exposure to radiation
Especially dangerous to young children and pregnant women
Half of all CT scans in the United States involve intravenously
injected radio contrast agents
Mild side affects of these agents include nausea, vomiting, and
rashes
Rare cases of extreme reactions include contrast-induced
nephropathy, occurring in approximate 2-7% of people who receive
these agents
Ionizing radiation in the form of x-rays are energetic enough to
directly damage DNA
Small increased risk of cancer

10. Citations
Siemens Medical Solutions. (n.d.). Retrieved from
http://www.imaginis.com/ct-scan/brief-history-of-ct
Stoppler, M. C. (n.d.). Retrieved from
http://www.medicinenet.com/cat_scan/article.htm
Images From:
http://www.callusdoc.com/AImages/canstockphoto4116197%20(1).jpg
http://media.web.britannica.com/eb-media/59/62659-004-A8C6FDA4.gif
http://assets.knowledge.allianz.com/img/ct_scan_head_q_1_48138.
http://dz-world-health.blogspot.com/2012_07_01_archive.html