Computed Tomography (CT) Scans

Brandon Lau Edward Liu4B IB Psychology

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

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

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

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

Results of CT ScanA 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 cross-sectional 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

Images are comparable to loaves of bread

StrengthsHas 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

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)

DangersExposure 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

Estimated 0.4% of current cancers in the United States are due to CTs performed in the past

CitationsSiemens 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