Computed Tomography Scans
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Transcript of Computed Tomography Scans
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