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Radiation Exposure from X-ray
and CT Examinations
Evan
Lum
What is an X-ray
• An x-ray is a form of electromagnetic radiation
which falls in between gamma rays and ultra
violet rays on the electromagnetic spectrum.
• They have a wavelength of anywhere between
0.01 nm and 10 nm.
• Corresponds to an energy of 0.1 to about 123 keV
(kiloelectron volts)
What is a CT scan?
• CT stands for computed tomography which is
a medical imaging method employing
tomography (imaging in sections) created by
computer processing.
• Using a series of x-ray images about a single
axis of rotation, CT produces volume data such
as 3D images of internal organs which can be
manipulated through a process called
“windowing”.
Medical Uses for X-ray
• Plain x-rays are mostly used
to detect pathology in the
skeletal system.
• Sometimes used for soft
tissue:
– Chest x-ray to identify lung
diseases like pneumonia or
lung cancer.
– Abdominal x-ray to detect
intestinal obstruction, free air
or free fluid.
Medical Uses for CT Scan
• Head – detect infarction, tumors, hemorrhage,
bone trauma.
• Lungs – shows internal aspects of the lungs which
plain x-ray can not.
• Cardiac – excellent imaging of coronary arteries
• Abdominal/Pelvic – sensitive method for
diagnoses of abdominal diseases.
• Extremities – can image complex fractures,
especially around joints. Also ligament injuries
and dislocations can be seen.
Radiation Exposure
• The Sievert is the SI unit for radiation dose
which is equivalent to one joule per kilogram.
• The average American is exposed to about 3
mSv per year from naturally occurring
radioactive materials and cosmic radiation
from outer space.
• This amount of radiation exposure over such a
long period of time is basically harmless to us.
Radiation from X-rays
• Extremities – 0.001 mSv per x-ray (not
harmful)
• Spine – 1.5 mSv per x-ray (about 6 months
worth of natural exposure)
• GI tract – 6-8 mSv per x-ray (2-3 years worth
of natural exposure)
• Each of these are considered not to be
relatively harmful
Radiation from CT Scan
•
•
•
•
Head – 2 mSv per CT scan (under 1 year)
Spine – 6 mSv per CT scan (2 years)
Chest – 7 mSv per CT scan (over 2 years)
Abdomen/Pelvis – 15 mSv per CT scan (5
years)
• Abdomen/Pelvis without contrast material –
30 mSv per CT scan (10 years)
• Coronary Computed Tomography Angiography
(CTA) – 16 mSv (5 years)
Why is this dangerous?
• Although radiation can be used to treat
cancer, it can also cause it.
• The delivery of energy waves through our
body can alter atoms’ molecular structure
causing cells in our body to mutate and
become cancerous.
Statistics
• Higher risk procedures can leave patients with
up to a 1 in 500 chance of getting cancer.
• The united states gives over 60 million CT
scans per year.
• It has been estimated recently that CT
scanning has been the cause of about 30,000
cases of cancer yearly.
What Can We Do?
• Due to their major contribution to the medical
field, the benefits of x-ray imaging and CT
scanning usually outweigh the risks from
radiation exposure.
• Something we can do to avoid this is avoiding
unnecessary procedures.
• This decision should only be made by a
professional not a patient!
Sources
• http://www.usatoday.com/news/health/2009-12-15radiation15_st_N.htm
• http://en.wikipedia.org/wiki/Xray_computed_tomography
• http://www.radiologyinfo.org/en/pdf/sfty_xray.pdf
• http://www.worldculturepictorial.com/blog/content/ct
-scan-study-shows-increased-radiation-exposurecancer-risks-tests-often-unnecessary
• http://www.hanskellner.com/2005/06/27/leftshoulder-xray/
• “The Physics of Medical Imaging”, by S. Webb, New
York: Adam Hilger, 1990.
THE
END