Radiation and Radiation Therapy
|picture above, Doctor Miller evaluating new X-ray equipment|
|Issues related to radiation safety are discussed in the sections
above, in general the dose of radiation received from diagnostic X-ray procedures is quite
small (go here) and the risk
of this causing a fatal cancer (go
here) or causing genetic problems (go here) is quite small. For every
total body rad (or 1cGy or 1000mRem or 1Rem or 10mSv) the odds of dying of
cancer go up only by 1/2500 (0.04%) which is quite small when you consider every one
already has a 23% risk of dying of cancer and about a 40% risk of developing cancer (go here.) The risk of
severe genetic defects in first generation offspring due to occupational radiation
exposure to one or both parents is estimated to be 4 in 1,000,000 (0.0004%)
per mSv. Under NRC guidelines (go
here) the limit exposure dose for occupational
workers is 5 rem/ year (50mSv) and the general public 0.5 rem (5mSv). (For
comparison, the exposure from a total body CT scan is 12mSv and the dose to Japanese
atomic bomb survivors was 20mSv.) Background radiation everyone is exposed to is
about 3.6mSv or 360mRem/year (see here).
For another discussion of the health risks of CT scan go
There is web site calculator that will calculate the cancer risk from diagnostic imaging here, using data here, here ,here, here, here, here and here
PET scanning is
non-invasive, but it does involve exposure to ionizing radiation. The total
dose of radiation is small, however, usually around 11 mSv. This can be
compared to 2.2 mSv average annual background radiation in the UK, 0.02 mSv
for a chest x-ray, up to 20 mSv for a CT scan of the chest. A policy change
suggested by the IFALPA member associations in year 1999 mentioned that an
aircrew member is likely to receive a radiation dose of 4–9 mSv per year.
The radiation risks to a pregnant
woman cause considerable concern. There is general agreement that fetal exposure of less
than 5 rads is not considered teratogenic.
It cannot be stated that there are no risks associated with lower doses, however. There
are numerous sites that discuss this topin in detail: a, b, c, d, f, g,).
Somewhat comic 1950"s propaganda film about radiation