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Radiation Exposure
Radiographs (X-rays) have a huge impact upon
our lives from airport scanners to cancer treatment but in many ways they
are a mystery to most people. Xrays have always been present but weren’t
discovered until 1895 by Wilhelm Roentgen. Since that time they have been
used for diagnosis and treatment of injury and disease.
An x-ray is a wave of electromagnetic energy. There are two types of
electromagnetic energy (waves), nonionizing (low frequency) and ionizing
(high frequency) energy. Examples of nonionizing waves are UV light, visible
light, microwaves and radio waves. Xrays are ionizing radiation which can
damage cells including the DNA by removing an electron (ionizing) from the
atoms in molecules. The higher the x-ray dose the greater the damage. Low
doses spread out over time are thought to be harmless because the body
repairs any damage. However, we know high doses cause cancer from studies of
atom bomb survivors in Japan. Radiation doses can be measured in many ways.
The more common ways to measure is the biological effect on the body. The
older unit of measure was the Rem, and millirem. The newer international
measure is the Sievert, millisievert or microsievert. The measurements are
similar to the meter and millimeter for distance.
Different parts of the body absorb and therefore are affected differently by
radiation. . The salivary glands are more affected by an xray scan of the
head than the jaw bone. Parts of the body that grow faster are affected more
than slower growing areas. Cancer cells grow very fast and are more affected
by radiation. This is why radiation is used to treat cancer tumors. The
whole body absorbed doses listed in the table are an average of all the body
parts
Ionizing radiation (x-rays) can come from many sources such as cosmic
radiation from our solar system, radioactive elements in the soil, and radon
from the air. The average person receives about 620 millirems (6,200uSv) per
year, half from the environment and half from medical procedures. The
following table shows the amount of radiation received to the whole body
from various x-rays sources.Whole Body
Absorbed Dose
|
SOURCE |
microSieverts
(uSv) |
millirems
(mrems) |
|
Air in a year |
2280 |
228 |
|
Cosmic rays in a year |
260 |
26 |
|
Ground in a year |
160-630 |
16-63 |
|
Computer screen in a year |
10 |
1 |
|
TV Screen in a year |
10 |
1 |
|
Living in a brick house a yr |
80 |
8 |
|
Sleeping next to someone a yr |
20 |
2 |
| ˝
pack of cigarettes per day (1yr) |
180 body (160,000 to lungs) |
18 body (16,000 to lungs) |
|
One hr of airplane travel |
5 |
.5 |
|
Airport body scanner |
.05 to .25 |
.005 to .025 |
|
1 dental x-ray film |
.3 |
.03 |
| Full
set of dental film xrays |
18 |
1.8 |
|
Full set dental digital xrays |
6 |
.6 |
|
Dental Cone Beam Computer Tomography (CBCT) |
5 to 206 |
.5 to 20.6 |
|
Chest xray |
100 |
10 |
|
Mammogram |
420 |
42 |
|
CAT scan of head |
2000 |
200 |
| CAT
scan of upper GI |
6000 |
600 |
|
CAT scan of chest |
7000 |
700 |
|
Radiation Treatment for cancer |
20,000,000 to 80 ,000,000 |
2,000,000 to 8,000,000 |
|
Amount of Short term xray exposure
thought to cause cancer (EPA) |
4,000,000 |
400,000 |
Two very important computer enhanced
developments have lessened the effect of xrays to our bodies. The first is
the use of digital sensors rather than film. Digital sensors are more
sensitive than film and much less radiation is needed. For example dental
film xray exposure is three times digital xray. The second development is
the ability to focus the xray beam in a more precise way which concentrates
the radiation to the smaller area of interest. This minimizes the effect of
the radiation to the body. For example a medical CAT scan of the head is 10
times more radiation than a “cone beam computerized tomograph “(CBCT) of the
head. Highly focused radiation is also used for cancer radiation treatment.
Delmarva Dental Services takes it responsibility to your health seriously.
We will be more than happy to discuss the risks versus the benefits of any
diagnostic or treatment procedure. |
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