X-Rays
- How It Works, Units of Radiation Exposure, X-Rays of the Lungs
for Diagnosing Mesothelioma
(August 12th, 2008)
 X-ray
is a form of electro-magnetic radiation with a wavelength of 10
to 0.01 nanometers; much like gamma rays but shorter than UV rays.
X-rays contain high energy radiation exposure because they have
an extremely short wavelength and high frequencies. Just like Computed
Tomography (CT) scans, X-Rays use ionizing radiation to create radio
waves to create visuals of different organs of the body including
the lungs. Once the x ray machine aims at the part of the body that
is to be visualized such as the lungs, it will emit a small burst
of radiation that will pass through the skin and record image of
internal organs of the body on a photographic film or a special
image recording plate. Different organs of the body will absorb
the x ray radiation in different ways. For instance dense bones
will absorb almost all of the radiation while soft tissues such
as muscles, fats & other organs will allow more of the x-rays
to pass through them. Due to this, bones appear white on x-rays
while soft tissues are presented in shades of grey and black. X-Rays
are also very similar to visible light rays where electromagnetic
energy is carried by particles known as photons. The difference
between x-rays and visible light rays is the energy levels of individual
photons, also known as the 'Wavelength.'
How Are Chest X-Rays Performed?
 A
chest x-ray diagram is shown on the left. Typically, the patient
stands up against the image recording plate and two photos of the
chest are taken. One is from the back and the other is from the
side of the body. The radiologist will instruct the patient to put
his hands on his hips and chest pressed against the image plate.
For the second photo, the patient's side is against the image plate
with arms elevated. Patients with difficulty standing can be positioned
lying down on the table. While the x-ray is taking place, the patient
will be asked to hold his breath and lay still for a few seconds
to reduce possibility of blurred images. After the x-ray is over,
the patient will not be let go until the radiologist confirms the
picture is of good quality and can be reviewed by doctors. This
entire process can take up to 15 minutes. Additional x-rays may
also be required after a few weeks or months; this is known as Serial
x-rays.
Sources of X Ray
 X
Ray Photons are produced when the electron beam flashes on the patient.
The electrons in the beam are contained in a heated cathode filament
and the point where the beam & the target meet is known as the
focal spot. The kinetic energy that is contained in the electron
beam is turned into heat and about 1% of it is converted to X-Ray
photons. Any excess heat is dissipitated via a heat sink. The X-Ray
beams that are created are projected on a film or a substance of
'matter.' Some of the x-ray beams will pass through the patient,
while the rest will be reflected. The resulting image created by
the dose of radiation exposure is then captured on a projected film,
semiconductor detectors or X-ray image intensifiers.
An X-ray Image Intensifier is a specialized piece of equipment
that uses x-ray beams to create 'live' image feeds that are displayed
on a computer screen. The Image intensifier is so sophisticated
such that the x-ray beams could be of low radiation exposure resulting
in a lower radiation exposure to the patient.
Benefits of X-Rays
i) X-Rays have no side effects
ii) X-Ray imaging is quick and cost effective
iii) X-Ray imaging is good for emergency diagnosis & treatment
iv) Radiation exposure does not remain in the patient's body after
x-ray is performed
v) X-Ray equipment is available at almost any clinical office, hospital
or treatment center
Risks of X-Rays
i) There is a small chance that cancer can be caused by radiation
exposure coming from the x-ray machine
ii) Pregnant women should not take x-rays as radiation exposure
could negatively affect the baby.
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