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Understanding the Workings of X-rays

posted 23 Nov 2010, 08:41 by Sam Mbale

X-rays are used in podiatry for many reasons. For example,
X-ray can be used to monitor the healing progress of a
surgical procedure, confirm a suspected fracture or to
confirm a bone infection. In other words, X-ray images are
tools to assist and improve patient care. There are,
however, potential harmful effects of X-ray radiation.

Therefore, the process of taking X-rays and common
precautions must be understood.  With an understanding of
the mechanism and nature of X-ray concerns, potential
negative effects can be lessened.

Properties of X-rays:

The nature of X-rays can be perplexing because it is a form
of energy similar to light. However, unlike light, there is
nothing directly or physically seen. A main component in
creating X-ray images is radiation, which is the
transmission of energy as waves or particles akin to light.
There are different types of radiation, ranging from lower
energy radiation like radio, television, microwaves, and
visible light to higher energy radiation like X-rays. Unlike
low energy waves, X-ray radiation can change the properties
of particles of an object that are exposed to the
high-energy emission.

Categorizing X-ray Radiation:

There are three categories of radiation that are found where
X-ray radiation is used.

The strongest is called the primary beam. This is the
radiation that is made inside the X-ray tube which is
located in the X-ray machine. The tube is made of glass that
is lined with lead. This is meant to contain the X-ray waves
and prevent X-ray overexposure to the patient and personnel
that are near the machine. The primary radiation exits the
tube and is directed toward the area of the patient being
examined.  Of the three categories of X-ray radiation,
primary radiation is the most dangerous and most intense.

The second type of X-ray radiation is referred to as
secondary radiation, made of scatter or leakage radiation.
Scatter radiation comes mostly from the patient when the
primary beam is reflected off of the patient's body. This
type of radiation emission is most dangerous to personnel in
the room. Leakage radiation is the energy waves that escape
out of the X-ray tube.

The final and third category of X-ray radiation is remnant
radiation, which is the energy waves that exit the patient
and produces the image on the film.

Potential Dangers of X-ray Radiation:

X-ray radiation passes through body tissue and has enough
energy to change the genetic make-up of cells that make up
the tissues in the body. This can result in the overgrowth
of cells. Of all the organs in the body, the lens of the
eyes, sexual organs, white blood cells, and the thyroid
gland are most sensitive to X-ray radiation. However, it
takes an exceedingly large amount of radiation to damage the
genetic components of cells and tissues.

In the case of pregnant women, the brain and spinal cord of
the fetus is most sensitive to radiation and thus X-ray
exposure is avoided during the 10th to 17th week of
pregnancy. This time period corresponds to the growth period
of these structures in the developing child. There are
industry-accepted doses of radiation that can be exposed to
a patient and rarely, if ever, does the amount of X-ray
radiation performed exceed the maximum amount. In podiatry,
it would require 5,000 X-ray exposures to be considered
harmful to a pregnant woman, and this number is even higher
for non-pregnant patients. Despite research showing low-risk
from X-ray radiation, precautions and safety procedures are
still practiced to fully protect the patient from potential

Protection from X-ray Radiation:

There are two main forms of protection against overexposure
of X-ray radiation, distance and shielding. Increased
distance between a person and the X-ray machine decreases
the amount of exposure to X-ray radiation. This is important
for health care personnel, who frequently administer X-ray

The second form of protection against radiation is
shielding. Commonly, a lead apron is worn by the patient to
protect against unnecessary exposure to radiation to other
parts of the body.

What to Expect When Taking X-rays:

A state certified radiology health care personnel places the
lead apron on the patient. If the patient is female of
childbearing age, she will be asked if she is pregnant. Then
the strength of the X-ray beam is adjusted. Next the body
part being studied will be correctly positioned. The person
taking the X-ray will make sure everyone has cleared the
area. A button is pushed to take the image accompanied by a
buzzing sound. This sound indicates that the image is taken.
In podiatry, there are at least two images taken for each
X-ray study. The reason for this is that the foot is a
three-dimensional object, but X-ray images are only a
two-dimensional representation of the foot. Therefore, more
than one X-ray view is needed to provide the podiatrist with
a better visualization of the possible problems in the feet.
Once the film has been processed, the film will have areas
of black, which represent the soft tissues.  The X-ray beam
has passes through these areas of the body and strikes the
film or sensor at near full strength causing these areas to
become fully exposed and appear black.  The image will also
have areas that appear white. This represents areas where
X-ray beams are stopped and absorbed therefore they do not
reach the film or sensor. This occurs when the X-ray strikes
hard tissue such as bone.

About the Author:

Bruce Lashley, DPM
Dr. Lashley is a podiatrist practicing in midtown Manhattan
for the past 27 years. He specializes in the conservative
and surgical management of the foot. In October 2009, Dr
Lashley moved his office to a new modern facility at 353
Lexington Avenue, in NYC. For more information on Dr.
Lashley visit his web site.