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| What
is ultrasound imaging and how does it work?
Ultrasound
imaging, also called ultrasound scanning or sonography,
is a method of obtaining pictures or images from different
organs inside the human body. It involves sending very
high frequency sound waves through your body. These sound
waves are reflected off your internal organs. The reflections
are then processed by special instruments and powerful
computers that subsequently create an image of the organs.
Ultrasound images are captured in real time and displayed
on a television monitor.
No
x-rays or any type of ionising radiation is involved in ultrasound
imaging.
The
principle of ultrasound imaging is very much like that of
sonar used by bats, dolphins and ships. In medical use, the
echo pattern of the returning sound waves that bounce off
internal organs is used to detect disease that changes the
appearance of organs or tissues, or abnormal masses such as
tumours. It is also used to detect blood flow in blood vessels,
as well as in organs to detect a blood clot or any other abnormality
in the blood vessels or the supply of blood to these organs.
The
ultrasound transducer (probe) functions as both a loudspeaker
to create the sounds and a microphone to record them. When
the transducer is pressed against the skin, it directs a stream
of high frequency sound waves into the body. As the sound
waves reflect from the body’s organs, the transducer
records tiny changes in the sounds pitch and direction. These
changes are instantly measured and interpreted by a computer,
which in turn creates a real time picture on the monitor.
The live images of the examination can be recorded by a number
of methods including thermal images, video, x-ray films, CD’s
and Magnetico-Optical Discs (MOD).
Blood
flow changes the pitch of the sound beam; this is called the
Doppler effect and can be shown on the image as colour, displayed
graphically or heard as high pitch sound.
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| Who
performs the examinations?
The
examination is performed by an ultrasound practitioner.
He or she is a doctor (radiologist), an ultrasonographer,
or a cardiac technician experienced in ultrasound. All
our staff are highly qualified and very experienced practitioners
who worked for years in the NHS and the private sector.
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What
does the equipment look like?
The
ultrasound machine may look like a large computer with a television
screen. The equipment consists of a monitoring system and
different shape transducers (probes) for different types of
examinations. They range in size from that of a fat pen to
one resembling a cigarette box.
The
ultrasound image can be seen in black and white on the monitor
or in colour if the operator examines blood flow in vessels
and organs.
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| How
should I prepare for the examination?
It
is preferable to wear a comfortable, loose-fitting two-piece
outfit for the examination.
There
are no general set instructions for all ultrasound examinations.
Different examinations require different preparations and
our staff will give you the relevant instructions for your
examination. Please, click on types of examinations
for more details.
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What
happens during the examination?
An
ultrasound examination is a painless procedure. There are
several methods of performing the examination depending on
the part of the body being examined.
Most
ultrasound examinations are performed using the percutaneous
(through the skin) approach. The patient is usually asked
to lie on an examination bed and a clear water-soluble warm
gel is applied to the skin to help the transducer make secure
contact with the skin. The ultrasound waves produced by the
transducer cannot penetrate air, so the gel helps to eliminate
air pockets between the transducer and the skin. The ultrasound
practitioner then presses the transducer against the skin
and moves it back and forth to image the area of interest.
Real time images of the area are displayed instantaneously
on the television monitor.
Some
organs in the pelvis may require a different approach. In
the ultrasound examination of the female pelvis, a trans-vaginal
approach is the method of choice because it gives superior
quality images. However, there are certain situations, including
patient’s preference, where a percutaneous approach
might be used.
During
the trans-vaginal ultrasound, a small transducer that
looks like a large pen is used. A protective cover is
placed over the transducer, lubricated with a small amount
of gel, and then inserted into the vagina. The procedure
is usually painless and it resembles the insertion of
a tampon. No speculum is used and it is simpler than a
smear test. This is an example of a trans-vaginal transducer
(probe).
The
patient will be awake throughout the examination. The
radiologist or ultrasonographer may explain the images
displayed on the monitor to you and you may ask questions
during the scan. The operator may ask you to take deep
breaths in or move into different positions to obtain
the best possible images.
Details
of procedures are explained in type of examinations.
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| How
do I get the results?
The
ultrasound practitioner, who is a doctor, an ultrasonographer,
or
a cardiac technician experienced in ultrasound, will analyse
the images and send a report with the interpretation of the
scan to the patient’s referring doctor. In cases of
screening, a letter would be sent to the patient to explain
the findings as well as a detailed report to the patient’s
doctor.
In
many situations, the ultrasound practitioner will be in a
position to explain to you the results at the time of examination.
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| What
are the benefits and risks of ultrasound imaging?
Benefits:
Ultrasound imaging is a painless procedure.
- It
does not use x-rays or any other type of ionising radiation
to produce an image.
- It
is non-invasive.
- It
can be used safely during pregnancy.
- Ultrasound
provides real time imaging, making it a good tool for guiding
some invasive procedures such as needle biopsies.
- Ultrasound
can visualise movement and function and therefore can examine
blood vessels and blood flow to different organs.
Risks:
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For standard diagnostic ultrasound there are no known harmful
effects to humans.
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Ultrasound has been used for medical diagnosis for over
thirty years, during which time no adverse effects have
been observed.
- Studies
in animals and humans did not show any side effects of the
use of diagnostic ultrasound.
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| What
are the limitations of ultrasound imaging?
Ultrasound
waves have difficulty penetrating bone and air. Therefore,
it can only see the outer surface of bony structures and organs
filled with gas, such as bowel and stomach, and not what lies
within. For visualisation of these organs, other imaging modalities
such as x-rays, CT scans and MRI may be undertaken.
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