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Level 3 Applied Science Unit 21 Assignment A+B
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This assignment is graded distinction. Level 3 Applied Science Unit 21A+B NQF
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Qualification Pearson BTEC Level 3 National Extended Diploma in Applied ScienceUnit number and
Unit 21: Medical Physics Applications
title
A: Explore the principles, production, uses and benefits of non-
ionising instrumentation techniques in medical applications
Learning aims
B: Explore the principles, production, uses and benefits of ionising
instrumentation techniques in medical applications
Assignment title Radiation use in medical diagnosis and treatment.
P1 Explain how non-ionizing technologies work and how they are used in medicine
P2 Explain, using flow charts or labelled diagrams, why these non-ionizing techniques are used for
diagnosis and treatment
Magnetic Resonance Imaging (MRI)
What is an MRI scanner?
An MRI scanner is a hospitality equipment, which is very heavy, weighing up to 100 tonnes, due to
the large magnets and electromagnets, which allow the MRI scanner to give the magnetic fields
that are needed to polarise the nuclei. The MRI scanner has many different properties, these
include: a main magnet, MRI scanner coils, radiofrequency coils and an output signal receiver.
The components of an MRI Scanner
Main Magnet The main magnet is a large magnet, and the most common used
magnet is the superconducting electromagnet, which consists of
coils that carry around electrical current, which is what causes the
magnetic field through the centre. The coil is superconductive,
which means that they last in the long term but they aren't
permanent. However, the main magnet depends on what the form
of the MRI scanner is, such as a closed MRI, or a tunnel open
MRI. A large main magnet will work by blowing off some liquid
helium coolant into the outside atmosphere. One disadvantage of
the main magnet is that they are expensive. Although the
advantage is that they will form a high field strength.
Also the main magnets must produce a magnetic field strength of
1.5 Tesla, and the principle of superconductivity resistance of a
wire is 0 if the temperature is low. In addition, the value of
magnetic field strength has to be constant over 90 cm.
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BTEC Assignment Brief v1.0
BTEC Internal Assessment QDAM January 2015
, MRI Scanner Coils The MRI scanner coils are made up of resistive magnets, which
are usually limited to the maximum field strengths of ± 0.6T.
These resistive electromagnets produce a gradient field, therefore
the variety of magnetic strengths over the body can help for the
signals. When the MRI scanner is running and scanning, these
coils are what makes the knocking sound, because the coils are
switching on and off.
Radiofrequency Coils The radiofrequency coils are an important aspect of the MRI
scanner because these are what products the radio input, this is
done by waves. These waves will send impulses to the nuclei,
which will therefore allow the signals of nuclear magnetic
resonance (NMR). The radiofrequency coils are also needed to
ensure there is a power output of up to 1kW, and keep it to that
power. If the radiofrequency coils were continuous, the relaxation
time wouldn’t be able to be measured, which is why the
radiofrequency waves are emitted in pulses, and after each pulse,
a coil picks up the emitted radiofrequency wave from the patient.
Output signal receiver The output signal of an MRI scanner are the tuning coils, which
are needed to pick up the output radio waves from the protons,
however it has to be in resonance. There are some different types
of output signal receivers, which are usually selected based on
what is needed to produce a clear and specific image. The signal
receiver will be linked to the computers used, which will process
the scans and information shown.
Computer There is a lot of data in a computer, and to keep it up to date and
correct, programming is needed, which involves different
applications, these are: Isolating different radio frequencies.
Linking the programme to a point in 3D space, which can only be
done if the magnetic field strength is known accurately at each of
the points within the volume being scanned. Finally, the relaxation
time for that point needs to be measured, which will be relative to
the type of material at that specific point. This is all used to
provide a display.
Uses of an MRI scanner
One process that is used in an MRI scan is nuclear magnetic resonance (NMR). The NMR is what
is used to produce the detailed images of the tissues. This is because the protons are able to be
detected and shown in the exact locations in the body. The NMR can also be used to give
information about the tissue type that the protons are in, which is because the protons can move
and re-align themselves within different speeds. The final results that are produced by the
computer will illustrate very detailed images, and it will show the MRI in action, to be evaluated by
the diagnostic radiographers. These images can be interpreted in many different ways by the
professionals. One example of how the images are interpreted is the colour of some areas of the
image, for example if there are brighter and darker areas, this may suggest that there are different
surroundings. Although, in most cases, the MRI scans will mainly look for the hydrogen atom
protons. An MRI scan can be used to examine many different areas of the body, such as the brain,
spine, blood vessels and the breasts. They can also be used for the detection of inflammation,
cysts and swelling, as well as being used for the development of neurological investigations for the
detection of tumors or abnormalities.
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BTEC Assignment Brief v1.0
BTEC Internal Assessment QDAM January 2015
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