Head CT scan
machine.
Getting Technical
as high as 20 Tesla. However, early in 1962 alloys of niobium
and titanium which were far more ductile and easier to work
with than the niobium-tin alloys were found to be suitable for
producing magnetic field strengths up to 10 Tesla which has
since proven to be high enough for many industrial and other
practical applications.
In 1963, commercial production of niobium-titanium
‘supermagnet wire’ began at Westinghouse Electric
Corporation and at Wah Chang Corporation, an American
company located in Albany, Oregon. Although niobium-
titanium has lower superconducting properties than those
of niobium-tin, niobium-titanium has, nevertheless, become
the most widely used supermagnet material on account of
having high ductility and ease of fabrication. Both niobium-
tin and niobium-titanium coil circuits are extensively used as
particle beam bending and focusing magnets in high-energy-
particle accelerators, MRI imaging machines and a host of
other applications. A European superconductivity consortium,
Conectus, estimated that in 2014, global economic activity
for which superconductivity was indispensable amounted to
about five billion euros, with Magnetic Resonance Imaging
(MRI) systems (mostly medical units) accounting for about
80% of the total.
X-RAYS AND MRIS
Recognition of the value of the research and development
work done in this new area of superconductivity is reflected
in the number of Nobel physics prizes awarded. One went
to Kamerlingh Onnes in 1913 and up to 2003, five further
Nobel prizes have been shared amongst eleven scientists and
researchers.
For the great majority of people MRI is one of the machines
which, similarly to X-rays, produces detailed images of internal
organs and bones in their bodies. As noted earlier, most MRI
machines are used for medical scans but from a technical point of
view, the only similarity between X-ray and MRI scans is that both
require high levels of computer control and computer power to
process electronic signals into high quality images. X-rays have
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RACA Journal I March 2020
been known experimentally and applied in practical ways for far
longer than magnetic resonance radiation although the name
‘X-rays’ came into being only in 1895 when the German scientist,
Wilhelm Röentgen, named it X-radiation to signify an unknown
type of radiation which he could not sufficiently identify. The
name caught on and has remained unchanged.
Röentgen is also credited with discovering their medical use
when he made a picture of his wife's hand on a photographic
plate which was the first photograph of a human body part
using X-rays.
In recognition of his pioneering work and research concerning
X-rays, Röentgen was awarded the first ever Nobel Prize for
physics in 2001. Modern scanning using X-rays, referred to as
radiography for medical applications, is now called CT scanning
which stands for ‘computerised tomography’.
A CT scan works by taking multiple X-rays at various angles
and then utilises those X-rays to form a three-dimensional image
of whatever organs or organ systems are being examined. A
computer examines all of the various X-rays taken at different
angles and processes the images to form a three-dimensional
computer model.
MRIs use and send radiofrequency waves into the body or
body parts positioned inside intense magnetic fields produced
by high amperage, supercooled coil windings. The magnetic
fields line up internal organ atoms either in a north or south
position with a few atoms that are unmatched (keep spinning
in a normal fashion). When radiofrequency radiation is then
applied the unmatched atoms spin in an opposite direction, and
when the radiofrequency is turned off, those unmatched atoms
return to the normal position which involves energy emissions.
These emissions send signals to a computer programmed to
transform the signals into an image.
MRI scanners are particularly well suited to image the non-
bony parts or soft tissues of the body. The brain, spinal cord and
nerves, as well as muscles, ligaments, and tendons are seen much
more clearly with MRI than with regular X-rays and CT, and for this
reason MRI is often used to image knee and shoulder injuries.
In the brain, MRI can differentiate between white matter
and grey matter and can also be used to diagnose aneurysms
and tumours. Because MRI does not use X-rays or other ionising
radiation, it is usually the choice when frequent imaging is
required for diagnosis or therapy.
One kind of specialised MRI, functional Magnetic Resonance
Imaging (fMRI) is used to observe brain structures and determine
which areas of the brain ‘activate’ (consume more oxygen) during
various cognitive tasks. It is used to advance the understanding
of brain organisation and offers a potential new standard in
assessing neurological status and neurosurgical risks.
Although as mentioned, MRI does not emit the ionising
radiation that is found in X-ray and CT imaging, it does employ
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