RACA Journal March 2020 | Page 60

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 58 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 www.hvacronline.co.za