CT A revolution in Medical Imaging

Talk by Kim Owen - GE Medical
8 March 2006

There was a good attendance of about 60 including a number of guests and prospective members to hear this talk. Kim's job is providing clinical and technical information on the range of GE Healthcare CT scanners to Hospital Consultants, Managers and Radiographers throughout the South West and the Midlands.
Positive Negative CT

Godfrey Hounsfield invented Computerised Tomography in 1970. He built a machine with an X-ray tube that fired X-rays through a subject to a detector on the opposite side. The x-rays differentiated between various body tissues that the detector converted into a picture of lighter or darker areas. The x-rays were concentrated in a beam and the whole device rotated about the subject making it possible to compute a picture of a thin slice of the subject. Using a bull's brain, the prototype could produce a picture in this way in an hour.

By 1972 the EMI company were producing a commercial machine with a narrow beam that could produce a picture in seconds. GE took over the business and they introduced slip ring technology in 1989. This permitted continuous omni-directional rotation so that images could be produced of many slices. Beams were made narrower (to less than a millimetre), rotational speeds increased, matrices of detectors were introduced, and colour pictures computed. Soon it became possible to scan the volume of a whole body in 10 seconds producing several hundred images of slices. Using greater computational power and refined software the multiple images of slices can be converted into a single three dimensional picture.

Scanning can be used to,
  1. Detect abnormalities either in individual patients or mass screening
  2. Establish rates of deterioration by scanning at intervals
  3. Investigate internal damage eg bone fractures
  4. Work out procedures for surgery eg heart surgery
  5. Monitor the responses to treatment eg tumour shrinkage

CT is now commonly used for investigations of the liver, lungs, intestines, pancreas, kidneys, blood vessels, brains etc. Many procedures that were considered very advanced just a few years ago, for example barium meal for colons, and catheterisation for heart investigations, are being replaced. The greatest impact is in cardiac conditions that are now a major killer in the UK and growing. CT scanners are now available in every accident and emergency department and advanced machines are available to nearly half of cardiac consultants.

Kim covered a lot of ground in a very short time demonstrating considerable presentational skills and a vast knowledge of scanner engineering and clinical procedures. She patiently answered the many questions that were put to her. A major concern amongst the audience was the dosage of radiation being given to patients, particularly by repeated scanning. Kim explained that the dosage given by any scan could be pre-calculated. Dosage could be reduced on repeat scanning by accepting lower resolution images. Manufacturers were putting great effort into reducing the amount of radiation that patients were subjected to.

John Gale thanked Kim for her excellent talk. Having enjoyed the benefits of investigations by these machines, he now had a appreciation of just how good they are!

John Coneybeare