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In this report I will start by exploring the history of the Computerised Tomography (CT) scanner and the technological advances which have made this type of medical imaging one of the most successful in its field. In addition, I will give a detailed expla

Extracts from this document...

Introduction

Content Page

Page Title  Page Number

Aim………………………………………………………………………………….…2

History……………………………………………………………………...…...…...2-3

Principles and Components of CT.

Gantry…………………………………………………………………………….....4-5

X-ray tube……………………………………………………………………………...5

Three-phase generator……………………………………………………………........6

Gantry.

Collimator………………………………………………...………………………...….7

Filter………………………………………………………….…………..………….7-8

Detector……………………………………………………..……………………........8

Image formation.

Formation…………………………………..………………………………………….9

CT image…………………...……………………………………………...................10

Image reconstruction………….……………………….…………………….……10-11

Advances.

Advances and Slip Ring……….……………………….…………………………12-13

Helical Scanning……………………………...……...……………………….……...13

Applications, Advantages and Risks………………...……………….………..….14-15

Summary ……………...……...……………………….………………...……...……16

Bibliography…………………………………………………….………………..17-18

Aim:

In this report I will start by exploring the history of the Computerised Tomography (CT) scanner and the technological advances which have made this type of medical imaging one of the most successful in its field. In addition, I will give a detailed explanation of the physics used to generate and manipulate a three-dimensional image. These images are used by physicians to diagnose cancers and vascular diseases or identify other injuries within the skeletal system, which can cause millions of deaths each year.  

This area of research has been chosen because I plan to enter the world of medicine in the next academic year. Medicine is constantly changing and developing. Cost containment and limitations reimbursed for high-tech studies such as CT and Magnetic Resonance imagining (MRI) are part of the future for the health care system. For CT to grow, or at least survive, it must provide more information than other imaging modalities in a cost-effective, time-efficient manner and at this present time it is able to achieve its aim.  

History:

Computed Tomography (CT) imaging is also known as "CAT scanning" (Computed Axial Tomography). Tomography is from the Greek words "tomos" meaning "slice" and “graphia” meaning "describing". The first CT scanner was invented in Britain by the EMI Medical Laboratories in 1973 and was designed by the engineer Godfrey N Hounsfield. Hounsfield was later awarded the Nobel Peace Prize for his contributions to medicine and science.  Figure 1.0 (below left) show the first ever CT scanner produced, with its designer Hounsfield:

Foster E. (1993)

...read more.

Middle

As the three separate coils are arranged 120° apart, the oscillations of each of these are 120° out phase. This means the purple (or neutral) wire can be quite thin since the different phases add up to approximately zero.image04.png

The potential difference generated needs to be high; high potential difference has a number of advantages in CT scanners. High potential difference reduces bone attenuation (greater penetration) allowing wider range of image (larger grey scale as bone is not merely white as on normal x-ray- (this will be explained later). In addition, the higher the radiation intensity at the detectors in the gantry, the better the information acquired.

Gantry:

The Collimator:

In this section we shall look at the gantry (figure 1.3) in more detail. Figure 1.6 shows a diagrammatic representation of the inside of a gantry. image58.png

According to Foster E (1993), inside the gantry is a beam restrictor called, collimator. Beam restrictors are lead obstacles placed near to the anode of the X-ray tube (figure 1.4) and are used to control the width of the X-ray beam allowed to pass through the patient. Beam restrictors are needed as they keep patient exposure to a minimum and also reduce scattered rays. This is very important as X-rays are produced by a centre spot on the anode; they are not all produced at the same point. In addition, restrictors also maintain beam width travelling through the patient, which as a result affects the image quality (stronger beam means better image). The most effective form of a beam restrictor is a collimator. This is situated in front of the X-ray tube and consists of two sets of four sliding lead shutters which move independently to restrict the beam.image05.png

The Filters:

image06.png

By looking at figure 1.6 we can see another apparatus positioned between the collimator and the X-ray tube.

...read more.

Conclusion

The websites I used are all recommended by The University of Hertfordshire to its undergraduates in radiography. This means they are also reliable sources of information. In addition, I also used a number of well recognised radiology books. By using different sources of information, I was able to eliminate any bias or inaccurate information provided in some sources.

To sum up, I believe the information provided is accurate and reliable.

Bibliography:

Book References

  • Allday J, Adams S (2000) Advanced Physics. Oxford University Press
  • Ball J, More D.A (2006) Essential Physics for Radiographers. Blackwell Publishing
  • Bushong C.S (2004) Radiologic Science for Technologist. Mosby Inc
  • Duncan T, (1987) Physics; A Textbook for Advanced Level Students. John Murray
  • Elliott A, McCormick A (2004) Health Physics. Cambridge University Press
  • Foster E (1993) Equipment for Diagnostic Radiographer. MTP Press Limited
  • Graham T.D (1996) Principles of Radiological Physics. Churchill Livingstone
  • Ogborn et al (2000) Advancing Physics A2. Institute of Physics
  • Roberts P.D, Smith L.N (1990) Radiographic Imaging. Churchill Livingstone
  • Thompson C, Wakeling J (2003) AS Level Physics. Coordinate Group Publication.

On Line References

  • Figure 1.0 obtained from, www.catscanman.net
  • Figure 1.1 obtained from, www.mh.org.au
  • Figure 1.3 and Figure 1.4 obtained from, www.impactscan.org/slides
  • Figure 1.5 obtained from, www.koehler.me.uk
  • Figure 1.6 and Figure 1.7 obtained from www.impactscan.org/slides
  • Figure 1.8 obtained from, www.itnonline.net
  • Figure 1.9 and Figure 2.0 obtained from www.sprawls.org/resources
  • Figure 2.1 obtained from, www.csmc.edu
  • Figure 2.2 and Figure 2.3 obtained from, www.sprawls.org/resources
  • Figure 2.4, Figure 2.5 and Figure 2.6 obtained from www.impactscan.org/slides
  • www.radiologyinfo.org (25 February 2009)
  • www.imaginis.com/ct-scan/ (12 March 2009)
  • www.bbc.co.uk/dna/h2g2 (15 February 2009)
  • www.impactscan.org/slides (12 March 2009)
  • www.sprawls.org/resources (14 March 2009)

Other References

  • Synergy Magazine
  • New Scientist Magazine
  • Nature Magazine

Acknowledgements

I would like to thank Basildon and Thurrock University hospital and the University of Hertfordshire for their support and information.

...read more.

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