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

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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) and Imaginis.com state that: “the first clinical CT scanners were installed between 1974 and 1976.” The original systems were dedicated to head imaging only, but "whole body" systems with larger patient openings became available in 1976. CT became widely available by about 1980. According to Imaginis.com, at this present time there are approximately 6,000 CT scanners in the United States and about 30,000 worldwide. However, it should be noted that many third-world counties do not have the financial capability to purchase CT scanners and as a result do not posses them.

The first consignment of CT scanners developed by the EMI took several hours to acquire the data for a single scan. In addition, it would take days to reconstruct a single image from this raw data. Bell J. (2006), suggest that modern CT scanners can collect up to 4 slices of data in about 350ms and reconstruct a 512 x 512 matrix from millions of data in less than a second.

Since its development 36 years ago CT has made advances in speed, patient comfort and resolution .A bigger volume can be scanned in less time and artefacts can be reduced as faster scans can eliminate faults caused from patient motion. Another advance took place in 1987. Bushong C.S (2004) suggests that, in the original CT scanners the x-ray power was transferred to the x-ray tube by high voltage cable; however modern CT scanners use the principle of slip ring. This is explained in more detail under ‘advances’. Figure 1.1 (below right) shows what a modern CT scanner looks like.    

CT examinations are now quicker as well as being more patient-friendly. Much research has been undertaken in this field, which as a result has led to the development of high-resolution imaging for diagnostic purposes. In addition, the research has also reduced the risk of radiation by being able to provide good images at the lowest possible x-ray dose.

Principles and Components of CT:

CT scanners are based on the x-ray principle; x-rays are high-energy electromagnetic waves which are able to pass through the body. Roberts P.D (1990) states, that as they are absorbed or attenuated at different levels, they are able to create a matrix of differing strength. In x-ray machines this matrix is registered on film, whereas in the case of CT the film is replaced by detectors which measure the strength of x-ray.

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To understand how a CT scanner works in more detail, I shall start by looking at the equipment used. Firstly, we must analyse the basic components which make a CT scanner work. These are the gantry, operating console and a computer. Figure 1.2 shows the order in which the information passes.

Figure 1.2 shows only basic components; other components will be explained later in the course of this report. Arguably, the most important part of a CT scanner is ...

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