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CT History

CT Introduction CT History CT how it works CT patient info

CT uses x-rays to make detailed anatomical image slices of the body. X-rays were discovered in 1895 by Wilhelm Conrad Roentgen but it wasn’t until the 1972 that CT was invented by Godfrey Hounsfield.

As a boy, Hounsfield developed a keen interest in mechanical and electrical gadgets while growing up on his father's farm. He joined EMI laboratories (England) in 1951 and in 1967 he envisioned extending the capability of a computer so that it could interpret X-ray signals, in order to make two-dimensional images of complex objects such as the human head. This idea led to the development of CT in 1972.

 

 

 

 

 

Godrey Hounsfield pictured with an early CT scanner

 

 

The initial CT scanner developed by Hounsfield took hours to obtain the data for a single slice and then took days to recreate this data into a single image. The scanner was also limited to scanning the head. In 1974 the first CT scanners for clinical practice were installed and in 1976 the first full body scanners were developed. Houunsfield was jointly awarded the Nobel Prize for medicine along with Allan Cormack in 1979. By the 1980’s CT scanning was widely accepted and used throughout the world for medical investigation and diagnosis.

Since its invention CT has been under constant research and development. As a result much progress has been made in improving the speed, image quality (resolution) and patient comfort of CT scanning.

                                

Early low resolution CT scanning         More recent higher resolution CT scan     Latest high detailed CT angiography

With improving CT scan times the advantage is that more detailed scans of the body can be performed in less time. Additionally faster scan times give more accurate images as they help eliminate inaccuracy caused by patient motion such as breathing and bowel movement. 

Conventional CT scanners are limited in that the rotating frame that holds the x-ray tube is unable to turn more than 3600 due to the arrangement of power cables supplying the x-ray tube. Therefore after each image slice the frame has to stop and rotate back to the starting position before another body slice can be imaged. During this time the patient is advanced a set distance through the CT scanner. This limitation was overcome in the mid 1980’s by the development of the power slip ring.  The power slip ring allows continuous rotation of the x-ray tube, with continuous movement of the patient through the CT scanner in a process known as spiral or helical CT scanning. Spiral CT gives faster scan times and allows three-dimensional imaging, such as of blood vessels - CT angiography.

The latest generation of CT scanners being developed are termed "multi-slice" spiral CT scanners. These rotate the x-ray tube faster than spiral scanners and are able to obtain more data as they collect multiple splices of data with one rotation.

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