Principle of CT( Computed tomography) scan.

The principle of CT is The internal structure of an object can be reconstructed from multiple projection of the object.

                     A X-ray tube emitting a fan beam from a small focus is coupled to a radiation detector. The x-ray tube and detector are moved together so the plane of interest object is scanned. The tube potential is about 120- 150 kVp and the beam pulse rate of 100 pulse per second. The x-ray beam are filtered. The detector are individually collimated. The detector are made either solid state crystal or xenon gas ionization chamber. Each detector are measured the intensity of the transmitted x-ray beam and called projection. About 100000 measurements are made and recorded in computer. The measurements are reconstructed with the help of algorithm and the final image is display on TV monitor.

The basic goals of computed tomography is given below.

 The image are cross sectional.

 To overcome the superimposition of structure.

 To improve the contrast of the image

 To measure small difference in tissue contrast.

 Not influenced by the property of neighboring region.