CIE A Level Physics (9702) 2019-2021

Revision Notes

27.4.5 8-Voxel Cube

8-Voxel Cube

  • When a section, or slice, is taken through the body, it is divided up into a series of small units called voxels
  • The image of each voxel has a particular intensity, known as a pixel
  • The pixels are built up from the measurements of X-ray intensity from several different directions around the section of the body being studied

Building up an Image

  • Take a section made up of 4 voxels
  • Each voxel in the section has a particular intensity
    • The lower the intensity, the more X-rays are absorbed
  • X-rays are directed at the sample from one direction
  • The detector measures the sum of the intensities in the row of voxels that the X-rays were directed through
  • The process is then repeated from several different directions
  • Once this data has been collected, the ‘background’ intensity must be deducted
    • The ‘background’ intensity is the total of each set of detector readings
  • After deduction, the result must be divided by the number of views of the section minus one
    • This corrects for the extra directions of the section that were viewed

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