PPT Slide

Measurement of Noise

• object of uniform material
  • eg cylindrical water filled phantom

• region of interest (ROI)
  • mean, standard deviation (SD)

ROI - region of interest

• SD is a measure of the spread of CT numbers around the mean value ? ‘noise’
  • 95% of values within +/- 2 SD

-2 SD +2 SD

mean

CT number

number of pixels

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