Figure 11. Image processing artefact. The prosthesis in this knee adds too many extreme pixel values to the image histogram. This results in an image where the difference between prosthesis and glue, or glue and bone is not well demonstrated. Artefact remedy: in computed radiography systems that provide different modes of operation, use of a different image processing mode will alleviate this problem. For example, a semi-automatic or fixed mode will cause the image histogram to be analysed differently from a fully automatic mode and will produce a more acceptable image in cases such as this.