A comparative examination of three Alderson phantoms by means of radiograms and computer tomograms shows that there are significant differences between the individual phantoms. Phantom I, for example, is inferior to phantom II because of the bad insertion of the bones into the surrounding plastic material (covered by air bubbles) and the inclusions of air in the soft parts. All phantoms have a rather strong osteoporosis of the skeleton which is most probably due to the production method [1,2]. Furthermore, the average absorption coefficients of the soft tissues show remarkable differences from one phantom to another.
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