The Effective Atomic Number of Tissue Equivalent Materials

The photoelectric cross-section for the tissue equivalent materials is in the first place dependent on the effective atomic number calculated on the basis of the exponent m, where m varies with photon energy and the elements involved.
In the present work, a graphical method was used to evaluate the effective atomic number Zeff for any material at any photon energy independent on the value of the parameter m. The results are in good agreement with the calculated values using the known empirical formula.