Calculated effective atomic number and Kerma values for tissue-equivalent and dosimetry materials

Abstract

The calculated value of the effective atomic number (ztau ) of 7.23 for lithium tetraborate (Li2B4O7) agrees closely with the value of 7.22 for soft tissue of composition C5H40O18N. For excised muscle specimens the experimental value (7.42) obtained by Spiers for ztau is very nearly equal to the corresponding calculated value (7.46) for the composition (ICRU) of striated muscle. A similar comparison shows that the composition for bone given by Woodard with a higher content of calcium and phosphorus gave a value of ztau =13.3, which is in closer agreement with the measured value of 13.8 obtained by Spiers. The calculated values of ztau and kerma per roentgen for lithium tetraborate and lithium fluoride for photon energies below 1 MeV show that lithium borate (Li2B4O7) is a better substitute for soft tissue than lithium fluoride.