Water and tissue equivalence properties of biological materials for photons, electrons, protons and alpha particles in the energy region 10 keV–1 GeV: a comparative study

Abstract

Purpose: To compare some biological materials in respect to the water and tissue equivalence properties for photon, electron, proton and alpha particle interactions as means of the effective atomic number (Z_eff) and electron density (N_e).

Methods: A Z-wise interpolation procedure has been adopted for calculation of Z_eff using the mass attenuation coefficients for photons and the mass stopping powers for charged particles.

Results: At relatively low energies (100 keV–3 MeV), Z_eff and N_e for photons and electrons were found to be constant while they vary much more for protons and alpha particles. In contrast, Z_eff and N_e for protons and alpha particles were found to be constant after 3 MeV whereas for photons and electrons they were found to increase with the increasing energy. Also, muscle eq. liquid (with sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) within low relative differences below 9%. Muscle eq. liquid (without sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) with difference below 10%.

Conclusions: The reported data should be useful in determining best water as well as tissue equivalent materials for photon, electron, proton and alpha particle interactions.

Keywords:

• Alpha particle
• effective atomic number
• electron density
• electron
• photon
• proton

Disclosure statement

The author reports no conflict of interest. The author alone is responsible for the content and writing of the paper.