A comparison of recent stopping power tables for light and medium-heavy ions with experimental data, and applications to radiotherapy dosimetry

By means of statistical analysis, we compare the recent stopping table from the International Commission on Radiological Units (ICRU Report 73), Ziegler's SRIM 2003 table and our MSTAR table with experimental data from our large data base, for ions from Li-3 to Ar-18. We compare the three tables with the same targets and within the same specific energy range (0.025-1000 MeV/nucleon), corresponding to the range of the ICRU table. We describe the agreement by the mean normalized difference Delta and by its standard deviation sigma. We find that MSTAR and SRIM describe the experimental data about equally well, with sigma between 6% and 8% for the region 0.025-1000 MeV/nucleon. For the ICRU table, vertical bar Delta vertical bar and sigma are mostly larger than for SRIM and MSTAR, with a between 8% and 23% for the same region. For solid compounds, the agreement is similar as for solid elements. We discuss the stopping power ratio s(water,air) which is important for external beam radiotherapy dosimetry, for protons and heavier ions up to Ar. At the beam energies required for therapy, we find that this ratio (neglecting secondaries) is essentially given by the mean excitation energies (I values) of water and air, and we find approximately 1.12 < s(water,air) < 1.14. (c) 2006 Elsevier B.V. All rights reserved.