Toossi MTB et al. / GZP6-TG43 177 B C FIGURE 5. Dose distributions (Gy) obtained by MC simulations (blue lines) and superimposition method (red lines) for GZP6 sources: (a) source No. 1; (b) source No. 2 and (c) source No. 5. Isodoses of 1-20 Gy are contoured in the figure and since the contours by the two methods are overlapped in many points, are almost not distinguishable. TABLE 6. 2D anisotropy functions for GZP6 60Co source (number 3) calculated by Monte Carlo code 1 0.858 … 0.990 0.992 1.011 1.025 1.000 0.995 0.978 1.019 … … … … … … … … 2 0.849 0.893 0.956 0.973 0.990 0.989 0.990 0.995 0.994 1.000 1.000 0.998 0.993 0.995 0.992 0.977 0.958 … 3 0.863 0.898 0.957 0.974 0.988 0.986 0.985 1.000 0.995 1.000 1.004 1.001 0.995 0.998 0.992 0.979 0.958 0.881 r (cm) 4 0.904 0.901 0.957 0.970 0.989 0.990 0.982 1.002 0.992 1.000 1.004 0.999 0.993 0.998 0.990 0.978 0.956 0.876 5 0.927 0.893 0.959 0.970 0.991 0.999 0.995 1.010 1.001 1.000 1.007 1.001 1.001 1.004 0.998 0.984 0.963 0.884 10 0.913 0.870 0.963 0.998 0.994 1.002 1.001 1.005 1.007 1.000 1.006 1.010 1.015 1.000 0.993 0.995 0.954 0.883 A  (degrees) 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 Our results are indicating that the dose rate con- stant, radial dose function and anisotropy function for GZP6 and Ralstron (type 2) 60Co sources are comparable. While the value of dose rate constant for the GZP6 and Ralstron (type 2) 60Co sources are close to that for the microSelectron 192Ir source (Table 3), radial dose function fall off for the 192Ir source is less steep compared to the cobalt sourc- es especially for lower radial distances from the source ( in Figure 3). It can be also noticed from the Figure 4 that the two cobalt sources have more iso- tropic anisotropy functions than the iridium source. The dosimetric data presented in this study for GZP6 source (number 3) can be utilized in clinical practice of the source and towards the improve- ment of its treatment planning system. Radiol Oncol 2012; 46(2): 170-178.