Instrumental and technical notes; new values of constants for use in calculating isodose curves by the method of Meredith and Neary.

One widely used method of calculating isodose curves is that developed by Meredith and Neary (1944). This method depends on calculated values of two constants, M and , based on a now out-dated survey of depth dose and back-scatter values reported by Mayneord and Lamerton (1941). It is the purpose of this paper to present revised values of these constants. Reference can be made to the original papers by Meredith and Neary for explanation of these constants and their use in calculating isodose curves. Meredith and Neary find that the variation of the dose of the secondary radiation for a standard primary surface dose with field radius r, can best be represented by the expression where M and λ are arbitrary constants determined for each set of irradiation conditions and for each depth. Kn is the modified Bessel function of the second kind, of order n. In plotting the scatter radius function F(λr) = (1−λrK1(λr)), the values of K1(λr) are taken from tables published by Flugge (1954). The scatter integrals for ...