The Absorbed Dose in Cylindrical Cavities within Irradiated Bone

A method is presented of measuring the energy absorbed near an interface in a medium exposed to a beam of X rays. The method developed is not simple and involves unavoidable inaccuracies since it employs a biological indicator. Nevertheless, direct measurements of the energy absorbed in small cavities within a high atomic number material have been made. A theoretical method for calculating the energy absorbed in cylindrical cavities has been developed. To do this, certain simplifying assumptions have been made, and in spite of these assumptions, awkward integrals are involved requiring numerical integration on a computer. The results of these calculations show good agreement between the experimental and theoretical results. Since the experimental method is very difficult and time consuming, it is not recommended as a routine method of measuring the energy absorbed near an interface. However, the good agreement between the experimental and theoretical results indicates that for most problems of this nature in radiotherapy and radiobiology, calculated values of the absorbed dose can be used with confidence. The data for monoenergetic photons may be used to calculate the absorbed dose for any continuous spectrum of radiation.