The Integration of Radiation Dosage and the Absorption of Energy in Tissue for X and Gamma Radiation

The problem of dosage integration has presented itself in a variety of ways to different workers in the past. Grimmett1 discussed the subject in relation to radiation protection in the case of a Radium Beam Unit, and a comprehensive survey of the integrated dosage and energy absorption was given by Gray,2 who determined the flow of energy from a radium source. The problem was considered in regard to surface absorption and erythema dose with X rays by Lauritsen,3,4 and a detailed discussion of the general aspects of the subject has been given by Mayneord5 in this journal. A method of treatment of the problem has also been outlined by the present author in Nature,6,7 and the following work gives details of the methods of calculation and the results obtained for beams of X and γ radiation. In this Institution at the present time the underlying principle adopted in the planning of treatment is to give a uniform tumour dose between 4000r and 6000r. In deep-seated lesions this can only be achieved by using a multiple field technique, and in consequence much radiation is absorbed which contributes not to the destruction of the tumour itself, but to that of the normal tissues of the body. The clinical importance of such radiation absorption has been realised for some considerable time by the medical staff here in Sheffield, and the results of the following calculations have been used in the X-ray therapy departments of the Sheffield Radium Centre.