Comparison of dosage distributions obtainable with 400 kVp X rays and 22 MeV X rays.

For the past year a 22-MeV betatron has been in operation in the Physics Department of the University of Saskatchewan. During this time it has been used for research in nuclear physics and in medical physics. The distribution of radiation within a water phantom has been carefully measured by some of the present authors (1949). The clinical possibilities of combinations of these distributions are considered in this paper and compared with those obtainable with conventional X rays generated at 400 kVp. For the machine to be of use clinically, it is necessary that the radiation from the betatron be carefully collimated. This has been done by the use of a laminated lead shield between the poles of the betatron and a solid lead shield 3 in. thick in front of the betatron. Through these shields was cut a channel into which could be inserted any one of a number of removable lead plugs. These lead plugs were cast with openings which would yield appropriate X-ray fields at distances of 70 and 105 cm. from the foca...