Physical Factors of Low Voltage “Contact” Roentgen Therapy

Abstract

MOST of the improvements in radiation therapy have been instituted with the aim of increasing the dose to the lesion without causing any harmful effects to the healthy tissue. In irradiating surface conditions and those accessible through the cavities of the body or through operative procedure this object may be attained by using rays at shorter skin-target distance and of longer wave lengths, that is, of less penetrability, thereby reducing the dose to the underlying normal tissue. Until recent years, before the advent of shockproofing, it has not been possible to reduce materially the target-skin distance with safety. The so-called Grenz-ray tube was devised by Bucky to permit operation at from 10 to 12 kv., using an 8 to 10 cm. distance, yet its use is limited to the treatment of only the most superficial layers of skin as the depth dose is only about 15 per cent at 1 mm. depth.2 Furthermore, the necessity of making the x-ray tube wall extremely thin to minimize inherent absorption makes the apparatus ...