A study of the explicit distribution of radiation in interstitial implantations. II. Correlation with clinical results in squamous-cell carcinomas of the anterior two-thirds of tongue and floor of mouth.

Abstract

excerpt In interstitial radiation therapy, the calculation of the explicit dose distribution throughout an implant is so laborious that it is rarely done by manual methods except for model cases. Systems have been developed which permit the calculation of a single dose rate that is taken as representative of a radium implant. The two methods in common use are the Quimby system (1) and the Paterson-Parker system (2). Both require that the needles be implanted to form standard geometrical patterns with the radium distributed according to the “;rules”; of the system. Ideal geometry, however, is seldom possible in practice; indeed, in some cases there is a deliberate deviation from rigid geometry in order to fit the anatomy or the disease. In any case, only one dose rate is given for an arrangement of needles about which there is a complex radiation distribution. As a result, the radiotherapist often must make decisions based on inadequate knowledge of the dose delivered from an interstitial implant. The adve...