Uniform analysis of dose distribution in interstitial brachytherapy dosimetry systems.

In brachytherapy, articles are published with dose and homogeneity specifications using different systems which are hard to compare. For the same "stated dose", the dose delivered, volume treated and activity chosen are not the same in different systems, due to the fact that the source placement rules are different. In this article, the authors have circumvented this problem by the use of an approach not applied hitherto, viz. by determining the value of the Uniformity index (UI) of an implant using different systems. This value takes into account the integral dose within the treatment volume and is compared with an idealized implant, where the dose is uniform and the target and treatment volumes are the same. This method of evaluation has been applied for single plane, multiple plane and cylindrical volume implants using the Manchester, Quimby and Paris systems. Although the results obtained are different, the degree of closeness of these values are striking, with some minor exceptions. Thus, it is possible to combine all the brachytherapy parameters, such as: dose, homogeneity, treatment volume within a single value to determine the quality of an implant.