Replacement of hairpin and loop implants by optimised straight line sources.

Abstract

Remote after loading is desirable for all forms of brachytherapy but is difficult in the oral cavity because the tight curvature at the top of implanted loops impedes passage of the source. For this reason we investigated differential loading of straight catheters to simulate a conventional loop or hairpin. Using a pulsed brachytherapy remote after loader the top four dwell positions of straight catheters were given two to four times the dwell time of other source positions. This raised the reference isodose to cover the surface mucosa without significantly changing either the total volume treated or the volume receiving > 150% of reference dose when compared with conventional loop implants of equivalent source length and separation. This optimised straight line implant should therefore be amenable to remote afterloading and have similar dose/volume characteristics to loops.