The invention relates to a radiation therapy delivery system for use in effecting radiation therapy of a pre-selected anatomical portion of an animal body in which the delivery means displaces said at least one energy emitting source along a path through at least part of one of at least one catheter in a continuous motion using a pre-determined velocity profile along said paths, said velocity profile determined by solving an optimization problem in three-dimensions defined for a function describing the spatial dose distribution. The invention relates also to a radiation therapy treatment planning system and a method for generating a radiation treatment plan for use in effecting radiation therapy of an anatomical portion of an animal body in which the movement of the radiation source through the anatomical portion is continuous.
