US Patent 7357770 Expandable brachytherapy device with constant radiation source spacing

A brachytherapy device may include an expandable outer cage, an expandable inner cage positioned within the outer cage and configured to receive radioactive material at its perimeter, and a movable actuator configured to cause the outer and inner cages to expand simultaneously in response to movement of the actuator between certain positions while maintaining a substantially constant separation distance between the outer and inner cages.