Abstract: A marking device for use in radiation therapy includes a longitudinal axis and a plurality of individual marking members. Each of the plurality of marking members includes a marking tip and a supply of marking fluid, such as an ink. disposed in each marking member. Each of the plurality of marking members is removably positioned relative to the others in succession along the longitudinal axis. In some embodiments, the marking device includes a hollow elongated body having a first end and a second marking end defining an opening, and the plurality of individual marking members are arranged in succession along the hollow body. In other embodiments, each marking member includes a body defining a recess adapted to receive a marking tip of another marking member, and each body includes a connector adapted to releasably interconnect adjacent marking members.