Designing and casting combined shielding/transmission blocks

It is sometimes necessary to limit the irradiation of closely located organs to different dosages because they have different levels of tolerance. One way this can be done is by using shielding blocks that transmit a specific portion of the beam through different sections of the block. This paper will focus on situations where this need may arise, and, on how blocks of varying thicknesses can be designed and cast using basic mould room facilities. Some of the problems and pitfalls encountered while using this basically straightforward technique are discussed. Further uses for such blocks are suggested. 1 refs., 9 figs