Irradiating with a prosthesis or metal pin in the radiation treatment field

This is a case study of a patient who had a liposarcoma of the tibia and also had a titanium pin directly in the treatment field. A total midline dose of 63 Gy was prescribed. The effects of the pin in the treated area was examined. Four different methods were used to examine and verify the delivered dose: (1) Treatment planning computerized isodose curves, (2) A parallel plate ion chamber and polystyrene phantom, (3) TLD, and (4) Film dosimetry. The results from all four methods of dose examination are compiled and are used to make a decision on what to do about the dose non-uniformity due to the dense titanium pin. If a prosthesis or metal pin is in the treatment area, one must determine the composition of the pin. Then one should verify or examine the results of the dose perturbations produced. One may or may not want to change the original dose prescription but the dose throughout the irradiated volume will be changed due to the metal pin. It is important to evaluate these effects, as discussed in this article, to accurately deliver a prescribed dose.