Characterization of the optical properties and stability of Presage following irradiation with photons and carbon ions.

摘要

BACKGROUND: The on-going development of both intensity-modulated radiotherapy (IMRT), including the more recent intensity-modulated arc therapy, as well as particle beam therapy, has created a clear need for accurate verification of dose distributions in three dimensions (3D). Presage is a new 3D dosimetry material that exhibits a radiochromic response when exposed to ionizing radiation. In this study we have 1) developed an improved optical set-up for measurements of changes in OD of Presage point dosimeters, 2) investigated the dose response of Presage for photons and carbon ions in the therapy range, 3) investigated the dose response of Presage for photons in the kGy range and 4) investigated the fading (i.e. bleaching) of Presage postirradiation. MATERIALS AND METHODS: Presage was examined in 1 x 1 x 4.5 cm(3) optical cuvettes; a cuvette holder assured accurate repositioning, and the optical setup included a reference detector to take into account laser intensity fluctuations. The cuvettes were measured pre- and postirradiation for a two week period. RESULTS: A linear response was observed between dose and optical response between 0 Gy and 100 Gy for gamma-radiation from Co-60 and for carbon ions (both plateau and SOBP) from 0 to 20 Gy. The dosimeter was found to have a saturation dose of approximately 100 Gy for photons. A linear energy transfer (LET) effect was not observed in the dose response of different LET radiation. The postirradiation change in optical fading was found to be 0.5% DeltaOD/day. CONCLUSIONS: Our study shows that Presage remains a dosimeter of interest for radiation therapy with other particles as well as photons in the therapy dose range.