Three-dimensional determination of absorbed dose by spectrophotometric analysis of ferrous-sulphate agarose gel

We describe a technique to obtain three-dimensional (3-D) imaging of an abs orbed dose by optical transmittance measurements of phantoms composed by ag arose gel in which a ferrous sulphate and xylenol orange solution are incor porated, The analysis of gel samples is performed by acquiring transmittanc e images with a system based on a CCD camera provided with an interference filter matching the optical absorption peak of interest. The proposed techn ique for 3-D measurements of an absorbed dose is based on the imaging of ph antoms composed of sets of properly piled up gel slices. The slice thicknes s was optimized in order to obtain a good image contrast as well as a good in-depth spatial resolution. To test the technique, a phantom has been irra diated with a collimated gamma-beam and then analysed. Proper software was adapted in order to visualise the images of all slices and to attain the 2- D profiles of the dose absorbed by each slice. (C) 1999 Elsevier Science B. V. All rights reserved.