Prompt imaging of absorbed dose in tissue-equivalent gel-phantoms and new toolkit for 3D data visualization

We have developed a general method for obtaining high level full volumetric shape and shape-transforming information from multi image sequences of absorbed dose, measured in tissue-equivalent phantoms. Shape and volume results are comparable to the usual treatment planning systems or Monte Carlo simulations for sub-millimeter verification. We carried out experiments regarding Fricke-gel dosimeters, i.e. Agarose-gel dosimeters in which a ferrous sulfate solution (Fricke solution) and a metal ion indicator (Xylenol Orange) are, incorporated. We have developed a prompt analysis technique based on visible-light transmittance measurements, detected through a CCD camera. Since the analysis procedures for dose determination require pixel by pixel elaboration of images and complicated processes, proper software has been developed. All images, after conversion to 2D numerical matrices, are processed using complex 2D filters. The so obtained results are composed in 3D visualization. By applying algorithms like marching cubes, the software gives the possibility of obtaining several surfaces rendered at different isodose levels, with desired sections. The major advantages of this method for absorbed dose measurement and visualization are related to the understanding of the morphology of 3D 'in vivo' experimental dosimetry. Tests performed within GammaKnife stereotactic facilities show very satisfactory results.