F. Foppiano, M.G. Pia, M. Piergentili Medical Linac IEEE NSS, October 2004, Rome, Italy

Intensity modulated radiation therapy step and shoot Dose distribution more homogeneous within the PTV Much sharper fall-off of dose at PTV boundary Inhomogeneous dose distribution to treat concave surface Progress in 3D medical imaging Normal tissues exposed to high doses can be reduced Beam aperture is shaped to the irregular form of the target Photon fluencies are modulated Head and neck breast prostate M.Piergentili

Problem Statement and General plan Geant4 AIDA/Anaphe OO tecnology Specific software process functionalities design Advanced software Microscopic validation of Geant4 processes Dosimetric validation of the sistem Experimental measurements Validation of the dosimetric system planning and developing the dosimetric system simulationanalysis + DIANE Statistical toolkit Commercial systems Analytic algoritms Es.: Eclipse, Plato speedy, but contain approximations Determine the dose distributions given in a phantom by the head of a linear accelerator M.Piergentili

Dosimetric system The actual analysis produces some histograms from which the user can calculate the Percent Depth Dose (PDD), the lateral profiles at the following depths in the phantom: 15 mm, 50 mm, 100 mm and 200 mm, and the isodoses curves in a plane Gaussian distribution for energy and momentum of primary particles Each pair of jaws can be rotated through an axis that is perpendicular to the beam axis The user can choose the position of every single leaf M.Piergentili

Dosimetric system Flattening filter MLC Primary collimators and target M.Piergentili

Design  Flexibility  Extensibility  Distributed responsibility Decorator M.Piergentili

Software tecnologies Mapped onto ISO Dinamic and static dimension Based on use cases Rational Unified Process Specific software process for this dosimetric system Software process artifacts M.Piergentili

Experimental measurements with ion chamber IAEA 398 Percent Depth Dose Squared fields 5x5 cm, 10x10 cm, 40x40 cm PTW Flexible. PTW MP3 M.Piergentili

Comparison with experimental data rangeDp-value -84  -60 mm  -48 mm  47 mm  59 mm  84 mm rangeDp-value -56  -35 mm  -22 mm  21 mm  32 mm  36 mm Kolmogorov-Smirnov test  events  100 CPU days on Pentium IV 3 GHz M.Piergentili

Comparison with experimental data D = 0.005; p-value = 1 rangeDp-value 0  14 mm  300 mm Kolmogorov-Smirnov test Voxels 5mm Voxels 1mm M.Piergentili

Experimental measurements with radiographics films Kodak X-Omat V films Scanner VXR16 Dosimetry Pro Software Rit 113 Grey toneOptical densityDose Spatial resolution = 89  m Field used to treat prostate cancer M.Piergentili

Comparison with experimental data film Dose distribution in a plane (dosimetric system) Isodose lines (RIT113) Isodose lines (dosimetric system) M.Piergentili

Conclusions Low-cost dosimetric system Package Low Energy Validation of physical processes in Geant4 Comparison with experimental measurements Future improvements Phase space Dynamic tecnique Thanks to Barbara Mascialino for the statistical analysis This is an Advanced Example of precision Submission of a paper to IEEE Transaction on Nuclear Science M.Piergentili