Combined conventional X-Rays and BNCT dosimetry

M.R. CASAL; M.S.HERRERA; S. GONZÁLEZ; D.M. MINSKY

Buenos Aires, Argentina

Congreso; 14th International Congress on Neutron Capture Therapy; 2010

International Society for NeutronCapture Therapy

Presentación Oral (M. Casal)Introduction: There has been increasing interest in combining BNCT with standard radiotherapy, either concomitantly or as a BNCT treatment of a recurrent tumor that was previously irradiated with a medical electron linear accelerator (LINAC). In this work we report the simulated dosimetry of  treatmets combining X-Rays and BNCT. Materials and Methods:  First, a model of a LINAC was developed. The machine is a Siemens Primus MD-2 linear accelerator, with two photon energies, located at the Radiation Therapy Department of  the Instituto Ángel Roffo. The accelerator configuration was modeled in MCNP using the information given by the manufacturer (Siemes OCS), and the parameters of the electron beam impinging on the target were adjusted with experimental data. The measurements were performed in a water phantom with a 0.3cc PTW ionization chamber. Once a good agreement between calculations and measurements was attained, a MCNP surface source was generated between the accelerator monitor chambers and the secondary collimators that define the beam size. This source, fully compatible with NCTPlan treatment planning system, was used in a further step to perform the calculations on a CT-scan stack. This stack was voxelized using NCTPlan in the same way it is done for BNCT treatments. The neutron beam for the BNCT irradiation corresponds to an accelerator-based BNCT (AB-BNCT) beam, currently under develpment. Calculations were performed using MCNP code. The resulting dose distributions from both beams were combined and displayed with NCTPlan. Dose Volume Histograms (DVH´s) were calculated and displayed with DVHTool, developed in our institution. Results and Discussions:.   The accelerator X-Ray source was combined with the model generated by NCTPlan, and calculations have been succesfully carried out. The resulting dose matrix was compatible with NCTPlan, and the dose distributions could be displayed and DVH´s calculated. The developed tool proved suitable for evaluating combined X-Rays and BNCT treatments, either as a mixed therapy, or as the result from a BNCT re-irradiation of a site previously treated with conventional radiotherapy.