Evaluation of Dose Distribution in Lung Tumor Radiotherapy with Boron Neutron Capture Therapy

Abstract

Introduction: Boron neutron capture therapy (BNCT) is recommended to treat glioblastoma. It is well known that neutrons are more effective treatment than photons to treat hypoxic tumors due to interaction with the nucleus and production of heavy particles. Objective: To evaluate the suitability of BNCT for treating lung cancer, neutron dose distributions was calculated in lung tumor volume and in peripheral organs at risk (OARs).Materials and Methods: Dose distribution to treat lung cancer was calculated by MCNPX code. An elliptical tumor with volume of 27cm3 was centered in the left lung of ORNL phantom and was irradiated with a rectangular field of neutron. Recommended neutron spectrums of MIT and CNEA-MEC were used as a neutron source. The tumor was loaded with different concentrations of Boron 0, 10, 30 and 60 ppm to evaluate the delivered dose to OARs. Results: neutron absorbed dose rate in the tumor was 2.2×10-3, 2.6×10-3, 3.4×10-3 and 4.7×10-3 Gy/s for boron concentrations of 0, 10, 30 and 60 ppm, respectively in MIT. Moreover, the similar results in CNEA-MEC was 1.2×10-3, 1.6×10-3, 2.5×10-3 and 3.7×10-3 Gy/s. Among all, heart absorbed the maximum neutron dose rate of 1.7×10-4 and 1.6×10-4 Gy/s in MIT and CNEA, respectively. For all energy’s bins of spectrums, the neutrons flux is decreased as it penetrates the lung. Conclusion: The implemented model was successful in calculating the dose to organs using BNCT. An Increase in boron concentrations in tumor results in an increase in the absorbed doses while dose uniformity deteriorates. Results showed that the MIT source is well suited to treat deep lung tumors while maintaining the OARs’ dose within the threshold dose.