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

Introduction: It is well known that neutrons are more effective treatments than photons to treat hypoxic tumors due to the interaction with the nucleus and the production of heavy particles. This study aimed to evaluate the suitability of Boron neutron capture therapy (BNCT) for the treatment of lung cancer. To this end, neutron dose distributions were calculated in lung tumor volume and peripheral organs at risk (OARs). Material and Methods: Dose distribution to treat lung cancer was calculated by MCNPX code. An elliptical tumor with a volume of 27cm^3 was centered in the left lung of the ORNL phantom and was irradiated with neutron spectrums of Massachusetts Institute of Technology (MIT) and CNEA-MEC. 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 rates in the tumor were 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 for MIT. Moreover, similar results for CNEA-MEC were 1.2×10^-3, 1.6×10^-3, 2.5×10^-3, and 3.7×10^-3 Gy/s. The 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 bins of spectrums, the neutrons flux is decreased as it penetrates the lung. Conclusion: An increase in boron concentrations in tumors increases the absorbed doses while deteriorates dose uniformity. The results show that the MIT source is well suited to treat deep lung tumors while maintaining the OARs’ dose within the threshold dose.