Effect Of Respiratory Motion And Dynamic Boron Distribution On Dosimetry Of Boron Neutron Capture Therapy

Boron neutron capture therapy(BNCT)is a binary targeted cancer treatment way,which has unique therapeutic advantages for recurrent and inoperable malignancies in principle.The BNCT dose is determined by the neutron flux and boron concentration.The change of these two parameters during the treatment has an impact on the consistency of the treatment dose and the planned dose.In this study,we explored the four-dimensional(4D)dosimetry of BNCT based on the dynamic changes of lungs during the treatment of lung cancer and the dynamic distribution of boron drugs during BNCT.Respiratory motion modal based on 4D CT and non-uniform dynamic boron distribution model based on PET images was constructed.The Monte Carlo software TOPAS was used to obtain the dose distribution at different times.The main research contents and results are as follows:1)The influence of respiratory motion parameters on lung cancer with BNCT was studied.The dosimetric effects of single breathing movement direction and amplitude on BNCT were explored.The results showed that the tumor movement along the neutron beam axis had a greater effect on the tumor dose in different phases.Tumor dose differences increased with the tumor motion increases.Subsequently,the results showed that the difference between the 4D dose and the reference phase dose can reach 3% through the study of three real patient cases,and if considering other error factors during treatment,the total dose error may reach 5%.2)The effect of respiratory motion on the dose difference under different treatment conditions was studied.The dosimetric effects of respiratory motion under different tumor volume,J/?,and irradiation field conditions were explored.The results showed that the dosimetric effect of respiratory motion was greater as the tumor volume became larger.There was little difference on the dose effect of respiratory motion under different neutron source J/?.The tumor dose deviation caused by respiratory motion under the double-field plan is much higher than that of the single-field plan.3)The effect of non-uniform dynamic boron distribution on BNCT dosimetry was studied.The dose distribution under uniform and non-uniform boron distribution settings was explored,and the results showed that the uniform boron concentration setting overestimated the low-dose area of the tumor and underestimated the high-dose area of the normal tissue.Compared the dose difference at the set of dynamic and single boron distribution in the boron uptake between increasing stage and stationary stage,showed that there was a dose difference under the two settings,but the dose difference obtained in the stationary phase was smaller.This article first explored the four-dimensional dosimetry of BNCT taking the dynamic changes of organ and boron distribution into account during BNCT treatment,determined the dosimetric effect of respiratory motion parameters and treatment conditions on lung cancer treatment of BNCT,and preliminary discussed it under the non-uniform dynamic boron distribution in BNCT.The results provided some references and suggestions for the evaluation of BNCT dynamic dose in clinic.