Evaluation of dose enhancement with gold nanoparticles in kilovoltage radiotherapy using the new EGS geometry library in Monte Carlo simulation

Purpose: This study compared the dose enhancement predicted in kilovoltage gold nanoparticle-enhanced radiotherapy using the newly developed EGS lattice and the typical gold-water mixture method in Monte Carlo simulation. This new method considered the gold nanoparticle-added volume consisting of solid nanoparticles instead of a gold-water mixture. In addition, this particle method is more realistic in simulation. Methods: A heterogeneous phantom containing bone and water was irradiated by the 105 and 220 kVp x-ray beams. Gold nanoparticles were added to the tumour volume with concentration varying from 3-40 mg/mL in the phantom. The dose enhancement ratio (DER), defined as the ratio of dose at the tumour with and without adding gold nanoparticles, was calculated by the gold-water mixture and particle method using Monte Carlo simulation for comparison. Results: It is found that the DER was 1.44-4.71 (105 kVp) and 1.27-2.43 (220 kVp) for the gold nanoparticle concentration range of 3-40 mg/mL, when they were calculated by the gold-water mixture method. The DER was slightly larger and equal to 1.47-4.84 (105 kVp) and 1.29-2.5 (220 kVp) for the same concentration range, when the particle method was used. Moreover, the DER predicted by both methods increased with an increase of nanoparticle concentration, and a decrease of x-ray beam energy. Conclusion: The deviation of DER determined by the particle and gold-water mixture method was insignificant when considering the uncertainty in the calculation of DER (2%) in the nanoparticle concentration range of 3-40 mg/mL. It is therefore concluded that the gold-water mixture method could predict the dose enhancement as accurate as the newly developed particle method.

Automated summary

The study compared the dose enhancement predicted by the newly developed particle method and the gold-water mixture method in Monte Carlo simulation for kilovoltage gold nanoparticle-enhanced radiotherapy. Results showed that both methods yielded similar dose enhancement ratios within the uncertainty range for nanoparticle concentrations ranging from 3-40 mg/mL.