Room: Exhibit Hall | Forum 6
Purpose: The aim of this study is to determine the contrast enhancement of MV portal imaging in nanoparticle-enhanced radiotherapy. Monte Carlo simulation of macroscopic approach was carried out using the flattening-filter-free (FFF) and flattening-filter (FF) photon beams produced by a Varian TrueBeamÂ® linac.
Methods: Monte Carlo simulations using the EGSnrc-based code were used to predict the contrast of MV portal imaging using a heterogeneous phantom with variations of nanoparticle material (gold, platinum, iodine, silver and iron oxide), nanoparticle concentration (3 â€“ 40 mg/ml), photon beam type (FFF and FF) and beam energy (6 and 10 MV). The fractional contrast enhancement, which reflected the fractional increase of imaging contrast when nanoparticles were added to the target, was determined.
Results: Gold nanoparticles had the highest fractional contrast enhancement among other nanoparticle materials when the nanoparticle concentration, photon beam type and energy were not changed. Platinum nanoparticles had the second highest enhancement while iron oxide nanoparticles had the lowest enhancement. Moreover, the contrast enhancement was found increasing with an increase of nanoparticle concentration. For different photon beams, the FFF beam had higher contrast enhancement than the FF beam under the same beam energy. The 6 MV FFF beam had the highest fractional contrast enhancement of 0.19 (nanoparticle concentration = 40 mg/ml) and 0.02 (nanoparticle concentration = 3 mg/ml) for gold nanoparticles. Comparing the photon beam energy, the lower energy of 6 MV had higher contrast enhancement than the 10 MV for both the FFF and FF beams.
Conclusion: From the Monte Carlo results in this study, it is concluded that MV portal imaging contrast enhancement can be increased using gold nanoparticles, high nanoparticle concentration, FFF photon beam and lower photon beam energy of 6 MV compared to 10 MV.