Gold nanoparticles can be used to increase the dose of the tumor due to its high atomic number as well as being free from apparent toxicity. The aim of this study is to evaluate the effect of distribution of gold nanoparticles models, as well as changes in nanoparticle sizes and spectrum of radiation energy along with the effects of nanoparticle penetration into surrounding tissues in dose enhancement factor DEF. Three mathematical models were considered for distribution of gold nanoparticles in the tumor, such as 1-uniform, 2- non-uniform distribution with no penetration margin and 3- non-uniform distribution with penetration margin of 2.7 mm of gold nanoparticles. For this purpose, a cube-shaped water phantom of 50 cm size in each side and a cube with 1 cm side placed at depth of 2 cm below the upper surface of the cubic phantom as the tumor was defined, and then 3 models of nanoparticle distribution were modeled. MCNPX code was used to simulate 3 distribution models. DEF was evaluated for sizes of 20, 25, 30, 50, 70, 90 and 100 nm of gold nanoparticles, and 50, 95, 250 keV and 4 MeV photon energies. In uniform distribution model the maximum DEF was observed at 100 nm and 50 keV being equal to 2.90, in non-uniform distribution with no penetration margin, the maximum DEF was measured at 100 nm and 50 keV being 1.69, and in non-uniform distribution with penetration margin of 2.7 mm, the maximum DEF was measured at 100 nm and 50 keV as 1.38, and the results have been showed that the dose was increased by injecting nanoparticles into the tumor. It is concluded that the highest DEF could be achieved in low energy photons and larger sizes of nanoparticles. Non-uniform distribution of gold nanoparticles can increase the dose and also decrease the DEF in comparison with the uniform distribution. The non-uniform distribution of nanoparticles with penetration margin showed a lower DEF than the non-uniform distribution without any margin and uniform distribution. Meanwhile, utilization of the real X-ray spectrum brought about a smaller DEF in comparison to mono-energetic X-ray photons.

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Purpose: Skyshine radiation dose equivalent dose rate is known as scattered radiation by the room above air to points at the ground level points outside the Linear Accelerator (LINAC) room. Our aim was to estimate skyshine around the LINAC-based radiotherapy by a 4MV LINAC photon beam. Materials and Methods: Monte Carlo (MC) MCNP code calculation was conducted to skyshine at the control room, 60Co treatment room, physics, and simulator rooms. National Council on Radiation Protection and Measurements (NCRP) 151 was also used and it reported analytical formulation methods for photon beam calculation. A Flattering Filter (FF) equipped and Flattening Filter-Free (FFF) LINACs photon beams were derived and differences and agreements were discussed. Results: The results showed high skyshine for FF equipped relative to FFF LINACs. This effect may be attributed to photon beam hardening by FF in the LINAC head and higher transmission through the ceiling shield and more presence of photons on the roof above the air. NCRP 151 method results were higher than MC simulated photon beam skyshine dose equivalent dose rate and it may be the cause of the inflexible analytical method in contrast to MC simulation. Finally, FFF and FF-equipped LINACs result in skyshine compared and they compared to NCRP 151 report. MC simulation performed reasonably in estimation in different conditions. Conclusion: Our results showed that FF-equipped skyshine is higher than FFF LINAC and NCRP 151 is an inflexible method that does not take some effective parameters into account and calculates skyshine higher.

Background The effect of extremely low frequency electric field on cancer cell proliferation is studied in-vitro. Methods Prostate cancer cell culture type Du-145 has been grown in the form of spheroids. It is shown that ELF with 50Hz frequency is effectively suppressing the growth of spheroids and finally reduces their size. Results It is observed that low voltage low frequency electric filed applied for at least 2 hours a day over one week can stop the growth or even reduce the volume of multi-cellular tumor spheroids significantly. No effect for the case of electric field presence in order of 10 -30 minutes per day has been observed.

Recent studies on boron neutron capture therapy (BNCT) have focused on investigating the appropriate neutron sources based on accelerators for neutron production, such as 7Li(p,n)7 Be. The therapeutic abilities of BNCT have been studied for the possible treatment of lung cancer using thermal and epithermal neutron beams. For neutron transport, the Monte Carlo N-particle transport code was used, and doses in the organs of different Oak Ridge National Laboratory phantoms were evaluated. The right lung was meshed with voxels to obtain depth-dose distributions using 1 eV, 10 eV, 100 eV, 1 keV, 5 keV, 8 keV and 10 keV energy sources. These results suggest that BNCT with an epithermal neutron beam can be used to treat lung cancer. By evaluating the biological dose rate and dose-depth distribution curves in healthy tissues and tumors by simulating a lung phantom, the quantities in the phantom were also evaluated. Our calculations show that with increasing boron concentration applied to the tumor, the dose is increased and the 100 eV energy source has the greatest effect on the tumor dose.