[Radiosensitization effect of PEGylated gold nanoparticles in orthovoltage x-ray irradiation of the MCF-7 cancerous cell line]

Due to recent advances in nanotechnology it is now possible to accumulate high atomic-number nanomaterial such as gold nanoparticles [GNPs] in cancerous cells and take advantage of their absorbed dose enhancement property as radiosensitizing agents. This study aimed to investigate the absorbed dose enhancement factor due to the presence of PEGylated GNPs under the irradiation of an MCF-7 cancerous cell line using orthovoltage X-ray beams. We synthesized GNPs with an average diameter of 47 nm and joined them to polyethylene glycol. A total of 50 micro g/mL of the pegylated GNPs were incubated with MCF-7 cells for 1, 2, 6, 12, and 24 hours, after which we compared their cytotoxicities. Then, PEGylated GNPs [50micro g/mL] were incubated with MCF-7 cells for 12 and 24 hours and their radiosensitizing effect during 2Gy delivery of 120, 180 and 200 kVp X-ray beams were compared by the MTT assay. Cytotoxicity studies showed no significant effect of GNPs on cell viability. Significant differences in cell survival were observed between the groups irradiated with and without GNPs, which lead to an average absorbed dose enhancement factor of 1.22 +/- 0.06. According to the results, there was no radiosensitization difference due to the usage of 120, 180 and 200 kVp X-ray beams. However increased incubation time increased the dose enhancement factor. By using PEGylated GNPs we can decrease the prescribed X-ray dose, yet maintain the same level of cancerous cell killing

[Electron beam dosimetry in heterogenous phantoms using a MAGIC normoxic polymer gel

Nowadays radiosensitive polymer gels are used as a reliable dosimetry tool for verification of 3D dose distributions. Special characteristics of these dosimeters have made them useful for verification of complex dose distributions in clinical situations. The aim of this work was to evaluate the capability of a normoxic polymer gel to determine electron dose distributions in different slab phantoms in presence of small heterogeneities. Different cylindrical phantoms consisting gel were used under slab phantoms during each irradiation. MR images of irradiated gel phantoms were obtained to determine their R2 relaxation maps. 1D and 2D lateral dose profiles were acquired at depths of 1 cm for an 8 MeV beam and 1 and 4 cm for the 15 MeV energy, and then compared with the lateral dose profiles measured using a diode detector. In addition, 3D dose distributions around these heterogeneities for the same energies and depths were measured using a gel dosimeter. Dose resolution for MR gel images at the range of 0-10 Gy was less than 1.55 Gy. Mean dose difference and distance to agreement [DTA] for dose profiles were 2.6% and 2.2 mm, respectively. The results of the MAGIC-type polymer gel for bone heterogeneity at 8 MeV showed a reduction in dose of approximately 50% and 30% and 10% at depths 1 and 4 cm at 15 Mev. However, for air heterogeneity increases in dose of approximately 50% at depth 1 cm under the heterogeneity at 8 MeV and 20% and 45% respectively at 15 MeV. However, for air heterogeneity increae in dose of approximately 50% at depth 1 cm under the heterogeneity at 8 MeV and 20% and 45% respectively at 15 MeV were observed. Generally, electron beam distributions are significantly altered in the presence of tissue inhomogeneities such as bone and air cavities, this being related to mass stopping and mass scattering powers of heterogeneous materials. A the same time, hot and cold scatter lobes under heterogeneity regions due to scatter edge effects were also seen. However, these effects [increased dose, reduced dose, hot and cold spots] at deeper depths, are compensated with the contributions of scattered electrons. Our study showed that normoxic polymer gels are reliable detectors for determination of electron dose distributions due to their characteristics such as tissue equivalence, energy independence, and 2D and 3D dose visualization capabilities