m zabihzadeh

Producing the ideal therapeutic electron beams from a clinical linear accelerator (Linac), is crucial to optimize dose delivery in radiotherapy. The aim of this study was to investigate the properties of electron beams with and without the scattering foil.

Varian Linac 2100CD head was simulated by means of MCNPX-2.7 program. After validation with measured data, scattering foils were removed and then different dosimetric properties of 6 and 9 MeV electron beams such as depth dose percentage, dose profile, range, surface dose, dose rate and photon contamination were calculated and compared for field sizes ranging from 0.25×0.25 to 10×10 cm2 in three states with primary and secondary scattering foil (SF), without primary scattering foil (PSFF) and without primary and secondary scattering foil (SFF).

By removing the scattering foils, dose rates and surface doses were increased more than 25 times in 0.25×0.25 cm2 field, and in the bigger fields, it was less in 10×10 cm2 field, almost 4 times and the photon contamination is reduced by 20% times in 0.25×0.25 cm2 field. Also, Adjacent organs receive a lower dose, Because the dose profile curve was shrieked, it was almost 1cm in field 2×2 cm2 and less than 1cm in other fields. The dose profile flatness was diminished in scattering foil-free (SFF) mode which is not crucial for the small fields.

Removing scattering foil improves dosimetric properties of electron beams specially to treat the superficial tumors and for the small field radiotherapy.

Presence of inhomogeneities such as lung tissue with low density can perturbs the dose distribution in the path of therapeutic photon beam and causes undesired cold or hot spots. The aim of this study was to investigate the effect of lung tissue inhomogeneities on dose distribution in thorax irradiation.

The Monte Carlo simulation (MC) code of EGSnrc-based BEAMnrc was used to calculate dose distribution for 6 MV- Siemens Primus linear accelerator (Linac) in a homogenous phantom. Dose perturbation and inhomogeneity corrected factors (ICFs) were calculated due to implementation of lung tissue depended to the lung density and field size.

The maximum increased dose in lung tissue with lung density of 0.5 and 0.25gr/cm3 was 15.9%, 16.2%, 15.6%, 23.8 %, 24.8% and 25.0% for 6 × 6, 10 × 10 and 20 × 20 cm2 field sizes, respectively. The maximum ICF for these field sizes was 1.16 and 1.25 for lung density of 0.5 and 0.25gr/cm3, respectively. The maximum dose reduction in lung tissue with density of 0.25 and 0.5gr/cm3 was 19.5% and 4.2 %, and the related ICF was estimated 0.84 and 0.95, respectively.

Involvement of lung tissue in the path of irradiation perturbs the dose distribution which is dependent to the lung density and field size. The ICFs resulted from our MC model could be useful to accurately calculate the dose distribution in radiotherapy of lung abnormalities.

Gamma irradiation has been shown as an effective technology to decrease or eliminate microbial contamination in raw and cooked meat products. However, irradiation-induced physicochemical changes are important to accept the technology by meat industries and consumers. The objective of this study was to assess effects of gamma irradiation (0, 2, 4, 6 and 8 kGy) on nitrite residue, lipid oxidation, total volatile nitrogen and color in two heated meat products (sausages) during refrigerated storage at 4 ºC for 28 days.

Two groups of emulsion meat products with various proportions of meat (40 and 65%) were irradiated at 2, 4, 6 and 8 kGy doses. Residual nitrite and TVN tests were carried out on Weeks 0, 7, 14, 21 and 28. The color test was carried out using the Hunter Lab system on Weeks 0 and 4 of storage.

Radiation at 8 kGy doses resulted in a significant decrease in nitrite in both groups (P < 0.05). The TVN value in radiated samples was significantly lower than that in non-irradiated samples (controls). Furthermore, high-dose radiation (doses of 6 and 8 kGy) in the two food products significantly decreased the red index (a-value) and significantly increased the TBA value (P <0.05).

Based on the results from chemical properties of the radiated products, irradiation is suggested at 2 and 4 kGy doses as appropriate doses.

Nowadays, consumption of meat products such as sausages has been increased. Studies have shown that meat products can contain heavy metals like lead and cadmium. Therefore, a measurement of toxic heavy metals in sausages is necessary. The purpose of this study was to measure the lead, cadmium, iron and zinc levels in sausages presented in the retail markets of Tehran.

Six types of sausages (German, Koktel, Hot dog, Lioner or Martadella, Dry and Ham) supplied in the chain stores and some of supermarkets in ten districts of Tehran were tested for determination of lead, cadmium, iron and zinc levels. The samples were prepared by wet digestion method and were analyzed by atomic absorption spectrophotometry.

The lead content of the tested products was 48.78 ppb. The amount of lead in German sausage was significantly higher than in other products. The amount of cadmium in all samples was 5.6 ppb. The level of iron and zinc was 18.10 and 14.65 ppm, respectively. Zinc content in dry sausages and ham was higher than in other products.

The amount of lead and cadmium in all the tested products was lower than the limit specified by the Codex. Considering the amount of consumption of meat products in Tehran, the amount of lead and cadmium intake was 9.24 and 1.05 µg/week, respectively, which is much less than that recommended by JECFA