International Journal of Radiation Research
Volume:5 Issue: 2, Apr 2007

Study in design to incorporate accelerated proliferation correction factors into linearquadratic and multiple-component models. Accelerated proliferation rate correction factor has been incorporated into the linearquadratic and the multiple component models by applying accelerated exponential cell growth to explain the tumor cell kinetics and estimates proper treatment results. Biological effectiveness and tumor control probability, in terms of BED (LQ model), BRD (MC model), TCP(LQ model) and TCP(MC model), were computed for three conventional and two accelerated hyperfractionated radiation therapy treatment schedules with using a range of accelerated proliferation rate constants to demonstrate the effect of the proliferation process. The results of the study show that the accelerated proliferation rate reduces the effectiveness of a treatment schedule delivered in a prolonged period of time. Care should be taken in the selection of a treatment protocol for a patient of head and neck cancer with an account of the cell kinetics of the tumor.

Several cell lines when cultured under proper condition can form three dimensional structures called multicellular tumor spheroids. Tumor spheroids are valuable in vitro models for studying physical and biological behavior of real tumors. A number of previous studies using a variety of techniques have shown no relationship between radiosensitivity and DNA strand breaks in monolayer and spheroid model of cell culture. In the present study, the radiosensitivity of cells grown as monolayer and spheroid were measured with colony assay and the role of DNA strand breaks in this sensitivity was examined using single cell gel electrophoresis assay also known as Comet assay. In the present experiment, spheroids showed more radioresistance than monolayers as judged by the number of colonies which they produced after radiation. Under the same experimental conditions, less level of DNA damage was detected in spheroids using "comet assay" technique. It was concluded that the loss of radioresistance which was observed in monolayer cultures might have been attributed to the higher level of DNA damage occurred in the cells.

From the time immemorial man has been exposed to ionizing radiation from the environment in which he lives. Radiation protection concepts and philosophy have been evolving over the past several decades. The radioprotective of effect of Aloe vera leaf extract (1000 mg /kg b.wt. orally for 15 consecutive days) has been studied against 6 Gy of gamma radiation in the intestine of Swiss albino mice at various post - irradiation intervals viz. 12 hrs, 24 hrs. and 3, 5, 10, 20 and 30 days. Crypt survival, villus length, apoptic cells, mitotic figures and goblet cells in jejunum were studied after irradiation. Irradiaton produced a significant decrease in crypt survival, mitotic figures and villus length; whereas goblet and apoptic cells showed a significant increase from sham irradiated animals. The major changes were observed on day 3 after irradiation. AVE pre-treated irradiated animals resulted in a significant increase in the number of crypt cells, mitotic figures and villus length; whereas the counts of apoptic and goblet cells showed a significant decrease from respective control group at all the autopsy intervals. Irradiated animals resulted in the elevation in lipid peroxidation and a reduction in glutathione acitivity. On contrary, AVE treatment before irradiation caused a significant depletion in lipid peroxidation and elevation in glutathione activity. The present study suggests the possible radioprotective ability of Aloe vera leaf extract.

Many in vitro studies suggested that choline incorporation into many types of tumors is related to cell proliferation. Whether in vivo choline incorporation is related also to cell proliferation or not was my question. Therefore, the aim of this pilot study was to investigate the relationship of in vivo [methyl- 14C]-choline incorporation and in vivo [methyl-3H]- thymidine incorporation. Four female nude mice were inoculated with MCF-7 breast tumor cells. Tumors were allowed to grow to a diameter of 0.5 cm and a diameter of 1 cm. Radioactivity of 370 kBq [methyl-14C]-choline and [methyl-3H]-thymidine each was injected. After 10 min, tumors were harvested and extracted with organic and aqueous solvents. The total [methyl-3H]-thymidine and [methyl-14C]-choline were determined and correlated using Spearman''s rank (rs) coefficient at 0.5 cm (n=4) and 1 cm (n=3) tumors. Spearman''s rank (rs) correlation coefficient showed high rs=0.8 (p=0.2; n=4) at 0.5 cm tumor compared to low rs=0.5 (p=0.7; n=3) at 1 cm tumor. In this preliminary pilot study, in vivo [methyl-14C]-choline incorporation may correlate with cell proliferation. More number of investigations is recommended.

Monte Carlo determination of TG-43 brachytherapy dosimetry parameters and dose distribution calculation for 131Cs source model CS-1 are presented in this study. The dose distribution was calculated around the 131Cs Model CS-1 located in the center of 30 cm ×30 cm ×30 cm water, and soft tissue phantoms cube using MCNP code by Monte Carlo method. The percentage depth dose (PDD) variation along the different axis, parallel and perpendicular, the source was calculated. Then, the isodose curves for 100%, 75%, 50% and 25% PDD were constructed. Finally, F(r,|θ|) and g(r) dosimetry parameters of TG-43 protocol have been determined. Results obtained show that the Monte Carlo method could only calculate dose deposition in high gradient region, near the source, accurately. The energy cut off was found to be 1 eV and the error in the calculations was less than 2%. The isodose curves of the CS-1 131Cs source were constructed from dose calculation by MCNP code. The calculated dosimetry parameters for the source were in agreement with previously published results.

In vivo dosimetry is a method for estimation of overall error in the delivered dose to the patients at the end of radiotherapy process. In this research, two methods for target dose calculation were evaluated on midline and central axis of photon beams in in vivo dosimetry of thorax fields. Entrance and exit doses for anterior and lateral fields of thorax were measured in thorax phantom using diode dosimeter. Also, the doses of some points on midline and central axis were measured in thorax phantom using ionization chamber. The dose at these points was calculated using entrance and exit doses by geometric and arithmetic mean methods. The calculated doses were compared with measured doses. In all cases, arithmetic mean method showed errors from %8.8 to 19% for points on midline and central axis in comparison to measurements. The range of errors for geometric method was from %1.5 to %8 depending on distance from midline. The results showed that doses of points on midline and central axis can be calculated with acceptable accuracy from entrance and exit doses using geometric mean in thorax fields.

The present research has focused on the effect of radioactivity on drinking water from five sites in the region of Zahedan city. The measurement of water activity in wells, river and spring has been used as a screening method. The determination of gamma emitters was performed by use the application of gamma spectrometry. The values of Radium concentration was between less than 2 mBq/l to 3±0.4 for water wells, 5±0.4 mBq/L for river, and less than 2 mBq/L for spring. All values of activity in the selected water samples were lower than the permissible limit for drinking water consumption. The water was safe for drinking, washing and agricultural use.

Ultraviolet (UV) radiation affects human organs such as skin, eyes and immune system, as well as animals and plants. The main natural source of UV radiation is the Sun. To study the effects of solar UV radiation there is a need to quantify variations of solar energy received on the earth surface at different intervals. To measure UV radiation a broadband fiber optic UV spectrometer was used. With the spectrometer, the energy received at earth surface was measured from wavelength 100 to 400 nm (the UV spectrum). Measurement duration was from January first to the end of December 2003, and from sunrise to sunset. The received UVC at the ground level was too low to be measured. The measured UVA was between 11 to 21 times higher than UVB energy during the measurement period. The minimum UV received on the ground level was in January and it was 14.5×105 J/m2 while the maximum was in July and it was 80.14×105 J/m2. Total UV radiation received on the ground level was during the year of measurement period 579 ×105 J/m2. The measurement showed that UVC intensity on the earth surface was negligible. As the wavelength increased the receiving UV energy at the ground level also increased. From the results, it has become clear that the main health consequences of solar UV were related to UVA band. As the intensity of the UVR during summer is too high, a method of UV health risk reduction should be devised.