فهرست مطالب ‎dariush sardari

Pancreatic cancer leaves little hope for survival among patients. This is due to its cancerous cell resistance to radiation and chemicals.

Synergistic effect between three modalities of pancreatic cancer treatment is investigated. These are radiation therapy, Hyperthermia and graphene oxide nanosheets. The aim is to overcome resistance of pancreatic cancer cell against radiation therapy.Cancerous cell lines were treated by each one of three modalities separately. Other samples were treated with various combinations of these modalities. Hyperthermia accomplished with placing cell lines for 15 min in 42°C. In the course of radiation therapy, the cancerous cells were irradiated by 6 MV Linac for two cases of 2 Gy and 3 Gy. The cell line viability was readout by MTT assay in 24 hours and 48 hours after treatment.

In single modality treatment it was shown that 24h after the treatment, the group treated by RT 3 Gy had the highest cell killing result. Following up the result in 48h readout, hyperthermia and 3 Gy radiotherapy had similar result. In double modality treatment, for both 24h and 48h viability readout, the group graphene -oxide plus 2 Gy radiotherapy showed cell survival amounting to 67.07% and 43.23% respectively being the lowest cell survival among all double combinations.

In triple modality treatment, the cell viability for 24h showed no significant improvement but in 48h the hyperthermia plus Graphene -oxide and 3 Gy radiotherapy had very low cell viability. Significant sensitizing effect for GO when combined by radiation therapy was observed.

In this study, Lithium Fluoride nanopowder with Mangnesium and Titanium impurities has been synthesized by Co-precipitation method. The synthesized powder was then pressed into 3.2*3.2*0.9 mm3 pills and sintered at 750⁰c for 10 minutes.  The peak 5 in LiF: Mg, Ti is regarded as the main peak and includes sub-peaks 5a and 5b, which occur at the temperatures lower and higher than that of peak 5, respectively. Peak 5a in LiF;Mg,Ti occurs due to the localized recombination of trapping/luminescence center (TC/LC) , in which the electron is released from the electron trap by obtaining energy from heat and recombines through the tunneling phenomenon with a hole located in the adjacent luminescence center. Concerning the standard TLD chips, which are composed of micron-sized particles, the peak 5a either does not occur or appears with very low intensity, which is insignificant in terms of dosimetry. Thus, the present study focuses on synthesizing thermoluminescence nanoparticles by co-precipitation method in several stages by citing models based on the maintenance of linear behavior of thermoluminescence nanopowder up to high doses and its relationship with localized electron-hole recombination. In addition, by making changes in the concentration of ingredients, the temperature of the reaction medium and the presence or absence of surfactant were evaluated to achieve particles in nano dimensions with suitable geometric shapes. The resulting nanopowder was irradiated with different doses of alpha and gamma and consequently, the increasing rate of the intensity of peak 5a compared to peak 5, as the main factor in nanodosimetry was observed after analyzing the glow curves. Based on the results, the LiF: Mg, Ti thermoluminescence nanopowder could increase the 5a/5 ratio and can be used as a convenient, inexpensive, and practical tool to estimate the amount of energy deposited by the beams in nanoscale.

In this research, air samples were collected at an air flow rate of 300 m3/h to 900 m3/h. These samples were collected during more than two months (Nov 2019-Jan 2020). After the decay of short-lived radionuclides, the samples were formed as a disc to prepare for measurement. Then, these discs were evaluated by two HPGe detectors with relative efficiencies of 40% and 70%. A prototype of a standard high volume air filter was proposed and constructed by a novel method, which provides a symmetric distribution of radionuclides and efficiency calibration curve was obtained for two HPGe detectors. This standard filter was solved the problem of the asymmetry and inhomogeneous distribution of radionuclides in standard air samples. 7Be concentrations were assessed in the collected samples. The average concentration of 7Be was measured as 3.80±0.46 mBq/m3.

The origins of radon gas are the amount of uranium decay in the soil that is released into space and through the interior gaps of  buildings. Radon can enter the respiratory system and cause radiation hazards. Recently research has identified Radon as the second leading cause of lung cancer after cigarette smoking. The indoor concentration of Radon progeny is mentioned as an important issue regard to the point of view of health. Therefore, a more accurate measurement of the concentration of radon gas in order to assess the exposure of people is of great importance. The purpose of this research  is to measure radon gas with two contemporary and retrospective methods in Ramsar homes, which is known as a high level background radiation area, as well as comparison with previous measurements. In order to measure the Concentration of contemporary radon by  passive method using a radon chamber and solid state nuclear track detectors, a retrospective of the activity of polonium 210 implanted in glass objects was used to measure the concentration of radon gas. The solid state nuclear track detectors used in this research are polycarbonate, which is the first time used in this world for this type of polymer for the retrospective method. The average concentration of measured for contemperory radon is about 416 Bq /m3 and the resrospective radon is about 1299 Bq /m3. According to the comparison of the results  with the US Environmental Protection Agency standards, it was found that 45% of the radon gas concentration is above 148 becquerel per cubic meter, which is indispensable for reducing radon gas in these buildings. At the same time, the difference in the concentration of rare earth radiant gas with contemporary radon gas can be related to the change in the ventilation rate and the change in the concentration of aerosols and the ratio of the surface to the volume of the room.

‎Collision of protons with background gas and beamline wall in proton therapy causes the creation of secondary particles‎, ‎e.g. neutrons‎, ‎which results in more difficulties in curing the tumors‎. ‎In the present simulation-based study‎, ‎the optimum diameter of proton beamline was determined to minimize the production of secondary particles in the presence of electric field with the magnitude of 50 kV/m‎, ‎perpendicular equal magnetic fields of 0.7 T‎, ‎and background gas of argon under Bounce boundary conditions via finite element method‎. ‎The results showed that the optimum diameter of the beamline for minimization of the secondary particles in the spot scanning proton therapy in the aforementioned conditions was 7 mm‎. ‎Also‎, ‎the values of drift velocities of protons were plotted in different time steps of 10 ns to 50 ns for the optimized size of the beamline‎. ‎Due to few interactions of forwarding particles with background gas‎, ‎the results showed that the forwarding particles in the propagation direction have greater velocities than those of rear particles‎. ‎The results can be used in spot scanning proton therapy for curing the localized cancers‎.

Radiotherapy is a main method for the treatment of breast cancer. This study aimed to measure the absorbed dose of thyroid gland using Gafchromic EBT2 film during breast cancer radiotherapy. In addition, the relationship between the absorbed dose and thyroid hormone levels was evaluated.

Forty‑six breast cancer patients, with the age ranged between 25 and 35 years, undergoing external radiotherapy were studied. The patients were treated with 6 and 18 MV X‑ray beams, and the absorbed thyroid dose was measured by EBT2 film. Thyroid hormone levels, thyroid‑stimulating hormone (TSH), triiodothyronine (T3), and thyroxin (T4), were measured before and after the radiotherapy. Pearson’s, Spearman’s, and Chi‑square tests were performed to evaluate the correlation between the thyroid dose and hormone levels.

The mean thyroid dose was 26 ± 9.45 cGy with the range of 7.85–48.35 cGy. There were not any significant differences at thyroid hormone levels between preradiotherapy and postradiotherapy (P > 0.05). There was a significant relationship between increased thyroid absorbed dose and changes in TSH and T4 levels (P < 0.05), but it was not significant in T3 level (P = 0.1).

Regarding the results, the thyroid absorbed dose can have an effect on its function. Therefore, the thyroid gland should be considered as an organ at risk in breast cancer radiotherapy.

The utilization of high-energy photons in the medical linear accelerator can lead to photoneutron production. This study aimed to evaluate the effect of the physical components of the head, including flattening filter (FF) andmultileaf collimator (MLC), as well as the dependence of therapeutic field size on the photoneutron spectrum, dose, and flux.
The present study reported the simulation of the fundamental linac head components of the Varian Clinac 2100 performing in X-ray mode with 18 MV energy by the FLUKA code. The percentage depth dose and lateral dose profile were measured using a PTW thimble chamber to ensure the simulation reliability.
Photoneutron spectrum analysis indicated that neutrons with highest relative biological effectiveness were delivered to the phantom surface, and opening the field from 0×0 to 40×40  shifted the spectrum by 24.545% to the higher energies. The target and the vicinity parts played the most prominent roles in neutron contamination. The relationship between the field size and the photoneutron dose was non-linear, and it reached a peak of 20×20 . Although using small fields formed by the MLC contribute to a lower dose compared to those shaped by the jaws, MLC-equipped machines result in 21.98% higher dose. Moreover, the flattening filter removal unexpectedly increased the isocenter photoneutron dose by 11.63%. This undesirable dose can be up to 2.54 mSv/Gy for the reference field at the isocenter while the out-of-field dose is about 0.5 mSv/Gy for most of the field dimensions.
As a result, it is critical to consider this unwanted absorbed dose, which is seriously influenced by the implemented therapeutic conditions.

Recently non-thermal plasma (NTP) is applied for many therapeutic applications. By NTP irradiating to the tissues or cell-lines, the water molecules (H2O) would be also activated leading to generate hydrogen peroxide (H2O2). By irradiating plasma to bio-solution, its main output including vacuum UV to UV causes the photolysis of H2O leading to generate hydroxyl (OH) molecules in couple forms with ability to convert to H2O2. Additionally, other plasma’s output the oxygen atoms could also penetrate under the liquid’s surface and react with H2O to generate H2O2. In NTP applications for killing unwanted-cells of microorganisms (e.g. sterilization) or cancerous tissues, the H2O2 molecule is the main reactive species for cell death via inducing DNA damage in mammalian cells. In this paper we proposed a mathematical model for NTP application describing the formation of hydroxyls in the bio solution and other subsequent reactions leading to DNA damage in vitro. The instant concentrations of the OH and H2O2, the main species for DNA oxidation were obtained and investigated in this simulation. In order to validate the model, the cellular response to NTP stimulation was compared with some experimental findings from viewpoint of DNA damage to show the significant consistency.

Employing High-energy photons in medical linear accelerators can lead to neutron contamination. The relative biological effect of neutrons is 20 times higher than photons. Consequently, its damage to the biological tissue is much higher and unobtrusive. In this study, we calculated neutron equivalent dose in a medical linear accelerator by the FLUKA Monte Carlo code system. The results show that using smaller treatment fields increases the neutron contamination dose in out-of-field areas. Furthermore, the areas outside the treatment field receive several times higher neutron dose than the photon dose. Most of the neutron dose distribution is at the surface of the human body. So it could increase the secondary cancer risk, including skin cancer.

Reduction of background track in solid state nuclear track detectors is an important topic in dosimetry. The main objective of this research is to optimize the reduction of background track using the chemical pre-etching process for removal of surface layer of the detector followed by electrochemical etching process. In this regard, the chemical reaction between a polycarbonate detector and ethylenediamine solution with various density portion of 20%, 30%, 40%, and 50% is studied. Accordingly, some empirical relationships between removed layer thickness and etching time in different solution density are derived. The results of experiments illustrate that best outcome in the uniformity of etching can be achieved at density of 40% with 50% of background track reduction.

Microbeam radiation therapy (MRT) is an innovative experimental method used for radioresistant tumours such as glioma especially in pediatric cancer. In MRT, the patient is irradiated with arrays of parallel and high-intensity X-ray microbeams. The MRT offers dose profiles consisting of a pattern of peaks and valleys. The peak-to-valley dose ratio (PVDR) is the most important metric determining the effectiveness of MRT. Its value has to be maximized in normal tissue, and minimized in cancerous tissue in order to avoid any recovery. The main aim of this study is to investigate the possible effect of beam parameters on PVDR. To do so, the 3D dose distributions in water and head equivalent phantoms are computed with various microbeam configurations using GEANT4 simulation. The results show that the most promising PVDR are obtained at 100keV and ESRF spectrum. In addition, using a 300keV beam is not suitable for microbeams separation distance below 400μm. By increasing radiation field size, microbeam’s width and their separation, PVDR decreases for all energies. PVDRs in the bone rapidly fall because of the dominant photoelectric phenomenon for such a high-Z material.

Depending on the location and depth of tumor, the electron or photon beams might be used for treatment. Electron beam have some advantages over photon beam for treatment of shallow tumors to spare the normal tissues beyond of the tumor. In the other hand, the photon beam are used for deep targets treatment. Both of these beams have some limitations, for example, the dependency of penumbra with depth, and the lack of lateral equilibrium for small electron beam fields. In this study, improvement of the penumbra and Dmax changes will be investigated. Also the effects of cut-outs on the beam parameters prepared as well. Patients and In first, we simulated the conventional head configuration of Varian 2300 for 16 MeV electron, and the results approved by benchmarking the percent depth dose (PDD) and profile of the simulation and measurement. In the next step, a perforated Lead (Pb) sheet with 1 mm thickness placed at the top of the applicator holder tray. This layer producing bremsstrahlung x-ray and a part of the electrons passing through the holes, in result, we have a simultaneous mixed electron and photon beam. For making the irradiation field uniform, a layer of steel placed after the Pb layer. The simulation was performed for 10 × 10, and 4 × 4 cm2 field size. The measured R50 and RP for 10 × 10 cm2 field were 6.5 and 7.8 cm, respectively. The photon percentage for 1 mm thickness with 0.2, 0.3, and 0.5 cm holes diameter Lead layer target was about 33%, 32%, and 28% and for 2 mm targets punched with 0.2, 0.3, and 0.5 cm holes, the x-ray percentages were 43%, 41%, and 35%. This study showed the advantages of mixing the electron and photon beam by reduction of pure electron’s penumbra dependency with the depth, especially for small fields, also decreasing of dramatic changes of PDD curve with irradiation field size.

In today’s world, 2.45-GHz radio-frequency radiation (RFR) from industrial, scientific, medical, military and domestic applications is the main part of indoor-outdoor electromagnetic field exposure. Long-term effects of 2.45-GHz Wi-Fi radiation on male reproductive system was not known completely. Therefore, this study aimed to investigate the major cause of male infertility during short- and long-term exposure of Wi-Fi radiation. This is an animal experimental study, which was conducted in the Department of Anatomical Sciences, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, IRAN, from June to August 2014. Three-month-old male Wistar rats (n=27) were exposed to the 2.45 GHz radiation in a chamber with two Wi-Fi antennas on opposite walls. Animals were divided into the three following groups: I. control group (n=9) including healthy animals without any exposure to the antenna, II. 1-hour group (n=9) exposed to the 2.45 GHz Wi-Fi radiation for 1 hour per day during two months and III.7-hour group (n=9) exposed to the 2.45 GHz Wi-Fi radiation for 7 hours per day during 2 months. Sperm parameters, caspase-3 concentrations, histomorphometric changes of testis in addition to the apoptotic indexes were evaluated in the exposed and control animals. Both 1-hour and 7-hour groups showed a decrease in sperm parameters in a time dependent pattern. In parallel, the number of apoptosis-positive cells and caspase-3 activity increased in the seminiferous tubules of exposed rats. The seminal vesicle weight reduced significantly in both1-hour or 7-hour groups in comparison to the control group. Regarding to the progressive privilege of 2.45 GHz wireless networks in our environment, we concluded that there should be a major concern regarding the timedependent exposure of whole-body to the higher frequencies of Wi-Fi networks existing in the vicinity of our living places.

SPECT is a diagnostic imaging technique the main disadvantage of which is the existence of Poisson noise. So far, different methods have been used by scientists to improve SPECT images. The Wavelet Transform is a new method for de-noising which is widely used for noise reduction and quality enhancement of images. The purpose of this paper is evaluation of noise reduction in SPECT images by wavelet. To calculate and simulate noise in images, it is common in nuclear medicine to use Monte Carlo techniques. The SIMIND software was used to simulate SPECT images in this research. The simulated and real images formed using the current typical (hexagonal) collimator were de-noised by different types of wavelets. The best type of wavelet was selected for SPECT images. The results demonstrated that the best type of wavelet in the simulated and real images increased Signal to Noise Ratio (SNR) by 33% and 45% respectively. Also, Coefficient of Variation (CV) decreased by 77% and 71% respectively, while Contrast of Recovery (CR) was reduced by only 4% and 9% respectively. Comparing the results for real SPECT images in this paper with previously acquired results in real PET images, it can be concluded that the images of both nuclear medicine systems using Wavelet Transform differ in SNR and CR by only 5% and 7% respectively, and in CV by about 20%. Therefore, wavelet transform is applicable for nuclear medicine image de-noising.