صدیقه سینا

Today, the use of lead-containing glasses and heavy transparent shields in various medical applications of radiation, including diagnostic radiology procedures, especially in angiography departments, has become very popular. In such departments, roof shields, transparent shields, and glasses made of lead glass are widely used for the radiation protection of personnel. In this study, the MCNPX Monte Carlo simulation code was used to design transparent and lead-free shields that can be used for radiation protection. For this purpose, two types of phosphate glass containing different percentages of heavy materials were simulated and compared with each other in terms of attenuation coefficients of photons with different energies. After simulating different glass types, the mass attenuation coefficients of each sample were calculated for single-energy photons. After that, by simulating the X-ray spectra used in angiography, the thicknesses of the first and second half-value layers were calculated for each spectrum. The results of this study show that the simulated values of the mass attenuation coefficient of glass types show good agreement with the results of XCOM. According to the results, the designed lead-free glass types have an attenuation comparable to leaded shields, which can be used as a suitable alternative to leaded glass types.

In this study, in order to produce and develop a new diagnostic radiopharmaceutical for the imaging of tumors overexpressed somatostatin receptor, [113mIn]In-DOTATATE labeled compound was prepared in optimal conditions using an in-house generator and its precilinical studies was performed. The final product was obtained with a radiochemical purity of nearly 99% (RTLC and HPLC) and a specific activity of 26.2×1015 Bq/mol. The investigation of the stability of the labeled compound showed a radiochemical purity of more than 96% for at least three hours in PBS buffer and in human blood serum.. The results of the biodistribution and the images assessment of the [113mIn]In-DOTATATE labeled compound in normal mice showed that the organs of the gastrointestinal tract such as the pancreas, stomach and intestine, which have cells expressing the somatostatin receptor, have high uptake.

The purpose of this study was to design and build a tin-113/indium-113m generator with desirable characteristics and reasonable cost. A generator such as this can produce ionic forms of indium-113m that are suitable for labeling applications. The theoretical calculations were conducted using the programs TALYS-1.8, ALICE-91, and SRIM. Tin-113, the mother of indium-113m, the target of natural indium was irradiated in a 30 MeV cyclotron accelerator. The theoretical efficiency of 740 kBq/μAh was calculated for tin-113 production in the cyclotron. Finally, tin-113 was produced with an experimental efficiency of 555 kBq/μAh. Zirconium chloride and 0.05 molar hydrochloride are used as column adsorbents and generator solvents, respectively. The generator's step efficiency in a period of 6 months was 82%. The radionuclide purity of indium-113m from the generator was more than 99.9% and the average amount of parent radionuclide was within the pharmacopeia permissible limits equal to 0.0005%. The amount of interfering metal ions in the solution was less than 0.1 ppm. The results show that the in-house produced tin-113/indium-113m generator has suitable features and reasonable costs and that indium-113m radionuclides can be used in ionic form for labeling purposes.

Staff training is one of the priorities of any organization. Therefore, reviewing and knowing the results and efficiency of staff training is a requirement of the training process. The purpose of this study is to evaluate the effectiveness of radiation protection training courses for medical and industrial centers It was November of 1399.

Method of research: 

The present study is descriptive-survey in terms of method and applied in terms of research purpose. For this purpose, 76 participants in the program have been studied. Data related to the evaluation of the effectiveness of the training course were held and also the components of the Kirk Patrick evaluation model were collected. Descriptive statistics and inferential statistics including t-tests were used to analyze the data.

The results show that radiation protection courses held by the Radiation Research Center of Shiraz University have been effective in both levels of reaction and learning and also these courses have been able to provide employee satisfaction.

Finally, it can be said that the participants in the training courses in general, have evaluated the effectiveness of the training courses at a desirable level and the mentioned trainings have increased knowledge and skills.

X-ray is one of the medical imaging methods, which helps physicians correctly diagnose diseases. Improper adjustment of X-ray tube parameters, different types of artifacts, and noise are factors affecting the quality of radiographic images. In some cases, poor quality of the images may lead to re-imaging, which increases the patient's dose. Today, artificial intelligence has made significant progress in various fields. Deep learning is one of the branches of artificial intelligence, which is widely used in medical imaging. In this article, the generative adversarial network is used as one of the most powerful available neural network models for resolution improvement, noise, and artifact reduction of chest X-rays. The values of RMSE, PSNR, and SSIM are calculated for 150 images with an average of 4.66, 34.92, and 0.923, respectively. These results show that trained networks have a high ability to improve the resolution of chest X-rays and make them more diagnostically valuable. Also, in cases where the image quality is low for any reason, there will be no need for re-imaging, and the patient will not receive the extra dose resulting from the re-imaging.

Patient dosimetry plays the essential role in nuclear medicine performed with various method in clinical and research approaches. There are many methods for internal dosimetry which Monte Carlo code with high accuracy has the crucial place compare to others. The principle reason that Monte Carlo couldn’t performed as the clinical method is the high computation time. This method could be use in the complex geometry such as patient but before the implementation of the code, accreditation should be done. This paper aim to present the method of validation the Gate Monte Carlo codes in PET nuclear medicine. The researches were carried out with experimental tests by head and TLD dosimeters and the results were compared with GATE outputs at the same geometry. In the second steps, ICRP110 phantom in two state of lunge to lunge as a source to target organ and liver to lung considered the MIRD internal dosimetry method had been simulated. The S factor were the results of the simulation codes compared with MCNPX Monte Carlo results in the same conditions. The result has shown the accordance between the simulation and experimental data with high accuracy and highlights the role of Monte Carlo in complex geometry as the high accurate and validate methods.

Determination of X-ray spectrum at various nuclear radiology centers is important in terms of device quality control. Due to the pile-up effect and dead time, this wonchr('39')t be possible by simple methods, and by placing the detector in front of the X-ray beams. Therefore, to obtain the X-ray spectrum, one can use indirect methods like spectroscopy Compton photons scattered at 90° angle. The primary spectrum is related to the Compton spectrum matrix by the response matrix in an equation system. As the coefficients matrix of this equation is ill-conditioned, MTSVD regularization mathematical method was used in this study for spectrum unfolding the X-ray spectra. Finally, the accuracy of the spectrometry was obtained by comparing the unfolded spectra with the IPEM78 theory spectrum. To compare the closeness of the unfolded spectra with the theory, the root-mean-square deviation was obtained, and the percentage error was used for comparison of the half value layer. According to the results obtained in this study, the indirect Compton method can unfold the X-ray spectrum by a good accuracy, i.e., less than 5%, and the relative error for obtaining the HVL, was found to be 2%.

TL dosimetry is known as one of the effective dose estimation methods in diagnostic radiology. Cephalometry is used by dentists, oral and maxillofacial surgeons to choose the appropriate treatment. The purpose of this study is to measure the entrance skin dose, and dose to different organs of the patients in cephalometry using TLD-100. The entrance skin, and organ dose were obtained by putting TLDs on the surface, and inside the Rando phantom. The dose to different organs like thyroid, eyes, maxilla, parotid, sub-lingual, and submandibular salivary glands were measured. According to the results obtained in this study, the entrance skin dose to neck, cheek, and temporal are 75.8, 58.1, 113.3 µGy, while minimum, and maximum organ doses were 2.5, and 107.8 µGy for right temporal, and right parotid salivary gland.

Apron used in diagnostic radiology to protect worker and patients who are exposed to unnecessary ionizing radiation, is based on lead. Although, this protection can prevent the passage of X-rays used in diagnostic radiology, but a lot of research is found that lead is a toxic metal. Therefore, a lead-free shield should be built which can be protect workers and patients from unnecessary ionizing radiation.
In this method, the absorption edge of different metals in the range of the energy spectrum of diagnostic radiology was investigated. Then, with the effect of overlapping edges, different combinations of metals as input Monte Carlo simulation was considered. Information obtained from the Monte Carlo simulation defines how the composition and percentage metals can have maximum impact on reducing the transmission of X-rays from the shield.
Findings: The results showed that for building lead-free shields, using 20% tin, 15% of tungsten and 45% of 20% bismuth-based polymer emulsion Poly vinyl Chloride (EPVC) combination is the best options which can reduce X-rays in the range of diagnostic radiology.
Characterized by the use of absorption edge overlap effect in different metals we can build a lead-free shield that decreases the intensity of X-rays in the range of diagnostic radiology much better than lead shield.

The amount of cosmic rays varies widely with the altitude, latitude and longitude in each region. In this study, the radiation doses due to the cosmic rays were estimated in two steps: in the first step, the neutron and gamma components of the radiation dose were measured for a roundtrip flight on 3 flight routes (Shiraz-Asaluye, Asaluye-Rasht and Shiraz-Mashhad) using a gamma-tracer photon detector and a Thyac 190N, neutron detector. The minimum values of the measured gamma and neutron doses of 0.15 and 0.04μSv were measured on the Asaluyeh-Shiraz route at the lowest altitude of 19000 ft, while for Rasht-Asaluyeh route at an altitude of 35000ft those values were found to be 2.52 and 1.09mSv, respectively. In the second step, a number of aircrew members were equipped with thermoluminescence dosimeters (TLD cards) for evaluating the gamma dose and polycarbonate dosimeters (SSNTD) for assessing the neutron dose for one year. The measured value of the annual effective dose received by the crew ranged between 0.5mSv/y and 1.16mSv/y, with an average of 0.9mSv/y for the gamma component and between 0.37mSv/y and 0.77mSv/y with an average of 0.61mSv/y for the neutron component. The results of this investigation are comparable with the investigations that have been conducted in other countries. For instance in UK, the reported annual effective dose of aircrew is about 2mSv, and in Canada, it is estimated to be between 1 to 5mSv, depending on the flight situations (such as the latitude and longitude of  the cities, the flight altitude, etc).

Brachytherapy is a type of radiotherapy in which radioactive sources are used in proximity of tumors normally for treatment of malignancies in the head, prostate and cervix.

The Cs-137 Selectron source is a low-dose-rate (LDR) brachytherapy source used in a remote afterloading system for treatment of different cancers. This system uses active and inactive spherical sources of 2.5 mm diameter, which can be used in different configurations inside the applicator to obtain different dose distributions. In this study, first the dose distribution at different distances from the source was obtained around a single pellet inside the applicator in a water phantom using the MCNP4C Monte Carlo code. The simulations were then repeated for six active pellets in the applicator and for six point sources.

The anisotropy of dose distribution due to the presence of the applicator was obtained by division of dose at each distance and angle to the dose at the same distance and angle of 90 degrees. According to the results, the doses decreased towards the applicator tips. For example, for points at the distances of 5 and 7 cm from the source and angle of 165 degrees, such discrepancies reached 5.8% and 5.1%, respectively. By increasing the number of pellets to six, these values reached 30% for the angle of 5 degrees.Discussion and

The results indicate that the presence of the applicator causes a significant dose decrease at the tip of the applicator compared with the dose in the transverse plane. However, the treatment planning systems consider an isotropic dose distribution around the source and this causes significant errors in treatment planning, which are not negligible, especially for a large number of sources inside the applicator.

Brachytherapy is the use of small encapsulated radioactive sources in close vicinity of tumors. Various methods are used to obtain the dose distribution around brachytherapy sources. TG-43 is a dosimetry protocol proposed by the AAPM for determining dose distributions around brachytherapy sources. The goal of this study is to update this protocol for presence of bone and air inhomogenities. To update the dose rate constant parameter of the TG-43 formalism, the MCNP4C simulations were performed in phantoms composed of water-bone and water-air combinations. The values of dose at different distances from the source in both homogeneous and inhomogeneous phantoms were estimated in spherical tally cells of 0.5 mm radius using the F6 tally. The percentages of dose reductions in presence of air and bone inhomogenities for the Cs-137 source were found to be 4% and 10%, respectively. Therefore, the updated dose rate constant (Λ) will also decrease by the same percentages. Discussion and It can be easily concluded that such dose variations are more noticeable when using lower energy sources such as Pd-103 or I-125.