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Relative electron densities of body tissues (ρe) for radiotherapy treatment planning are normally obtained by CT scanning of tissue substitute materials (TSMs) and producing a Hounsfield Unit–ρe calibration curve. Aiming for more accurate, simultaneous characterization of ρe and effective atomic number (Zeff) of real tissues, an in-house phantom (including 10 water solutions plus composite cork as TSMs) was constructed and scanned at 4 kVps. Dual-energy algorithms were applied to 80–140 and 100–140 kVp combination scans, for better differentiation of tissues with same attenuation coefficient at 120 kVp but different ρe and Zeff. Stoichiometric calibration and closeness of the ρe of the 11 TSMs to real tissues (≤ 0.5%) resulted in smaller ρe calculation discrepancies, compared to studies with commercial phantoms (p

Background: Integrated proton therapy - MRI systems are capable of delivering high doses to the target tissues near sensitive organs and achieve better therapeutic results; however, the applied magnetic field for imaging, influences the protons path, changes the penetration depth and deflects the particles, laterally, leading to dose distribution variations. Objective: To determine the effects of a magnetic field on the range and the lateral deflection of protons, analytically. Methods: An analytical survey based on protons energy and range power law relation, without using small angle assumption was done. The penetration depth and lateral deflection of protons with therapeutic energy ranges 60- 250 MeV in the presence of uniform magnetic fields of 0-10T intensities, were calculated analytically. Calculations were done for relativistic conditions with Mathematica software version 7.0, and MATLAB 7.0 was applied to plot curves and curve fittings. Results: In the presence of a magnetic field, the depth of Bragg peak was decreased and it was shifted laterally. A second order polynomial model with power equation for its coefficients and a power model with quadratic polynomial coefficients predicted the maximum lateral deflection (ymax) and maximum penetration depth (zmax) variations with energy and magnetic field intensity, respectively. Conclusion: The applied correction for deflection angle will give more reliable results in initial energy of 250 MeV and 3T magnetic field intensity. For lower energies and magnetic field intensities the differences are negligible, clinically

Background: The use and effectiveness of traditional lead gonad shields in pediatric pelvic radiography has been challenged by several literatures over the past two decades. The aim of this study was to develop a new radioprotective gonad shields to be use in pediatric pelvic radiography. Materials and Methods: The commercially available 0.06 mm lead equivalent bismuth garment has cropped squarely and used as ovarian shield to cover the entire region of pelvis. In order to prevent deterioration of image quality due to beam hardening artifacts, a 1-cm foam as spacer was located between the shield and patients pelvis. Moreover, we added a lead piece at the cranial position of the bismuth garment to absorb the scatter radiations to the radiosensitive organs. In girls, 49 radiographs with shield and 46 radiographs without shield was taken. The radiation dose was measured using thermoluminescent dosimeters (TLDs). Image quality assessments were performed using the European guidelines. For boys, the lead testicular shields was developed using 2 cm bismuth garment, added to the sides. The prevalence and efficacy of testicular shields was assessed in clinical practice fromFebruary 2016 to June 2016. Results: Without increasing the dose to the breast, thyroid and the lens of the eyes, the use of bismuth shield has reduced the entrance skin dose(ESD) of the pelvis and radiation dose to the ovaries by 62.2% and 61.7%, respectively (P

In recent years, the use of gold nanoparticles in radiation therapy has been introduced as a new approach in radiotherapy. The aim of this study is to investigate the effect of gold nanoparticles (GNPs) in plaque brachytherapy for choroidal melanoma using Monte Carlo (MC) simulation. MCNPX code was used for simulation of human eye, 103Pd (model 200) brachytherapy source and the 20 mm COMS eye plaque that was loaded with 24 103Pd seeds and standardized by Collaborative Ocular Melanoma Study (COMS). The tumour was defined from the inner surface of choroid with 0.55 cm height and latticed with gold nanospheres and it was filled with different concentrations of 5, 10 and 15 mg/g GNPs, separately. Dose rate and dose enhancement factor in tumour and normal tissues of the eye (without gold) was examined for this case and compared with gold–water mixture of the same concentrations distributed in the tumour. The results show that with increasing the concentration of GNPs, the dose in the tumour increases and the dose to the normal tissues decreases. Furthermore, the time that is required to deliver the prescribed dose to the tumour decreases. In the gold nanosphere case for 5, 10 and 15 mg/g concentrations, the DEF in the apex of the tumour are 1.28, 1.46, 1.44 and at the distance of 6.5 mm in the normal tissue (outside the tumour) this factor would be 0.82, 0.73 and 0.68. The comparison between two cases of gold nanospheres and gold–water mixture shows that when the gold concentrations are defined as mixed with water, the dose enhancement in the first depths are higher than when the gold-nanoparticles are distributed inside the tumour. Furthermore due to more reduced particle flux for water-mixture case, by an increase in the depth the dose enhancement in gold-nanosphere increases compared with gold–water mixture case.

Introduction In radiotherapy, megaelectron volt (MeV) electrons are employed for treatment of superficial cancers. Magnetic fields can be used for deflection and deformation of the electron flow. A magnetic field is composed of non-uniform permanent magnets. The primary electrons are not mono-energetic and completely parallel. Calculation of electron beam deflection requires using complex mathematical methods. In this study, a device was made to apply a magnetic field to an electron beam and the path of electrons was simulated in the magnetic field using finite element method. Methods A mini-applicator equipped with two neodymium permanent magnets was designed that enables tuning the distance between magnets. This device was placed in a standard applicator of Varian 2100 CD linear accelerator. The mini-applicator was simulated in CST Studio finite element software. Deflection angle and displacement of the electron beam was calculated after passing through the magnetic field. By determining a 2 to 5cm distance between two poles, various intensities of transverse magnetic field was created. The accelerator head was turned so that the deflected electrons became vertical to the water surface. To measure the displacement of the electron beam, EBT2 GafChromic films were employed. After being exposed, the films were scanned using HP G3010 reflection scanner and their optical density was extracted using programming in MATLAB environment. Displacement of the electron beam was compared with results of simulation after applying the magnetic field. Results Simulation results of the magnetic field showed good agreement with measured values. Maximum deflection angle for a 12 MeV beam was 32.9° and minimum deflection for 15 MeV was 12.1°. Measurement with the film showed precision of simulation in predicting the amount of displacement in the electron beam. Conclusion A magnetic mini-applicator was made and simulated using finite element method. Deflection angle and displacement of electron beam were calculated. With the method used in this study, a good prediction of the path of high-energy electrons was made before they entered the body.

Background Increasing the x-ray film to focus distance (FFD), has been recommended as a practical dose optimization tool for patients undergoing conventional radiological procedures. In the previous study, we demonstrated a 32% reduction in absorbed dose is achievable due to increasing the FFD from 100 to 130 cm during pediatric chest radiography. The aim of this study was to examine whether increasing the FFD from 100 to 130 cm is equally effective for other common radiological procedures and performing a literature review of published studies to address the feasibility and probable limitations against implementing this optimization tool in clinical practice. Materials and Methods Radiographic examination of the pelvis (AP view), abdomen (AP view), skull (AP and lateral view), and spine (AP and lateral view), were taken of pediatric patients. The radiation dose and image quality of a radiological procedure is measured in FFD of 100 cm (reference FFD) and 130 cm (increased FFD). The thermo-luminescent dosimeters (TLD) were used for radiation dose measurements and visual grading analysis (VGA) for image quality assessments. Results: Statistically significant reduction in the ESD ranged from 21.91% for the lateral skull projection to 35.24% for the lateral spine projection was obtained, when the FFD was increased from 100 to 130 cm (P0.05). Conclusion Increasing the FFD from 100 to 130 cm has significantly reduced radiation exposure without affecting on image quality. Our findings are commensurate with the literatures and emphasized that radiographers should learn to use of an updated reference FFD of 130 cm in clinical practice.

Background Access to appropriate images of fetal brain can greatly assist to diagnose of probable abnormalities. The aim of this study was to compare the suitability of T2-True Fast Imaging with Steady State Free Precession (T2-TRUFI), and T2-Half-Fourier Acquisition Single-Shot Turbo Spin-Echo (T2- HASTE( magnetic resonance imaging (MRI) to extract the fetal brain using the level set algorithm.Materials and Method: T2-TRUFI and T2-HASTE MRI of the uterus were performed. The fetal brain was cropped from the image manually, with an adequate margin of maternal tissues; and then the fetal brain was extracted using level set. The outcome was statistically analyzed to compare its success, error (Sensitivity and Specificity), and similarities (Dice and Jaccard), with those of images obtained by radiologist.Results: The mean values of statistical tests to evaluate the similarity (Dice and Jaccard) and the success and error (Sensitivity and specificity) between two T2-TRUFI and T2-HASTE were calculated as 97.35%, 94.98%, 95.88%, 95.88%, 99.45%, 91.10%,83.82%, 86.44% and 99.11%, respectively. However, the results from two images showed high scores to extract the fetal brain, but images from the T2-HASTE technique resulted in better visually output.ConclusionBased on our results, the T2-HASTE MR images are preferred to fetal brain extraction by level set algorithm compared to the T2-TRUFI MR images.

Considering the non-invasive nature of magnetic resonance spectroscopy (MRS) and its ability to detect prostate lesions, the present study aimed to investigate the accuracy of MRS techniques in distinguishing between prostate cancer (PCa) and prostatitis.Thirty-three patients (18 patients with PCa and 15 patients with prostatitis) were recruited for this study. Magnetic resonance imaging (MRI) and MRS were performed using 1.5-T system GE- modle Optima 450 Discovery (GE Medical Systems, US). The (Cho+Cr)/Cit ratio of hypointense T2 areas were calculated. The diagnostic accuracy including sensitivity and specificity indices, with 0.95 confidence interval as well as PPV and NPV were calculated for each variable. The receiver operating characteristic (ROC) area under the curve (AUC) was outlined and investigated. The mean quantitative values between the two groups (PCa and Prostatitis) were compared using independent t test.The mean ratios of Cho+Cr/Cit in PCa was 1.54 ± 0.63 and 0.83 ± 0.48 for PCa and prostatitis, respectively, indicating a significant statistical difference (P = 0.00). A reduction in citrate was seen in both PCa and prostatitis tissue. Significant elevation in choline peak was shown for PCa. Moreover, creatinine level was low in both normal tissue and PCa without significant difference. Sensitivity, specificity, accuracy, PPV and NPV of MRS were 94.4% (95% CI, 74.2-99), 80% (95% CI, 54.8-93), 96%, 85% and 92.4%, respectively.The results of this study indicate an acceptable level of sensitivity, specificity and accuracy of MRS in the differential diagnosis of PCa and prostatitis.

Background: Lead has been widely used for internal shielding. It is recognized as a toxic material that pollutes the environment and does not fit well the patient's body because of its inflexibility. Objectives: In this study, a specific combination (70% W, 18.61% Ni, and 11.39% C) of lead-free and flexible putty metal was introduced and validated for internal shielding by Monte Carlo study. Methods: To evaluate the putty metal for internal shielding by Monte Carlo study, Varian 2100 C/D was validated within measurements. Then, using the given energy spectrum of Varian 2100 C/D, the shield thickness and backscatter factors were calculated by Monte Carlo study and compared with those of lead. Results: The results showed that this putty metal shield required a comparable thickness compared to lead for providing protection. In addition, it is nontoxic and flexible and can be easily cut. Internal shielding with high atomic number materials causes dose enhancement that is not taken into account in treatment planning systems. This study showed that this composition as an internal shield causes 5% - 7% reduction in electron backscatter factor compared to lead. Conclusions: It can be concluded that lead can be replaced by putty metal with a specific combination (70% W, 18.61% Ni, and 11.39% C). It is lead-free and flexible and its required thickness for protection is acceptable under clinical condition. It causes a 5% - 7% reduction in electron backscattering.

Background: Noninvasive quantification of liver fat by gradient echo (GRE) technique is an interesting issue in quantitative magnetic resonance imaging. In this study, the fat content in patients with nonalcoholic fatty liver disease (NAFLD) was quantified with GRE sequences with different T1 and T2* weighting. Methods: This prospective, cross-sectional study was performed on thirty NAFLD patients. Sixteen GRE sequences with different T1 weighting were performed with four echo times. In each sequence, repetition time (TR) or flip angle was changed and other parameters were fixed. Forty-eight fat indexes (FIs) from 16 sequences were calculated based on three methods. To determine the relationship between FIs and histological findings, Pearson's correlation coefficient was used at the level of 1% significance. Results: Mean FIs which obtained from Eq. 3 have the maximum values in comparison to other FIs. The maximum FI was 23.58%, which related to heavily T1 weighted sequence obtained with method 3. The minimum FI was −2.49%, which related to the minimal T1 weighted obtained with method 2. FIs increase with a flip angle, especially at low flip angles. Increase the TR parameter decrease the FIs gradually. Calculated FIs with methods 1 and 3 stronger correlated with histological findings relative to calculated FIs with method 2. Conclusion: For fat quantification, T1 relaxation effects probably more critical than T2*. Flip angle parameter could be a major factor causing the overestimation of liver fat content. Sequences with low flip angle are more suitable for fat quantification with methods 1 and 3. In fat quantification with GRE techniques, it is possible that the third and fourth echoes are unnecessary.

Background: High-radiation therapeutic gain could be achieved by the modern technique of microbeam radiation treatment (MRT). The aim of this study was to investigate the dosimetric properties of MRT. Methods: The EGSnrc Monte Carlo (MC) code system was used to transport photons and electrons in MRT. The mono-energetic beams (1 cm × 1 cm array) of 50, 100, and 150 keV and the spectrum photon beam (European Synchrotron Radiation Facility [ESRF]) were modeled to transport through multislit collimators with the aperture's widths of 25 and 50 μm and the center-to-center (c-t-c) distance between two adjacent microbeams (MBs) of 200 μm. The calculated phase spaces at the upper surface of water phantom (1 cm × 1 cm) were implemented in DOSXYZnrc code to calculate the percentage depth dose (PDD), the dose profile curves (in depths of 0–1, 1–2, and 3–4 cm), and the peak-to-valley dose ratios (PVDRs). Results: The PDD, dose profile curves, and PVDRs were calculated for different effective parameters. The more flatness of lateral dose profile was obtained for the ESRF spectrum MB. With constant c-t-c distance, an increase in the MB size increased the peak and valley dose; simultaneously, the PVDR was larger for the 25 μm MB (33.5) compared to 50 μm MB (21.9) beam, due to the decreased scattering photons followed to the lower overlapping of the adjacent MBs. An increase in the depth decreased the PVDRs (i.e., 54.9 in depth of 0–1 cm). Conclusion: Our MC model of MRT successfully calculated the effect of dosimetric parameters including photon's energy, beam width, and depth to estimate the dose distribution.

Background: Gonad shielding has been recommended during pelvic x-rays since the 1950s. The popular method of gonad shielding is placement a lead shield in the midline of the pelvis. The aim of this study was to evaluate the prevalence and utility of gonad shielding in pediatrics undergoing pelvic x-rays.Materials and MethodsFollowing study approval, we retrospectively retrieved data from the digital image library of ten radiology depertments of Khuzestan provience-Iran to identify pediatric patients who underwent pelvic x-ray (anteriorposterior [AP] view). All the images were reviewed for the probable evidence of gonad shield. If there was evidence of shielding, the accuracy positioning of the shield was also investigated by a single assistant radiologist.ResultsIn all 1745 pelvic x-rays (942 girls and 803 boys) were identified of which the shield was present in 51 (5.41%) radiographs of girls and 132 (16.43%) radiographs of boys. When a shield was present; the shields has adequate positioning only in 8 (15.68%) radiographs in girls and 59 radiographs in boys. Inaccurate placement and absence of gonad shields were more common in girls than the boys. Due to the shield has concealed the anatomical criteria of the pelvis, retakes of the examination was required in 11 (21.56%) radiographs of girls and 14 (10.6%) radiographs of boys.ConclusionThe current methods of gonad shielding in girls pelvic x-ray was not effective nor is justifiable. We no longer advocate of gonad shielding during girls pelvic x-ray. However in boys it is controversial and depends on the skill and effort of radiographers.

Background: Increasing the x-ray focus to film distance (FFD) has been advocated as an effective method to reduce the patients’ radiation dose. The aim of this study was to investigate the efficacy of this technique in patients' dose and image quality in pediatric chest x-ray.Material and methods: Sixty pediatric patients were x-ray imaged at FFDs of 100 and 130 cm. Dose measurements were performed using thermo-luminescent dosimeters (GR200). The quality of images was independently assessed using the anatomical criteria recommended by the European guidelines.Results: Increasing the FFD from 100 to 130 cm has reduced the entrance skin dose (ESD) of patients by 32.2% (p 0.05).Conclusion: Increased FFD to 130 cm reduce the pediatric radiation dose with no significant changes in image quality.

Background It is remain a main concern that pediatric chest radiographies contribute to the significant radiation exposure to the thyroid gland as a more susceptible organ to radiation induced cancer. The aim of this study was to evaluate the entrance surface dose (ESD) of pediatric chest radiography compared to the diagnostic reference levels (DRL) and evaluation the efficacy of the lead (Pb) shield in radiation dose reduction to the thyroid gland.Materials and Methods After assessing each patient against specific inclusion-exclusion criteria, 40 pediatric patients who were undergoing anterior-posterior (AP) projection of the chest x-ray were considered eligible for this study. The ESD of the chest and also ESD of thyroid gland with and without a 1 mm butterfly-shaped lead shield which placed on the thyroid gland were measured using high sensitive thermo luminescent dosimeters (TLD-GR 200).Results The average of ESD for chest radiography was 0.068+ 0.006 mGy (0.021 - 0.232 mGy). The unshielded average thyroid ESD was 0.065 + 0.003 mGy compared to the shielded average thyroid ESD of 0.001 + 0.0005 mGy. The use of Pb-shield produced a statistically significant decrease in the average thyroid dose by about 97% (P< 0.001). Conclusion The use of Pb-thyroid shield in the AP projection of pediatric chest radiography has potential to reduced radiation dose without compromising image quality.

One of the main and primarily phase to success of radiotherapy is accurately localization of the target volume and health peripheral tissues by radiotherapy simulator. The aim of this study is to investigate the some specific quality control tests necessary to provide adequate confidence of radiotherapy simulator performance Various essential parameters for quality control of Acuity- Varian radiotherapy simulator such as matching of mechanical measurements and electrical readouts, isocenter check, Congruence between optical field and radiation field, laser positioning system, kVp accuracy of X-ray beam, flat panel performance (resolution and low contrast sensitivity), etc were checked by quality control test tools. All investigated tests for matching of mechanical measurements and electrical readouts of field size, rotation and movement of table, gantry and flat panel detector were within the tolerance limits. The accuracy and reproducibility of KV passed the acceptable values. All the lasers were aligned with isocenter. However resolution of flat panel was within tolerance limit but low contrast sensitivity was not passed. The various quality control tests carried out on Acuity-Varian radiotherapy simulator were within recommended limits except the low contrast sensitivity that is in borderline of tolerance.

Background: In radiation therapy, estimation of surface doses is clinically important. This study aimed to obtain an analytical relationship to determine the skin surface dose, kerma and the depth of maximum dose, with energies of 6 and 18 megavoltage (MV). Materials and Methods: To obtain the dose on the surface of skin, using the relationship between dose and kerma and solving differential equations governing the two quantities, a general relationship of dose changes relative to the depth was obtained. By dosimetry all the standard square fields of 5cm×5cm to 40cm×40cm, an equation similar to response to differential equations of the dose and kerma were fitted on the measurements for any field size and energy. Applying two conditions: a) equality of the area under dose distribution and kerma changes in versus depth in 6 and 18 MV, b) equality of the kerma and dose at x=d max and using these results, coefficients of the obtained analytical relationship were determined. By putting the depth of zero in the relation, amount of PDD and kerma on the surface of the skin, could be obtained. Results: Using the MATLAB software, an exponential binomial function with R-Square >0.9953 was determined for any field size and depth in two energy modes 6 and 18MV, the surface PDD and kerma was obtained and both of them increase due to the increase of the field, but they reduce due to increased energy and from the obtained relation, depth of maximum dose can be determined. Conclusions: Using this analytical formula, one can find the skin surface dose, kerma and thickness of the buildup region.

Introduction: Electrical impedance of tissues on low frequencies includes useful information about functional and structural changes in tissues. This property is used in Electrical Impedance Tomography (EIT) imaging modality for the detection of lesions in tissues.Objective: The goal of this article is to study changes in electrical impedance of tissues in the presence of gold nanoparticles.Materials and Methods: Spherical gold nanoparticles with size of 20-25 nm were synthesized with Turkevich method. Size distribution and shape of nanoparticles were characterized by transmission electron microscopy (TEM). Electrical impedance of two types of phantoms (chicken fat and muscle paste tissues) was measured by 4-electrode method with and without gold nanoparticles.Results: Results demonstrate a reduction in electrical impedance of tissues in the presence of gold nanoparticles. However, this reduction is not the same for fat and muscle tissues. Reductions in resistive impedance are for fat and muscle tissues on the frequency of 1 KHz, respectively. A reduction in electrical impedance is accompanied by a rise in electrical conductance leading to increase in EIT signal.Conclusion: As signal enhancement is different for fat and muscle tissues; presence of gold nanoparticles could be used to improve EIT image contrast.

Occurrence of radiation-induced secondary cancer risk following mantle field radiotherapy for Hodgkin's lymphoma (HL) patients with long survival demands well-established radiotherapy strategy. Organs doses and resulted secondary cancer risk due to out-of field photons were calculated during mantle field radiotherapy for Hl patient. The male and female mathematical phantom of the Oak Ridge National Laboratory (ORNL) and validated 6MV photon beam of a Varian 2300 C/D were modeled by MCNPX 2.4.0 MC code. Using suitable lungs and thyroid shields for AP and PA fields, the organ specific absorbed doses, effective dose, and secondary cancer risk were calculated following to mantle field radiotherapy for HL. Among the out-of-field organs, the nose, eyes, head and neck's skins and sinuses have the higher received doses. The total effective doses and secondary cancer risk for a male and female were estimated to be 199, 234 mSv and 1.72, 1.87 respectively. During mantle field radiotherapy for Hodgkin's lymphoma, accurately estimations of organs dose near to the field's edge and suitable shielding of critical in-field organs are crucial factor to establish an optimal treatment plan.

In some linear accelerators (Linac), the collected charges in beam monitor chamber (BMC) is partly caused by the backscattered particles from the accelerator components downstream the BMC that influence the Linac output factors. In the intensity modulated radiation therapy technique, the desired dose distribution can be achieved through an unflattened beam. Although removing the flattening filter provides some advantages, the amount of backscatter radiation into BMC can be changed. In this study, contribution of backscattered particles into the BMC response of a Varian 2300 C/D Linac with and without a flattening filter was determined for 6, 18 MV photon beams. The experimental procedure included telescopic method and calculation procedure consisted of Monte Carlo simulation (MCNPX, version 2.4.0), were used to investigate the contribution of backscattered particles into the BMC performance. Our results showed a 2.3 and 3 increase in backscatter for a 0.5 x 0.5 cm2 field compared to a 40 x 40 cm2 field for 6 MV and 18 MV, respectively. The energy deposition from backscattered radiation is mainly caused by backscattered electrons. Removing the flattening filter did not change the BMC performance for a conventional Linac with a flattening filter. However, this result was not valid for small fields (e.g. 0.5 x 0.5 cm2, 18 MV). The corrected backscatter factors is necessary to taking into account the contribution of backscattered radiation in the monitor chamber response for small fields in the case of the free flattening filter Linacs (18 MV). © 2015, Oriental Scientific Publishing Company. All rights reserved.

Gonad shielding has been extensively advocated during pelvic radiography at or below reproductive ages. The popular practice of gonad shielding is placement of a lead shield in the midline of the pelvis. The aim of this study was to address the prevalence of gonad shielding and find out whether the current practice of gonad shielding can be considered as an effective method to reduce radiation exposure in patients undergoing pelvic radiography.National and international electronic databases, including PubMed, MEDLIN, EMBASE, and Google-Scholar, were searched up to January 2016. The database searches were supplemented with manual searches of reference lists. Two authors independently assessed the eligibility of all studies and extracted data.The searches yielded a total of 243 publications. After assessing each identified study against specific inclusion exclusion criteria, 18 studies were deemed as relevant for this review. The total prevalence rate of gonad shielding was estimated at 58% (95% CI: 40 to 74%). It was estimated that only 34% (95% CI: 25 to 44%) of the radiographs had correct positioning of the shield. Also, incorrect positioning of the shield was statistically significantly higher in females than males (85% vs. 52 %; P-value0.001).Our study demonstrates that the current practice of gonad shielding during female pelvic radiography should be no longer considered as an effective method to reduce radiation exposure. Training the best qualified radiographers is the key to accurate positioning of the shield in male subjects.

Aims and Objectives: Brachytherapy using removable ophthalmic plaques loaded with suitable small sealed radioactive seeds adjacent to the ocular's tumor has been widely used as an effective treatment. The aim of this study was to investigate the dose distribution in a modeled eyeball followed to loading of an ocular melanoma tumor with different concentrations of gold nanoparticles (GNPs) as dose enhancement agent by Monte Carlo (MC) calculations. Materials and Methods: The MC code of MCNPX 2.6.0 was used to modeling of COMS standard eye plaque loaded with 24 125I sources (6711 model) located on the sclera of modeled eyeball with detailed structures and materials. A choroidal melanoma tumor was simulated and loaded with different concentrations of spherical gold GNPs (50 nm in diameter). Dose enhancement factors (DEFs) of ocular components were calculated. Results: The dosimetric properties of 125I source (6711 model) and dose distribution of COMS standard eye plaque were calculated successfully as recommended by TG-43U1; AAPM. Loading of tumor with GNPs increased dose to the tumor and decreased dose to the normal tissues; the DEF was increased up to 2.280 and 2.030 for tumor apex, while it was decreased to 0.760 and 0.892 for macula and for gold-tumor mixture and nanolattice distributions, respectively. Conclusion: Loading the choroidal tumor volume with GNPs improves the dose distribution by increasing dose to the tumor and decreasing dose to the health components in ocular brachytherapy with 125I seeds 20-mm COMS plaque.

The present study examines the effects of dose variation on brachytherapy treatment with Ir-192 source in the presence and absence of tissue heterogeneities.The effect of source location and distance between the heterogeneity and the source on dose distribution were evaluated using Monte Carlo simulation (MCNP4C code). Soft tissue heterogeneity showed no significant effect on dose distribution. Increasing the distance between the source and the phantom center, decreases dose delivery because of reduced scattering. Despite the surrounding heterogeneities, Ir-192 source can alter dose distribution in comparison with the homogeneous water phantom.

In recent years, the use of gold nanoparticles in radiation therapy has been introduced as a new approach in radiotherapy. The aim of this study is to investigate the effect of gold nanoparticles (GNPs) in plaque brachytherapy for choroidal melanoma using Monte Carlo (MC) simulation. MCNPX code was used for simulation of human eye

Introduction: Since the heart of the electronic brachytherapy system is a tube of a miniature x-ray and due to the increasing use of electronic brachytherapy, there is an urgent need for acquiring knowledge about the X-ray spectrum produced, and distribution of x-ray dose. This study aimed to assess the optimal target thickness (TT), the X-ray source spectrum, and the absorbed dose of two miniature sources of hemispherical and hemispherical- conical used in electronic brachytherapy systems, through a Monte Carlo simulation. Methods: Considering the advantages of MCNPX Code (2.6.0), two input files corresponding to the characteristics of the investigated miniature sources were prepared for this code and then were used for simulation. The optimal thickness (OT) of gold and tungsten targets was determined for the energy levels of 40, 45, and 50 kilo-electron-volts. Results: In this study, the values of the size of the optimal thickness of 0.92, 1.01 and 1.06 μ for gold target and values of 0.99, 1.08 and 1.34 μ for tungsten target were obtained for energies 40, 45 and 50 keV that using these values, the optimum thickness of 0.92, X-ray spectrum within and outside targets, axial and radial doses for the used energy were calculated for two miniature sources. Conclusion: It was found that the energy of incident electron, target shape, cross-sectional area of the produced bremsstrahlung, atomic number of materials constituting of the target and output window are the factors with the greatest impacts on the produced X-ray spectrum and the absorbed dose

Background: Fetography has named the radiography of the fetus in utero. Due to the potential risk of radiation-induced cancers and other malignant effects, this procedure has avoided and has completely replaced by ultrasonography. However it has observed that this invasive procedure has still followed in some clinical departments. Objectives: The aim of this study was to assess the current status of the fetography and its prevalence as an un-recommended diagnostic procedure in teaching hospitals of Ahvaz, Iran. Methods: The radiology and ultrasonography reception systems of two teaching hospitals of Ahvaz have investigated to identify pregnant patients who has undergone fetal presentation imaging (cephalic or breech) between 21 March 2013 and 21 March 2015. Results: In general 3741 pregnant women who have undergone fetal-presentation imaging during two past years have identified. There was significant statistically differences between X-ray and ultrasonography examinations (2528 vs. 1213; P value < 0.05), as those have accounted for 67.5% and 32.5% of the performed examinations, respectively. Women younger than 30 years, who were more sensitive to radiation, accounted for 51.2% of the X-ray examinations. The number of fetographies has increased as much as 2.2 fold during 2013 to 2015. Discussion: Women of the investigated hospital have received avoidable fetal irradiation due to fetography then it was a reason for concern. Ultrasonography should be the first-line imaging modality for pregnant women, especially in the case of fetal-presentation.