Showing papers in "Iranian Journal of Medical Physics in 2020"

A Feasibility Study to Reduce the Contamination of Photoneutrons and Photons in Organs/Tissues during Radiotherapy

Abstract: Introduction: Due to out-of-field effects in radiation therapy, the determination and reduction of both unwanted photon and photoneutron doses are essential for the reasonable assessment of the risks to healthy tissues. Material and Methods: By the application of a multilayer shield throughout the phantom and using two models for photoneutron and photon sources, doses were estimated in a 15-MV linac in tissues and organs. Different neutron moderators were used, and the best materials, such as polyethylene, polystyrene, polyvinyl chloride, paraffin, and water, were reported for shielding purpose. Boron carbide and steel were utilized as neutron and gamma absorbents. Various lengths of the shield in line with phantom stature were also assessed in this study. Results: Except for the target organ, with the shield throughout the phantom, both photoneutron and photon doses approximately reduced by 57-89% and 88-95%, respectively. Extra photoneutron dose in the photon source was also reported due to the shield. Then, unwanted doses, especially photon dose remarkably decreased with increasing the steel thickness. The smaller dimensions of the shield caused also a considerable reduction of the photoneutron and photon doses in the phantom. Conclusion: The application of a multilayer shield reduces the photon dose remarkably in healthy tissues. Therefore, it is recommended to use shielding materials to decrease photoneutron and photon doses, which can cause a reduction in the risk of secondary cancer. Due to the relatively high mass of the shield, it is necessary to design a proper device to maintain and move the structure.

Assessment of Annual effective Dose for Different Age Groups based on Radon Concentrations in the Groundwater of Qassim, Saudi Arabia

Abstract: Introduction: Given that the groundwater is a radon contaminated and used as a source for drinking water, then measuring the amount contamination is of high necessity. Material and Methods: The measurement was performed using RAD-7 detector. Results: The measured radon concentration values ranged 1.20-15.43 Bq/l with the mean of 5.18±0.39 Bq/l. The estimated total annual effective doses based on radon concentrations in drinking water were within the range of 6.34-81.62 µSv/y for infants, 2.34-30.04 µSv/y for children, and 3.07-39.42 µSv/y for adults. Moreover, the corresponding mean values were estimated at 27.41±2.06, 10.08±0.76, and 13.23±0.99 µSv/y, respectively. Conclusion: The total annual effective dose in all samples were within the global average level of ingestion exposure dose value (0.1 mSv/y from radon concentrations) reported by the United Nations Scientific Committee on Effects of Atomic Radiations. Therefore, there are no risks for the consumption of these water samples.

Fabrication and Characterization of Bolus Material Using Propylene Glycol for Radiation Therapy

Abstract: Introduction: This study aimed to evaluate the efficacy of a synthesized bolus in the reduction of damage to body tissues and the protection of the organ at risk (OAR) in radiotherapy application. Several properties of the synthesized bolus, including density, transmission factor, and effective mass attenuation coefficient, were investigated. Material and Methods: The materials used comprising of propylene glycol (PG), silicone rubber (SR), and aluminum (Al). The dimension of the synthesized bolus was measured using an acrylic case with a size of 11×11 cm² and thickness sizes of 0.5, 1, and 1.5 cm. Furthermore, the boluses were irradiated by linear accelerator with the photon beam energies of 6 and 10 MV, using linier accelerator (LINAC) Varian 2300ix. Results: In this research,the density of synthesized bolus was evaluated by mass per volume equation. The results showed that the density of bolus was similar to the density of tissue/water, fat, and air. . Furthermore the bolus with the composition of PG 24%, SR 8%, and Al 1.5% of all energies, transmission factors of 0.978 and 0.984, thickness of 1.5 cm, and effective mass attenuation coefficients of 0.0144 and 0.0107 cm²/g had the closest properties to the body tissues in terms of dosimetry characterization. Conclusion: The results revealed that the synthesized bolus could increase the percentage surface dose, reduce skin-sparing effect, and protect OAR. The findings indicated that the synthesized bolus had a potential application in clinical therapy.

Quality Assurance of LINAC by Analyzing the Profile of 6-MV and 10-MV Photon Beams Using Star Track Device

Abstract: Introduction: According to the American Society of Radiation Oncology, all patients receive radiation therapy during their illness, where radiation is delivered by the medical linear accelerator (Linac). The aim of this study was to evaluate the quality assurance (QA) of the Linac in analyzing the used dose profile in the treatment of cancer tumors. Material and Methods: This experimental study was performed using Linac (synergy device type) at Baghdad Radiotherapy and Nuclear Medicine laboratories, Baghdad, Iraq. The Star Track device was used for the routine quality assurance of the Linac, using photon beam for the reference Dmax and source to surface distance of 100 cm. The Star Track consists of 453 vented parallel plate ionization chambers. Results: The flatness and symmetry of beams for the reference field size did not exceed from ±2%, as they were within the allowed range. Moreover, the penumbra region showed a change in value that did not exceed from ±0.2 cm. using the Star Track method; maximum differences in beam symmetry and beam flatness were measured at 0.76%±2% and 1.17%±2%, respectively. Moreover, the maximum difference in the penumbra region was estimated at 0.12±0.2 cm. Conclusion: The results indicated, the Star Track could successfully calculate the characteristics of dose profile during a time period of 2,500 ms, showing the superiority of this instrument over other verification devices.

Specific Activity and Radiation Hazard of Radionuclides in Wheat and Bean Produced Near Shazand, Iran

Abstract: Introduction: Radionuclides found in foods are harmful to human health. Wheat and bean are among the most important food ingredients in the world. Therefore, this study aimed to determine the specific activity of natural radionuclides in wheat and bean produced near the refinery complex plant. Material and Methods: In order to determine the specific activity of radionuclides, the gamma-ray spectrometry method was used employing a high-purity germanium detector with a relative efficiency of 80%. Results: Our findings showed that the specific activity of the 226Ra isotope of radium had the ranges 232Th isotope of thorium was in the range of not detected (ND)-4.09 and ND-3.62 Bq/kg with the mean values of 2.19 and 2.69 Bq/kg for wheat and bean samples, respectively.The specific activity of the 40K isotope of potassium was obtained as 103.19-168.94 and 129.22-568.98 Bq/kg with the mean values of 142.21 and 458.37 Bq/kg for wheat and bean samples, respectively. The annual effective dose for wheat and bean intake was 0.11-0.52 and 0.02-0.18 mSv, respectively. Furthermore, the mean of excess lifetime cancer risk for wheat and bean samples was calculated as 1.06×10-3 and 0.11×10-3, respectively. The latter values are lower than the world average for bean samples. Conclusion: According to the results of this study, the radiological parameters of wheat were higher than the global average and reference value, which may be due to ash dispersion in this area. For bean, these parameters were lower than the mean value. As a result, it could be concluded that bean is not considered as a threat to consumer health.

Absorbed Dose Assessment from Short-Lived Radionuclides of Radon (222Rn) Decay Chain in Lung Tissue: A Monte Carlo Study

Abstract: Introduction: Internal exposure to radon gas progeny can lead to serious biologic damages to the lung tissue. The aim of this study was to evaluate the absorbed dose by lung tissue due to the exposure from short-lived radioactive products of radon (222Rn) decay using Monte Carlo simulation. Material and Methods: A lung equivalent phantom including 64 air sacs was simulated by MCNPX code. Then, the absorbed dose from short-lived radioactive products of radon decay chain including 218Po, 214Po, 214Pb and 214Bi was calculated for both suspended and deposited states of daughter nuclides inside the lung. Results: The results showed that alpha decay has more contribution to the lung absorbed dose in comparison with the beta and gamma decay. Furthermore, the received dose by the lung was higher when the radon progenies were deposited inside the lung so that the maximum received dose to lung was 100 times higher than that of calculated in suspended state. Conclusion: Short-lived daughter radionuclides of radon decay chain, especially alpha emitter products, can be considered as dangerous internal radiation sources. The biological effects of these daughter radionuclides is more severe when are suspended inside the respiratory system.

Measurement of Radon Concentrations and Surface Exhalation Rates using CR-39 detector in Soil Samples of Al-Diwaniyah Governorate, Iraq

Abstract: Introduction: Natural radioactivity in the soil is considered a major indicator of radiological contamination. Primordial radionuclides are the main source of natural radioactivity. Natural radioactivity transfers radionuclides into the environment and poses radiation hazards to people's health. Therefore, the present study aimed to determine the radon concentration and surface exhalation rate in soil samples collected from different locations of industrial, agricultural, and residential of Al-Diwaniyah governorate, southern Iraq. Material and Methods: In the present study, five different depths of 0, 10, 20, 30, and 40 cm were taken from each location. The radon concentration and exhalation rate were measured using CR-39 detectors (Pershore Moulding Ltd, UK). The CR-39 detectors were left inside plastic cans with soil samples. The tracks of nuclear particles were recorded using an optical microscope. Results: Results of the present study showed that the radon concentrations in soil samples ranged from 163.58 to 689.89 Bq/m3 with a mean value of 350.64 Bq/m3, while surface exhalation rate was found to be ranged from 0.015 Bq/m2.h to 0.063 Bq/m2.h with an average value of 0.031 Bq/m2.h. The obtained results demonstrated that the radon concentration and exhalation rate decreased with increased depth of soil. Conclusion: Based on the current findings, it was found that radon concentrations in all the examined soil samples were within the acceptable value of 600 Bq/m3, according to the International Commission on Radiological Protection and International Atomic Energy Agency. However, the sample S13 from AL-Hamad village with a mean value of 642.51±22.95 Bq/m3 was an exception.

Establishment of Diagnostic Reference Levels and Estimation of Effective Dose from Computed Tomography Head Scans at a Tertiary Hospital in South Africa

Abstract: Introduction: Head scans are the most frequently performed computed tomography (CT) examinations worldwide. However, there is growing concern over the probability of increased cancer risks among the exposed populations. Diagnostic reference levels (DRLs) identify radiation dose that is not commensurate with clinical objectives. The aim of this study was to establish DRLs for CT head procedures and estimate effective dose (ED). Material and Methods: The dose absorbed by the head slice of a Rando Alderson phantom was measured using calibrated lithium fluoride thermoluminescent dosimeters (TLDs) exposed to a CT scanner operated on clinical parameters. The measurements were done at the periphery and center of the slice, and repeated twice with a new set of TLDs. The radiation dose absorbed by the TLDs was read using a Harshaw TLD reader, Model 5500. The measured doses were used to calculate the weighted CT dose index (CTDIw), CT dose index volume (CTDIv), and dose length product (DLP). Finally, the ED was calculated using the formula; ED = k × DLP, where k was considered as 0.0021. Results: The mean absorbed dose was 30.9 mGy, while the established CTDIv and DLP values for the head protocol were 40 mGy and 990 mGy.cm, respectively. Additionally, the ED was calculated as 2.1 mSv. These values compared well with some international values. Conclusion: According to the results of the present study, the established CTDIv, DLP, and ED for head scan were well-compared with some international values, except in the cases using different scan lengths and scanner algorithms.

Utilization of Electronic Portal Imaging Device (EPID) For Setup Verification and Determination of Setup Margin in Head and Neck Radiation Therapy

Abstract: Introduction: Radiation therapy involves a multistep procedure; therefore, the error in patient set up is an inherent part of the treatment. Main purpose of this study was to determine the clinical target volume (CTV) to planning target volume (PTV) in head and neck cancer patients. Material and Methods: A total of 15 patients who had daily portal images during the treatment courses were randomly selected in the present study. Systematic (Σ) and random (σ) errors were evaluated in three directions. The Isogray treatment planning system and Elekta linear accelerator were used in this study. Moreover, we had used MOSIAQ software as arecord and Verify system. Setup margins were calculated using three published margin recipes, including the International Commission on Radiation Units and Measurements (ICRU) report 62, as well as Stroom’s and van Herk’s formulae. Results: Average magnitude of the translational errors was reported between 0.7 and 10 mm. The systematic and random errors for head and neck cancer patients were 3.55 (2.58-4.52) and 1.83 (1.56-2.10) mm, respectively. According to the ICRU report 62, as well as Stoorm’s and van Herk’s formulas, the required margins to cover the target were obtained within the ranges of 3.1-4.9, 6.4-10.5, and 7.7-12.7 mm, respectively. Conclusion: According to the results of the present study, 6.5-10.5 mm extension in CTV to PTV margin can ensure that 90% of the head and neck cancer patients will receive a minimum cumulative CTV dose higher than or equal to 95% of the prescribed dose.

An Enumeration Survey on Diagnostic X-Ray Generators and Essential Safety Parameters in Mizoram, India

Abstract: Introduction: Best radiography practice involves operational optimal machine performance, delivering cost-effective healthcare services under appropriate safety conditions for workers and the public. The present study aimed to investigate the safety status of diagnostic X-ray installations in Mizoram, India. Material and Methods: Linearity of time (sec), linearity of current (mA), output reproducibility, table dose (μGy/mAs), peak voltage (kVp) accuracy, and 16 essential safety parameters of 135 X-ray machines were considered in this study. A battery-operated dosimeter and wide-range digital kVp meter were used to measure output radiation and effective peak potential of X-ray tube. Data analysis was performed using SPSS software to obtain the mean, standard deviation, and coefficient of variation. Results: Among different electronic parameters, 59.2% linearity of time, 82.6% linearity of current, 89.7% kVp accuracy, 35.1% output reproducibility, and 92.8% table dose were beyond the acceptable limits. Based on 16 essential safety parameters, it was observed that 98.7% of X-ray machines did not receive proper quality assurance test, 1.9% of the installations employed lead-line patient entrance doors, 46.8% of the machines were operated without any protective barriers and 83.1% of the units were operated without personnel monitoring service. Conclusion: The present study had concluded with more problems than the previous studies in different parts of the world in this regard. Due to the absence of proper quality control (QC) programs, many installations did not follow standard installation guidelines. The authors recommended that proper QC should be implemented by the frequent monitoring of each and every diagnostic X-ray installation.

Concentration Measurement of 12 Elements in Five Herbal Plants Using Neutron Activation Analysis Approach

Abstract: Introduction: Nowadays, many people use medicinal plants to manage diseases; therefore, detailed knowledge of the type and level of elements present in these plants is of prominent importance.The present study aimed to determine the weight fraction of 12 elements in the five most common medicinal plants in Iran. The names of these plants are caraway (Carum carvi), savory (Satureja hortensis), purslane (Portulaca oleracea), fenugreek (Trigonella foenum-graecum), and milk thistle (Silybum marianum) which were purchased from herbal pharmacies. Material and Methods: The neutron activation method was used to determine the elements. In the current study, neutrons from the research reactor core in Tehran, Iran were used and gamma spectra from radionuclides were recorded using a high purity germanium detector. The mass fractions of 12 elements were determined in the five abovementioned plants. Results: Caraway had the maximum amounts of elements of Fe (8,789 ppm), Cr (8 ppm), and Na (517 ppm) among the selected plants. The savory contained maximum levels of Mn (95 ppm), Cl (3,702 ppm), Ca (18,328 ppm), K (21,562 ppm), and V (2.7 ppm) and the lowest amount of Fe (195 ppm), Zn (13 ppm), Ca (2,243 ppm), Al (99ppm), Mn (26 ppm), and Mg (177ppm) were observed in fenugreek. Conclusion: The highest levels of Cr and Mg were obtained for caraway (8 ppm) and pursalne (3,915 ppm), respectively. These elements can help to decrease blood cholesterol and triglyceride levels. Furthermore, the results showed that these herbs were rich in essential nutrients for metabolic functions.

Effects of Low Dose Gamma Ray on Some Hematological Parameters in Adult Rats

Abstract: Introduction: The study aimed to find the low dose effect gamma ray on some hematological parameters in male albino rats obtained from the Mosul University, IRAQ, and also studied the radioprotective effect of black seed oil on the hematological parameters. Material and Methods: The system is made of 241Am as gamma source .The rats were exposed to gamma radiation for limit period .Hematological investigations in which the red blood cells (RBC) also white blood cells (WBC) were found by the result of Neubauer haemocytometer method hemoglobin(Hb) concentration obtained due to cyanomethaemoglobin test. The packed cell volume (PCV) was determined using the micro-centrifuge method. Platelets were achieved. Results: All hematological parameters found significantly decreased in all groups receiving daily dose of 6 mGy/h for 7h/day for 25, and 50 days compared with those in the control group. However group 2. Treated with 400 mg/kg wt /day for 25 days, showed a significant increase in the mentioned parameters. Groups 3 and 4 were exposed to gamma ray in two stages(at a daily dose 6 mGy/h for 7h /day for 25 and 50 days) .Group 4 showed a significant enhancement in hematological parameter when treated with black seed oil , compared with group3 which had a significant decrease in these parameters compared with the control group. Conclusion: The present work showed the function of black seed oil considered as an advanced material in decreasing the oxidant stress on hematological parameters againstgamma ray with limited dose.

Comparison of Ultraviolet Protection Factor of Pure Cotton and Cotton Coated with Titanium Dioxide Nanoparticles using the Electrospinning Method with Two Ultraviolet-C Generators

Abstract: Introduction: Protection against harmful effects of ultraviolet radiation (UV) is measured under Ultraviolet Protection Factor (UPF) scale. The utilization of protective clothing is the best way to deal with the damage caused by ultraviolet radiation. The purpose of this study was to compare the ultraviolet ray protective factor of pure cotton and cotton coated with titanium dioxide (TiO2) nanoparticles using the electrospinning method with two natural and artificial generators. Material and Methods: This is an analytical-descriptive study in which, a pure cotton fabric and a cotton fabric coated with nanoparticles of dioxiditenium were coated for 10, 20 and 40 minutes, as an example, with the titanium dioxide with two types of sunlight and artificial light (widespread and dotted) beams. UV radiation divided into three spectra A, B and C that we use UV-C to measurement. Finally, the comparison of the average UV-c radiation penetration from different fabrics were conducted. We use SPSS Ver.22 to analyze data and p-value<0.05. Results: The highest and the lowest amount of penetration were for pure and coated cotton fibers for 40 min of UV-C radiation, respectively. As the beam decreases, the UPF rises. In nano-coated fabrics, the amount of beam penetration is lower and absorption is higher giving higher UPF. Conclusion: Due to the very low UPF, cotton fabrics are not suitable for utilization in areas with UV radiation. Therefore, in order to protect against UV radiation, fabrics coated with TiO2 nanoparticles can be used in the domain of health care.

Investigation of LINAC Structural Effects on Photoneutron Specified Parameters Using FLUKA code

Abstract: Introduction: 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. Material and Methods: 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. Results: 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. Conclusion: As a result, it is critical to consider this unwanted absorbed dose, which is seriously influenced by the implemented therapeutic conditions.

Comparison of Pulse Sequences of Magnetic Resonance Imaging for Optimization of Timing and Image Quality

Abstract: Introduction: The present study aimed to three frequently used pulse sequences of magnetic resonance imaging (MRI) to assess the image quality of theses pulse sequences at short acquisition time. Material and Methods: For the purpose of study two tissue equivalent gels were prepared. One gel was made from Polysaccharide and Agarose, whereas second gel was obtained from Ferrous Benzoic Xylenol Orange (FBX) which is tissue equivalent material. 6MV photons were used to irradiate FBX gel from linear accelerator with 25 Gray dose. Imaging parameters are performed in repetition time (TR) for experimental variations. The quantitative analysis included contrast-to-noise ratio (CNR) and signal to noise ratio (SNR). Results: As evidenced by obtained results at 1.5 Tesla, Fast Spin Echo (FSE) and Fast Fluid Attenuated Inversion Recovery (FLAIR) were most comparable in SNR although, acquisition time of FSE is 62%, 9 %, and 15% less than FLAIR at different values of 4000ms, 4200ms and 4600ms of TR. CNR of Conventional Spin Echo (CSE) was 143% and 93% better than FSE and FLAIR respectively. The time difference between CSE and FSE was 6 min and 34 sec while this difference was 6 min and 43 sec between CSE and FLAIR. Conclusion: FSE and FLAIR produced optimal image quality for many tissues. Their reduced acquisition time could make them perfect option for patients who cannot tolerate longer imaging time. Nonetheless long acquisition time cannot undervalue importance of CSE since it has yielded significantly higher contrast and SNR in T2-weighted images among other pulse sequences of MRI.

Radiation Shielding Features of Ordinary and High-Density Concretes Loaded With PbO Micro and Nanoparticles against High-Energy Photons

Abstract: Introduction: The present study aimed to evaluate the impact of PbO nano and micro-sized fillers on ordinary and heavy concretes for different photon energies. Material and Methods: The MCNPX Monte Carlo code (version 2.6.0) was used for all simulations in the present study. A model of narrow-beam geometry was validated and utilized to calculate the linear attenuation of samples. Three concentrations of PbO, including the weight of 23%, 37.5%, and 50% were simulated. The nano- and microparticle-loaded concretes were simulated using the Lattice and Universe properties of MCNPX code. Finally, the mass attenuation coefficients of studied concretes were analyzed and compared in this study. Results: Among all the studied concretes, the highest increase of 11% in attenuation coefficient was seen for concretes doped with PbO nanoparticles. The particle size effect was not observed for 18 MeV photon beam, and maximum difference between nano-fillers and micro-fillers was observed for photon energies around 1 MeV. Conclusion: The difference between nano-fillers and micro-fillers was not significant for heavy concretes in comparison to that for ordinary concrete. It is recommended to apply PbO nanoparticles as effective filler in the ordinary concrete composition for providing higher shielding performance.

Effect of Phantom Size and Tube Voltage on the Size-Conversion Factor for Patient Dose Estimation in Computed Tomography Examinations

Abstract: Introduction: This study aimed to establish the conversion factors to normalize the output dose of volumetric computed tomography dose index (CTDIvol) to the patient dose (i.e. size-specific dose estimate (SSDE)) for various phantom diameters and tube voltages. Material and Methods: In-house cylindrical acrylic phantoms with physical diameters ranging from 8 to 40 cm were developed in this study. Each phantom had a hole in the center and four holes in the peripheral areas. The phantoms were scanned by a Siemens Somatom Definition AS CT Scanner using different tube voltages (i.e. 80, 100, 120, and 140 kVps) and with 200 mAs and 10 mm slice thickness. In addition, the doses in every hole and phantom were measured using a Raysafe X2 CT Sensor. The weighted SSDE (SSDEw) values were calculated using the five holes in every measurement. The size-conversion factors for the body and the head CTDI phantoms were established by dividing the SSDEw for various sizes with the SSDEw at the water-equivalent diameter of 33.90 cm and 16.95 cm, respectively. Results: The results revealed that the size-conversion factor exponentially decreased with an increase in the phantom size. It was also found that the size-conversion factor was affected by the tube voltages. Furthermore, the different size-conversion factor between 80 and 140 kVp was more than 15% in very thin and obese patients. Conclusion: Higher accuracy of the size-specific dose estimation can be achieved considering the impact of the tube voltages beside the size of the patient.

Design and construction of an affordable phantom for electron density measurement and linearity tests of computed tomography systems

Abstract: Introduction: The performance of computed tomography is routinely checked using phantoms, which are known as important diagnostic imaging tools. Depending upon the aim of the study, different phantoms are designed, while trying to satisfy certain levels of diversities in their application. Material and Methods: The present study describes the construction of an inexpensive phantom designed for simultaneous measurements of 12 different samples. The body of the phantom, test tube holders, and test tubes were made of materials of low attenuation coefficient. Body of the phantom was filled with water. Test tubes filled with solutions of known chemical compositions were mounted on the test tube holders. The whole phantom was scanned at 80, 100, 120, 140 kVp to evaluate the performance of the CT system. Using Hounsfield Unit (HU) data from these liquid samples of known electron density, the phantom was calibrated for electron density measurements. Results: The system's accuracy and reproducibility were verified by measuring the HU values for some known materials. According to the results obtained from the experimental datawith liquid samples, the accuracy of the water and noise was within ±3.2 HU and 0.6%, respectively. Moreover, the image uniformity error was less than ±2 HU, and CT system's linearity for calibration was estimated with 99.9% confidence. Conclusion: The present system gives satisfactory results with known samples and can be used with confidence for characterizing unknown materials.

Use of Amorphous Silicon (ASi) Electronic Portal Imaging Devices for Other applications for Linear Accelerator Quality Assurance

Abstract: The success of radiation therapy depends critically on the accuracy of patient alignment in treatment position day after day. Electronic portal imaging devices (EPIDs) are widely used to monitor patient position during daily radiotherapy sessions. To verify other applications for medical linear accelerator quality assurance (linac QA), images of a 10×10 cm² and 18×18 cm² open field were acquired. The EPID was positioned at a fixed detector distance of 150 cm. The wedge profile and wedge factors with high level of accuracy were demonstrated. The profiles acquired using EPID deviated in shape and magnitude by up to 16% from the ion chamber profiles. The use of EPID for linac QA could be simplified by improving the available software analysis tools, thus making it more efficient. The study showed that the EPID aSi500 has the potential to be used as a relative dosimeter, making it a very simple and efficient tool for daily QA. All EPID measurements were performed using the linear accelerator model Varian DMX. The physical characteristics measured in this work suggest that the SLIC-EPID can be an efficient tool for daily QA.

Introduction of a Reliable Software for the Calculation of the Gamma Index

Abstract: Introduction: The gamma index is a known parameter for radiotherapy dose verification. Many free and commercial programs have been written for the calculation of this index. However, the verification of the results has been overlooked in many of the programs. The present study tested the validity of three gamma index calculator programs. Material and Methods: The gamma indices for three measured and calculated dose distribution pairs presented in Low et al., Medical Physics, (1998) were calculated using three programs to compare with the results of the published paper. They included an executable program working in Gnuplot software environment (i.e., Gamma_index.exe), simple implementation of the formulas by MATrix LABoratory (MATLAB) software (i.e., Simple m-file), and CalcGamma MATLAB-based program distributed at GitHub website (i.e., Geurts). The resulted gamma distributions were compared with the three figures of the study by Low et al. Results: According to the results, it was observed that neither Gamma_index.exe nor Simple m-file calculated gamma indices was valid, with up to 31% difference in pass rates. On the other hand, Geurts showed fairly good agreement with the gamma indices presented in Low et al. paper. Conclusion: Use of gamma index calculator programs, such as Gamma_index.exe should strongly be prohibited without verification. Furthermore, the implementation of the gamma index formulas without enough preprocessing of the data results in invalid values. Geurts is a reliable program that can be used in its current form or it can be changed to stand-alone executable software for the use in studies and clinics.

Investigation of Neutron Contamination of Flattening Filter and Flattening Filter-Free 10-MV Photon Beams in Elekta InfinityTM Accelerator

Abstract: Introduction: This study aimed to measure the neutron contamination of flattening filter (FF) and flattening filter-free (FFF) 10-MV photon beams delivered by the Elekta InfinityTM accelerator. Material and Methods: The photoneutron spectrum produced by the Linac head was evaluated using a Monte Carlo (MC) simulation. The geometry and composition of the head Linac material were modelled based on information obtained from the manufacturer. In this simulation, MC N-Particle Transport Code software (MCNP6) was utilized to model the Linac head and simulate the particle transport. Evaluation of neutron contamination was carried out for the Linac with FF and without it (i.e., FFF). In this regard, the FFF beam was built by removing the FF from the Linac components. The scoring plane, as the neutron spectra calculation area for FF and FFF beams, was placed 99 cm from the target. Results: The neutron type produced by the head Linac Elekta InfinityTM 10-MV photon mode was mostly thermal and fast. Although there were differences in the neutron intensity of FF and FFF beams, the type of neutrons produced by these two modes had the same energy. Based on the photoneutron reaction energy threshold, it can be concluded that the neutrons produced from the head Linac were the result of photoneutron interactions of high-energy photons with molybdenum-96 and tungsten-184 isotopes. Conclusion: The photoneutron quantity did not change for FF and FFF beams; however, a larger quantity of neutrons was produced in the FF beam.

Modified Technique for the Visualization of C6/C7 in Lateral Cervical Spine Radiography

Abstract: Introduction: In the Swimmer’s view, the C6 and C7 can be visualized as superimposed on the shoulders. This study aimed to explore the technique to demonstrate C1 to C7 in the lateral spine and improve the diagnostic value in that region. Material and Methods: An experimental study was carried out using a RANDO phantom to obtain images of the lateral cervical spine. Twelve radiographs were taken using different kVps at different centering points. The image quality of the radiographs was evaluated by two radiographers using the modified image quality criteria score sheet adapted from the Commission of European Communities on image quality. A dose area product meter was utilized to estimate the entrance surface dose (ESD); however, CALDose_X5 Monte Carlo software was used to estimate the effective dose. Results: The findings indicated that a higher centering point at 2 inches above the pinna of the ear can clearly visualize the lower cervical spine (C6/C7) and cervicothoracic junction (C7/T1). The results of the Kruskal-Wallis test revealed significant differences (p 0.05) in the ESD between different utilized centering points. The effective dose of the modified technique was reported to be lower, compared to that for the Swimmer’s view. Conclusion: The modified lateral technique can be used to replace the Swimmer’s view to adequately demonstrate the lower cervical spine and cervicothoracic junction with a lower radiation dose while not harming the patient due to movement during positioning.

Diagnostic Reference Level of Computed Tomography Examinations and Need for Dose Optimization in Ondo State, Nigeria

Abstract: Introduction: The present study was conducted to obtain State diagnostic reference levels (DRLs) of five routine computed tomography (CT) examinations from two CT centers in Ondo State and to identify factors responsible for dose variation and escalation in these CT centers. Material and Methods: Acquisition parameters and CT dose indices were collected from the storage drives of the two CT centers namely Federal Medical Centre, Owo and Trauma Center, Ondo, Ondo State, Nigeria, for six months on electronic spreadsheets for cranial, sinus, chest, abdomen and pelvis examinations. In addition, dose indices for multiphase examinations were collected to analyze chest and abdominal doses. Wilcoxon rank-sum test was used to assess variations in dose distributions of the two health institutions. Results: The following diagnostic reference levels (DRLs) were obtained at 91 mGy; 1943 mGy.cm, 69 mGy; 1159 mGy.cm, 45 mGy; 1064 mGy.cm, 50 mGy; 2545 mGy.cm and 26 mGy; 622 mGy.cm in cranial, sinus, chest, abdomen and pelvis examinations respectively. Conclusion: Estimated State DRLs exceed national and other DRLs indicating that there is a need to improve the quality of CT-examination for a better benefit to risk ratio.However, benchmarking DRLs to median dose levels (Achievable dose levels) instead of the upper quartile will be a good starting point in achieving the optimal dose level.

Reversal Trend of Hounsfield Unit Values of Substances with High and Low Effective Atomic Numbers

Abstract: Introduction: In dual-energy computed tomography (DECT), the Hounsfield values of a substance measured at two different energies are the basic data for finding the chemical properties of a substance. The trends of Hounsfield unit (HU) alterations following the changes in energy are different between the materials with high and low Zeff. The present study aimed to analyze the basic principles related to the attenuation coefficient of x-ray photons and a quantitative explanation is given for the mentioned behavior or trend. Material and Methods: A mathematical expression was derived for the HU difference between two different scanner voltages. Attenuation coefficients of diverse substances, such as methanol, glycerol, acetic acid, the aqueous solution of potassium hydroxide, and water were calculated for x-ray scanners operating differently at distinct applied voltages and with diverse inherent or added filters. Results: Findings of the current study demonstrated that the negative or positive outcome of HU(V1) - HU(V2) equation is not determined by the electron density of a substance. However, it is affected by the effective atomic number (Zeff) of the material and machine parameters specified by the source spectrum. Conclusion: According to our results, the sign of HU difference [HU(V1) – HU(V2)] for the variable cases of V2 and V1 gives an indication of the effective atomic number of the material under study. The obtained results might be of diagnostic value in the DECT technique.

Characterization of Wedge Factors and Dose Distributions in Radiotherapy with Symmetric and Asymmetric Physical Wedged Beams of 6 MV Photon Beam

Abstract: Introduction: Physical wedge by modify photon beam shape and intensity has been utilized in radiotherapy to obtain uniformly dose distribution in tumor site with reduced hot spots. Calculation of dosimetric parameters for both symmetric and asymmetric wedged fields is proved necessary during linear accelerator (Linac) commissioning. The present study aimed to achieve output factors and dose profiles for symmetric and asymmetric wedged fields of 6 MV beams. Material and Methods: The Siemens PRIMUS Linac head for 6 MV beam was simulated by BEAMnrc and all dose calculations were performed by DOSXYZnrc code. Percentage depth dose (PDD) and profiles for open and wedged (15° and 45°) fields were compared with corresponding measurements. Wedge factors for 10 x 10 cm2 field were obtained as a function of lateral distance as well for half beam wedged fields. Results: Based on the results of the present study, the calculated doses were in agreement with the measured data. The output factors on the central axis of symmetric wedged beams decreased to 0.693 and 0.307 for 15˚, and 45˚ wedges. The total photon fluence of 15˚ and 45˚ physical wedged fields reduced to 71.6% and 27.7% of open field, respectively. Conclusion: The output factor for asymmetric wedged fields was found to be lower than corresponding symmetric open and wedged fields, particularly at field edges. Lack of scattering photons near the half beam edges resulted in dose fall-off in these regions possible to be overestimated by treatment planning system and consequently caused cold spots at target volume.

Assessment of Maximum Entrance Skin Dose of Patients Undergoing Cardiac Interventional Procedures and Its Correlation with Other Dosimetric Parameters

Abstract: Introduction: In recent years, the number of complex coronary angiography (CA) is increasing rapidly. These procedures have a significant contribution to medical exposure to the general population. Exposure of patients to high doses of x-rays could cause deterministic effects on the skin. Therefore, the assessment of radiation doses of patients is of great importance. This study aimed to assess maximum entrance skin dose (MESD) of patients who underwent interventional cardiology procedures. Moreover, it was attempted to determine the correlation between MESD and other relevant dosimetric parameters. Material and Methods: The MESDs of 32 patients who underwent CA procedures were measured by an array of thermoluminescence dosimeters (TLDs). In this study, a Perspex tray consisting of 5 rows and 6 columns was used to hold the TLDs. Its long axis was perpendicular to the long axis of the table, and the top edges of the tray were approximately equal to the patient’s shoulders. Results: The results revealed a linear relationship between dose area product (DAP) values and MESDs (R2=0.89; P=0.00). In addition, there was a significant association between MESD and fluoroscopy time (R2=0.89). Moreover, a weak correlation was observed between MESD and the number of frames per second (R2=0.23). Conclusion: According to the results, the recorded DAP values and fluoroscopy time can be used to estimate the MESDs of patients undergoing coronary fluoroscopy procedures.

Radiological Hazard Assessment of Radionuclides in Sediment and Water Samples of International Meighan Wetland in Arak, Iran

Abstract: Introduction: There are natural and artificial radioactive nuclei in our environment, as well as in the structure of the living organism. Currently, industrial and municipal pollution has also an impact on increasing the level of radiation. The present study investigated the effect of inlet water from Arak Wastewater Treatment Plant on international Meighan Wetland and assessed the radiological indicators of sediments and water samples in this area. Material and Methods: In this study, the specific activity of radionuclides in water and sediment samples taken from the water entry areas of the international Meighan wetland was determined using a high purity germanium detector (Baltic Scientific Instrument LTD, 005- Latvia). Radiological indices for collected samples were calculated, and the topographical maps of radiation dose distribution were plotted using Surfer software (version 13). Results: Specific activities of 226Ra, 232Th, 40K, and 137Cs in sediment samples were in the range of 14.44-26.58, 22.78-34.56, 360.84-447.79, and 0.7-13.03 , respectively. The average values ​​of the external hazard index for sediment samples were calculated at 0.25. Conclusion: According to the obtained results, it can be concluded that pollution is more embedded in the Treatment Plant's basin, and a small amount goes to the wetlands. Radioactivity in the research area is normal, and topographic maps show that the distance from the entrance reduces the activity of radium and increases the activity of cesium. Assessment of hazard indicators showed that radiation levels in this area are not dangerous to human health.

An Evaluation of Effects of Black Grape and Ginger Extracts on Hematological Alteration and Lipid Peroxidation of Hepatocyte in Irradiated Albino Mice

Abstract: Introduction: Exposure to ionizing radiation can trigger adverse biological effects on healthy tissues, such as causing hematological toxicity and potential injury to different organs. Ionizing radiation has sufficient energy to liberate electrons from atoms leaving them with unpaired electrons; hence ionizing them and producing free radicals. In the current study, the risk of exposing to 6 Gy x-irradiation on alteration of some hematological parameters and liver tissue lipid peroxidation activity in albino mice in the presence and absence of black grape and ginger extracts as antioxidants have been investigated. Material and Methods: Albino mice were exposed to 6 Gy wholebody xirradiation in the absence and presence of black grape and ginger extracts (10mL/Kg). Results: The results of the present study showed a significant decrease in mice red blood cell count, hemoglobin, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin, following the exposure to 6 Gy x-irradiation (P≤0.05), while all the mentioned parameters were relatively shifted toward the normal values in the mice that received black grape and ginger extracts as a treatment prior to the radiation. Accordingly, our results demonstrated a noticeable increase in the malondialdehyde analysis (MDA) level in the 6 Gy group, while a slight depletion in the MDA level was observed in the group of mice that received black grape and ginger extracts, compared to that of the control group. Conclusion: the administration of black grape and ginger extracts prior to irradiation may protect the mice from excess hepatocyte lipid peroxidation and alteration of hematological parameters.

Transfer of Radio-Adaptation via Serum: A Preliminary Report

Abstract: Introduction: Adaptive response is one of the important concepts in radiobiology. The present report aimed to transfer the radio-adaptation via serum. Material and Methods: In total, 50 male adult Wistar rats were randomly divided into 6 groups, including control, serum control, low-dose (100cGy), low-dose/lethal, serum/lethal, and lethal (8Gy). Exposure was carried out by a linear accelerator (Elekta Synergy® Platform) with a 40×40cm field size. The animals were monitored in terms of the endpoints of the survival rate, and at the first stage, the rats were exposed to the low doses of radiation. Subsequently, the serum was injected intraperitoneally under sterile conditions 6 h after low-dose exposure. The Kaplan Meier Survival Curve was used to evaluate the survival rate (p <0.05). Results: There was a significant difference among different groups regarding the survival rates. Moreover, a statistically significant difference was observed between low-dose/lethal and low-dose/serum, low-dose/lethal and lethal, and low-dose/serum and lethal (P=0.001). Similarly, there was a statistically significant difference between the control and experimental groups regarding the survival rates (P=0.001). Conclusion: To the best of our knowledge, this method can lead to immunological responses or unknown mechanisms that result in the increased survival adaptive response to subsequent high-dose radiation.

A New Method to Improve Automated Classification of Heart Sound Signals: Filter Bank Learning in Convolutional Neural Networks

Abstract: Introduction: Recent studies have acknowledged the potential of convolutional neural networks (CNNs) in distinguishing healthy and morbid samples by using heart sound analyses. Unfortunately the performance of CNNs is highly dependent on the filtering procedure which is applied to signal in their convolutional layer. The present study aimed to address this problem by applying filter bank learning concept in CNNs. Material and Methods: In proposed method, the filter bank of CNN is updated based on a cross-entropy minimization rule to extract higher-level features from spectral characteristics of the heart sound signal. The deeper level of the extracted features in parallel with their spectral-based nature leads to better discrimination between healthy and morbid heart sounds. The proposed method was applied to three different heart sound datasets of PASCAL-A, PASCAL-B, and Kaggle, including normal and abnormal categories. Results: The proposed method obtained a true positive rate (TPR) between minimally 86% and maximally 96% (if FPR=0%) among all the examined datasets. In addition, the false-positive rate (FPR) was obtained as 7-8% (if TPR=100%) among the mentioned datasets. Finally, the accuracy was achieved in the range of 93-98% when the FPR was 0% and within the range of 96-96.5% when the TRP was 100%. Conclusion: Increased TPR in the proposed method (96% for the proposed method vs. 87% for CNN) in parallel with a decrease in its FPR (7% for the proposed method vs. 10% for CNN) showed the proposed method's superiority against its well-known alternative in automated self-assessment of the heart.