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Publisher: Mashhad University of Medical Sciences   (Total: 14 journals)   [Sort by number of followers]

Showing 1 - 14 of 14 Journals sorted alphabetically
Archives of Bone and Joint Surgery     Open Access   (Followers: 7)
Avicenna J. of Phytomedicine     Open Access  
Intl. J. of Pediatrics     Open Access   (Followers: 4)
Iranian J. of Basic Medical Sciences     Open Access  
Iranian J. of Medical Physics     Open Access   (SJR: 0.138, h-index: 4)
Iranian J. of Neonatology     Open Access   (Followers: 2)
Iranian J. of Otorhinolaryngology     Open Access   (SJR: 0.266, h-index: 4)
J. of Cardio-Thoracic Medicine     Open Access   (Followers: 2)
J. of Evidence-based Care     Open Access   (Followers: 7)
J. of Fasting and Health     Open Access   (Followers: 1)
J. of Midwifery and Reproductive Health     Open Access   (Followers: 13)
J. of Paramedical Sciences & Rehabilitation     Open Access  
Nanomedicine J.     Open Access  
Reviews in Clinical Medicine     Open Access   (Followers: 2)
Journal Cover Iranian Journal of Medical Physics
  [SJR: 0.138]   [H-I: 4]   [0 followers]  Follow
    
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   ISSN (Online) 2345-3672
   Published by Mashhad University of Medical Sciences Homepage  [14 journals]
  • Determination of Radionuclide Concentration in Human Teeth in Najaf
           Governorate, Iraq

    • Abstract: Introduction: 238U decays with alpha particles emission into 234Th and the series ends with 206Pb. The unstable nucleus loses the energy with emitting ionizing alpha particles for reaching a stable state. It is undergoing alpha decay with decay energy (4.679 MeV). Alpha particles enter the human and animal bodies through inhalation of air or ingestion of contaminated food and water. This study aimed to perform a radiological analysis on the natural alpha particle emission rates of the human teeth as the biomarkers of radiation exposure and environmental pollution. Materials and Methods: This study was conducted on 68 teeth samples of 27 males and 41 females collected from the hospitals distributed across Najaf governorate, including many districts in Iraq. Alpha particle emission rates were measured using CR-39 nuclear track detector. Results: The mean emission rate of alpha particles in the female teeth was 0.0396±0.0070 mBq cm-2, which was relatively higher than that in the male teeth (0.0390±0.0048 mBq cm-2). Nevertheless, there was no significant difference between the female and male teeth regarding the emission rate of alpha particles. Furthermore, the emission rate of alpha particles in the teeth of the samples taken from Kufa (0.0417±0.0057 mBq cm-2) was higher than those obtained from Najaf (0.0384±0.0053 mBq cm-2). Conclusion: As the findings of this study revealed, Najaf governorate had a lower emission rate of alpha particles as compared to other sites of the worldwide. Therefore, it could be concluded that there is no negative consequence threatening the people’s health in this regard.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Film Reject Analysis and Radiation Doses Received by Patients in Selected
           Hospitals in ...

    • Abstract: Introduction: A reject rate is the percentage of diagnostic images repeated due to errors during radiological examinations. The present study aimed to evaluate the patient radiation doses and analyze the film reject rate as part of quality assurance program in three diagnostic centers in Nigeria.Materials and Methods: This study was conducted in three hospitals, namely Federal Medical Center (FMC), General Hospital (GH), and Sacred Heart Hospital (SHH), located in Abeokuta, Ogun State, Southwestern Nigeria. For the purpose of the study, the accepted and rejected radiographs during different X-ray examinations were recorded. A total of 376 rejected and accepted radiographs were evaluated in the three hospitals, and the economic losses due to rejected films were determined. The quality control (QC) tests, which involve kilo voltage (kV), milliampere seconds (mAs), etc, were carried out on the facilities of two out of three hospitals using Victoreen 6000m QC kits. The results of the QC tests and exposure parameters were used to estimate the patient doses for different examinations carried out during the study.Results: Based on the results of the study, the SHH  had the highest estimated annual loss of $225, followed by the FMC and GH with annual monetary losses of $208 and $166, respectively. In addition, the anteroposterior projection of the lumbosacral spine had the highest mean dose (15±1.64 mGy) in this study, which was observed in the SHH. Additionally, at FMC, all the estimated doses were low.Conclusion: Regarding the monetary loss and increase in patient dose burden involved in repeated examinations, it is essential to train personnel on the factors leading to repeated exposures.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Radiobiological Model-Based Comparison of Three-Dimensional Conformal and
           Intensity-Modulated ...

    • Abstract: Introduction: Radiobiological modeling of radiotherapy plans are used for treatment plan comparisons. The current study aimed to compare the three-dimensional conformal radiation therapy (3DCRT) and intensity-modulated radiation therapy (IMRT) plans for nasopharyngeal cancer using radiobiological modeling.Materials and Methods: This study was conducted on 10 patients with nasopharyngeal carcinoma, who were planned for 3DCRT and IMRT treatments by using the TiGRT treatment planning system. The planning target volume (PTV) doses of 70 and 72 Gy were administered for the 3DCRT and IMRT plans, respectively. The BIOLPLAN software and the Niemierko’s equivalent uniform dose (EUD) model were utilized for the estimation of tumor control probability (TCP) and normal tissue complication probability (NTCP). The NTCPs of the spinal cord, brain stem, parotid glands, middle ears, temporomandibular joints (TMJ), mandible, and thyroid were calculated by using two radiobiological models.Results: According to the results, the mean TCPs for 3DCRT and IMRT plans were 89.92%±8.92 and 94.9%±3.86, respectively, showing no statistically significant difference (P=0.08). The NTCPs of the parotid glands, thyroid gland, spinal cord, TMJ, and mandible were considerably lower in the IMRT plans, compared to those in the 3DCRT plans. On the other hand, the calculated NTCPs for the middle ears and brain stem increased for the IMRT plans, which were not statistically significant. On average, the NTCPs of the critical organs were lower based on the EUD model than the Lyman-Kutcher-Burman model.Conclusion: From the radiobiological point of view, the IMRT plans were significantly advantageous over the 3DCRT plans with some small variations in each patient. On average, the two radiobiological models generated different NTCPs depending on the studied organs. Consequently, more studies are needed for the optimization of radiobiological models for the prediction of the treatment outcomes in radiation therapy.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Assessment of Occupational Exposure to External Radiation among Workers at
           the Institute of ...

    • Abstract: Introduction: Assessment of occupational exposure to external radiation and the analysis of associated trends are imperative to observe changes that have taken place over time due to regulatory operations or technological advancements. Herein, we describe the occupational radiation exposure to workers employed in Nuclear Medicine (NM), Radiotherapy (RT), and Diagnostic Radiology (DR) departments at the Institute of Radiotherapy and Nuclear Medicine, Peshawar, Pakistan, and to evaluate the related trends during 2009-2016.Materials and Methods: A retrospective analysis of the dose records of 4320 film dosimeters was performed during 2009-2016. The analyzed quantities included annual collective effective dose, annual average effective dose, distribution of workers, and their annual average effective doses in various effective dose intervals, as well as the maximum and minimum annual individual effective doses.Results: The annual average effective doses in RT, NM, and DR were within the ranges of 1.07-1.45, 1.25-1.55, and 1.03-1.60 mSv, respectively. The majority (90%) of the workers received effective doses in the interval of 1-4.99 mSv, while 10% of the workers received doses within the range of the minimum detectable level-0.99 mSv.  The minimum and maximum annual individual effective doses were 0.30 mSv and 3.96 mSv as recorded in RT and NM, respectively. The annual average effective doses measured for NM, RT, and DR were 1.39, 1.23, and 1.30 mSv, respectively. These values are comparable with the worldwide annual average effective doses.Conclusion: All the workers received doses below the annual dose limit. The status and trends of doses showed that radiation protection conditions were adequate.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Consideration of Individual Brain Geometry and Anisotropy on the Effect of
           tDCS

    • Abstract: Introduction: The response variability between subjects, which is one of the fundamental challenges facing transcranial direct current stimulation (tDCS), can be investigated by understanding how the current is distributed through the brain. This understanding can be obtained by means of computational methods utilizing finite element (FE) models. Materials and Methods: In this study, the effect of realistic geometry and white matter anisotropy on the head electrical current density intensity (CDI) distribution was measured using a magnetic resonance imaging (MRI)-derived FE model at the whole brain, below electrodes, and cellular levels. Results: The results revealed that on average, the real geometry changes the CDI in gray matter and the WM by 29% and 55%, respectively. In addition, WM anisotropy led to an 8% and 36% change of CDI across GM and WM, respectively. The results indicated that for this electrode configuration, the maximum CDI occurs not below the electrode, but somewhere between the electrodes, and its locus varies greatly between individuals.  In addition, by investigating the effect of current density components on cellular excitability, significant individual differences in the level of excitability were detected. Conclusion: Accordingly, consideration of the real geometry in computational modeling is vital. In addition, WM anisotropy does not significantly influence the CDI on the gray matter surface, however, it alters the CDI inside the brain; therefore, it can be taken into account, especially, when stimulation of brain’s internal regions is proposed. Finally, to predict the outcome result of tDCS, the examination of its effect at the cellular level is of great importance.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Determination of Optimum Planar Imaging Parameters for Small Structures
           with Diameters Less ...

    • Abstract: Introduction: The limited spatial resolution of the gamma camera hinders the absolute quantification of planar images of small structures. The imaged structures are affected by partial volume effects (PVEs), which can spread activity and lead to underestimation of the regional distribution.  The use of optimum planar parameters reduces the impact of the limited spatial resolution of the gamma camera and the statistical noise inherent to low photon count, thus improving quantification. In this study, we aimed to determine the optimum planar imaging parameters for small structures. Materials and Methods: A thyroid protocol was used to acquire planar images of the spheres A, B, and C (16 mm, 12 mm, and 11 mm in diameter, respectively) whilst filled with a targeted activity concentration of technetium-99m. One sphere was mounted at the centre of the Jaszczak Phantom and the other two adjacent to its walls using capillary stems fitted on the spheres. The phantom was filled with distilled water. The targeted activity concentrations used were 74 kBq/mL, 100 kBq/mL, 150 kBq/mL, and 300 kBq/mL. Images of the same count per pixel were acquired on 64  64, 128  128, 256  256, 512  512, and 1024  1024 pixels using a vertical detector mounted 5 cm above the phantom. All the images were quantified using ImageJ software, version 1.48a, Java 1.70_51 [64-bit]. Results: The optimum planar imaging parameters established were a matrix size of 128 128 pixels and technetium-99m solution of activity concentration of 300 kBq/ml. Conclusion: The use of optimal imaging parameters reduces the impact of PVEs, leading to improved quantitative accuracy.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Mass Attenuation Coefficients of Human Body Organs using MCNPX Monte Carlo
           Code

    • Abstract: Introduction: Investigation of radiation interaction with living organs has always been a thrust area in medical and radiation physics. The investigated results are being used in medical physics for developing improved and sensitive techniques and minimizing radiation exposure. In this study, mass attenuation coefficients of different human organs and biological materials such as adipose, blood, bone, brain, eye lens, lung, muscle, skin, and tissue have been calculated. Materials and Methods: In the present study, Monte Carlo N-Particle eXtended (MCNP-X) version 2.4.0 was used for determining mass attenuation coefficients, and the obtained results were compared with earlier investigations (using GEometry ANd Tracking [GEANT4] and FLUKA computer simulation packages) for blood, bone, lung, eye lens, adipose, tissue, muscle, brain, and skin materials at different energies. Results: The results of this study showed that the obtained results from MCNP-X were in high accordance with the National Institute of Standards and Technology data. Conclusion: Our findings would be beneficial for use of present simulation technique and mass attenuation coefficients for medical and radiation physics applications.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Monte Carlo Study of Several Concrete Shielding Materials Containing
           Galena and Borated Minerals

    • Abstract: Introduction: The heavyweight concretes have been widely used for constructing medical or industrial radiation facilities with photon sources.Materials and Methods: In this study, heavy concretes containing galena (PbS) and several borated minerals are proposed as suitable materials against photons. The shielding properties of 21 galena concretes containing seven borated minerals with three mixing patterns were evaluated using MCNP4C Monte Carlo code. The attenuation of the gamma radiation is computed under the conditions of narrow and beam geometries. The x-ray sources with 40, 60, 90, and 120 kVp and gamma rays of 99mTc, 131I, 137Cs, and 511 keV annihilation photons were considered. The photon flux values and the x-ray spectrum after applying all the concretes were compared to the ordinary ones. Regarding the results, more photon attenuations obtained by using high density concretes simulation in comparison to ordinary concrete.Results: The results revealed that the concretes containing orthopinokiolite as the borated material made by the third mixing pattern, had the most photon attenuation. According to the results, the shielding properties of the concretes containing different borated minerals were alike against high photon energies, whereas in low energy photons the attenuation depended on the type of borated mineral used in the concretes.Conclusion: The high-density heavy-weighted concretes could be effectively used as multi-purpose shield for radiotherapy rooms and nuclear reactors due to the borated minerals.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • The Effect of Breast Reconstruction Prosthesis on Photon Dose Distribution
           in Breast Cancer ...

    • Abstract: Introduction: Siliconeprosthetic implants are commonlyutilizedfor tissue replacement and breast augmentation after mastectomy. On the other hand, some patients require adjuvant radiotherapy in order to preventlocal-regional recurrence and increment ofthe overall survival. In case of recurrence, the radiation oncologist might have to irradiate the prosthesis.The aim of this study was to evaluate the effect of silicone prosthesis on photon dose distribution in breast radiotherapy. Materials and Methods: The experimental dosimetry was performed using theprosthetic breast phantom and the female-equivalent mathematical chest phantom. A Computerized Tomographybased treatment planning was performedusing a phantom and by CorePlan Treatment Planning System (TPS). For measuring the absorbed dose, thermoluminescent dosimeter(TLD) chips (GR-207A) were used. Multiple irradiations were completed for all the TLD positions, and the dose absorbed by the TLDs was read by a lighttelemetry (LTM) reader. Results: Statistical comparisons were performed between the absorbed dosesassessed by the TLDs and the TPS calculations forthe same sites. Our initial resultsdemonstratedanacceptable agreement (P=0.064) between the treatment planning data and the measurements. The mean difference between the TPS and TLD resultswas 1.99%.The obtained findings showed that radiotherapy is compatible withsilicone gel prosthesis. Conclusion: It could be concludedthat the siliconbreast prosthesis has no clinicallysignificant effectondistribution of a 6 MV photon beam for reconstructed breasts.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • Field-In-Field Plan Versus Tangential Wedged Beam Plan in Chest Wall
           Radiotherapy of ...

    • Abstract: Introduction: In this study, dose distribution of the chest wall in post-mastectomy breast cancer patients was evaluated and compared in the tangential wedged beam (TWB) and field-in-field (FIF) plans.Materials and Methods: Thirty-six patients with left-sided breast cancer were enrolled in this study. The FIF and TWB plans were generated for each patient to compare dosimetric parameters of the chest wall. The maximum dose (Dmax), homogeneity index (HI), conformity index (CI), and uniformity index (UI) were defined and used for comparison of the dosimetric parameters of the planning target volume (PTV) in both FIF and TWB plans. The percentage of volumes receiving at least 10, 20, 30, and 40 Gy of the left lung and 5, 10, 20, 25 and 30 Gy of the heart were used to compare the dosimetric results of the organs at risk. Statistical analysis was performed using SPSS, version 20.Results: The FIF plan had significantly lower HI (P=0.000) than the TWB plan, indicating that the FIF plan was better than the TWB plan in PTV. The V40lung (15.36±4.35 vs. 18.37±4.42) and V30heart (8.15±3.75 vs. 10.94±3.94; P=0.000) were significantly lower in the FIF plan than in the TWB plan. In addition, the monitor unit (MU) was significantly lower in the FIF plan than in the TWB plan (227.76 vs. 323.59; P=0.000).Conclusion: The FIF plan significantly reduced the dose volume of the left lung and heart in post-mastectomy radiotherapy compared to the TWB plan. Therefore, the FIF plan is recommended for this purpose.
      PubDate: Thu, 30 Nov 2017 20:30:00 +010
       
  • A study on slab-wooden dust-slab phantom for the development of thorax
           phantom

    • Abstract: Introduction: Human body is a heterogeneous medium and the determination of accurate dose distribution inside it plays a crucial role in radiotherapy. Present study focus on analyzing the density and isodose depth profiles of 6 mega voltage (MV) beam in a SP34 slab -wooden dust (pine) - SP34 slab (SWS) heterogeneous phantom.Materials and Methods: Density of SP34 slab, wooden dust of pine and thoracic region of selected patients were calculated using CT images. Depth of isodose lines were measured for 6 MV on CT images of chest, SP34 slab phantom and SWS phantom. Dose at depths 2 cm, 13 cm and 21 cm was measured in both the phantoms. Patient specific QA was done using both the phantoms.Results: Mean density of lung, SP34 slabs and wooden dust were found to be 0.29, 0.99 and 0.27 gm/cc respectively. Depths of different isodose lines in SWS phantom were found to be equivalent to that of the mean depths of isodose lines in actual patients. The percentage variation between planned and measured doses was found to be higher in case of SWS phantom as compared to that in case of SP34 phantom. The percentage variation between planned and measured doses in patient specific QA were found to be higher in case of SWS phantom as compared to that in SP34 phantom. Conclusion: Density and isodose depth profiles of SWS phantom are found to be equivalent to that of the actual human thoracic region. Key words: Hounsfield number; patient specific quality assurance; SP34 slab phantom; thorax phantom; SWS phantom.
      PubDate: Mon, 27 Nov 2017 20:30:00 +010
       
  • Verification of Monitor unit calculations for eclipse Treatment Planning
           System by in- house ...

    • Abstract: Introduction: Computerized treatment planning is a rapidly evolving modality depends efficiently on hardware and software. Despite various ICRU recommendations suggest 5% deviation in dose delivery the overall uncertainty shall be less than 3.5% as suggested by B.J. Minjnheer. J. In house spread sheets are developed by the clinical medical physicist to cross verify the dose calculated by the TPS. The Task Group 40 & 114 recommends that the calculation results of any TPS should be independently verified.Materials and Methods: The Monitor unit verification calculation(MUVC) verification was tested for pre-approved and executed treatment plans taken from our Treatment Planning System (TPS) database (Make: Varian Medical System, Model, Eclipse version 13.7).. A total of 108 square fields and 120 MLC shaped fields for Head & Neck cancers, Ca-Cervix, Ca-Oesophagus were taken for evaluation. In house developed spreadsheet based on Microsoft Excel was used in this study. The dose calculation parameters such as Output Factor (O.F), Percentage Depth Dose (PDD) and off axis ratio (OAR) data were taken from the TPS. Results The overall MU ratio lies in the range of 0.999 to 1.02 for square field geometries which showed that there was a deviation of 1% between the TPS calculated and the spread sheet calculated. The MU ratios were 0.995 for Head & Neck plans & 1.012 for Cervix plans with a standard deviation of 0.024 & 0.029 respectively. However we observed the mean MU ratio for Esophagus plans were 1.026 with the standard deviation of 0.040.Conclusion: The independent spreadsheet was designed and tested for most of the routine treatment sites and geometries. The designed spreadsheet is having good agreement with the Eclipse TPS version 13.8 for homogenous treatment sites such as Head & Neck and Cervix
      PubDate: Thu, 09 Nov 2017 20:30:00 +010
       
  • Radiological Assessment of the Artificial and Natural Radionuclide
           Concentrations of Some Wheat ...

    • Abstract: IntroductionArtificial and natural radionuclides there are in environmental materials such as water, soil, rocks, plant, animals, and human body tissues As such, humans and environments are at constant exposure of these radiation types. In this research specific activities of radionuclides and risk assessment of some samples of wheat and barley in Najaf zone (Iraq) were determined.Materials and MethodsIn this study, natural and artificial radioactivity concentrations were determined in wheat and barley and surrounding soil using gamma-ray spectrometry method employing high-purity germanium (HPGe) detector with 88% relative efficiency. According to measured specific activities of radionuclides in food samples and annual consumption excess lifetime cancer risk due gamma radiations were calculated.ResultsSpecific activities of 226Ra, 232Th, 40K and 137Cs in soil samples varied within the ranges of 29.37-38.86, 23.24–45.70, 291.15–549.78 and 1.25–10.82 Bq/kg, respectively. Moreover, specific activities of, 226Ra, 232Th, and 137Cs in the most of wheat and barley samples were lower than minimum detectable activity (MDA). Excess lifetime cancer risk due to the ingestion of wheat and barley were calculated as 0.013×10-3 and 0.006×10-3 respectively, which are lower than the maximum acceptable value (10-3).ConclusionResults of this study showed that the specific activities of natural radionuclides in soil were close to world average. In all soil samples observed artificial radio cesium nuclides. this radionuclide originated from nuclear accidents or weapon test which shows pollution of the studied regions by radioactive dust.
      PubDate: Sat, 04 Nov 2017 20:30:00 +010
       
  • Evaluating the Practice of Chest Radiography Using Different Digital
           Imaging Systems and their ...

    • Abstract: Introduction: The study was undertaken to evaluate the practice of chest radiography using different digital imaging system and its’ influence on dose and image quality. Materials and Methods: The study was carried out in two hospitals for four months from March 2016 to June 2016. Sixty ambulatory patients aged 21 to 60 years who were able to cooperate without difficulty and weighed between 60 to 80 kilograms were selected randomly. The active-matrix, flat panel imagers technology was employed in the DR system for Hospital A while Hospital B used the single read out CR system. The DAP meter was utilized in measuring the entrance surface air kerma. The chest radiographs were evaluated by two radiologists. Results: The mean entrance surface doses (ESD) of 0.098mGy for PA chest for Hospital A was lower than that of 0.161mGy obtained for Hospital B. However, the ESD at both centres were lower than 0.3mGy recommended by The International Atomic Energy Agency (IAEA). The quality of the images for chest radiography for the two hospitals were adequate to make a diagnosis with the ESD and effective dose lower than that recommended by IAEA and UNSCEAR. Conclusion: The study serves to highlight the practice of chest radiography with two different systems and its’ influence on image quality and dose. It can be concluded that there are significant difference in image quality and radiation dose for chest radiography practice using CR and DR in this study.
      PubDate: Sat, 04 Nov 2017 20:30:00 +010
       
  • Indoor radon measurements in the residential areas of Khorram Abad City,
           Iran

    • Abstract: Introduction: Exposure to indoor radon increases the risk of lung cancer. This study examines the levels of indoor radon in dwellings of Khorram Abad city, by using alpha track passive samplers (CR-39) for three months during the winter season of 2016. Materials and Methods: In the present study, the concentration of indoor radon in 56 dwellings was detected. A passive sampling instrument (alpha track detector with CR-39 polycarbonate films) was used to measure indoor radon gas concentrations. The distribution map of indoor radon concentration was prepared using Arc GIS software. Results: The results showed radon concentrations in the dwellings vary from 1.08 to 196.78 Bq/m3, with a mean (±SD) value of 43.43 (±40.37) Bq/m3. The average annual effective dose received by the residents of the study area was estimated to be 1.09 mSv. Our results showed a significant difference between the average radon concentration in villas and apartments, with a higher level in villas. Conclusion: Indoor radon concentration in 10.1% of dwellings was determined to be higher than the limit (100 Bq/m3) recommended by the World Health Organization (WHO).
      PubDate: Sat, 28 Oct 2017 20:30:00 +010
       
  • Optimization of Dose and Image Quality in CR and DR for Common Digital
           Radiographic Examinations

    • Abstract: IntroductionA fine balance of image quality and radiation dose can be achieved by optimization to minimize stochastic and deterministic effects. This study aimed in ensuring that images of acceptable quality for common radiographic examinations in digital imaging were produced without causing harmful effects. Materials and MethodsThe study was conducted in three phases. The pre-optimization involved ninety physically abled patients aged between 20 to 60 years and weighed between 60 and 80 kilograms for four common digital radiographic examinations. Kerma X_plus, DAP meter was utilized to measure the entrance surface dose (ESD) while effective dose (ED) was estimated using CALDose_X 5.0 Monte Carlo software. The second phase, an experimental study utilized an anthropomorphic phantom (PBU-50) and Leeds test object TOR CDR for relative comparison of image quality. For the optimization phase, the imaging parameters with acceptable image quality and lowest ESD from the experimental study was related to patient’s body thickness. Image quality were evaluated by two radiologists using the modified evaluation criteria score lists. ResultsSignificant differences were found for image quality for all examinations. However significant difference for ESD were found for PA chest and AP abdomen only. The ESD for three of the examinations were lower than all published data. Additionally, the ESD and ED obtained for all examinations were lower than that recommended by radiation regulatory bodies. ConclusionOptimization of image quality and dose was achieved by utilizing an appropriate tube potential, calibrated automatic exposure control and additional filtration of 0.2mm copper.
      PubDate: Thu, 26 Oct 2017 20:30:00 +010
       
  • Assessment of X-ray Crosstalk in a Computed Tomography Scanner with Small
           Detector Elements ...

    • Abstract: IntroductionCrosstalk is a leakage of X-ray or light produced in a matrix of radiation detectors or array of photodiodes in one element to other elements impacting on the spatial resolution and contrast of the image. The purpose of this research is assessment of X-ray crosstalk in a Computed Tomography (CT) scanner with small detector elements to estimate the effect of various parameters such as X-ray tube voltage, detector element sizes, scintillator material, impurities in the scintillator material and the material of detector separators on X-ray crosstalk. Materials and methods This study was done using Monte Carlo simulation. In the first step X-ray tube and its energy spectrum in the energies of 80, 100, 120 and 140 keV were simulated. The energy spectrums in these energies were validated by using SpekCalc and t-test. Then other important parts of CT, means filters, detectors and grid were simulated. X-ray crosstalk between CT detectors were calculated in air and also in presence of water phantom to comprise the effect of scattered photons. Finally the influences of some important parameters on the X-ray crosstalk were evaluated. Results In real condition in CT scan with small elements, means when using phantom, crosstalk increases 16-50%. The lowest possible used energies show the reduced crosstalk. Conclusion To decrease the X-ray crosstalk, the voltage of X-ray tube should be as low as possible. The detector elements with small surface and high thickness increase the crosstalk. The amount of crosstalk is reduced by using the proper material for detectors.
      PubDate: Sun, 22 Oct 2017 20:30:00 +010
       
  • Effect of helium neon (632.8 nm) laser and sodium hypochlorite ‎on
           the calf thymus double ...

    • Abstract: Introduction: Low energy helium neon laser (He-Ne) beam light is used in ‎combination with sodium hypochlorite (Na2HOCl3) in the clinical practice. This ‎study aimed to investigate the effect of He-Ne laser (632.8nm) and/or Na2HOCl3 ‎on the calf thymus double strands deoxyribonucleic acid (ctdsDNA). ‎Materials and Methods: ctdsDNA solutions (30µg/ml) exposed to the He-Ne ‎laser (632.8 nm) light in the absence or presence of different concentrations of ‎sodium hypochlorite (Na2HOCl3) up to 60 seconds duration. The levels of nucleic ‎acids that released as uncontaminated and contaminated proteins were used as ‎markers of DNA damage in terms of hypochromasia (DNA strand breakage) and ‎hyperchromasia (separation of DNA strands).‎Results: The mean ±SE concentration of nucleic acids was insignificantly (p > ‎‎0.05) decreased after exposure to laser light irradiation (hypochromasia effect). ‎Laser irradiation insignificantly and inconsistency protect the ctdsDNA molecules ‎from the effect of Na2HOCl3. Sodium hypochlorite at concentrations of 1 and 3 ‎mmol reduced the levels of the nucleic acids that released from contaminated ‎protein by 29.2% and 78.3% of the pre-incubated levels (hyporchromasia effect). ‎Helium-Neon laser (632.8 nm) irradiation induced hypochromasia effect in the ‎uncontaminated and contaminated protein, while Na2HOCl3 induced a remarkable ‎hyperchromasia effect at higher concentrations. ‎Conclusion: He-Ne laser light (632.8 nm) irradiation for short time exerts minor ‎significant effect on the ctdsDNA molecule, and it does not interact with ‎Na2HOCl3 as a synergistic combination against the ctdsDNA molecule. ‎
      PubDate: Sat, 23 Sep 2017 20:30:00 +010
       
  • A Validation Study on Radiation properties of a Novel LiF: Mg, Ti Known as
           IAP-100 (Iranian)

    • Abstract: INTRODUCTION: LiF dosimeter has the most application in medicine. This study aims to evaluate some dosimetric properties of a novel LiF: Mg, Ti known as IAP-100.METHODS AND MATERIALS: An ELEKTA Precise linear accelerator was used to calibrate dosimeters at 6MV energy. In this survey responses of dosimeters to dose were evaluated up to1000 cGy. Background effect was investigated in two different states of dosimeters, including irradiated and unirradiated. Thermoluminescence response dependence to dose rate was investigated. Energy dependence was evaluated in diagnostic and therapeutic ranges. Also, fading effect was evaluated by reading the dosimeters each two hours up to 12 hours post-irradiation.RESULTS: The dosimeters had linear response up to 250 cGy. Passing one day from annealing the dosimeters showed no significant difference compared to the ones which were irradiated two weeks post-annealing. Readout values of dosimeters received 120 cGy at three dose rates of 21, 212, 425 cGy.min-1, were calculated as 125, 123, 121 cGy respectively. Measured values of delivering 80, 120 and 150 cGy prescribed doses at 6MV, 10MV and 15MV were accurate at 6 MV and about 1.5 times more than the prescribed dose at 10 and 15 MV. Thermoluminescence response in diagnostic energy range showed an increasing trend with increasing energy. DISSCUSION: Energy responses of the dosimeter in Megavoltage range are similar at 10 and 15 MV energy values. The increasing thermoluminescence response with increasing energy contradicts with the A.A. Nunn study. The decreasing trend with increasing dose rate is not considered to be statistically significant.CONCLUSIONS: Due to the reproducibility and linear response of the dosimeters in an acceptable dose range, they could be used in diagnostic and therapeutic fields. Effect of absorbed doses from background on low dose studies, mainly in diagnostic radiology range, could be evaluated in more details at subsequent surveys.
      PubDate: Sat, 23 Sep 2017 20:30:00 +010
       
  • Determination of dose-equivalent response of a typical diamond
           microdosimeter in space ...

    • Abstract: Introduction: Microdosimeters are helpful for dose equivalent measurement in unknown radiation fields. The favorable physical and mechanical properties of the detector-grade chemical vapor deposition diamond materials have made the diamond microdosimeters suitable candidate for radioprotection applications in space. The purpose of this work is the investigation of the dose equivalent response of a typical diamond microdosimeter with laser-induced graphitized electrodes for use in space radiation fields.Material and methods: The Geant4 Monte Carlo simulation toolkit was applied to simulate the particle transport within the microdosimeter, and to determine the mean chord length and the dose equivalent response of the microdosimeter, based on the lineal energy dependent quality factor. Results: The linear stopping power of the protons and alpha particles with energies higher than 5 MeV and 10 MeV respectively can be estimated within 20% of deviation using the microdosimeter response. The fluence to dose equivalent conversion coefficients calculated affirms that there is an adequate agreement between the calculated coefficients and other research group results. Conclusion: The reasonable agreement between the dose equivalents calculated in this study and the results reported by other researchers implies that the considered diamond microdosimeter could be an appropriate detector for application in space radiation fields.
      PubDate: Tue, 12 Sep 2017 19:30:00 +010
       
  • The dosimetric Effects of different Multileaf Collimator width on Physical
           Dose Distributions

    • Abstract: Purpose: The study aims to evaluate the dosimetric Effects of different Multileaf Collimator width on Physical Dose Distributions Methods: Forty two Intensity-modulated radiation therapy (IMRT) plans based on the different MLC devices are generated and analyzed to study the effect of MLC width on the plan quality. Results: Improvement in IMRT plan quality using 0.4 cm leaf width in comparison with 1 cm leaf width was evaluated. The 0.4 cm leaf-based plans result in significantly higher Dmean, D98, D95 and V95 (58.86 Gy, 95.11%, 96.57%, 104% and 97.92% respectively) compared to the 1 cm leaf plans (58.66 Gy, 92.56%, 94.56%, 104.14% and 95.72% respectively). Conformation number CN for PTV in 0.4 cm leaf plans is significantly (p < 0.05) better (0.74) than plans with 1 cm leaf (0.67). Also, the 0.4 cm leaf plans significantly (p < 0.05) improve the dose homogeneity, where homogeneity index HI =1.08 for 0.4 cm leaf compared to 1.10 for 1 cm leaf. Using 0.4 cm leaf significantly (p < 0.05) decreases the Integral dose ID to normal tissue compared to 1 cm leaf from 56.09 to 49.46 Gy.Kg.Conclusion: No significant clinical difference between the two plans for a serially functioning normal structure, while the differences in mean doses were statistically significant for parallel functioning normal tissues.
      PubDate: Mon, 11 Sep 2017 19:30:00 +010
       
  • Local diagnostic reference levels for some common diagnostic X-ray
           examinations in Sabzevar ...

    • Abstract: One of the most effective means towards optimization of radiation protection for patients undergoing diagnostic radiology examinations are the diagnostic reference levels. The national diagnostic reference levels (NDRLs) form an efficient, concise and powerful standard for optimizing radiation protection of a patient. the 3rd quartiles of measured ESDs were compared with data previously published. Entrance surface doses (ESD) were directly measured by thermoluminescence dosimeter (TLD) chips sealed in sachet and attached to the skin of patient at the center of x-ray beam axis. In this study, 3rd quartiles of measured ESDs for patients undertaking a particular examination were selected, based on this assumption ESDs for x-ray examination included in this study are as follows: Chest PA- 0.71 mGy, Chest AP- 0.83 mGy, Lumbar Spine AP- 2.53 mGy, Lumbar Spine Lat- 4.38 mGy, Pelvis AP- 1.71 mGy, Abdomen AP- 2.56 mGy Cervical AP-1.14, Cervical Lat-0.76, Skull PA- 1.22 and Skull Lat- 1.01 mGy. Our results were compared with iran DRLs and those reported by NRPB for UK. It is evident that ESDs obtained in this work for Chest PA, Cervical AP, Cervical Lat, AP and LAT Skull Abdomen AP, Pelvis AP, Lumbar AP and Lumbar Lat examination do not exceed DRL values worked out by NPRB. On the contrary for Chest PA higher ESDs were acquired in this study compared with DRLs suggested by NRPB. The differences are related to different film screen combination speed and techniques used in the radiological departments included in these two studies.
      PubDate: Thu, 07 Sep 2017 19:30:00 +010
       
  • Impacts of Low-Level Exposure to Radiation on Natural Ecosystems in Najaf
           and Dhi Qar cities, Iraq

    • Abstract: Introduction: Exposure rates of the background radiation found in selected locations of Najaf and Dhi Qar cities, Iraq. Materials and Methods: Exposure rate measurements have been made using a portable survey meter (SEI Inspector). The frequently recorded readings of the gamma-ray dose rate were observed (82 and 101 nGy h-1). Results: The lowest absorbed dose rates found to be 44 nGyh-1 in Najaf (outside building) and the highest found to be 174±8.7 nGy h-1 in Dhi Qar city (outside building). Overall, absorbed dose rates fell within the range in listed regions worldwide. Conclusions: The selected location in the Najaf and Dhi Qar cities have normal values and not harmful, and not biological effects on people in study area.Results: The lowest absorbed dose rates found to be 44 nGyh-1 in Najaf (outside building) and the highest found to be 174±8.7 nGy h-1 in Dhi Qar city (outside building). Overall, absorbed dose rates fell within the range in listed regions worldwide. Conclusions: The selected location in the Najaf and Dhi Qar cities have normal values and not harmful, and not biological effects on people in study area.
      PubDate: Wed, 06 Sep 2017 19:30:00 +010
       
  • Telecobalt machine beam intensity modulation with Alumimium compensating
           filter using missing ...

    • Abstract: Introduction: This research work sought to generate intensity modulated beams with Alumimium compensating filters for a conventional telecobalt machine based on outputs of a forward planning treatment planning system. Materials and Methods: Bolus placed on the surface of a tissue equivalent phantom were used to achieve beam intensity modulation during treatment planning with the treatment planning system, and the treatment plans replicated on the telecobalt machine with the bolus represented with compensating filters placed at a certain distances from the phantom surface. An equation was proposed for converting a bolus thickness to a compensating filter thickness such that dose at any point within the phantom would be the same as planned. Correction factors were introduced into the proposed equation to account for the influences of field size, treatment depth and applied bolus thickness. The proposed equation was obtained by taking dose measurements on the beam central axis with a particular thickness of the compensating filter mounted on a block tray within beams from the telecobalt machine for various depths and field sizes in a full scatter water phantom, and the same measurements repeated without the compensating filter, such that the heights of water within the phantom were adjusted to get the same dose as before for respective measurements. Results: Dosimetric verification of outputs of the proposed approach in a solid water phantom with calibrated Gafchromic EBT2 films were found to be comparable to that of the treatment planning system with deviations within ± 4.73% (mean of: 2.98±1.05 %). Conclusion: The discrepancies between measured and TPS estimated doses were within the tolerance of ± 5% recommended for dose delivery in external beam radiotherapy, hence the use of the proposed approach for clinical application is recommended.
      PubDate: Wed, 30 Aug 2017 19:30:00 +010
       
 
 
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