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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: 6)
J. of Fasting and Health     Open Access   (Followers: 1)
J. of Midwifery and Reproductive Health     Open Access   (Followers: 12)
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
    
  This is an Open Access Journal Open Access journal
   ISSN (Online) 2345-3672
   Published by Mashhad University of Medical Sciences Homepage  [14 journals]
  • 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
       
  • Effects of Mobile Phone Radiation on Surface Tension and Volume Flow Rate
           of Human Blood groups

    • Abstract: Introduction: The great use of electrical appliances in different life applications is one of the most obvious concerns because of its possible health drawbacks. These investigation reports results of electromagnetic field effect emitted from mobile phones on some biophysical parameters of human blood belonging to blood groups A, B, AB & O collected from the normal persons. The parameters observed are surface tension, volume flow rate of blood. This article displays a comparative data of the above parameters for control group and test group.Materials and Methods: The blood samples were collected from healthy persons and stored in heparin as anticoagulant. The test samples were exposed with mobile phone up to 1 hour with the interval of 15 min. The parameters such as surface tension and volume flow rate of normal and irradiated blood samples were measured using capillary viscometer, developed at Biophysics Laboratory, Nizam College, Osmania University, Hyderabad, India.Results: It is interesting to note that surface tension of blood, irrespective of blood group, is increased significantly, when blood exposed to radiation produced by mobile phone. Volume flow rate decreases significantly in A, B and AB blood groups, and increases in blood group O, when blood exposed to radiation produced by mobile phone.Conclusion: Mobile phone radiation has significant effect on surface tension and volume flow rate of human blood of different blood groups. 
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Assessment of Patient Radiation Dose in Interventional Procedures at
           Shahid Madani Heart Center ...

    • Abstract: Introduction: Coronary angiography is the most common angiographic procedure for diagnosis and treatment of the heart diseases. Herein, we aimed to evaluate the entrance surface dose (ESD), dose area product (DAP), as well as cancer risk in interventional cardiology procedures. Materials and Methods: This study was conducted during July-December 2015 at Shahid Madani Heart Center in Khorramabad, Iran. A total of 225 adult patients including 122 females and 103 males regardless of the risk factors for coronary diseases were participated. Of them, 199 and 26 patients underwent diagnostic coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA), respectively. Each patient underwent CA or PTCA separately. All the procedures were carried out using Siemens angiography system with the pulsed fluoroscopy of 10-30 pulses/s and cine frame rate of 15 frames/s. DAP, ESD, fluoroscopy time (FT), as well as the number of sequences and frames per sequence were collected for each 199 CA and 26 PTCA procedures. Results: The median values of DAP were 19.77±14.88 and 57.11±33.36 Gy.cm2 in CA and PTCA, respectively. In addition, the median values of ESD were 323.12±245.39 and 1145.22±594.42 mGy in CA and PTCA, respectively. FTs were 114.59±74.33 s in CA and 424.15±292.93 s in PTCA. Conclusion: The average patient dose and cancer risk estimates in both CA and PTCA were consistent with the reference levels. However, in agreement with other interventional procedures, dose levels in the interventional cardiology are influenced by staff and clinical protocols, as well as the type of equipment. 
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Finite Element Analysis of Tissue Conductivity during High-frequency and
           Low-voltage ...

    • Abstract: Introduction: Irreversible electroporation (IRE) is a process in which the membrane of the cancer cells are irreversibly damaged with the use of high-intensity electric pulses, which in turn leads to cell death. The IRE is a non-thermal way to ablate the cancer cells. This process relies on the distribution of the electric field, which affects the pulse amplitude, width, and electrical conductivity of the tissues. The present study aimed to investigate the relationship of the pulse width and intensity with the conductivity changes during the IRE using simulation.Materials and Methods: For the purpose of the study, the COMSOL 5 software was utilized to predict the conductivity changes during the IRE. We used 4,000 bipolar and monopolar pulses with the frequency of 5 kHz and 1 Hz, width of 100 µs, and electric fields of low and high intensity. Subsequently, we built three-dimensional numerical models for the liver tissue.Results: The results of our study revealed that the conductivity of tissue increased during the application of electrical pulses. Additionally, the conductivity changes increased with the elevation of the electric field intensity.Conclusion: As the finding of this study indicated, the IRE with high-frequency and low electric field intensity could change the tissue conductivity. Therefore, the IRE was recommended to be applied with high frequency and low voltage. 
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Decision Support System for Age-Related Macular Degeneration Using
           Convolutional Neural Networks

    • Abstract: Introduction: Age-related macular degeneration (AMD) is one of the major causes of visual loss among the elderly. It causes degeneration of cells in the macula. Early diagnosis can be helpful in preventing blindness. Drusen are the initial symptoms of AMD. Since drusen have a wide variety, locating them in screening images is difficult and time-consuming. An automated digital fundus photography-based screening system help overcome such drawbacks. The main objective of this study was to suggest a novel method to classify AMD and normal retinal fundus images. Materials and Methods: The suggested system was developed using convolutional neural networks. Several methods were adopted for increasing data such as horizontal reflection, random crop, as well as transfer and combination of such methods. The suggested system was evaluated using images obtained from STARE database and a local dataset. Results: The local dataset contained 3195 images (2070 images of AMD suspects and 1125 images of healthy retina) and the STARE dataset comprised of 201 images (105 images of AMD suspects and 96 images of healthy retina). According to the results, the accuracies of the local and standard datasets were 0.95 and 0.81, respectively. Conclusion: Diagnosis and screening of AMD is a time-consuming task for specialists. To overcome this limitation, we attempted to design an intelligent decision support system for the diagnosis of AMD fundus using retina images. The proposed system is an important step toward providing a reliable tool for supervising patients. Early diagnosis of AMD can lead to timely access to treatment.
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Evaluation of Effect of Different Computed Tomography Scanning Protocols
           on Hounsfield Unit and ...

    • Abstract: Introduction: In radiotherapy treatment planning system (TPS), basic input is the data from computed tomography (CT) scan, which takes into account the effect of inhomogeneities in dose calculations. Measurement of CT numbers may be affected by scanner-specific parameters. Therefore, it is important to verify the effect of different CT scanning protocols on Hounsfield unit (HU) and its impact on dose calculation. This study was carried out to analyse the effect of different tube voltages on HU for various tissue substitutes in phantom and their dosimetric impact on dose calculation in TPS due to variation in HU–relative electron density (RED) calibration curves. Materials and Methods: HU for different density materials was obtained from CT images of the phantom acquired at various tube voltages. HU-RED calibration curves were drawn from CT images with various tissue substitutes acquired at different tube voltages used to quantify the error in dose calculation for different algorithms. Doses were calculated on CT images acquired at 120 kVp and by applying CT number to RED curve obtained from 80, 100, 120, and 140 kVp voltages. Results: No significant variation was observed in HU of different density materials for various kVp values. Doses calculated with applying different HU-RED calibration curves were well within 1%. Conclusion: Variation in doses calculated by algorithms with various HU-RED calibration curves was found to be well within 1%. Therefore, it can be concluded that clinical practice of using the standard HU-RED calibration curve by a 120 kVp CT acquisition technique is viable.
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Dose Evaluation for Common Digital Radiographic Examinations in Selected
           Hospitals in Pahang ...

    • Abstract: Introduction: In digital radiography, radiographers tend to increase exposure factors to acquire an acceptable image quality thereby increasing radiation dose to patients.  Regarding this, the present study aimed to re-evaluate the exposure parameters and to ascertain the entrance surface dose (ESD) and effective dose (ED) of posterior-anterior (PA) chest, abdomen, and anterior-posterior (AP) lumbosacral spine radiography.Materials and Methods: This study was conducted on 180 physically able patients with age of 20-60 years and weight of 60-80 kg referred to Hospital Sultan Haji Ahmad Shah (HOSHAS) and Hospital Tengku Ampuan Afzan (HTAA).Image acquisition was performed using digital radiography. The ESD and ED were determined using CALDose_X 5.0 software.Results: The ESD and ED for PA chest were 0.098 mGy and 0.012 mSv in HOSHAS, while in HTAA were 0.161 mGy and 0.021 mSv respectively. Regarding the abdomen, the ESD and ED were 2.57 mGy and 0.311 mSv in HOSHAS and 2.16 mGy and 0.262 mSv in HTAA respectively. For AP lumbosacral spine, the ESD and ED for HOSHAS were 2.65 mGy and 0.222 mSv, while in HTAA were 2.357 mGy and 0.201 mSv respectively. Conclusion: The findings revealed the use of high kVp, automatic exposure control, correct focus image receptor distance, tight collimation and additional filter resulted in a lower ESD. The ESD and ED obtained in this study were comparable with those reported by other studies and lower than the values recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation in 2008.
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Detection of Melanoma Skin Cancer by Elastic Scattering Spectra: A
           Proposed Classification Method

    • Abstract: Introduction: There is a strong need for developing clinical technologies and instruments for prompt tissue assessment in a variety of oncological applications as smart methods. Elastic scattering spectroscopy (ESS) is a real-time, noninvasive, point-measurement, optical diagnostic technique for malignancy detection through changes at cellular and subcellular levels, especially important in early diagnosis of invasive skin cancer, melanoma. In fact, this preliminary study was conducted to provide a classification method for analyzing the ESS spectra. Elastic scattering spectra related to the normal skin and melanoma lesions, which were already confirmed pathologically, were provided as input from an ESS database. Materials and Methods: A program was developed in MATLAB based on singular value decomposition and K-means algorithm for classification. Results: Accuracy and sensitivity of the proposed classifying method for normal and melanoma spectra were 87.5% and 80%, respectively. Conclusion: This method can be helpful for classification of melanoma and normal spectra. However, a large body of data and modifications are required to achieve better sensitivity for clinical applications.
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Evaluation of Tumor Control and Normal Tissue Complication Probability in
           Head and Neck Cancers ...

    • Abstract: Introduction: The ultimate goal of radiation treatment planning is to yield a high tumor control probability (TCP) with a low normal tissue complication probability (NTCP). Historically  dose volume histogram (DVH) with only volumetric dose distribution was utilized as a popular tool for plan evaluation  hence present study aimed to compare the radiobiological effectiveness of the cobalt-60 (Co-60) gamma photon and 6MV X-rays of linear accelerators (Linac) in the radiotherapy of head and neck tumors.  Materials and Methods: TCP and NTCP were calculated using DVH through the BIOPLAN software developed by Sanchez-Nieto and Nahum . The treatment planning was performed for all the patients using both treatment modalities (i.e., Co-60 and 6 MV Linac). The TCP was also manually calculated using a mathematical formula proposed by Brenner’s et al. Results: The average TCP calculated by the BIOPLAN for Co-60 and 6 MV X-rays were 44.6% and 60.8%, respectively. Furthermore, the average NTCPs obtained for the organ at risk, namely optic nerve, for Co-60 and 6 MV X-ray were 0.24 % and 0.03 %, respectively. Regarding the spinal cord, the average NTCPs for Co-60 gamma photon and 6 MV X-ray of Linac were 0.05 % and 0.002%, respectively. Conclusion: As the findings of the present study indicated, Co-60 unit could provide comparable TCP along with minimal NTCP, compared to the high-cost technologies of Linac. The design of treatment plans based on the radiobiological parameters facilitated the judicious choice of physical parameters for the achievement of high TCP and low NTCP.
      PubDate: Thu, 31 Aug 2017 19:30:00 +010
       
  • Determination of optimum planar imaging parameters for small structures
           with diameters less ...

    • Abstract: Background: The limited spatial resolution of the gamma camera hinders absolute quantification of planar images of small structures. The imaged structures are affected by the partial volume effects (PVEs) which spread activity hence underestimation. 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. The study aimed at determination of optimum planar imaging parameters for small structures.Materials and Methods: A thyroid protocol was used to acquire planar images of spheres A, B and C (diameters 16 mm; 12 mm and 11 mm 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 activity free 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 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, technetium-99m solution of activity concentration 300 kBq/mL. Conclusion: Use of optimal imaging parameters reduces the impact of PVEs leading to improved quantitative accuracy.
      PubDate: Wed, 30 Aug 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
       
  • Field-in-Field plan versus Tangential Wedged Beams plan in chest wall
           radiotherapy of ...

    • Abstract: Introduction In this study dose distribution of the chest wall in post-mastectomy breast cancer patients were evaluated and compared in the tangential wedged beams (TWB) and field-in-field (FIF) plans.Materials and Methods36 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), the mean dose (Dmean), the homogeneity index (HI), the conformity index (CI) and the uniformity index (UI) were defined and used for comparison of the dosimetric parameters of the planning target volume (PTV) in both the FIF and the TWB plans. Dmean and 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. All statistical analysis was performed using the SPSS version 20 software.ResultsThe FIF plan had significantly lower HI (p = 0.000) than TWB plan, which means that FIF plan was better than TWB plan in the PTV. The V10lung (25.28±5.91 vs. 27.19±6.22), V40lung (15.36±4.35 vs. 18.37±4.42), V10heart (11.34±4.40 vs. 14.06±4.31) and V30heart (8.15±3.75 vs. 10.94±3.94) were significantly lower in the FIF plan than in the TWB plan. Dmean heart (5.08±1.84 vs. 6.39±1.95) and Dmean left lung (10.50±2.51 vs. 11.70±2.69) with (p=0.000), were significantly lower in the FIF plan than in the TWB plan. Also the Monitor Unit (MU) was significantly lower in the FIF plan than the TWB plan (227.76 vs. 323.59).ConclusionUsing the FIF plan significantly reduced the dose volume of the left lung and heart in chest wall radiotherapy of post-mastectomy patients compared using the TWB plan. Therefore the FIF plan is recommended for post-mastectomy radiotherapy.
      PubDate: Wed, 16 Aug 2017 19:30:00 +010
       
  • Assessment of Occupational Exposure from External Radiation to Workers at
           IRNUM, Pakistan ...

    • Abstract: Introduction: Assessment of occupational exposure from 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 improvements. This study was conducted to reveal and describe the occupational radiation exposure of workers employed in Nuclear Medicine (NM), Radiotherapy (RT) and Diagnostic Radiology (DR) at Institute of Radiotherapy and Nuclear Medicine (IRNUM) Peshawar, Pakistan and to evaluate the related trends over a period of 2009-2016.Materials and Methods: A retrospective analysis of the dose record of 4320 film dosimeters was done for the time interval of 2009-2016. A film badge dosimetry service was provided by Radiation Dosimetry Laboratory, Islamabad, Pakistan on a monthly basis. The quantities analyzed during this study include annual collective effective dose, annual average effective dose, distribution of workers and their annual average effective dose in various effective dose intervals.Results: The annual average effective doses in RT, NM and DR were in the range of 1.07-1.45, 1.25-1.55 and 1.03-1.6 mSv respectively. Majority (90%) of workers received doses falling in the effective dose interval of 1-4.99 mSv, while 10% of the workers received doses in the range of MDL-0.99 mSv. The annual average effective dose values measured for NM, RT and DR averaged over a block of 8 years, are found to be 1.39, 1.23 and 1.30 mSv, respectively. These values are comparable with worldwide annual average effective dose cited by UNSCEAR.Conclusion: All workers received doses below the annual dose limit. The status and trends of doses show that radiation protection conditions were adequate. The establishment of PNRA as an independent regulatory body gives fruitful outcomes as reflected by the status and trends of occupational exposure in the present study and indicator that the doses could be further abridged in the succeeding years.
      PubDate: Sun, 13 Aug 2017 19:30:00 +010
       
  • Radiobiological model based comparison of three dimensional conformal and
           intensity modulated ...

    • Abstract: Introduction: in the current study, radiobiological modeling was used to compare the three dimensional conformal radiation therapy (3DCRT) and intensity modulated radiation therapy (IMRT) plans of nasopharyngeal cancer.Methods and materials: 10 nasopharynx (NPC) patients were planned for 3D-CRT and IMRT treatments by using TiGRT treatment planning system. The PTV dose of 70 and 72 Gy was administered for 3DCRT and IMRT plans respectively. The Biolplan software and the Niemierko’s equivalent uniform dose (EUD) model were utilized for tumor control probability (TCP) and normal tissue complication probability (NTCP) calculations. NTCP of spinal cord, brain Stem, parotid glands, middle ears, temporo-mandibular joints (TMJ), mandible, and thyroid were calculated by using two radiobiological models. Results: The mean TCP’s for 3DCRT and IMRT were 89.92%±8.92 and 94.9%±3.86, respectively, with no statistically significant difference (p-value=0.08). The NTCPs of parotid glands, thyroid gland, spinal cord, TMJ and mandible were considerably lower for IMRT plans. On the contrast, the calculated NTCP’s for middle ears and brain stem increased for IMRT plans which were not statistically meaningful. On average, the EUD model estimated NTCP of critical organs lower than the LKB model.Conclusion: From radiobiological point of view, the IMRT plans were significantly advantageous over the 3DCRT plans with some small variations in each patient. On average, two radiobiological models generated different NTCPs depending on the studied organs. Consequently, more studies are needed for optimization of radiobiological models for prediction of treatment outcome in radiation therapy.
      PubDate: Fri, 21 Jul 2017 19:30:00 +010
       
  • The effect of breast reconstruction prosthesis on photon dose distribution
           in breast cancer ...

    • Abstract: ABSTRACTIntroductionSubcutaneous prosthetic implants are routinely used for cosmetic augmentation and for tissue replacement following mastectomy. On the other, some patients require adjuvant radiotherapy for prevention of local-regional recurrence and increase overall survival. In the event of recurrence, the radiation oncologist may be forced to irradiate the prosthetic device. The aim of this study was to evaluate changes in photon dose distributions due to the breast prosthesis.Materials and Methods Experimental dosimetry was performed by using the prosthetic breast phantom and the female-equivalent mathematical chest phantom. A CT-based treatment planning was done within the phantom by CorePlan treatment planning system (TPS). For measuring the absorbed dose, Thermoluminescent Dosimeters (TLD) chips (GR-207A) were utilized. Multiple irradiation experiments were performed for all TLD positions, and the absorbed dose by TLDs was read by LTM reader. SPSS statistical software was used for data analyses.ResultsStatistical comparisons were done between absorbed dose values by TLDs and TPS calculations at same sites. Our initial results have shown acceptable agreement (p=0.064) between treatment planning data and measurements. The mean difference was 1.99% between TPS and TLD results.The obtained findings showed that radiotherapy and use of silicon gel prosthesis were compatible. ConclusionIt appears to ours that the silicon breast prosthesis has no clinical significant effect in the 6 MV photon beam distribution for reconstructed breast patients.
      PubDate: Mon, 03 Jul 2017 19:30:00 +010
       
  • Determination of radionuclides concentration in human teeth in Najaf
           governorate, Iraq

    • Abstract: Introduction: This study concentrated on the radiological analysis of natural alpha particle emission rates from human teeth as biomarkers of radiation exposure and environmental pollution. Materials and Methods: Sixty eight teeth samples (27 males, 41 females) collected from hospitals distributed across the Najaf governorate including many districts in Iraq. Alpha particle emission rates measured using nuclear track detector (CR-39). Results: The emission rate of alpha particles in female teeth was 0.0396 ±0.0070 mBq cm-2, which is somewhat higher than male teeth (0.0390 ±0.0048 mBq cm-2). There are not significant differences between emission rate of alpha particles in female and male teeth. Whereas, the emission rate of alpha particles in the teeth in Kufa (0.0417±0.0057 mBq cm-2) somewhat larger than in the teeth in Najaf (0.0384±0.0053 mBq cm-2). Conclusion: It is concluded that the emission of alpha particle rate was low, as compared with results obtained from worldwide researches, so has no negative consequence for people health.
      PubDate: Thu, 22 Jun 2017 19:30:00 +010
       
  • Films 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. In this study, analysis of film reject rate was undertaken as part of quality assurance programme in selected diagnostic centers in Nigeria and patient radiation doses were also evaluated.Materials and Methods: A survey of both accepted and rejected radiographs used during different X-ray examinations was carried out in three hospitals in Abeokuta, Ogun State, Nigeria. A total of 376 rejected and accepted radiographs were evaluated in the three hospitals, and the losses due to rejected films were evaluated. Quality control (QC) tests which involve: kilo-voltage (kV), milli-Ampere seconds (mAs) etc, were carried out on the facilities of two out of three hospitals investigated using Victoreen 6000m QC kits. The results of the QC tests and exposure parameters were used to estimate patient radiation doses for different examinations carried out during the study.Results: Results of the study showed that Sacred Heart Hospital (SHH) has the highest estimated annual loss of $225. At Federal Medical Centre (FMC) and General Hospital (GH), estimated annual monetary losses of $208 and $166, respectively, were obtained. A mean dose of 15 ± 1.64 mGy was recorded at SHH in lumbosacral AP projection and this is the highest in this study. At FMC, all the estimated doses were low.Conclusions: Owing to 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: Mon, 12 Jun 2017 19:30:00 +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 physics and radiation physics. The investigated results are being used in various applications of medical physics for improved and sensitive techniques and minimum exposure for radiation protection. 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 Methods: In the present study, Monte Carlo N-Particle Transport Code System-eXtendend (MCNPX-version 2.4.0) has been used for determination of mass attenuation coefficients and compared with earlier investigations GEANT4 and FLUKA for blood, bone, lung, eye lens, adipose, tissue, muscle, brain, and skin materials at different energies. Results: The results of this study showed that obtained results from MCNPX were in high accordance with standard NIST data. Conclusion: It can be concluded that recent study would be useful for use of standard simulation geometry and mass attenuation coefficients for medical physics and radiation physics applications.
      PubDate: Sat, 03 Jun 2017 19:30:00 +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 of four subjects 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 white matter by 29% and 55%, respectively. In addition, on average, white matter anisotropy led to an 8% and 36% change of CDI across gray matter and white matter, respectively. The quantitative 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 at three different points, significant differences in the level of excitability of the subjects were detected. Conclusion: A consideration of individualized geometry results in significant differences in predicting current distribution and provides an opportunity to investigate individual differences. Accordingly, consideration of the real geometry in computational modeling is vital. In addition, white matter anisotropy does not significantly influence the CDI on the gray matter surface, however, it highly alters the CDI inside the brain; therefore, it can be taken into account to obtain accurate results, more specially, 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: Sun, 21 May 2017 19:30:00 +010
       
  • A Monte Carlo study of new concrete shielding materials containing Galena
           and borated minerals ...

    • Abstract: Heavy-weight concretes are suitable materials for use in constructing medical or industrial radiation facilities with photon sources. In this study, heavy concretes containing Galena (PbS) and several borated minerals are proposed as suitable materials for use in photon fields. The shielding properties of 21 Galena concretes containing 7 borated minerals with three mixing patterns were evaluated using MCNP4C Monte Carlo code. To calculate the X and  radiation attenuation of the concretes, narrow and broad beam geometries were simulated. The X-ray sources with 40, 60, 90, and 120 kvp and gamma rays of 99mTc, 131I, 137Cs, and 511keV annihilation photons were considered. The values of photon flux and the X-ray spectrum after all the concretes were compared with those of ordinary concrete. The photon attenuations caused by heavy concretes simulated in this study were more than ordinary concrete. The results revealed that the concrete containing Orthopinokiolite as the borated material made by the third mixing pattern had the best photon attenuation, i.e. 34% reduction in 40kVp. According to the results, the shielding properties of concretes containing different borated minerals were similar in high photon energies, while in low energies the attenuation depended on the type of borated mineral used in the concretes.
      PubDate: Tue, 09 May 2017 19:30:00 +010
       
 
 
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