فهرست مطالب

Medical Physics - Volume:15 Issue: 2, Spring 2018

Iranian Journal of Medical Physics
Volume:15 Issue: 2, Spring 2018

  • تاریخ انتشار: 1397/02/10
  • تعداد عناوین: 8
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  • Amirhossein Davoudian Talab, Zahra Farzanegan, Farshid Mahmoudi * Pages 66-70
    Introduction
    Because radiology technologists are exposed to protracted low‐dose ionizing radiation and considering the possible effects of low‐dose radiation on blood factors, we aimed to investigate the effects of occupational exposure on blood factors of radiographers working in radiology departments of Khuzestan Province, Iran.
    Materials And Methods
    This case‐control study was conducted in Khuzestan Province, Iran, during 2015. Blood samples were obtained from 95 radiology technologists and 85 matched, nonradiated controls. The participants were chosen using the cluster sampling method. The data were collected by performing complete blood count (CBC) assay with a Sysmex cell counter. To analyze the data, t‐test and Pearson correlation coefficient were run in SPSS, version 16.
    Results
    T‐test demonstrated that the mean values of blood factors were not significantly different between the two groups (P>0.05), and there was no significant difference between the two groups (radiographer and non‐radiographer) by gender.
    Conclusion
    In this study, occupational exposure did not have any deleterious effects on radiographers’ blood factor levels, but with increasing age and work experience in radiographers, number of white blood cell decreased.
    Keywords: ionizing radiation, occupational exposure, blood cells
  • Priyusha Bhaskar Bagdare *, Swati Dubey, Sanjay Kumar Ghosh, Om Prakash Gurjar, Virendra Bhandari, Krishna Lal Gupta, Saurabh Karnawat Pages 71-77
    Introduction
    The determination of accurate dose distribution is an issue of fundamental importance in radiotherapy, especially with regard to the fact that the human body is a heterogeneous medium. Therefore, the present study aimed to analyze the density and isodose depth profiles of 6 MV beam in a SP34 slab-wooden dust (pine)-SP34 slab (SWS) heterogeneous phantom.
    Materials And Methods
    The density of SP34 slab, wooden dust of pine, and thoracic region of 10 patients were calculated using computed tomography (CT) images. The depths of isodose lines were measured for 6 MV beam on the CT images of the chest, SP34 slab phantom, and SWS phantom. Dose calculation was performed at the depths of 2, 13, and 21 cm in both phantoms. Furthermore, patient-specific quality assurance (QA) was implemented using both phantoms.
    Results
    The mean densities of the lung, SP34 slabs, and wooden dust were 0.29, 0.99, and 0.27 gm/cc respectively. The mean depths of different isodose lines in the SWS phantom were found to be equivalent to those in actual patients. Furthermore, the percentage variation between the planned and measured doses was higher in the SWS phantom as compared to that in the SP34 phantom. Furthermore, the percentage variation between the planned and measured doses in patient-specific QA was higher in the SWS phantom as compared to that in the SP34 phantom.
    Conclusion
    As the findings indicated, the density and isodose depth profiles of the SWS phantom were equivalent to those of the actual thoracic region of human.
    Keywords: Hounsfield number, patient specific quality assurance, SP34 slab phantom, thorax phantom, SWS phantom
  • Hadi Kalani *, Nazanin Goharian, Sahar Moghimi, Nima Vaezi Pages 78-86
    Introduction
    Researchers have employed surface electromyography (EMG) to study the human masticatory system and the relationship between the activity of masticatory muscles and the mechanical features of mastication. This relationship has several applications in food texture analysis, control of prosthetic limbs, rehabilitation, and teleoperated robots.
    Materials And Methods
    In this paper, we proposed a model by combining the concept of fuzzy interface systems and principal dynamic mode analysis (PDM). We hypothesized that the proposed approach would provide nonlinear and dynamic characteristics improving the estimation results compared to those obtained by the classical PDM analysis and still having the benefits of a PDM model including the sparse presentation of the system dynamics. After developing PDM, the nonlinear polynomial function of the PDM model was replaced with adaptive neuro-fuzzy inference system (ANFIS) network architecture. After training, the relevant fuzzy rules were extracted and used for creating the fuzzy block (as the nonlinear function block) and predicting the output signal. The proposed approach was later employed to predict bite force using EMG of the temporalis and masseter muscles.
    Results
    Our proposed method outperformed the classical PDM analysis (in terms of our evaluation criteria) in predicting masticatory force . The inter-subject evaluation of the model performance proved that the model created using the data of one subject could be used for predicting masticatory force in other subjects.
    Conclusion
    The proposed model can be helpful in food analysis to predict masticatory force based on the electrical activity of the masseter and temporalis muscles.
    Keywords: Bite Force, Electromyography, Fuzzy Logic, Mastication
  • Hemalatha Athiyaman *, Athiyaman Mayilvaganan, Arun Chougule, Kumar Hs Pages 87-100
    Introduction
    Computerized treatment planning is a rapidly evolving modality that depends on hardware and software efficiency. Despite ICRU recommendations suggesting 5% deviation in dose delivery the overall uncertainty shall be less than 3.5% as suggested by B.J. Minjnheer. J. In house spreadsheets are developed by the medical physicists to cross-verify the dose calculated by the Treatment Planning System (TPS).
    Materials And Methods
    The monitor unit verification calculation (MUVC) verification was tested for pre-approved and executed treatment plans taken from the TPS. A total of 108 square fields and 120 multileaf-collimators (MLC) shaped fields for Head & Neck cancers, cervical and esophageal cancers were taken for evaluation. In house developed spreadsheet based on Microsoft Excel was developed. 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 fell within the range of 0.999 to 1.02 for square field geometries showing deviation of 1% between the TPS calculation and the spread sheet calculation. The MU ratios were 0.995 for Head & Neck plans & 1.012 for cervix plans with the standard deviation of 0.024 & 0.029 respectively. However we observed the mean MU ratio for Esophagus plan was 1.026 with the standard deviation of 0.040.
    Conclusion
    The spreadsheet was tested for most of the routine treatment sites and geometries. It has good agreement with the Eclipse TPS version 13.8 for homogenous treatment sites such as head &and neck and carcinoma cervix.
    Keywords: Radiotherapy Planning, Computer Assisted Radiotherapy, Radiotherapy Dosage
  • Soo-Foon Moey *, Zubir Ahmad Shazli, Inayatullah Shah Sayed Pages 101-107
    Introduction
    The study was undertaken to evaluate the practice of chest radiography using different digital imaging systems and its influence on dose and image quality.
    Materials And Methods
    The study was carried out in two hospitals 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 kg were selected randomly. The active matrix flat panel imagers technology was employed in the direct radiography (DR) system for Hospital A, whilst Hospital B used the single read out computed radiography (CR) system. The dose area product (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 (ESDs) for posteroanterior chest in Hospital A (0.098 mGy) was lower than that obtained in Hospital B (0.161 mGy). However, the ESDs at both centres were lower than the recommended value by the International Atomic Energy Agency (IAEA; 0.3 mGy). The quality of the images for chest radiography in both hospitals was adequate to make a diagnosis with ESDs and effective doses lower than those recommended by IAEA and United Nations Scientific Committee on the Effects of Atomic Radiation (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 were significant differences in image quality and radiation dose for chest radiography practice using CR and DR.
    Keywords: digital radiography, Image Quality, Radiation Dosage, Thoracic Radiography
  • Fateme Moghbeli, Mostafa Langarizadeh *, Ali Younesi, Amir Reza Radmard, Mohammad Sadegh Rahmanian, Azam Orooji Pages 108-116
    Introduction
    The present study aimed to suggest an unsupervised method for the segmentation of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in axial magnetic resonance (MR) images of the abdomen.
    Materials And Methods
    A self-organizing map (SOM) neural network was designed to segment the adipose tissue from other tissues in the MR images. The segmentation of SAT and VAT was accomplished using a new level set method called distance regularized level set evolution (DRLSE). To evaluate the suggested method, the whole-body abdominal MRI was performed on 23 subjects, and three slices were selected for each case.
    Results
    The results of the automatic segmentation were compared with those of the manual segmentation and previous artificial intelligent methods. According to the results, there was a significant correlation between the automatic and manual segmentation results of VAT and SAT.
    Conclusion
    As the findings indicated, the suggested method improved detection of body fat. In this study, a fully automated abdominal adipose tissue segmentation algorithm was suggested, which used the SOM neural network and DRLSE level set algorithm. The proposed methodology was concluded to be accurate and robust with a significant advantage over the manual and previous segmentation methods in terms of speed and accuracy.
    Keywords: Image Processing, Magnetic Resonance, Neural Network, Segmentation, Visceral Fat
  • Kheirollah Mohammadi, Hamid Gholamhosseinian, Omid Baziar *, Aghil Mohammadi, Shahram Bayani Roodi Pages 117-125
    Introduction
    LiF dosimeter has the most application in medicine. This study aimed to evaluate some dosimetric properties of a novel LiF: Mg, Ti.
    Materials And Methods
    An ELEKTA Precise linear accelerator was used to calibrate dosimeters at 6 MV. In this survey, responses of dosimeters were evaluated up to 1000 cGy. Background effect was investigated in two different dosimeter states including irradiated and unirradiated.Thermoluminescence response dependence to dose rate was investigated, as well. Energy dependence was evaluated in diagnostic and therapeutic ranges. Furthermore, fading effect was evaluated by reading the dosimeters every 2 h up to 12 h post-irradiation.
    Results
    The dosimeters had linear response up to 250 cGy. Readout values of dosimeters receiving 120 cGy at three dose rates of 21, 212, 425 cGy.min-1 were calculated equal to 125, 123, 121 cGy, respectively. The measured values of delivering 80, 120, and 150 cGy prescribed doses at 6 MV, 10 MV, and 15 MV were accurate at 6 MV and about 1.5 times higher than the prescribed doses at 10 and 15 MV. Thermoluminescence response in diagnostic energy range showed an uprising trend with increasing energy.
    Conclusion
    The raising thermoluminescence response with increasing energy contradicts with the findings of Nunn. Due to the reproducibility and linear response of dosimeters in an acceptable dose range, they could be used in diagnostic and therapeutic fields. Effects of absorbed doses from background in low-dose studies, mainly in diagnostic radiology range, could be evaluated in more detail in future surveys.
    Keywords: Radiation Dosimeters, Reproducibility of Results, Reading, Calibration
  • Reza Pourimani *, Seyed Mohsen Mortazavi Shahroudi Pages 126-131
    Introduction
    Artificial and natural radionuclides exist in the environmental materials, such as water, soil, rocks, and plant as well as in animals and human body tissues. Therefore, human being and environment are at constant radiation exposure. Regarding this, the present study aimed to determine the specific activities of radionuclides and perform the risk assessment wheat and barley samples in Karbala, Iraq.
    Materials And Methods
    In this study, natural and artificial radioactivity concentrations were determined in wheat and barley samples, as well as their surrounding soil, using gamma ray spectrometrymethod by means of a high-purity germanium (HPGe) detector with 88% relative efficiency. According to the measured specific activities of radionuclides in food samples and according to annual consumption of wheat and barley by adult person excess lifetime cancer risk due to ingestion of radionuclides was calculated.
    Results
    Specific activities of 226Ra, 232Th, 40K, and 137Cs in the soil samples varied within the ranges of 29.37-38.86, 23.24-45.70, 291.15-549.78, and 1.25-10.82Bq/kg, respectively. The 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).
    Conclusion
    As the findings of the present study indicated, the specific activities of natural radionuclides in the soil were close to that of the world average. The observation of artificial radiocaesium, which is released by nuclear accidents or weapon test, in all soil samples was indicative of the pollution of the studied regions by radioactive dust.
    Keywords: Barley, Dose, Radionuclides, Soil, Wheat