فهرست مطالب

Journal of Biomedical Physics & Engineering
Volume:8 Issue: 3, May-Jun 2018

  • تاریخ انتشار: 1397/05/30
  • تعداد عناوین: 13
|
  • N. Singh*_N. K Painuly_L. N Chaudhari_A. Chairmadurai_T. Verma_D. Shrotiya_C. P Bhatt Page 1
    Aims: The aims of the present work are (1) to evaluate dose calculation accuracy of two commonly used algorithms for 15 MV small photon fields in a medium encompassing heterogeneity and (2) to compare them with measured results obtained from gafchromic film EBT2.
    Materials And Methods
    Authors employed kailwood (Pinus Wallichiana) to mimic lung. Briefly, seven Kailwood plates, each measuring 25x25 cm2 of varying thicknesses totaling 13 cm equivalent to the mean thickness of an adult human lung, were sandwiched between 5 cm tissue equivalent material from top and 10 cm below. Physical measurements were performed using Radiochromic film EBT2. The field sizes of 1x1, 2x2, 5x5 and 10x10 cm2 were selected at 100 cm SSD. Simulations were performed using EGSnrc/DOSRZnrc Monte Carlo code. The dose variation inside the inhomogeneity and near the interface was calculated using AAA & XVMC algorithm.
    Results
    Preliminary results show that there is large variation of dose inside inhomogeneity. The maximum variation of dose inside the inhomogeneity for 1x1 cm2 was found 40% by AAA and 4.5% by XVMC compared to measured/simulated results. For the field size of 2x2 cm2, these figures were 27% by AAA & 3.5% by XVMC. For 5x5 cm2 field size, the variation is small which becomes insignificant for larger fields.
    Conclusion
    The results presented in this work indicate that for smaller fields, XVMC algorithm gives more realistic prediction, while there is the need for caution on using AAA algorithm for dose calculations involving small area irradiation encompassing heterogeneities and low-density media.
    Keywords: EGSnrc, Monte Carlo Simulation, Gafchromic Film, AAA, XVMC
  • A. S Talebi_M. Maleki_P. Hejazi *_M. Jadidi_R. Ghorbani Page 2
    Background
    One of the most significant Intensity Modulated Radiation Therapy treatment benefits is a high target to normal tissue dose ratio. To improve this advantage, an additional accessory such as a compensator is used to delivering doses. Compensator-based IMRT treatment is usually operated with an energy higher than 10 MV. Photoneutrons, which have high linear energy transfer and radiobiological effectiveness, are produced by colliding high-energy photon beams with linear accelerator structures, then they deliver the unwanted doses to patients and staff. Therefore, the neutron energy spectra should be determined in order to calculate and reduce the photoneutron risk.
    Objective
    We have conducted a comprehensive and precise study on the influence of brass compensator thickness and field size on neutron contamination spectrum in an Elekta SL 75/25 medical linear accelerator with and without the flattening filter by Monte Carlo method.
    Materials And Methods
    MCNPX MC Code version 2.6.0 was utilized to simulate the detailed geometry of Elekta SL 75/25 head components based on Linac’s manual. This code includes an important feature to simulate the photo-neutron interactions. Photoneutrons spectrum was calculated after the Linac output benchmarking based on tuning the primary electron beam.
    Results and
    Conclusion
    Based on the Friedman and Wilcoxon nonparametric tests results (P
    Keywords: Photoneutron, Spectrum, MCNP, Compensator, Field Size
  • M. Ostovari, N. Riahi Alam, M. Zabihzadeh*, M. M. Gharibvand, M. Hoseini-Ghahfarokhi Page 3
    Introduction
    Electrical impedance of tissues on low frequencies includes useful information about functional and structural changes in tissues. This property is used in Electrical Impedance Tomography (EIT) imaging modality for the detection of lesions in tissues.
    Objective
    The goal of this article is to study changes in electrical impedance of tissues in the presence of gold nanoparticles.
    Materials And Methods
    Spherical gold nanoparticles with size of 20-25 nm were synthesized with Turkevich method. Size distribution and shape of nanoparticles were characterized by transmission electron microscopy (TEM). Electrical impedance of two types of phantoms (chicken fat and muscle paste tissues) was measured by 4-electrode method with and without gold nanoparticles.
    Results
    Results demonstrate a reduction in electrical impedance of tissues in the presence of gold nanoparticles. However, this reduction is not the same for fat and muscle tissues. Reductions in resistive impedance are for fat and muscle tissues on the frequency of 1 KHz, respectively. A reduction in electrical impedance is accompanied by a rise in electrical conductance leading to increase in EIT signal.
    Conclusion
    As signal enhancement is different for fat and muscle tissues; presence of gold nanoparticles could be used to improve EIT image contrast.
    Keywords: Contrast Agent, Electrical Impedance, Gold Nanoparticle, Medical Imaging
  • S. Masjoodi_H. Hashemi_M. A Oghabian *_G. Sharifi Page 4
    Background
    Presurigical planning for glioma tumor resection and radiotherapy treatment require proper delineation of tumoral and peritumoral areas of brain. Diffusion tensor imaging (DTI) is the most common mathematical model applied for diffusion weighted MRI data. Neurite orientation dispersion and density imaging (NODDI) is another mathematical model for DWI data modeling.
    Objective
    We studied whether extracted parameters of DTI, and NODDI models can be used to differentiate between edematous, tumoral, and normal areas in brain white matter (WM).
    Material and
    Methods
    12 patients with peritumoral edema underwent 3T multi-shell diffusion imaging with b-values of 1000 and 2000 smm-2 in 30 and 64 gradient directions, respectively. We fitted DTI and NODDI to data in manually drawn regions of interest and used their derived parameters to characterize edematous, tumoral and normal brain areas.
    Results
    We found that DTI parameters fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) all significantly differentiated edematous from contralateral normal brain WM (p
    Conclusion
    The combination of two diffusion based methods, i.e. DTI and NODDI parameters can distinguish and characterize WM fibers involved in edematus, tumoral, and normal brain areas with reasonable confidence. Further studies will be required to improve the detectability of WM fibers inside the solid tumor if they hypothetically exist in tumoral parenchyma.
    Keywords: MRI, NODDI, Diffusion Tensor Imaging, Edema, Brain Tumor
  • B. Zeinali-Rafsanjani_R. Faghihi *_M. A Mosleh-Shirazi_M. Saeedi-Moghadam_M. Lotfi_R. Jalli_S. Sina_L. Mina Page 5
    Introduction
    Proton magnetic resonance spectroscopy (MRS) is a well-known device for analyzing the biological fluids metabolically. Obtaining accurate and reliable information via MRS needs a homogeneous magnetic field in order to provide well-defined peaks and uniform water suppression. There are lots of reasons which can disturb the magnetic field homogeneity which can be corrected by a process known as shimming. This study is intended to recall the importance of shimming and also the significant role of quality control (QC) in achieving an accurate quantification.
    Material and
    Method
    An acrylic cylindrical quality control phantom was designed as an analog of brain MRS test phantoms in order to control the accuracy of the obtained signal of a 1.5 T Siemens MRI system which belonged to one of Shiraz hospitals. The signal of NAA, Cho, Cr, the combination of these metabolites and also the distilled water, which was used in this study, was evaluated using separate phantoms. A QC test was performed using Siemens QC phantom and a standard test phantom.
    Results
    The spectrum of our home- made phantom had a significant difference with the expected spectrum. The results of checking the spectrum of metabolites separately also confirmed that there was a systemic problem that affects all the signals originated from all metabolites and even the pure distilled water. The MRS system could not pass QC tests, and peak broadening was common in all spectra. The complex spectrum of standard test phantom was not produced successfully by the MRS system.
    Discussion
    By a simple check of the water peak characteristics, lots of information can be obtained, one of which is the status of shimming that has a considerable effect on the accuracy of the spectrum. Thus, performing an automatic or manual shimming is not a criterion of the spectrum accuracy, and performing a periodic quality control using a test phantom by a specialist is necessary.
    Conclusion
    Briefly, the quality control of MRS and all the other clinical device must be taken seriously. Sometimes QC can be the boundary of a right or a wrong decision for the patient.
    Keywords: Magnetic resonance spectroscopy, Shimming, Quality control, Quality assurance
  • M. Ebrahimian, M. Razeghi, A. Zamani, Z. Bagheri, K. Rastegar, A. Motealleh * Page 6
    Background
    Transcutaneous electrical nerve stimulation (TENS) is a noninvasive, inexpensive and safe analgesic technique used for relieving acute and chronic pain. However, despite all these advantages, there has been very little research into the therapeutic effects of TENS on brain activity. To the best of our knowledge, there is no evidence on the effect of high frequency TENS on the gamma band activity.
    Objective
    Investigation of the effect of high frequency TENS on the electroencephalographic (EEG) gamma band activity after inducing ischemic pain in healthy volunteers is considered.
    Methods
    The modified version of Submaximal effort tourniquet test was carried out for inducing tonic pain in 15 right-handed healthy volunteers. The high frequency TENS (150µs in duration, frequency of 100 Hz) was applied for 20 minutes. Pain intensity was assessed using Visual Analog Scale (VAS) in two conditions (after-pain, after-TENS). EEG gamma band activity was recorded by a 19-channel EEG in three conditions (baseline, after-pain and after- TENS). The repeated measure ANOVA and paired-sample T- tests were used for data analysis.
    Results
    EEG analysis showed an increase in gamma total power after inducing pain as compared to baseline and a decrease after the application of TENS (mean±SD: .043±.029 to .088±.042 to .038±.022 μV2 ).The analysis of VAS values demonstrated that the intensity of induced pain (mean±SD: 51.53±9.86) decreased after the application of TENS (mean±SD: 18.66±10.28). All these differences were statistically significant (p
    Conclusion
    The results of this study revealed that the high frequency TENS can reduced the enhanced gamma band activity after the induction of tonic pain in healthy volunteers. This finding might help as a functional brain biomarker which could be useful for pain treatment, specifically for EEG-based neurofeedback approaches.
    Keywords: Transcutaneous Electric Nerve Stimulation (TENS), Gamma rhythm, Oscillations, Pain measurement, Tourniquet pain test, Electroencephalography (EEG)
  • L. Abbasi, Z. Rojhani-Shirazi *, M. Razeghi, H. Raeisi Shahraki Page 7
    Background
    Deficits in upper body movement have received little attention during gait in cerebral palsy (CP) children with crouch gait pattern (CGP).
    Objective
    Purpose of this research is to describe the correlation of trunk movement with the excessive knee flexion and ankle kinematic in CP children with CGP.
    Methods
    Gait analysis data from 57 limbs of diplegic CP children with CGP and 26 limbs of normal children was gathered. Kinematic parameters of trunk in relation to the pelvis were extracted in the sagittal, transverse and coronal planes. CP limbs were clustered using K-means cluster analysis according to the knee flexion angle at initial contact and the mean position of ankle joint during the stance phase of gait cycle, to three clusters. Pearson correlation coefficient between knee, ankle and trunk kinematic variables was assessed. Differences between clusters were analyzed with Kruskal–Wallis and post hoc tests.
    Results
    The results revealed: 1) crouch clusters had more trunk obliquity and rotation mean position than normal; 2) the range of motions of the trunk obliquity and rotation exhibited significant differences between crouch and normal clusters; 3) the level of excessive knee flexion had positive correlation with the trunk mean position in all planes; 4) the ankle kinematic at stance phase was associated with the trunk mean position in all planes.
    Conclusion
    The results revealed the trunk mean position is correlated with the excessive knee flexion severity and ankle joint kinematic in CP children with CGP.
    Keywords: Trunk Kinematic, Cerebral Palsy, Crouch Gait Pattern, Excessive Knee Flexion, Gait
  • M. Ghoddusi Johari_M. H Dabaghmanesh_H. Zare_A. R Safaeian_Gh Abdollahifard * Page 8
    Background
    Diabetes is a serious chronic disease, and its increasing prevalence is a global concern. If diabetes mellitus is left untreated, poor control of blood glucose may cause long-term complications. A big challenge encountered by clinicians is the clinical management of diabetes. Many IT-based interventions such ad CDSS have been made to improve the adherence to the standard care for chronic diseases.
    Objective
    The aim of this study is to establish a decision support system of diabetes management based on diabetes care guidelines in order to reduce medical errors and increase adherence to guidelines.
    Materials And Methods
    To start the process, at first the existing guidelines in the field of diabetes mellitus such as ADA 2017 and AACE guideline 2017 were reviewed, and accordingly, flowcharts and algorithms for screening and managing of diabetes were designed. Then, it was passed on to the information technology team to design software.
    Results
    The most significant outcome of this research was to establish a smart diabetic screening and managing software, which is an important stride to promote patient's health status, control diabetes and save patient's information as an important and reliable source.
    Conclusion
    Health care technologies have the potential to improve the quality of diabetes care through IT-based intervention, such as clinical decision support systems. In a chronic disease like diabetes, the critical component is the disease management. The advantages of this web-based system are on-time registration, reports of diabetic prevalence, uncontrolled diabetes, diabetic complications and reducing the rate of mismanagement of diabetes, so that it helps the physicians in order to manage the patients in a better way.
    Keywords: Diabetes Mellitus, Clinical Decision Support System (CDSS), Information Technology, Quality of Care, Clinical Performance in Diabetes Care
  • S. Kazemi, P. Katibeh * Page 9
    Background
    Migraine headache without aura is the most common type of migraine especially among pediatric patients. It has always been a great challenge of migraine diagnosis using quantitative electroencephalography measurements through feature classification. It has been proven that different feature extraction and classification methods vary in terms of performance regarding detection and diagnostic accuracy. Previous work on the subject was controversial, hence a comparison of these methods seems necessary.
    Objectives
    The aim of this research is to compare two parametric and non-parametric feature extraction methods and also two classification methods in order to obtain optimal combinations of diagnostic accuracy.
    Materials And Methods
    Having recorded background EEG from 24 pediatric migraineurs and 19 control subjects, data was processed by Welch’s and Yule-Walker’s methods. Features were selected using genetic algorithm, and then given to a support vector machine and the linear discriminant analysis for the classification. Accuracy was calculated for all combinations having the dominant frequency and the correlated absolute power of each EEG wave band (theta, alpha, and beta) and for all wave bands combined.
    Results
    The highest migraine detection accuracy of 93% was obtained utilizing Welch’s method for EEG feature extraction alongside support vector machine for a classifier. Besides, Yule-Walker autoregressive method showed better performance than Welch’s, when only power bands (and not the dominant frequency) were used as classification input.
    Conclusion
    The superiority of Welch’s method over Yule-Walker’s and the support vector machine over linear discriminant analysis can be great help for further researches on computer aided EEG-based diagnosis of migraine.
    Keywords: Migraine, Quantitative Electroencephalography, Welch, Yule-Walker Autoregressive Method, Support Vector Machine, Linear Discriminant Analysis
  • F. Zarei, B. Zeinali-Rafsanjani * Page 10
    Rationale and
    Objective
    The objective of this study is to evaluate the methodological adherence of diagnostic accuracy studies published in radiology journals, which were indexed in different databases with the STARD standard guide 2015.
    Materials And Methods
    The different databases were searched in order to find suitable journals. Among 84 English radiology journals, 31 journal were selected randomly. In order to find the articles, the same search fields and search terms were used. All the items of STARD checklist 2015 were considered to take in to account in assessment of the adherence of the articles to the standard. Total STARD score for each article was calculated by summing the number of reported items.
    Results
    151 articles from 31 journals were evaluated to check the adherence of their structure to STARD standard. Based on the results the articles had the most adherence with the STARD standard in material and method part the item of participants, discussion section, and title or abstract. On the contrary, most of the articles were not adhere to other information which are new items in STARD 2015. Among radiology diagnostic accuracy articles only one article (0.66%) had a registration number and 10 (6.62%) articles had a link to full study protocol. More than 60% of articles adhered to the ethics (69.54%) and source of support (63.58%).
    Conclusions
    The radiology diagnostic accuracy studies were adhered to 69.45% STARD items, which shows an improvement in reporting the diagnostic accuracy articles in comparison to previous studies.
    Keywords: STARD Statement, Diagnostic Accuracy, Adherence
  • S. V Ghasemzade *_F. Jamshidi Page 11
    Inertial navigation systems are of the most important and practical systems in determining the velocity, position and attitude of the vehicles and different equipment. In these systems, three accelerometers and three gyroscopes are used to measure linear accelerations and angular velocities of vehicles, respectively. By using the output of these sensors and special inertial algorithms in different frames, parameters of vehicle such as position, velocity and attitude can be calculated. These systems are used in medical equipment including, but not limited to MRI devices, intelligent patient beds, surgical robots and angiography equipment. In this paper, inertial navigation systems, inertial sensors such as accelerometers, gyroscopes and inertial navigation algorithm are introduced. Afterwards, different applicable samples of inertial navigation system in medical equipment are described. According to the study carried out in this paper, it is presented and proved that applying inertial navigation in medical equipment is granted with precise and fast positioning as well as attitude determination. Moreover, as this technique of utilizing inertial navigation is applied to medical devices, a high efficiency system in terms of specifying the position and attitude will be achieved.
    Keywords: Inertial Navigation System, Position, Velocity, Roll, Pitch, Yaw, Accelerometer, Gyroscope
  • A. Ghadimi-Moghadam_S. M J. Mortazavi *_A. Hosseini-Moghadam_M. Haghani_S. Taeb_M. A Hosseini_N. Rastegariyan_F. Arian_L. Sanipour_S. Aghajari_S. A R. Mortazavi_A. Soofi_M. R Dizavandi Page 12
    MRI workers are occupationally exposed to static and time-varying gradient magnetic fields. While the 24-hour time-averaged exposure to static magnetic fields is about a few mT, the maximum static field strength can be as high as 500 mT during patient setup. Over the past several years, our laboratory has performed extensive experiments on the health effects of exposure of animal models and humans to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons and MRI. This study is to investigate the adverse health effects in MRI workers and also to assess the effect of exposure of MRI workers to static magnetic fields on their cognitive functions. In the first phase of this study a questionnaire was designed to collect information from 120 MRI personnel. The collection of data about the adverse health effects was based on self-reporting by the participants. In the second phase, 47 volunteer university students were asked to continuously move around a 1.5 T MRI scanner. Visual reaction time and working memory tests were performed on all participants before and after the experiment. Forward digit span and backward digit span were used for assessing the working memory. Furthermore, participants were asked to report the symptoms they had experienced during the movement. The first phase of our study showed increased frequencies of adverse health effects in MRI workers. In this study the rates of self-reported symptoms such as a headache, sleep problems, myalgia, palpitation, fatigue, concentration problems, attention problems, nervousness and backpain were possibly affected by static magnetic field. Furthermore we found that reaction time and working memory could be influenced by the movements of the body around a MRI scanner. It can be concluded that movement through a high magnetic field can also lead to some adverse cognitive effects in MRI staff.
    Keywords: Static Magnetic Fields (SMF), Electromagnetic Fields (EMFs), MRI, Health Effects, Cognitive Functions
  • M. Khateri, S. Cheraghi, A. Ghadimi, H. Abdollahi * Page 13
    Bell’s palsy is an idiopathic peripheral nerve palsy involving the facial nerve. It accounts for 60 to 75% of all cases of unilateral facial paralysis. The main mechanisms to induce BP remain unclear, but infection, ischemic condition and immunodeficiency may contribute to the development of Bell’s palsy. Accumulating evidence has shown several factors can trigger the reactivation of latent HSV including psychological stressors, physical stressors and immunosuppression. Ionization and non-ionization radiations are of importance of physical stressors. Some data have shown radiation can reactivate HSVs. Based on preliminary studies showing radiation reactivation of HSVs, we aimed to hypothesize radiation (in both forms of ionization and non-ionization) may cause Bell’s palsy. In the future, the role of radiotherapy, radiofrequency radiation from mobile phones and wireless devices in HSV reactivation and Bell’s palsy should be investigated.
    Keywords: Radiation, Mobile Phone, Herpes Virus, Bell's Palsy, Hypothesis