فهرست مطالب

  • Volume:6 Issue: 3, 2019
  • تاریخ انتشار: 1398/07/08
  • تعداد عناوین: 8
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  • Golshan Mahmoudi, Hossein Ghadiri Pages 114-116

    Advancements in Computed Tomography (CT) have increased dramatically during recent years, offering a more effective non-invasive technique for examining patients without having to resort to exploratory surgeries that were once routine clinical practice. The growing importance of CT as a diagnostic tool increases the need for solutions that improve diagnostic information yet lower radiation to patients. However, these advancements in CT technology are no longer driven solely by hardware components. Software, including reconstruction and image processing, is an important element to diagnostic accuracy. Today image reconstruction techniques are one of the most important strategies for reducing radiation dose in CT.


    Image reconstruction in CT is a mathematical process to build the map of attenuation coefficient, a real-valued function associated with the object of interest, from x-ray measured projection data acquired at different angles around the patient. Generally, image reconstruction algorithms can be divided into two major categories: analytical methods and iterative methods. Below, we will explain CT image reconstruction methods and the corresponding advantages and disadvantages.

  • Soroor Kalantari, Jafar Zamani, Hamidreza Salighehrad, Fardin Samadi, Hanieh Mobarak Pages 117-122
    Purpose

    Neuroimaging techniques hold many promises to detect Alzheimer Disease (AD) at early stages before clinical symptoms fully develop, suggesting decreased regional Cerebral Blood Flow (CBF). Perfusion deficiencies are present from very early clinical phases of AD, i.e. Mild Cognitive Impairment (MCI) and persist well into the latest stages, demonstrating a pattern of increased hypo-perfusion with the disease development. Accurate quantification such as quantification model and noise reduction method is necessary to achievement of good results in insufficient Post Labeling Delay (PLD) time.

    Material and Method

    Arterial Spin Labeling (ASL) is a non-invasive MRI technique to extract brain regional CBF, which in recent years gained wide acceptance for its value in clinical and neuroscience applications. In the present work, 44 participants in 2 groups were imaged (normal control and MCI) using single-Post Label Delay (single-PLD) model-fitting ASL Perfusion at 1.5T. Images were de-noised with Independent Component Analysis (ICA) algorithm and then preprocessing such as motion correction, distortion correction, normalization, and tissue segmentation analyzed with SPM12. Calibration image that needed to calculate absolute perfusion was estimated from the data by fitting a curve to the control images in the dataset. Absolute CBF values were finally extracted from the kinetic model quantification.

    Results

    Perfusion decreases in the right precuneus (28%), right inferior partial cortex (22%) and right middle frontal cortex (20%) cortex in MCI subjects.

    Conclusion

    According to the results, ASL-MRI is able to calculate perfusion changes associated with MCI.

    Keywords: Magnetic Resonance Imaging, Arterial Spin Labeling, Cerebral Blood Flow, Independent Component Analysis, Mild Cognitive Impairment
  • Hossein Amiri, Reza Nadafi Pages 123-138
    Purpose

    Several studies were carried out in the field of neural microelectrode that caused the different generation of neural electrode appeared. Neural microelectrode has an important effect on the BCI interference and also is used in medical applications such as the detection and treatment process of different diseased. Therefore, achieving the structure of the electrode that has the high ability at recording and stimulating is so essential. This article aims at studying the different structure of Microelectrode, according to MEMS technology, and comparing their properties.

    Materials and Methods

    In this research, we introduce 7 designs for microelectrode fabrication that 3 designs are according to research that has been carried out so far and 4 designs have been proposed by authors and their fabricated process described. The microelectrode performance was determined by cost, biocompatibility, mechanical and electrical properties.

    Results

    The mechanical analysis was carried out using software and displacement, stress, and critical load factor calculated.

    Conclusion

    At last, the performance of the designed electrode was compared according to those parameters and the application of each design on the practical experiment described.

    Keywords: Micro Electro Mechanical System, Brain-Computer Interference, Neural Microelectrode
  • Hossein Amiri, Bahador Makkiabadi, Ali Khani, Soheil Ahmadzade Pages 133-138
    Purpose

    Passive Acoustic Thermometer (PAT) is a safe method for internal temperature estimation that works based on acoustic radiation of materials with a specific temperature. Several experimental studies have been carried out so far in the field of PAT. While, to the best of our knowledge, there is no simulation-based research reported yet.

    Materials and Methods

    In this article (for the first time) we proposed a simulation framework for evaluating the PAT methodologies. This framework supports the generation of acoustic radiation, signal processing, parameter estimation, and temperature reconstruction processes. At the moment, the proposed framework estimates the temperature in the frequency domain and uses the frequency spectrum of the acquired ultrasound signals captured by a single transducer.

    Results

    Using the proposed framework, we tried to implement previously practical experiments and the results of the simulation are consistent with those of the practical experiment. The mean error of temperature estimation was below 0.45 °C. The results show that it is possible to use this framework to evaluate the PAT in different scenarios.

    Conclusion

    Therefore, this method enhances the possibility of examination of different conditions and algorithms. It also reduces the cost of practical experiment.

    Keywords: Internal Temperature, Passive Acoustic Thermometer, Hyperthermia Therapy
  • Nader Riahi Alam, Maziar Jalalvandi, Hasan Hashemi, Yousef Nadery Pages 139-147
    Purpose

    The nerve signals are often contaminated by the non-nerve signals in the same frequency range, i.e. low frequencies in the range of 0.1 Hz. Among the different medical imaging tools, Functional Magnetic Resonance Imaging (fMRI) has been widely used by scientists and scholars due to its high spatial resolution for brain mapping.

    Materials and Methods

    Also, the use of Functional Near-Infrared Spectroscopy (NFIRS) has continued to rise and regarding its high temporal resolution, it is considered as the complement of FMRI.

    Results

    However, the effect of non-nerve functions is observed in both methods. Specially, by showing that non-nervous Low Frequency Oscillations (LFOs) 1) are merely non-nervous, because they can be measured by the environmental NIRS; 2) their internal origin is close to the heart; 3) in comparison with the available LF models based on respiration and the merely non-nervous changes in heart, they are unique in their spatial and temporal features, it seems that the systemic signals are moving through the cerebral arteries.

    Conclusion

    In this paper, LF Oscillations (LFOs) are compared with simultaneous NIRS/FMRI. Also, we discuss the non-neurological effects during simple motions of the wrist in FMRI showing that a significant portion of them, especially in motion state networks, are non-nerve and we measure the sensitivity of NIRS to non-neural LFOs through mapping of nerve and non-nerve LFOs with an extra high spatial and temporal resolution.

    Keywords: Functional Magnetic Resonance Imaging, Functional Near-Infrared Spectroscopy, Low Frequency Oscillations, Noise
  • Forough Sodaei, Jafar Zamani, Nahid Abyari, Hamidreza Saligheh Rad, Fardin Samadi, Hanieh Mobarak Pages 148-152
    Purpose

    The purpose of this study is to evaluate the brain alterations in epileptic patients and normal adults in order to help differential diagnosis using volumetric Magnetic Resonance Imaging (MRI).

    Materials and Methods

    The study case group included 11 subjects, 6 patients of whom with focal and secondary generalized seizures and 5 of whom were healthy people as a control group. Measurements and evaluations of the brain important regions were performed with volBrain software within 4 different pipelines.

    Results

    Statistical results showed that the significant quantitative assessments were observed in the areas as follows: right Hippocampus (P-value<0.05), right cerebellar (P-value<0.1), thalamus Asymmetry (P-value<0.1), right CA1 (P-value<0.1), left SR-SL-SM (P-value<0.1), right subiculum (P-value<0.1), left cerebellum cortical thickness (P-value<0.05) and some cerebellar lobules.

    Conclusion

    Structural MRI demonstrated significant brain alterations in epileptic subjects comparing normal adults. Assessment of brain lesions did not show any defect in Brain which implies that patients have disappearing lesions caused by seizures. Significant quantitative assessments were shown in the right lobule III, lobule IX mean cortical thickness, right cerebellum grey matter, right hippocampus and right cerebellar areas.

    Keywords: Epilepsy, Magnetic Resonance Imaging, Volumetry, Brain Lesions
  • Vahid Vaezzadeh, Farideh Pak Pages 153-155
    Purpose

    Lead shielding in the forms of thyroid straps and apron are known as protection devices in medical imaging. Recent data and guidelines do not recommend the routine use of lead shielding in dentistry imaging even for pregnant women. This study was conducted to investigate whether the application of these shielding is appropriate in our dental radiography.

    Materials and Methods

    The study was conducted in five dental radiography centers that performed panoramic and intra oral imaging. A questionnaire consisting of five items was developed and technicians were asked to fill it out for a period of one month.

    Results

    The results of this study showed that 72% of children and 70.3% of adults received protection by thyroid shielding. For 24% of children and 24.7% of adults no shielding was reported. In panoramic imaging of 55.5% children and 14.4% adult, thyroid shielding was used. Apron was applied for 33.3% of children and 54.4% of adults. No shielding was used for 11.1% of children and 30% of adults. Apron shielding in panoramic imaging for children was 33.3% and for adults 54.4%

    Conclusion

    The results of this survey showed, in general, a routine behavior exists in shielding application for dental radiography which has not been updated. Then, it seems that there is a need for updating knowledge regarding appropriate use of thyroid and apron shielding for this imaging modality.

    Keywords: Dental Imaging, Panoramic Imaging, Intra Oral Imaging, Thyroid Shielding, Apron
  • Behnoosh Teimourian Fard, Mohmmadreza Ay, Kiarash Amirmozaffari Pages 156-160
    Purpose

    Cardiac PSECT imaging is widely used for many clinical practices such as the diagnostic of coronary artery diseases (CAD) and myocardial perfusion imaging (MPI). In this work, we introduced the ProSPECT system, a dedicated cardiac SPECT system with open-gantry design.

    Materials and Methods

    In we assessed the performance of the system based on NEMA-NU1-2007 standards. The ProSPECT system was characterized by measurement of planar, tomographic and clinical parameters.

    Results

    Planar measurements showed that 7.6 mm and 8.9% of spatial resolution and energy resolution at 140 keV, respectively. The tomographic resolution at 250 mm radius of rotation was 12.3 mm. Also, the maximum LOR and COR error for the tomographic imaging is obtained 1.1 mm and 1.8 mm respectively. The clinical images that obtained using the system confirmed by expert nuclear medicine physician.

    Conclusion

    It concluded that the ProSPECT imaging is qualified for cardiac SPECT imaging.

    Keywords: Cardiac Single Photon Emission Computed Tomography, Nuclear Medicine, National Electrical Manufacturers Association, Calibration