Research Center for Science and Technology in Medicine

Tehrān, Iran

Research Center for Science and Technology in Medicine

Tehrān, Iran

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Abdoli M.,University of Groningen | Ay M.R.,Tehran University of Medical Sciences | Ay M.R.,Research Center for Science and Technology in Medicine | Ay M.R.,Research Institute for Nuclear Medicine | And 6 more authors.
Medical Physics | Year: 2010

Purpose: The presence of metallic dental fillings is prevalent in head and neck PET/CT imaging and generates bright and dark streaking artifacts in reconstructed CT images. The resulting artifacts would propagate to the corresponding PET images following CT-based attenuation correction (CTAC). This would cause over- and/or underestimation of tracer uptake in corresponding regions thus leading to inaccurate quantification of tracer uptake. The purpose of this study is to improve our recently proposed metal artifact reduction (MAR) approach and to assess its performance in a clinical setting. Methods: The proposed MAR algorithm is performed in the virtual sinogram space to overcome the challenges associated with manipulating raw CT data. The corresponding bins of the virtual sinogram affected by metallic objects are obtained by forward projection of segmented metallic objects in the original CT image. These bins are then substituted by weighted values of three estimates: the affected bins in the original sinogram, the bins in the corrected sinogram using spline interpolation, and the sinogram bins in the neighboring column of the sinogram matrix. The optimized weighting factors (α, Β, and γ) were estimated using a genetic algorithm (GA). The optimized combination of weighting coefficients was obtained using the GA applied to 24 clinical CT data sets. The proposed MAR method was then applied to 12 clinical head and neck PET/CT data sets containing dental artifacts. Analysis of the results was performed using Bland and Altman plots and a method allowing analysis in the absence of gold standard called regression without truth (RWT). The proposed method was also compared to an image-based MAR method. Results: Optimization of the weighting coefficients using the GA resulted in an optimum combination of parameters of α=0.26, Β=0.67, and γ=0.07. According to Bland and Altman plots generated for both CT and PET images of the clinical data, the proposed MAR algorithm is efficient for reduction of streak artifacts in CT images and such reduce the over- and/or underestimation of tracer uptake. The RWT method also confirmed the effectiveness of the proposed MAR method. The obtained figures of merit revealed that attenuation corrected PET data corrected using CTAC after applying the MAR algorithm are more similar to the assumed gold standard. Comparison with the knowledge-based method revealed that the proposed method mainly corrects the artifactualregions without modifying the unaffected regions. The knowledge-based method globally modifies the images including those that do not include metallic artifacts. Conclusions: The proposed MAR algorithm improves the quality and quantitative accuracy of clinical head and neck PET/CT images and could be easily integrated in clinical setting. © 2010 American Association of Physicists in Medicine.


Ghafariana P.,Shahid Beheshti University | Ghafariana P.,Tehran University of Medical Sciences | Aghamiria S.M.R.,Shahid Beheshti University | Ay M.R.,Research Center for Science and Technology in Medicine | And 6 more authors.
Nuclear Medicine Communications | Year: 2010

Objective Cardiac positron emission tomography (PET)/CT imaging is a noninvasive procedure allowing the assessment of coronary artery disease (CAD). CT-based attenuation correction of PET data is essential for accurate quantitative analysis in PET/CT imaging. Coronary artery calcium scoring CT (CaScCT) is used as a noninvasive tool for the diagnosis of atherosclerosis in patients with medium risk for CAD. In addition to the CaScCT examination, current cardiac rest/stress NH3 or 18F-fluorodeoxyglucose viability PET/CT protocols incorporate a correlated low-dose CT scan for attenuation correction purposes (ACCT). As a result, the patient receives a non-negligible radiation dose. The aim of this study is to evaluate the possibility of using CaScCT images for AC of myocardial rest/stress/viability PET data with the aim of reducing patient dose. Methods Since in cardiac PET/CT protocols, the CaScCT examination is usually reconstructed using a small field-of-view, the CaScCT data were reconstructed again with extended field-of-view (ExCaScCT) and used for AC of the corresponding PET data. The feasibility study was performed using 10 patients including four NH3 perfusion and six 18F- fluorodeoxyglucose viability examinations acquired on the Biograph TP 64 PET/CT scanner. The assessment of PET images corrected using both ACCT and ExCaScCT images was carried out through qualitative assessment performed by an expert nuclear medicine specialist in addition to the regression analysis and the Bland-Altman plots, and 20-segment myocardial bull's eye view analysis. Results Despite the good agreement between PET images corrected using ACCT and ExCaScCT images as expressed by the correlation coefficient and slope of the regression line in viability (0.949± 0.041 and 0.994 ± 0.124) and stress perfusion examinations (0.944 ± 0.008 and 0.968 ±0.055), the rest perfusion examinations had weak correlation (0.454± 0.203 and 0.757± 0.193). This is attributed to the fact that the CaScCT scan is performed immediately after the stress/viability ACCT in our protocol that leads to a small misalignment between the CaScCT and stress/viability ACCT images, whereas there is a large misalignment between the CaScCT and rest ACCT images. The bull's eye view analysis showed that the difference between the uptake values was larger in the inferior wall because of diaphragm motion. Conclusion Our preliminary results seem to suggest that the calcium score study could be used for attenuation correction of cardiac PET images, thus allowing the elimination of ACCT in viability and stress perfusion studies and as such reduce patient dose. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Marsousi M.,Ryerson University | Marsousi M.,Research Center for Science and Technology in Medicine | Ahmadian A.,Tehran University of Medical Sciences | Ahmadian A.,Research Center for Science and Technology in Medicine | And 4 more authors.
Ultrasound in Medicine and Biology | Year: 2011

In this article, an automatic method for detection of all chambers in apical two- and four-chamber views is proposed. The method is based on four evolving ellipses with their sizes and alignments (centre point) gradually changing through iterations until they reach to the point that approximates the chamber boundaries. The interaction between the internal, external and inter-elliptic forces controls the simultaneous evolution of ellipses. Since no prior assumption of the approximate location is required with our approach, the specialists are not required to locate the centre points of chambers in apical images, making the overall segmentation fully automated. Moreover, the resultant ellipse inside a chamber could be used as the initial contour in segmentation techniques such as active contour models, where the initial contour has a significant role for higher accuracy and faster convergence. The simplicity of equations developed in our approach make for a computationally faster algorithm, compared with former approaches that utilize morphologic operators. Our evolving ellipse does not go beyond the gaps, a problem that normally exists within boundaries in echo images, making our overall segmentation process more robust against the gaps. To evaluate the proposed method, a subset of 80 images is selected and three observers are requested to manually draw best ellipses inside the images and compare them with our results. The obtained dice coefficient results (87.62 ± 4.53% for observer-1, 83.18 ± 6.20% for observer-2, 86.02 ± 5.16% for observer-3) indicate that the proposed method has a useful performance. © 2011 World Federation for Ultrasound in Medicine & Biology.


Sanikhani H.,Sharif University of Technology | Akbari J.,Sharif University of Technology | Shahidi A.R.,Research Center for Science and Technology in Medicine | Darki A.A.,Sharif University of Technology
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2010

Standing-wave ultrasonic motors are a modern class of positioning systems, which are used to deliver a high precision linear or rotary motion with an unlimited stroke. The design process should be performed through an effective optimization algorithm in order to guaranty proper and efficient function of these motors. An optimization method of ultrasonic motors is proposed based on the combination of finite element method and factorial design as a design of experiments in this study. The results show the ability of this method in optimal design of ultrasonic motors especially those which have a complex structure and multi modes operation principle. © 2013 ASME.


Darki A.A.,Sharif University of Technology | Shahidi A.R.,Research Center for Science and Technology in Medicine | Zohoor H.,Sharif University of Technology | Sanikhani H.,Sharif University of Technology
ASME International Mechanical Engineering Congress and Exposition, Proceedings | Year: 2010

Dynamic modeling of piezo-driven compliant mechanisms is necessary to predict dynamic behavior of nanopositioning systems, and also to optimize their controlling methods. Dynamic tests on a real system or dynamic analyses on a FEM model is very time consuming when they must be carried out iteratively. According to previous works, obtaining static specifications of model is possible within a reasonable error margin. But all geometric dimensions and mass distribution details of the whole moving parts should be considered to calculate dynamic specifications of the model. In this paper, a functional method is described to obtain dynamic specifications of an planar compliant mechanism, by means of a reference Frequency Response Function (FRF) diagram. On the other hand, an equivalent analytical FRF is derived from the MassSpring model. A Genetic Algorithm optimization process is performed on the mass matrix for matching of the two FRF diagrams. Results show that a diagonal 3-by-3 mass matrix can nearly follow dynamic behavior of FEM model. It also is verified that results from the optimized dynamic model and the FEM model will have similar response to step excitation. Copyright © 2010 by ASME.


Fallahi A.,Hamedan University of Technology | Khotanlou H.,Bu - Ali Sina University | Pooyan M.,Shahed University | Hashemi H.,Advanced Diagnostic and Interventional Radiology Research Center | Oghabian M.A.,Research Center for Science and Technology in Medicine
Biomedical Engineering - Applications, Basis and Communications | Year: 2014

Uterine fibroids are common tumors of female pelvis. Uterine volume measurement before and after surgery has an important role in predicting the outcome and later on in comparing with the result of the uterine fibroid shrinkage surgery. Because of inhomogeneity and different shapes and sizes of uterus and fibroids, segmentation of uterus is a difficult task. In this paper, using T1 and Enhanced-T1 MR images uterine is initially segmented using a new clustering algorithm named neighborhood information affected possibilistic fuzzy C-means (NIAPFCM). NIAPFCM uses membership, typicality and spatial neighborhood information to cluster each voxel. Finally, the redundant parts are removed by superimposing the segmented region of the T1-enhanced image over the registered T1 image. Gaussian mixture model (GMM) is applied to the extracted region histogram as a model for accurate tresholding. The results obtained using the proposed method are evaluated by comparing with manual segmentations using volume-based and distance-based metric methods. Also, the result of NIAPFCM is compared with fuzzy C-means (FCM) and possibilistic fuzzy C-means (PFCM) algorithms. We found this algorithm efficient, which provides good and reliable results. © 2014 National Taiwan University.


Ai J.,Research Center for Science and Technology in Medicine | Javidan A.N.,Tehran University of Medical Sciences | Mehrabani D.,Shiraz University of Medical Sciences
Iranian Red Crescent Medical Journal | Year: 2010

In the last few decades, the idea of being able to repair the brain by introducing new cells to repair the damaged areas has become an accepted potential treatment for neurodegenerative diseases. The stromal cell fraction of many tissues and organs has shown in vitro neurogenic differentiation; however, these cell types are limited by availability, invasiveness of extraction and in some cases limited proliferative capacity. Human endometrial adult stem cells have many clinical advantages over the other stem cells. Here, we propose the hypothesis that endometrial adult stem cells may be induced into neural cells. © Iranian Red Crescent Medical Journal.


Karimifard S.,Tehran University of Medical Sciences | Karimifard S.,Research Center for Science and Technology in Medicine | Ahmadian A.,Tehran University of Medical Sciences | Ahmadian A.,Research Center for Science and Technology in Medicine
BioMedical Engineering Online | Year: 2011

Background: Electrocardiography (ECG) signal is a primary criterion for medical practitioners to diagnose heart diseases. The development of a reliable, accurate, non-invasive and robust method for arrhythmia detection could assists cardiologists in the study of patients with heart diseases. This paper provides a method for morphological heart arrhythmia detection which might have different shapes in one category and also different morphologies in relation to the patients. The distinctive property of this method in addition to accuracy is the robustness of that, in presence of Gaussian noise, time and amplitude shift.Methods: In this work 2nd, 3rdand 4thorder cumulants of the ECG beat are calculated and modeled by linear combinations of Hermitian basis functions. Then, the parameters of each cumulant model are used as feature vectors to classify five different ECG beats namely as Normal, PVC, APC, RBBB and LBBB using 1-Nearest Neighborhood (1-NN) classifier. Finally, after classifying each model, a final decision making rule apply to these specified classes and the type of ECG beat is defined.Results: The experiment was applied for a set of ECG beats consist of 9367 samples in 5 different categories from MIT/BIH heart arrhythmia database. The specificity of 99.67% and the sensitivity of 98.66% in arrhythmia detection are achieved which indicates the power of the algorithm. Also, the accuracy of the system remained almost intact in the presence of Gaussian noise, time shift and amplitude shift of ECG signals.Conclusions: This paper presents a novel and robust methodology in morphological heart arrhythmia detection. The methodology based on the Hermite model of the Higher-Order Statistics (HOS). The ability of HOS in suppressing morphological variations of different class-specific arrhythmias and also reducing the effects of Gaussian noise, made HOS, suitable for detection morphological heart arrhythmias. The proposed method exploits these properties in conjunction with Hermitian model to perform an efficient and reliable classification approach to detect five morphological heart arrhythmias. And the time consumption of this method for each beat is less than the period of a normal beat. © 2011 Karimifard and Ahmadian; licensee BioMed Central Ltd.


Marsousi M.,Research Center for Science and Technology in Medicine
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2010

In this paper, a fully automated method for segmenting Left Ventricle (LV) in echocardiography images is proposed. A new method named active ellipse model is developed to automatically find the best ellipse inside the LV chamber without intervention of any specialist. A modified B-Spline Snake algorithm is used to segment the LV chamber in which the initial contour is formed by the predefined ellipse. As a result of using active ellipse model, the segmentation is extricated from dealing with gaps within myocardium boundary which are highly problematic in echocardiography image segmentation. Based on the results obtained from different studies, the proposed method is faster and more accurate than previous approaches. Our method is evaluated on 20 sets of echocardiography images of patients; and acquired results (92.30 ± 4.45% dice's coefficient) indicate the proposed method has remarkable performance.


PubMed | Research Center for Science and Technology in Medicine
Type: | Journal: Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference | Year: 2010

In this paper, a fully automated method for segmenting Left Ventricle (LV) in echocardiography images is proposed. A new method named active ellipse model is developed to automatically find the best ellipse inside the LV chamber without intervention of any specialist. A modified B-Spline Snake algorithm is used to segment the LV chamber in which the initial contour is formed by the predefined ellipse. As a result of using active ellipse model, the segmentation is extricated from dealing with gaps within myocardium boundary which are highly problematic in echocardiography image segmentation. Based on the results obtained from different studies, the proposed method is faster and more accurate than previous approaches. Our method is evaluated on 20 sets of echocardiography images of patients; and acquired results (92.30 4.45% dices coefficient) indicate the proposed method has remarkable performance.

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