Development of a patient-specific finite element model of the transcatheter aortic valve implantation (TAVI) procedure

Transcatheter Aortic Valve Implantation (TAVI) is a procedure developed for replacing the defective aortic valve of a patient as an alternative to open heart Surgical Aortic Valve Replacement (SAVR). In the TAVI procedure a prosthetic valve, which is assembled on to a stent, is crimped and delivered to the patient's aortic root site through several available percutaneous means. The percutaneous nature of TAVI, which is its core advantage in comparison to other SAVR procedures, can however also be its main disadvantage. This is due to lack of direct access to the calcified leaflets, and hence reliance on the host tissue for the proper positioning and anchorage of the deployed prosthetic valve. Therefore, it is desired to have a preoperative quantitative understanding of patient-specific biomechanical interaction of the stent and the native valve to be able to maximise the chance of success of the procedure. The aim of this study was to develop a patient-specific Finite Element (FE) model of the Transcatheter Aortic Valve Implantation (TAVI) procedure for two patients, using a model of the 23 mm percutaneous prosthetic aortic valve developed by Strait Access Technologies (SAT), for the purpose of its post-operative performance. In this regard, the image processing software ScanIP was used to extract the 3D models of the patient-specific aortic roots and leaflets from the provided Multi-Slice Computer Tomography (MSCT) images of the patients. An anisotropic hyperelastic material model was implemented for the roots and leaflets, using two and one families of collagen fibres for their tissues respectively. The stent is made of a cobalt-chromium alloy and its mechanical response was modelled as an isotropic elastoplastic material, with a linear elastic initial response, followed by plastic behaviour with isotropic hardening. The prosthetic leaflets are made of polymer and were modelled as an isotropic hyperelastic material, using the provided experimental test data. The results for the first patient showed that the stent maintained its structural integrity after deployment, and successfully pushed the native leaflets back to keep the aortic root clear of all impediments. No obstruction of the coronary ostia was observed, and prosthetic leaflets were seen to function normally. The stent radial recoil was calculated to be between 2 to 4.28 % after deployments. Its foreshortening was calculated to be approximately 20%. The stent was observed to move back and forth by approximately 3 mm in the last simulation step in which cardiac cycle pressure were applied to the aortic root and prosthetic leaflets. Also, two openings were observed between the stent and aortic root wall during this simulation step, which indicates the possibility of paravalvular leakage. From the second patient simulation, it was observed that the 23 mm stent was not a good choice for this patient, and will cause severe damage or tissue tearing. The maximum principal stress in the aortic root and valve tissues were observed to follow approximately the defined collagen fibre directions

Comparison of Iris Fixated and Scleral Fixated intra Ocular Lens for Correction of Aphakia in Traumatic Cataract with no Proper Capsular Support

Purpose: To compare visual outcomes and complications of iris fixated and scleral fixated intra ocular lens (IOL) implantation in patients suffering from traumatic cataract with no proper capsular support.Patients and Methods: This prospective interventional study was performed in Farabi Eye Hospital, Tehran, Iran, between May 2015 and May 2016. Twenty five patients with traumatic cataract and no proper capsular support for IOL implantation in the bag or sulcus were included and randomly underwent either iris fixated or sulcus fixated IOL implantation. Follow up visits were performed one day, one week, four weeks, three months and six months after surgery. In each visit visual acuity, intra ocular pressure, placement of IOL and anterior chamber reaction were studied. Results: Thirteen eyes of 13 patients underwent iris fixation and 12 eyes of 12 patients underwent scleral fixation of IOL. The average patient age at presentation was 29.12 ± 16.32. In the follow up visit one week after IOL fixation three patients in each group had significant anterior chamber inflammation. There was no statistically significant difference between the two groups regarding the number of patients with elevated IOP (P = 0.96), dislocated IOL (P = 0.480) and complications such as wound dehiscence and iridocorneal adhesion. Also no statistically significant difference regarding the mean BCVA three months after surgery was observed (P = 0.55).Conclusion: We did not observe any significant difference in outcome of iris and scleral fixation of IOL in traumatic eye injuries with no effective capsular support.&nbsp

Rigorous performance assessment of the algorithms for resolving motor unit action potential superpositions

It is necessary to decompose the intra-muscular EMG signal to extract motor unit action potential (MUAP) waveforms and firing times. Some algorithms were proposed in the literature to resolve superimposed MUAPs, including Peel-Off (PO), branch and bound (BB), genetic algorithm (GA), and particle swarm optimization (PSO). This study aimed to compare these algorithms in terms of overall accuracy and running time. Two sets of two-to-five MUAP templates (set1: a wide range of energies, and set2: a high degree of similarity) were used. Such templates were time-shifted, and white Gaussian noise was added. A total of 1000 superpositions were simulated for each template and were resolved using PO (also, POI: interpolated PO), BB, GA, and PSO algorithms. The generalized estimating equation was used to identify which method significantly outperformed, while the overall rank product was used for overall ranking. The rankings were PSO, BB, GA, PO, and POI in the first, and BB, PSO, GA, PO, POI in the second set. The overall ranking was BB, PSO, GA, PO, and POI in the entire dataset. Although the BB algorithm is generally fast, there are cases where the BB algorithm is too slow and it is thus not suitable for real-time applications.This work was supported by the Spanish Ministry of Economy and Competitiveness - Spain (DPI2017-83989-R).Peer ReviewedPostprint (author's final draft

Incidence and Disability-Adjusted Life Years (Dalys) Attributable to Leishmaniasis In Iran, 2013

Background: Leishmaniasis covers a range of clinical manifestations. Estimation of the burden of leishmaniasis may help guide healthcare management personnel and policy-makers in applying effective interventions. The present study aimed to calculate the incidence and burden of cutaneous and visceral leishmaniasis in Iran in 2013.Methods: To evaluate the epidemiological aspects of the disease in Iran, published studies over the past 20 years were searched and the viewpoints of relevant  specialists in Iran were obtained. Data were collected from the Ministry of Health and from the Tehran University of Medical Sciences. To calculate years of life lost due to premature death, standard expected years of life lost was used. Standard life table of Global Burden of Disease (GBD) 2010 with the life expectancy of 86.02 years for both sexes was used to calculate the remaining potential years of life at any age from death.Results: The overall incidence of cutaneous and visceral leishmaniasis was  calculated as 22 and 0.092 per 100000 population of Iran, respectively. The  burden of leishmaniasis was 99.5 years: 95.34 and 4.16 years for cutaneous and visceral, respectively. Sensitivity was analyzed and deaths predicted by the  Institute of Health Metrics and Evaluation added, the burden of visceral  leishmaniasis was 726 years.Conclusion: The share of leishmaniasis burden in Iran is lower than the global burden of the disease. GBD 2010 standard method is recommended to calculate the burden of leishmaniasis in different countries and set local priorities on the basis of these measures.Keywords: Incidence, Disability-adjusted life years, Cutaneous leishmaniasis, Visceral leishmaniasis, Ira

An Accurate and Real-time Method for Resolving Superimposed Action Potentials in MultiUnit Recordings

Objective: Spike sorting of muscular and neural recordings requires separating action potentials that overlap in time (superimposed action potentials (APs)). We propose a new algorithm for resolving superimposed action potentials, and we test it on intramuscular EMG (iEMG) and intracortical recordings. Methods: Discrete-time shifts of the involved APs are first selected based on a heuristic extension of the peel-off algorithm. Then, the time shifts that provide the minimal residual Euclidean norm are identified (Discrete Brute force Correlation (DBC)). The optimal continuous-time shifts are then estimated (High-Resolution BC (HRBC)). In Fusion HRBC (FHRBC), two other cost functions are used. A parallel implementation of the DBC and HRBC algorithms was developed. The performance of the algorithms was assessed on 11,000 simulated iEMG and 14,000 neural recording superpositions, including two to eight APs, and eight experimental iEMG signals containing four to eleven active motor units. The performance of the proposed algorithms was compared with that of the Branch-and-Bound (BB) algorithm using the Rank-Product (RP) method in terms of accuracy and efficiency. Results: The average accuracy of the DBC, HRBC and FHRBC methods on the entire simulated datasets was 92.16\ub117.70, 93.65\ub116.89, and 94.90\ub115.15 (%). The DBC algorithm outperformed the other algorithms based on the RP method. The average accuracy and running time of the DBC algorithm on 10.5 ms superimposed spikes of the experimental signals were 92.1\ub121.7 (%) and 2.3\ub115.3 (ms). Conclusion and Significance: The proposed algorithm is promising for real-time neural decoding, a central problem in neural and muscular decoding and interfacing

Surgical Treatment of a Dens Invagination Type (І) in a Maxillary Lateral Incisor with 6-Year Follow-Up

Dens invagination is a developmental anomaly that requires specific treatment approaches. The invagination is enamel-lined in the crown of the tooth truly negligible, and usually there is no extension on the level of the external amelocemental junction. A well ending surgical root canal treatment of an invaginated tooth with a retrograde filling is presented in this case report. Periapical radiographic examination, after 3 months and 6 years of follow-up, showed periapical healing with osseous formation

Molecular and parasitological study of cutaneous leishmaniasis in Bushehr province, southwest of the Islamic Republic of Iran: a cross-sectional study during 2009–2012

Cutaneous leishmaniasis (CL) is one of the most important parasitic disease in Iran. CL is distributed among more than half of 31 provinces of Iran. Studies on epidemiological aspects of the disease and Leishmania species identification among infected humans are necessary for providing a comprehensive prevention and control program thus; this descriptive cross-sectional study was conducted on all CL suspected patients who referred to Health Centers of Bushehr province from 2009 to 2012. Physical examinations were carried out in suspected individuals and CL cases were confirmed by microscopical examinations. Prepared slides from suspicious cases of CL were fixed with absolute methanol and stained by Giemsa 10 %. All the Giemsa-stained slides examined under a light microscope with high magnification (1,0009) and classified them based on grading of Leishmania parasites. DNA from each slide was extracted, separately. The ribosomal internal transcribed spacer 1 was amplified with specific primers and PCR products were digested by restrict enzymes (HaeIII), run them in 3 % gel agarose for electrophoresis and visualized on a UV transilluminator after staining with ethidium bromide. SPSS version 21 was used for data analyses. A total of 726 suspected CL cases were referred to Health Centers of Bushehr province from 2009 to 2012 and samples were only prepared from 188 of the patients whereas 43 (5.9 %) of them were microscopy positive. The most frequent of CL was observed in November (14 %) and December (12 %). The most distribution of CL lesions were observed on hands (32 %), feet (26 %), and face (21 %), respectively. The highest frequency of CL was observed in 1–9 years old (30 %). Altogether, 50 % of the patients showed one skin lesion and 2–10 skin lesions were occurred in the remained CL patients. Totally, 27 out of 43 (63 %) of the Giemsa stained slides were positive by PCR–RFLP assay because all the PCR–RFLP negative slides were prepared 3–4 years ago and kept without cover slip, and also observed scarce amastigotes during microscopy observations. Leishmania species were identified in 21 desirable slides which 14 of them were L. major and 7 of the remained isolates were identified L. tropica using PCR–RFLP

A real-time and convex model for the estimation of muscle force from surface electromyographic signals in the upper and lower limbs

Surface electromyography (sEMG) is a signal consisting of different motor unit action potential trains and records from the surface of the muscles. One of the applications of sEMG is the estimation of muscle force. We proposed a new real-time convex and interpretable model for solving the sEMG—force estimation. We validated it on the upper limb during isometric voluntary flexions-extensions at 30%, 50%, and 70% Maximum Voluntary Contraction in five subjects, and lower limbs during standing tasks in thirty-three volunteers, without a history of neuromuscular disorders. Moreover, the performance of the proposed method was statistically compared with that of the state-of-the-art (13 methods, including linear-in-the-parameter models, Artificial Neural Networks and Supported Vector Machines, and non-linear models). The envelope of the sEMG signals was estimated, and the representative envelope of each muscle was used in our analysis. The convex form of an exponential EMG-force model was derived, and each muscle’s coefficient was estimated using the Least Square method. The goodness-of-fit indices, the residual signal analysis (bias and Bland-Altman plot), and the running time analysis were provided. For the entire model, 30% of the data was used for estimation, while the remaining 20% and 50% were used for validation and testing, respectively. The average R-square (%) of the proposed method was 96.77 ± 1.67 [94.38, 98.06] for the test sets of the upper limb and 91.08 ± 6.84 [62.22, 96.62] for the lower-limb dataset (MEAN ± SD [min, max]). The proposed method was not significantly different from the recorded force signal (p-value = 0.610); that was not the case for the other tested models. The proposed method significantly outperformed the other methods (adj. p-value < 0.05). The average running time of each 250 ms signal of the training and testing of the proposed method was 25.7 ± 4.0 [22.3, 40.8] and 11.0 ± 2.9 [4.7, 17.8] in microseconds for the entire dataset. The proposed convex model is thus a promising method for estimating the force from the joints of the upper and lower limbs, with applications in load sharing, robotics, rehabilitation, and prosthesis control for the upper and lower limbs

A preliminary study to assess saddle induced discomfort and non-traumatic perineal injuries for male cyclists

8th World Congress of Biomechanics, DUBLIN, IRELANDE, 08-/07/2016 - 08/07/2016According to the studies conducted on large samples of amateur and professional road cyclists, between 33 to 41% complained of problems such as neuropathic pain, perineal chronic numbness, saddle sores and nodules, impotence and erectile dysfunction [1,2]. A research project has been initiated aiming to conduct a comprehensive assessment of the saddle related discomfort, and the mechanism of onset of non-traumatic injuries through performing MRI scans, along with pressure mapping and motion capture experiments for two common cycling postures: "tops" and "drops" (Figure 1). A novel approach has been taken in this study for scanning cyclist's perineal anatomy by making use of a PARAmed upright open MRI scanner. The advantage of this scanner is its capacity to accommodate a cyclist in realistic postures for imaging. However, due to its usage of 0.5 tesla magnet, the optimum resolution for a good compromise between image acquisition time and ability in subject-specific computational model generation of the thin structures of the perineum was a concern. Therefore, a pilot study was conducted to examine the image quality, and assess the levels of tissue deformations for the two mentioned postures

A comprehensive review of the movement imaginary brain-computer interface methods: Challenges and future directions

Brain-computer interface (BCI) aims to translate human intention into a control output signal. In motor-imaginary (MI) BCI, the imagination of movement modifies the cortex brain activity. Such activities are then used in pattern recognition to identify certain movement classes. MI-BCI could be used to enhance the life quality of physically impaired subjects. Several challenges exist in MI-BCI, including selecting appropriate channels, usually linked with a suitable classifier choice. The entire procedure must be real time in practical applications. A variety of channel selection and classification methods were used for MI-BCI in the literature. Also, hybrid machine learning (ML) and deep learning (DL) methods were used in the literature. In this chapter, different channel selection, ML and DL methods, validation frameworks, and performance indices of EEG-based methods were investigated. Three hundred and twenty-two papers published between January 2000 and March 2021 were analyzed in this systematic review. Specific challenges and future directions were then provided.Peer ReviewedPostprint (author's final draft