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COMPUTER SCIENCE (1194 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 872 Journals sorted alphabetically
3D Printing and Additive Manufacturing     Full-text available via subscription   (Followers: 20)
Abakós     Open Access   (Followers: 4)
ACM Computing Surveys     Hybrid Journal   (Followers: 27)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 8)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 12)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 15)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 5)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 7)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 12)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 17)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 15)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 5)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 4)
ACM Transactions on Economics and Computation     Hybrid Journal  
ACM Transactions on Embedded Computing Systems (TECS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Information Systems (TOIS)     Hybrid Journal   (Followers: 19)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 7)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 9)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 6)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 8)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 9)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Full-text available via subscription   (Followers: 29)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Informatica Malaysia     Open Access  
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Ad Hoc Networks     Hybrid Journal   (Followers: 11)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 28)
Advanced Science Letters     Full-text available via subscription   (Followers: 10)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 7)
Advances in Artificial Intelligence     Open Access   (Followers: 15)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 19)
Advances in Computer Engineering     Open Access   (Followers: 4)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 51)
Advances in Engineering Software     Hybrid Journal   (Followers: 27)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 13)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Human-Computer Interaction     Open Access   (Followers: 20)
Advances in Materials Sciences     Open Access   (Followers: 14)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Remote Sensing     Open Access   (Followers: 44)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 5)
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 9)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
AI EDAM     Hybrid Journal  
Air, Soil & Water Research     Open Access   (Followers: 11)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 11)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 5)
American Journal of Sensor Technology     Open Access   (Followers: 4)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 7)
Analysis in Theory and Applications     Hybrid Journal   (Followers: 1)
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 4)
Annals of Data Science     Hybrid Journal   (Followers: 11)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Software Engineering     Hybrid Journal   (Followers: 13)
Annual Reviews in Control     Hybrid Journal   (Followers: 6)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applied and Computational Harmonic Analysis     Full-text available via subscription   (Followers: 1)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 12)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 11)
Applied Computer Systems     Open Access   (Followers: 2)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 33)
Applied Medical Informatics     Open Access   (Followers: 10)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 16)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Applied System Innovation     Open Access  
Architectural Theory Review     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 145)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
arq: Architectural Research Quarterly     Hybrid Journal   (Followers: 7)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 7)
Asia Pacific Journal on Computational Engineering     Open Access  
Asia-Pacific Journal of Information Technology and Multimedia     Open Access   (Followers: 1)
Asian Journal of Computer Science and Information Technology     Open Access  
Asian Journal of Control     Hybrid Journal  
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
Australian Educational Computing     Open Access   (Followers: 1)
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 4)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 11)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Big Data and Cognitive Computing     Open Access   (Followers: 2)
Biodiversity Information Science and Standards     Open Access  
Bioinformatics     Hybrid Journal   (Followers: 293)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 21)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 37)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 47)
British Journal of Educational Technology     Hybrid Journal   (Followers: 145)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 12)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 1)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal   (Followers: 2)
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 15)
Capturing Intelligence     Full-text available via subscription  
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cell Communication and Signaling     Open Access   (Followers: 2)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access   (Followers: 3)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
ChemSusChem     Hybrid Journal   (Followers: 7)
China Communications     Full-text available via subscription   (Followers: 7)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
CIN Computers Informatics Nursing     Full-text available via subscription   (Followers: 11)
Circuits and Systems     Open Access   (Followers: 15)
Clean Air Journal     Full-text available via subscription   (Followers: 1)
CLEI Electronic Journal     Open Access  
Clin-Alert     Hybrid Journal   (Followers: 1)
Cluster Computing     Hybrid Journal   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Communication Methods and Measures     Hybrid Journal   (Followers: 12)
Communication Theory     Hybrid Journal   (Followers: 21)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Algebra     Hybrid Journal   (Followers: 3)
Communications in Computational Physics     Full-text available via subscription   (Followers: 2)
Communications in Partial Differential Equations     Hybrid Journal   (Followers: 3)
Communications of the ACM     Full-text available via subscription   (Followers: 52)
Communications of the Association for Information Systems     Open Access   (Followers: 16)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access   (Followers: 1)
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 8)
Computación y Sistemas     Open Access  
Computation     Open Access   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 9)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 16)
Computational Linguistics     Open Access   (Followers: 23)
Computational Management Science     Hybrid Journal  
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 5)
Computational Methods and Function Theory     Hybrid Journal  
Computational Molecular Bioscience     Open Access   (Followers: 2)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Particle Mechanics     Hybrid Journal   (Followers: 1)
Computational Research     Open Access   (Followers: 1)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computational Science and Techniques     Open Access  
Computational Statistics     Hybrid Journal   (Followers: 14)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 30)
Computer     Full-text available via subscription   (Followers: 94)
Computer Aided Surgery     Open Access   (Followers: 6)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Communications     Hybrid Journal   (Followers: 16)
Computer Journal     Hybrid Journal   (Followers: 9)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 23)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 12)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 2)
Computer Music Journal     Hybrid Journal   (Followers: 19)
Computer Physics Communications     Hybrid Journal   (Followers: 7)

        1 2 3 4 5 6 | Last

Journal Cover
Biomedical Engineering, IEEE Transactions on
Journal Prestige (SJR): 1.267
Citation Impact (citeScore): 5
Number of Followers: 37  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9294
Published by IEEE Homepage  [191 journals]
  • Frontcover
    • Abstract: Presents the front cover for this issue of the publication.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • IEEE Engineering in Medicine and Biology Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • IEEE Transactions on Biomedical Engineering (T-BME)
    • Abstract: These instructions give guidelines for preparing papers for this publication. Presents information for authors publishing in this journal.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • IEEE Transactions on Biomedical Engineering Handling Editors
    • Abstract: Presents a listing of the EMBS Handling editors.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • MRI-Guided Robotically Assisted Focal Laser Ablation of the Prostate Using
           Canine Cadavers
    • Authors: Yue Chen;Sheng Xu;Alexander Squires;Reza Seifabadi;Ismail Baris Turkbey;Peter A. Pinto;Peter Choyke;Bradford Wood;Zion Tsz Ho Tse;
      Pages: 1434 - 1442
      Abstract: Objective: a magnetic resonance imaging (MRI)-conditional needle guidance robot is developed to enhance MRI-guided focal laser ablation (FLA) therapy in patients with focal prostate cancer. Methods: inspired by the workflow of the manual FLA therapy, we developed an MRI-conditional robot with two degrees of freedom to provide the guidance for laser ablation catheter. This robot is powered by pneumatic turbine motors and encoded with the custom-designed optical encoder. The needle could be inserted manually through the designed robotic system, which keeps the patients inside MRI bore throughout the procedure. The robot hardware is integrated with the custom ablation planning and monitoring software (OncoNav) to provide an iterative treatment plan to cover the whole ablation zone. Virtual tumors were selected in three canine cadavers as targets to validate the performance of the proposed hardware and software system. Results: phantom studies show that the average targeting error is less than 2 mm and the workflow of the entire procedure lasts for 100 minutes. Canine cadaver experiment results show that all the targets were successfully ablated in no more than three administrations. Significance: MRI-guided prostate FLA is feasible using the proposed hardware and software system, indicating potential utility in future human trials.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • A Time-Varying Nonparametric Methodology for Assessing Changes in QT
           Variability Unrelated to Heart Rate Variability
    • Authors: Michele Orini;Esther Pueyo;Pablo Laguna;Raquel Bailón;
      Pages: 1443 - 1451
      Abstract: Objective: To propose and test a novel methodology to measure changes in QT interval variability (QTV) unrelated to RR interval variability (RRV) in nonstationary conditions. Methods: Time-frequency coherent and residual spectra representing QTV related (QTVrRRV) and unrelated (QTVuRRV) to RRV, respectively, are estimated using time-frequency Cohen's class distributions. The proposed approach decomposes the nonstationary output spectrum of any two-input one-output model with uncorrelated inputs into two spectra representing the information related and unrelated to one of the two inputs, respectively. An algorithm to correct for the bias of the time-frequency coherence function between QTV and RRV is proposed to provide accurate estimates of both QTVuRRV and QTVrRRV. Two simulation studies were conducted to assess the methodology in challenging nonstationary conditions and data recorded during head-up tilt in 16 healthy volunteers were analyzed. Results: In the simulation studies, QTVuRRV changes were tracked with only a minor delay due to the filtering necessary to estimate the nonstationary spectra. The correlation coefficient between theoretical and estimated patterns was $>0.92$ even for extremely noisy recordings (signal to noise ratio (SNR) in QTV $=-text{10}$ dB). During head-up tilt, QTVrRRV explained the largest proportion of QTV, whereas QTVuRRV showed higher relative increase than QTV or QTVrRRV in all spectral bands ($Pleq 0.05$ for most pairwise comparisons). Conclusion: The proposed approach accurately tracks changes in QTVuRRV. Head-up tilt induced a slightly greater increase in QTVuRRV than in QTVrRRV. Significance: T-e proposed index QTVuRRV may represent an indirect measure of intrinsic ventricular repolarization variability, a marker of cardiac instability associated with sympathetic ventricular modulation and sudden cardiac death.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Curved-Array-Based Multispectral Photoacoustic Imaging of Human Finger
    • Authors: Na Huang;Ming He;Haosheng Shi;Yuan Zhao;Man Lu;Xianbing Zou;Lei Yao;Huabei Jiang;Lei Xi;
      Pages: 1452 - 1459
      Abstract: Objective: In this study, we present the design, fabrication, and evaluation of a curved-array-based photoacoustic imaging system designed for imaging vasculatures inside human finger joints with multispectral strategy. Methods: The transducers were fabricated with polyvinylidene fluoride (PVDF) film with a size of 30 mm × 2.8 mm and a curvature radius of 82 mm. A detailed comparison between the PVDF transducer and commercial piezoelectric ceramic transducers was performed. In addition, phantom and in vivo mouse experiments were carried out to evaluate the system performance. Furthermore, we recruited healthy volunteers and did multispectral photoacoustic imaging of blood vessels in finger joints. Results: The transducers have an average center frequency of 6.6 MHz and a mean bandwidth of 95%. The lateral and axial resolutions of the system are 110 and 800 μm, respectively, and the diameter of the active imaging is larger than 50 mm. We successfully captured the drug-induced cerebral bleeding spots in intact mouse brains, and recovered both morphology and oxygen saturation of the blood vessels in human finger joints. Conclusions: The PVDF transducer has a better performance in bandwidth compared with commercial transducers. The curved design of the transducer offers a better sensitivity and a higher axial resolution compared with the flat design. Significance: Based on the phantom, animal, and human experiments, the proposed system has the potential to be used in clinical diagnosis of early-stage arthritis.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Simple, Transparent, and Flexible Automated Quality Assessment Procedures
           for Ambulatory Electrodermal Activity Data
    • Authors: Ian R. Kleckner;Rebecca M. Jones;Oliver Wilder-Smith;Jolie B. Wormwood;Murat Akcakaya;Karen S. Quigley;Catherine Lord;Matthew S. Goodwin;
      Pages: 1460 - 1467
      Abstract: Objective: Electrodermal activity (EDA) is a noninvasive measure of sympathetic activation often used to study emotions, decision making, and health. The use of “ambulatory” EDA in everyday life presents novel challenges—frequent artifacts and long recordings—with inconsistent methods available for efficiently and accurately assessing data quality. We developed and validated a simple, transparent, flexible, and automated quality assessment procedure for ambulatory EDA data. Methods: A total of 20 individuals with autism (5 females, 5–13 years) provided a combined 181 h of EDA data in their home using the Affectiva Q Sensor across 8 weeks. Our procedure identified invalid data using four rules: First, EDA out of range; second, EDA changes too quickly; third, temperature suggests the sensor is not being worn; and fourth, transitional data surrounding segments identified as invalid via the preceding rules. We identified invalid portions of a pseudorandom subset of our data (32.8 h, 18%) using our automated procedure and independent visual inspection by five EDA experts. Results: Our automated procedure identified 420 min (21%) of invalid data. The five experts agreed strongly with each other (agreement: 98%, Cohen's κ: 0.87) and, thus, were averaged into a “consensus” rating. Our procedure exhibited excellent agreement with the consensus rating (sensitivity: 91%, specificity: 99%, accuracy: 92%, κ: 0.739 [${rm{95% ,CI,}}= ,0.738$ , 0.740]). Conclusion: We deve-oped a simple, transparent, flexible, and automated quality assessment procedure for ambulatory EDA data. Significance: Our procedure can be used beyond this study to enhance efficiency, transparency, and reproducibility of EDA analyses, with free software available at
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Unambiguous Identification and Visualization of an Acoustically Active
           Catheter by Ultrasound Imaging in Real Time: Theory, Algorithm, and
           Phantom Experiments
    • Authors: Viksit Kumar;Richard Liu;Randall R. Kinnick;Adriana Gregory;Azra Alizad;Marek Belohlavek;Mostafa Fatemi;
      Pages: 1468 - 1475
      Abstract: Objective: Ultrasound-guided biopsies and minimally invasive procedures have been used in numerous medical applications, including catheter guidance. The biggest challenge for catheter guidance by ultrasound lies in distinguishing the catheter from neighboring tissue, as well as the ability to differentiate the catheter body from its tip. Methods: In our previous work, we introduced a functional prototype of an acoustically active catheter, in which a miniature piezoelectric crystal allowed accurate localization of the catheter tip by pulsed wave (PW) Doppler imaging and Doppler spectrogram. In this paper, the theory behind the symmetric Doppler shift due to the interaction of ultrasound wave with a vibrating piezoelectric crystal is explained. The theory is validated in an experimental continuous flow phantom setup. A novel algorithm, symmetric frequency detection algorithm, is presented for identification and visualization of the catheter tip in real time along with B-mode and PW Doppler. Results: The catheter tip is identified with a distinct color differentiable from common Doppler colors with a frame rate varying from 22 to 50 Hz. The catheter tip can be visualized in a small region of 2.4 mm in the elevational direction. Conclusion: The algorithm can be implemented in most clinical ultrasound machines with minor additions to the PW Doppler processing algorithm. The algorithm is optimized to be robust for a variety of blood flow velocities and is shown to perform well when the signal from the blood is on par in amplitude with the catheter signal. Significance: Unambiguous and distinct visualization of catheter tip facilitates real-time tracking of the catheter and aids minimally invasive procedures.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • A Procedure for the Automatic Analysis of High-Resolution Manometry Data
           to Support the Clinical Diagnosis of Esophageal Motility Disorders
    • Authors: Alessandro Frigo;Mario Costantini;Chiara Giulia Fontanella;Renato Salvador;Stefano Merigliano;Emanuele Luigi Carniel;
      Pages: 1476 - 1485
      Abstract: Objective: Degenerative phenomena may affect esophageal motility as a relevant social-health problem. The diagnosis of such disorders is usually performed by the analysis of data from high-resolution manometry (HRM). Inter- and intraobserver variability frequently affects the diagnosis, with potential interpretative and thus therapeutic errors, with unnecessary or worse treatments. This may be avoided with automatic procedures that minimize human intervention in data processing. Methods: In order to support the traditional diagnostic process, an automatic procedure was defined considering a specific physiomechanical model that is able to objectively interpret data from HRM. A training set (N = 226) of healthy volunteers and pathological subjects was collected in order to define the model parameters distributions of the different groups of subjects, providing a preliminary database. A statistical algorithm was defined for an objective identification of the patient's healthy or pathological condition by comparing patient parameters with the database. Results: A collection of HRMs including subjects of the training set has been built. Statistical relationships between parameters and pathologies have been established leading to a preliminary database. An automatic diagnosis procedure has been developed to compare model parameters of a specific patient with the database. The procedure was able to match the correct diagnosis up to 86% of the analyzed subjects. Conclusion: The success rate of the automatic procedure addresses the suitability of the developed algorithms to provide a valid support to the clinicians for the diagnostic activity. Significance: The objectivity of developed tools increases the reliability of data interpretation and, consequently, patient acceptance.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Automatic Temporal Segmentation of Vessels of the Brain Using 4D ASL MRA
    • Authors: Renzo Phellan;Thomas Lindner;Michael Helle;Alexandre X. Falcão;Nils Daniel Forkert;
      Pages: 1486 - 1494
      Abstract: Objective: Automatic vessel segmentation can be used to process the considerable amount of data generated by four-dimensional arterial spin labeling magnetic resonance angiography (4D ASL MRA) images. Previous segmentation approaches for dynamic series of images propose either reducing the series to a temporal average (tAIP) or maximum intensity projection (tMIP) prior to vessel segmentation, or a separate segmentation of each image. This paper introduces a method that combines both approaches to overcome the specific drawbacks of each technique. Methods: Vessels in the tAIP are enhanced by using the ranking orientation responses of path operators and multiscale vesselness enhancement filters. Then, tAIP segmentation is performed using a seed-based algorithm. In parallel, this algorithm is also used to segment each frame of the series and identify small vessels, which might have been lost in the tAIP segmentation. The results of each individual time frame segmentation are fused using an or boolean operation. Finally, small vessels found only in the fused segmentation are added to the tAIP segmentation. Results: In a quantitative analysis using ten 4D ASL MRA image series from healthy volunteers, the proposed combined approach reached an average Dice coefficient of 0.931, being more accurate than the corresponding tMIP, tAIP, and single time frame segmentation methods with statistical significance. Conclusion : The novel combined vessel segmentation strategy can be used to obtain improved vessel segmentation results from 4D ASL MRA and other dynamic series of images. Significance: Improved vessel segmentation of 4D ASL MRA allows a fast and accurate assessment of cerebrovascular structures.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Three-Dimensional Noninvasive Imaging of Ventricular Arrhythmias in
           Patients With Premature Ventricular Contractions
    • Authors: Long Yu;Qi Jin;Zhaoye Zhou;Liqun Wu;Bin He;
      Pages: 1495 - 1503
      Abstract: Objective: Noninvasive imaging of cardiac electrical activity promises to provide important information regarding the underlying arrhythmic substrates for successful ablation intervention and further understanding of the mechanism of such lethal disease. The aim of this study is to evaluate the performance of a novel 3-D cardiac activation imaging technique to noninvasively localize and image origins of focal ventricular arrhythmias in patients undergoing radio frequency ablation. Methods: Preprocedural ECG gated contrast enhanced cardiac CT images and body surface potential maps were collected from 13 patients within a week prior to the ablation. The electrical activation images were estimated over the 3-D myocardium using a cardiac electric sparse imaging technique, and compared with CARTO activation maps and the ablation sites in the same patients. Results : Noninvasively-imaged activation sequences were consistent with the CARTO mapping results with an average correlation coefficient of 0.79, average relative error of 0.19, and average relative resolution error of 0.017. The imaged initiation sites of premature ventricular contractions (PVCs) were, on average, within 8 mm of the last successful ablation site and within 3 mm of the nearest ablation site. Conclusion: The present results demonstrate the excellent performance of the 3-D cardiac activation imaging technique in imaging the activation sequence associated with PVC, and localizing the initial sites of focal ventricular arrhythmias in patients. These promising results suggest that the 3-D cardiac activation imaging technique may become a useful tool for aiding clinical diagnosis and management of ventricular arrhythmias.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Low-to-High Cross-Frequency Coupling in the Electrical Rhythms as
           Biomarker for Hyperexcitable Neuroglial Networks of the Brain
    • Authors: Vasily Grigorovsky;Berj L. Bardakjian;
      Pages: 1504 - 1515
      Abstract: Objective: One of the features used in the study of hyperexcitablility is high-frequency oscillations (HFOs,>80 Hz). HFOs have been reported in the electrical rhythms of the brain’s neuroglial networks under physiological and pathological conditions. Cross-frequency coupling (CFC) of HFOs with low-frequency rhythms was used to identify pathologic HFOs in the epileptogenic zones of epileptic patients and as a biomarker for the severity of seizure-like events in genetically modified rodent models. We describe a model to replicate reported CFC features extracted from recorded local field potentials (LFPs) representing network properties. Methods : This study deals with a four-unit neuroglial cellular network model where each unit incorporates pyramidal cells, interneurons, and astrocytes. Three different pathways of hyperexcitability generation—Na $^{+}$- ${rm K}^{+}$ ATPase pump, glial potassium clearance, and potassium afterhyperpolarization channel—were used to generate LFPs. Changes in excitability, average spontaneous electrical discharge (SED) duration, and CFC were then measured and analyzed. Results: Each parameter caused an increase in network excitability and the consequent lengthening of the SED duration. Short SEDs showed CFC between HFOs and theta oscillations (4–8 Hz), but in longer SEDs the low frequency changed to the delta range (1–4 Hz). Conclusion: Longer duration SEDs exhibit CFC features similar to those reported by our team. Significance: First, Identifying the exponential relationship between network excitability and SED durations; second, highlighting the importance of glia in hyperexcitability (-s they relate to extracellular potassium); and third, elucidation of the biophysical basis for CFC coupling features.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • An MRI-Compatible Hydrodynamic Simulator of Cerebrospinal Fluid Motion in
           the Cervical Spine
    • Authors: Suraj Thyagaraj;Soroush Heidari Pahlavian;Lucas R. Sass;Francis Loth;Morteza Vatani;Jae-Won Choi;R. Shane Tubbs;Daniel Giese;Jan-Robert Kroger;Alexander C. Bunck;Bryn A. Martin;
      Pages: 1516 - 1523
      Abstract: Goal: Develop and test an MRI-compatible hydrodynamic simulator of cerebrospinal fluid (CSF) motion in the cervical spinal subarachnoid space. Four anatomically realistic subject-specific models were created based on a 22-year-old healthy volunteer and a five-year-old patient diagnosed with Chiari I malformation. Methods : The in vitro models were based on manual segmentation of high-resolution T2-weighted MRI of the cervical spine. Anatomically realistic dorsal and ventral spinal cord nerve rootlets (NR) were added. Models were three dimensional (3-D) printed by stereolithography with 50-μm layer thickness. A computer controlled pump system was used to replicate the shape of the subject specific in vivo CSF flow measured by phase-contrast MRI. Each model was then scanned by T2-weighted and 4-D phase contrast MRI (4D flow). Results: Cross-sectional area, wetted perimeter, and hydraulic diameter were quantified for each model. The oscillatory CSF velocity field (flow jets near NR, velocity profile shape, and magnitude) had similar characteristics to previously reported studies in the literature measured by in vivo MRI. Conclusion: This study describes the first MRI-compatible hydrodynamic simulator of CSF motion in the cervical spine with anatomically realistic NR. NR were found to impact CSF velocity profiles to a great degree. Significance: CSF hydrodynamics are thought to be altered in craniospinal disorders such as Chiari I malformation. MRI scanning techniques and protocols can be used to quantify CSF flow alterations in disease states. The provided in vitro models can be used to test the reliability of these protocols across MRI scanner manufacturers and machines.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • A High-Resolution Minimicroscope System for Wireless Real-Time Monitoring
    • Authors: Zongjie Wang;Akash Boddeda;Benjamin Parker;Roya Samanipour;Sanjoy Ghosh;Frederic Menard;Keekyoung Kim;
      Pages: 1524 - 1531
      Abstract: Objective: Compact, cost-effective, and high-performance microscope that enables the real-time imaging of cells and lab-on-a-chip devices is highly demanded for cell biology and biomedical engineering. This paper aims to present the design and application of an inexpensive wireless minimicroscope with resolution up to 2592 × 1944 pixels and speed up to 90 f/s. Methods: The minimicroscope system was built on a commercial embedded system (Raspberry Pi). We modified a camera module and adopted an inverse dual lens system to obtain the clear field of view and appropriate magnification for tens of micrometer objects. Results: The system was capable of capturing time-lapse images and transferring image data wirelessly. The entire system can be operated wirelessly and cordlessly in a conventional cell culturing incubator. The developed minimicroscope was used to monitor the attachment and proliferation of NIH-3T3 and HEK 293 cells inside an incubator for 50 h. In addition, the minimicroscope was used to monitor a droplet generation process in a microfluidic device. The high-quality images captured by the minimicroscope enabled us an automated analysis of experimental parameters. Conclusion: The successful applications prove the great potential of the developed minimicroscope for monitoring various biological samples and microfluidic devices. Significance: This paper presents the design of a high-resolution minimicroscope system that enables the wireless real-time imaging of cells inside the incubator. This system has been verified to be a useful tool to obtain high-quality images and videos for the automated quantitative analysis of biological samples and lab-on-a-chip devices in the long term.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Analysis of Energy-Based Metrics for Laparoscopic Skills Assessment
    • Authors: Behnaz Poursartip;Marie-Eve LeBel;Rajni V. Patel;Michael D. Naish;Ana Luisa Trejos;
      Pages: 1532 - 1542
      Abstract: Objective: The complexity of minimally invasive surgery (MIS) requires that trainees practice MIS skills in numerous training sessions. The goal of these training sessions is to learn how to move the instruments smoothly without damaging the surrounding tissue and achieving operative tasks with accuracy. In order to enhance the efficiency of these training sessions, the proficiency of the trainees should be assessed using an objective assessment method. Several performance metrics have been proposed and analyzed for MIS tasks. The differentiation of various levels of expertise is limited without the presence of an external evaluator. Methods: In this study, novel objective performance metrics are proposed based on mechanical energy expenditure and work. The three components of these metrics are potential energy, kinetic energy, and work. These components are optimally combined through both one-step and two-step methods. Evaluation of these metrics is accomplished for suturing and knot-tying tasks based on the performance of 30 subjects across four levels of experience. Results: The results of this study show that the one-step combined metric provides 47 $%$ and 60$%$ accuracy in determining the level of expertise of subjects for the suturing and knot-tying tasks, respectively. The two-step combined metric provided 67$%$ accuracy for both of the tasks studied. Conclusion: The results indicate that energy expenditure is a useful metric for developing objective and efficient assessment methods. Significance: These metrics can be used to evaluate and determine the proficiency levels of trainees, provide feedback and, consequently, enhance surgical simulators.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Generalisability of a Virtual Trials Method for Glycaemic Control in
           Intensive Care
    • Authors: Jennifer L. Dickson;Kent W. Stewart;Christopher G. Pretty;Marine Flechet;Thomas Desaive;Sophie Penning;Bernard C. Lambermont;Balázs Benyó;Geoffrey M. Shaw;J. Geoffrey Chase;
      Pages: 1543 - 1553
      Abstract: Background: Elevated blood glucose (BG) concentrations (Hyperglycaemia) are a common complication in critically ill patients. Insulin therapy is commonly used to treat hyperglycaemia, but metabolic variability often results in poor BG control and low BG (hypoglycaemia). Objective: This paper presents a model-based virtual trial method for glycaemic control protocol design, and evaluates its generalisability across different populations. Methods: Model-based insulin sensitivity (SI) was used to create virtual patients from clinical data from three different ICUs in New Zealand, Hungary, and Belgium. Glycaemic results from simulation of virtual patients under their original protocol (self-simulation) and protocols from other units (cross simulation) were compared. Results: Differences were found between the three cohorts in median SI and inter-patient variability in SI. However, hour-to-hour intra-patient variability in SI was found to be consistent between cohorts. Self and cross-simulation results were found to have overall similarity and consistency, though results may differ in the first 24–48 h due to different cohort starting BG and underlying SI. Conclusions and Significance: Virtual patients and the virtual trial method were found to be generalisable across different ICUs. This virtual trial method is useful for in silico protocol design and testing, given an understanding of the underlying assumptions and limitations of this method.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • A Potential-Based Inverse Spectral Method to Noninvasively Localize
           Discordant Distributions of Alternans on the Heart From the ECG
    • Authors: Jaume Coll-Font;Burak Erem;Dana H. Brooks;
      Pages: 1554 - 1563
      Abstract: T-wave alternans (TWA), defined as the beat-to-beat alternation in amplitude of the T-waves, has been shown to be linked to ventricular fibrillation (VF). However, current TWA tests have high sensitivity but low specificity in determining who is at risk. To overcome this limitation, it might be helpful to determine the spatial distribution of any regions on the heart that alternate in opposite phase. Understanding these spatial distributions in relation to the regular activation of the heart could help explain the mechanism for the genesis of VF and thus disambiguate the low specificity of TWA. Goal: Image the spatial distribution of TWA on the heart surface from ECG measurements. Methods: We introduced the inverse spectral method (ISM), a tailored inverse (or ElectroCardioGraphic Imaging) solution designed specifically to noninvasively image cases of TWA on the heart. Results: We evaluate the ISM on its capacity to reliably detect the spatial distributions of TWA compared against a standard TWA detection method applied directly to the electrograms on the heart surface. We report on results from both a series of synthetic simulations of TWA generated using the ECGSIM software and a set of continuous epicardial surface voltage recordings from a canine experiment. ISM detected TWA distributions that matched the phase of the true underlying out-of-phase regions over $64%$ and $80%$ of the heart surface, respectively. Conclusion: Our results suggest that ISM is capable of reliably detecting the different regions present in a TWA distribution across a wide variety of TWA locations on the heart in simulation and in the face of transients and nonidealities in the canine recordings.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Computerized Lung Sound Screening for Pediatric Auscultation in Noisy
           Field Environments
    • Authors: Dimitra Emmanouilidou;Eric D. McCollum;Daniel E. Park;Mounya Elhilali;
      Pages: 1564 - 1574
      Abstract: Goal: Chest auscultations offer a non-invasive and low-cost tool for monitoring lung disease. However, they present many shortcomings, including inter-listener variability, subjectivity, and vulnerability to noise and distortions. This work proposes a computer-aided approach to process lung signals acquired in the field under adverse noisy conditions, by improving the signal quality and offering automated identification of abnormal auscultations indicative of respiratory pathologies. Methods: The developed noise-suppression scheme eliminates ambient sounds, heart sounds, sensor artifacts, and crying contamination. The improved high-quality signal is then mapped onto a rich spectrotemporal feature space before being classified using a trained support-vector machine classifier. Individual signal frame decisions are then combined using an evaluation scheme, providing an overall patient-level decision for unseen patient records. Results: All methods are evaluated on a large dataset with $>$1000 children enrolled, 1–59 months old. The noise suppression scheme is shown to significantly improve signal quality, and the classification system achieves an accuracy of 86.7% in distinguishing normal from pathological sounds, far surpassing other state-of-the-art methods. Conclusion: Computerized lung sound processing can benefit from the enforcement of advanced noise suppression. A fairly short processing window size ( $
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Pressure in the Cochlea During Infrared Irradiation
    • Authors: Nan Xia;Xiaodong Tan;Yingyue Xu;Wensheng Hou;Teresa Mao;Claus-Peter Richter;
      Pages: 1575 - 1584
      Abstract: Objective: The purpose of the study is to demonstrate laser-evoked pressure waves in small confined volumes such as the cochlea. Methods: Custom-fabricated pressure probes were used to determine the pressure in front of the optical fiber in a small dish and patch pipettes to measure temperature changes. Pressure probes were inserted into scala tympani (ST) or vestibuli during laser stimulation. With a sensitive microphone the pressure was measured in the outer ear canal. Results: Heating was spatially confined. The heat relaxation time was 35 ms. During laser stimulation in the cochlea at 17 μJ/pulse, the pressure in the outer ear canal (EC) was 43.5 dB (re 20 μPa). The corresponding intracochlear pressure was calculated to be about 78.5 dB (re 20 μPa) using the middle ear reverse transfer function of −35 dB. At 164 μJ/pulse, the pressure in the EC was on average 63 dB (re 20 μPa) and the intracochlear pressure was estimated to be 98 dB (re 20 μPa), which is similar to the value obtained with the pressure probe, 100 dB (re 20 μPa). Side-emitting optical fibers were used to steer the beam path. The pressure values were independent of the orientation of the beam path. Evoked compound action potentials of the auditory nerve were maximum when spiral ganglion neurons were in the beam path. Conclusion: Pressure waves are generated during infrared laser stimulation. The intracochlear pressure was independent from the orientation of the beam path. Significance: Neural responses required the spiral ganglion neurons to be directly irradiated.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Modeling Touch and Palpation Using Autoregressive Models
    • Authors: Shlomi Laufer;Carla M. Pugh;Barry D. Van Veen;
      Pages: 1585 - 1594
      Abstract: Objective: The human haptic system uses a set of reproducible and subconscious hand maneuvers to identify objects. Similar subconscious maneuvers are used during medical palpation for screening and diagnosis. The goal of this work was to develop a mathematical model that can be used to describe medical palpation techniques. Methods: Palpation data were measured using a two-dimensional array of force sensors. A novel algorithm for estimating the hand position from force data was developed. The hand position data were then modeled using multivariate autoregressive models. Analysis of these models provided palpation direction and frequency as well as palpation type. The models were tested and validated using three different data sets: simulated data, a simplified experiment in which participant followed a known pattern, and breast simulator palpation data. Results: Simulated data showed that the minimal error in estimating palpation direction and frequency is achieved when the sampling frequency is five to ten times the palpation frequency. The classification accuracy was $99%$ for the simplified experiment and $73%$ for the breast simulator data. Conclusion: Proper palpation is one of the vital components of many hands-on clinical examinations. In this study, an algorithm for characterizing medical palpation was developed. The algorithm measured palpation frequency and direction for the first time and provided classification of palpation type. Significance: These newly developed models can be used for quantifying and assessing clinical technique, and consequently, lead to improved performance in palpation-based exams. Furthermore, they provide a general tool for the study of human haptics.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Quantitative Testing of fMRI-Compatibility of an Electrically Active
           Mechatronic Device for Robot-Assisted Sensorimotor Protocols
    • Authors: Andria J. Farrens;Andrea Zonnino;Andrew Erwin;Marcia K. O’Malley;Curtis L. Johnson;David Ress;Fabrizio Sergi;
      Pages: 1595 - 1606
      Abstract: Objective: To develop a quantitative set of methods for testing the functional magnetic resonance imaging (fMRI) compatibility of an electrically-active mechatronic device developed to support sensorimotor protocols during fMRI. Methods: The set of methods includes phantom and in vivo experiments to measure the effect of a progressively broader set of noise sources potentially introduced by the device. Phantom experiments measure the radio-frequency (RF) noise and temporal noise-to-signal ratio (tNSR) introduced by the device. The in vivo experiment assesses the effect of the device on measured brain activation for a human subject performing a representative sensorimotor task. The proposed protocol was validated via experiments using a 3T MRI scanner operated under nominal conditions and with the inclusion of an electrically-active mechatronic device — the MR-SoftWrist — as the equipment under test (EUT). Results: Quantitative analysis of RF noise data allows detection of active RF noise sources both in controlled RF noise conditions, and in conditions resembling improper filtering of the EUT’s electrical signals. In conditions where no RF noise was detectable, the presence and operation of the EUT did not introduce any significant increase in tNSR. A quantitative analysis conducted on in vivo measurements of the number of active voxels in visual and motor areas further showed no significant difference between EUT and baseline conditions. Conclusion and significance: The proposed set of quantitative methods supports the development and troubleshooting of electrically-active mechatronic devices for use in sensorimotor protocols with fMRI, and may be used for future testing of such devices.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Optimization of the Working Conditions for Magnetic Nanoparticle-Enhanced
           Microwave Diagnostics of Breast Cancer
    • Authors: Gennaro Bellizzi;Gennaro Giovanni Bellizzi;Ovidio M. Bucci;Lorenzo Crocco;Marko Helbig;Sebastian Ley;Jürgen Sachs;
      Pages: 1607 - 1616
      Abstract: Magnetic nanoparticle-aided microwave imaging is recently gaining an increasing interest as a potential tool for breast cancer diagnostics. This is due to the peculiar features of magnetic nanoparticles, which are biocompatible, can be selectively targeted to the tumor, and may change their microwave magnetic response when modulated by a polarizing magnetic field. This latter aspect is particularly appealing, as it enables the physical separation of the microwave signal due the malignancy, targeted by the nanoparticles, from that due to healthy tissue. This increases the specificity of the diagnostic tool, in principle allowing a diagnosis based solely on the detection of the signal due to the nanoparticles response. In this respect, a proper choice of the polarizing field modulation can remarkably increase the detection performances. This paper deals with this issue, by providing the mathematical framework for such an optimization and a procedure for estimating the required quantities from a set of proper measurements. The procedure is then experimentally demonstrated by applying it to a recently developed ultrawideband radar system for the magnetic nanoparticle-aided detection of breast cancer. For such a system, the optimal magnetic field modulation is determined.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Three-Dimensional Segmentation of the Ex-Vivo Anterior Lamina Cribrosa
           From Second-Harmonic Imaging Microscopy
    • Authors: Sundaresh Ram;Forest Danford;Stephen Howerton;Jeffrey J. Rodríguez;Jonathan P. Vande Geest;
      Pages: 1617 - 1629
      Abstract: The lamina cribrosa (LC) is a connective tissue in the posterior eye with a complex mesh-like trabecular microstructure, through which all the retinal ganglion cell axons and central retinal vessels pass. Recent studies have demonstrated that changes in the structure of the LC correlate with glaucomatous damage. Thus, accurate segmentation and reconstruction of the LC is of utmost importance. This paper presents a new automated method for segmenting the microstructure of the anterior LC in the images obtained via multiphoton microscopy using a combination of ideas. In order to reduce noise, we first smooth the input image using a 4-D collaborative filtering scheme. Next, we enhance the beam-like trabecular microstructure of the LC using wavelet multiresolution analysis. The enhanced LC microstructure is then automatically extracted using a combination of histogram thresholding and graph-cut binarization. Finally, we use morphological area opening as a postprocessing step to remove the small and unconnected 3-D regions in the binarized images. The performance of the proposed method is evaluated using mutual overlap accuracy, Tanimoto index, F-score, and Rand index. Quantitative and qualitative results show that the proposed algorithm provides improved segmentation accuracy and computational efficiency compared to the other recent algorithms.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Closed-Loop Vagus Nerve Stimulation Based on State Transition Models
    • Authors: Hector M. Romero-Ugalde;Virginie Le Rolle;Jean-Luc Bonnet;Christine Henry;Philippe Mabo;Guy Carrault;Alfredo I. Hernández;
      Pages: 1630 - 1638
      Abstract: Objective: Vagus nerve stimulation (VNS) is a potential therapeutic approach in a number of clinical applications. Although VNS is commonly delivered in an open-loop approach, it is now recognized that closed-loop stimulation may be necessary to optimize the therapy. In this paper, we propose an original generic closed-loop control system that can be readily integrated into an implantable device and allows for the adaptive modulation of multiple VNS parameters. Methods: The proposed control method consists of a state transition model (STM), in which each state represents a set of VNS parameters, and a state transition algorithm that optimally selects the best STM state, minimizing the error between an observed physiological variable and a given target value. The proposed method has been integrated into a real-time adaptive VNS prototype system and has been applied here to the regulation of the instantaneous heart rate, working synchronously with cardiac cycles. A quantitative performance evaluation is performed on seven sheep by computing classical control performance indicators. A comparison with a proportional–integral (PI) controller is also performed. Results: The STM controller presents a median mean square error, overshoot, and settling time, respectively, equal to 622.21 ms $^2$, 72.8%, and 7.5 beats. Conclusion: The proposed control method yields satisfactory accuracy and time response, while presenting a number of benefits over classical PI controllers. It represents a feasible approach for multiparametric VNS control on implantable devices. Significance: Closed-loop multiparametric stimulation may improve response and minimize side effects on current pathologies treated by VNS.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Euler Elastica Regularized Logistic Regression for Whole-Brain Decoding of
           fMRI Data
    • Authors: Chuncheng Zhang;Li Yao;Sutao Song;Xiaotong Wen;Xiaojie Zhao;Zhiying Long;
      Pages: 1639 - 1653
      Abstract: Objective: Multivariate pattern analysis methods have been widely applied to functional magnetic resonance imaging (fMRI) data to decode brain states. Due to the “high features, low samples” in fMRI data, machine learning methods have been widely regularized using various regularizations to avoid overfitting. Both total variation (TV) using the gradients of images and Euler's elastica (EE) using the gradient and the curvature of images are the two popular regulations with spatial structures. In contrast to TV, EE regulation is able to overcome the disadvantage of TV regulation that favored piecewise constant images over piecewise smooth images. In this study, we introduced EE to fMRI-based decoding for the first time and proposed the EE regularized multinomial logistic regression (EELR) algorithm for multi-class classification. Methods: We performed experimental tests on both simulated and real fMRI data to investigate the feasibility and robustness of EELR. The performance of EELR was compared with sparse logistic regression (SLR) and TV regularized LR (TVLR). Results: The results showed that EELR was more robustness to noises and showed significantly higher classification performance than TVLR and SLR. Moreover, the forward models and weights patterns revealed that EELR detected larger brain regions that were discriminative to each task and activated by each task than TVLR. Conclusion: The results suggest that EELR not only performs well in brain decoding but also reveals meaningful discriminative and activation patterns. Significance: This study demonstrated that EELR showed promising potential in brain decoding and discriminative/activation pattern detection.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Screening for Cognitive Impairment by Model-Assisted Cerebral Blood Flow
    • Authors: Toni Lassila;Luigi Yuri Di Marco;Micaela Mitolo;Vincenzo Iaia;Giorgio Levedianos;Annalena Venneri;Alejandro F. Frangi;
      Pages: 1654 - 1661
      Abstract: Objective: Alzheimer's disease (AD) is a progressive and debilitating neurodegenerative disease; a major health concern in the ageing population with an estimated prevalence of 46 million dementia cases worldwide. Early diagnosis is therefore crucial so mitigating treatments can be initiated at an early stage. Cerebral hypoperfusion has been linked with blood-brain barrier dysfunction in the early stages of AD, and screening for chronic cerebral hypoperfusion in individuals has been proposed for improving the early diagnosis of AD. However, ambulatory measurements of cerebral blood flow are not routinely carried out in the clinical setting. In this study, we combine physiological modeling with Holter blood pressure monitoring and carotid ultrasound imaging to predict 24-h cerebral blood flow (CBF) profiles in individuals. One hundred and three participants [53 with mild cognitive impairment (MCI) and 50 healthy controls] underwent model-assisted prediction of 24-h CBF. Model-predicted CBF and neuropsychological tests were features in lasso regression models for MCI diagnosis. Results: A CBF-enhanced classifier for diagnosing MCI performed better, area-under-the-curve (AUC) = 0.889 (95%-CI: 0.800 to 0.978), than a classifier based only on the neuropsychological test scores, AUC = 0.818 (95%-CI: 0.643 to 0.992). An additional cohort of 25 participants (11 MCI and 14 healthy) was recruited to perform model validation by arterial spin-labeling magnetic resonance imaging, and to establish a link between measured CBF that predicted by the model. Conclusion: Ultrasound imaging and ambulatory blood pressure measurements enhanced with physiological modeling can improve MCI diagnosis accuracy.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
  • Localization of Origins of Premature Ventricular Contraction by Means of
           Convolutional Neural Network From 12-Lead ECG
    • Authors: Ting Yang;Long Yu;Qi Jin;Liqun Wu;Bin He;
      Pages: 1662 - 1671
      Abstract: Objective: This paper proposes a novel method to localize origins of premature ventricular contractions (PVCs) from 12-lead electrocardiography (ECG) using convolutional neural network (CNN) and a realistic computer heart model. Methods: The proposed method consists of two CNNs (Segment CNN and Epi-Endo CNN) to classify among ventricular sources from 25 segments and from epicardium (Epi) or endocardium (Endo). The inputs are the full time courses and the first half of QRS complexes of 12-lead ECG, respectively. After registering the ventricle computer model with an individual patient's heart, the training datasets were generated by multiplying ventricular current dipoles derived from single pacing at various locations with patient-specific lead field. The origins of PVC are localized by calculating the weighted center of gravity of classification returned by the CNNs. A number of computer simulations were conducted to evaluate the proposed method under a variety of noise levels and heart registration errors. Furthermore, the proposed method was evaluated on 90 PVC beats from nine human patients with PVCs and compared against ablation outcome in the same patients. Results: The computer simulation evaluation returned relatively high accuracies for Segment CNN (∼78%) and Epi-Endo CNN (∼90%). Clinical testing in nine PVC patients resulted an averaged localization error of 11 mm. Conclusion: Our simulation and clinical evaluation results demonstrate the capability and merits of the proposed CNN-based method for localization of PVC. Significance: This paper suggests a new approach for cardiac source localization of origin of arrhythmias using only the 12-lead ECG by means of CNN, and may have important applications for future real-time monitoring and localizing origins of car-iac arrhythmias guiding ablation treatment.
      PubDate: July 2018
      Issue No: Vol. 65, No. 7 (2018)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
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Fax: +00 44 (0)131 4513327
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