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Biomedical Engineering, IEEE Transactions on

Issue 1 • Date Jan. 2011

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Displaying Results 1 - 25 of 32
  • Table of contents

    Publication Year: 2011 , Page(s): C1
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  • IEEE Transactions on Biomedical Engineering publication information

    Publication Year: 2011 , Page(s): C2
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  • Table of contents

    Publication Year: 2011 , Page(s): 1 - 2
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  • Closed-Loop Anesthetic Drug Concentration Estimation Using Clinical-Effect Feedback

    Publication Year: 2011 , Page(s): 3 - 6
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (174 KB) |  | HTML iconHTML  

    This letter presents a novel closed-loop approach to anesthetic drug concentration estimation using clinical-effect measurement feedback. Compared with the open-loop prediction used in current target-controlled infusion systems, closed-loop estimation exploits the discrepancy between the measured and predicted clinical effects to make corrections to the drug-concentration estimate, achieving improved robustness against variability in the patient pharmacokinetics and pharmacodynamics. A robust estimator, which processes drug administration and clinical-effect measurements to estimate the plasma- and effect-site drug concentrations, is designed using -synthesis theory. Initial proof of principle of the closed-loop estimation is demonstrated using the Monte Carlo simulation of surgical procedures with a wide range of patient models. Closed-loop estimation results in statistically significant reductions in median percentage, median absolute percentage, and maximum absolute percentage drug-concentration errors compared to open-loop prediction. View full abstract»

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  • Advancements in Noncontact, Multiparameter Physiological Measurements Using a Webcam

    Publication Year: 2011 , Page(s): 7 - 11
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    We present a simple, low-cost method for measuring multiple physiological parameters using a basic webcam. By applying independent component analysis on the color channels in video recordings, we extracted the blood volume pulse from the facial regions. Heart rate (HR), respiratory rate, and HR variability (HRV, an index for cardiac autonomic activity) were subsequently quantified and compared to corresponding measurements using Food and Drug Administration-approved sensors. High degrees of agreement were achieved between the measurements across all physiological parameters. This technology has significant potential for advancing personal health care and telemedicine. View full abstract»

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  • A Novel Method for Assessing Sense of Body Ownership Using Electroencephalography

    Publication Year: 2011 , Page(s): 12 - 15
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB) |  | HTML iconHTML  

    A successful substitution of an upper limb is possible when the prosthesis is recognized by amputees as a part of their body scheme. A new system alternative to functional magnetic resonance imaging for evaluating the sense of ownership during the rubber hand experiment, using noninvasive electroencephalography recordings, is described, and encouraging results are presented. View full abstract»

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  • Temporal Sequence Parameters in Isodistributional Surrogate Data: Model and Exact Expressions

    Publication Year: 2011 , Page(s): 16 - 24
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB) |  | HTML iconHTML  

    In this paper, a set of formulae for the temporal spontaneous baroreceptor reflex (sBRR) sequence parameters in isodistributional (ID) surrogate data is derived. This is facilitated by representing successive positive or negative amplitude changes as a Markov chain model. The obtained analytical tool measures the effect of random fluctuations on the overall number of sequences, estimated from the original biomedical time series. The formulae are tested using ID surrogates of systolic blood pressure and pulse-interval signals recorded from 13 healthy male Wistar rats at baseline conditions. View full abstract»

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  • From Vascular Corrosion Cast to Electrical Analog Model for the Study of Human Liver Hemodynamics and Perfusion

    Publication Year: 2011 , Page(s): 25 - 35
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (830 KB) |  | HTML iconHTML  

    Hypothermic machine perfusion (HMP) is experiencing a revival in organ preservation due to the limitations of static cold storage and the need for better preservation of expanded criteria donor organs. For livers, perfusion protocols are still poorly defined, and damage of sinusoidal endothelial cells and heterogeneous perfusion are concerns. In this study, an electrical model of the human liver blood circulation is developed to enlighten internal pressure and flow distributions during HMP. Detailed vascular data on two human livers, obtained by combining vascular corrosion casting, micro-CT-imaging and image processing, were used to set up the electrical model. Anatomical data could be measured up to 5-6 vessel generations in each tree and showed exponential trend lines, used to predict data for higher generations. Simulated flow and pressure were in accordance with literature data. The model was able to simulate effects of pressure-driven HMP on liver hemodynamics and reproduced observations such as flow competition between the hepatic artery and portal vein. Our simulations further indicate that, from a pure biomechanical (shear stress) standpoint, HMP with low pressures should not result in organ damage, and that fluid viscosity has no effect on the shear stress experienced by the liver microcirculation in pressure-driven HMP. View full abstract»

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  • Modeling Transient Pupillary Light Reflex Induced by a Short Light Flash

    Publication Year: 2011 , Page(s): 36 - 42
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    A pupillary light reflex (PLR) model was proposed in this paper by considering the iris muscle mechanical properties and modulation inputs from both parasympathetic and sympathetic systems. The model can describe very well the experimental PLR responses induced by a short light flash of various intensities. In addition, an inverse method was developed to fit numerically this model to experimental PLR data. The model was tested in experimental human PLR data to extract separately the parasympathetic and sympathetic modulations during PLR. The results indicated a higher parasympathetic and a lower sympathetic activity in females than in males, which was consistent with previous findings in cardiovascular studies. This new model may help improve our understanding of the PLR process and could be applied to analyze autonomic nervous interaction during pupillary responses. View full abstract»

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  • Effects of the Antiarrhythmic Drug Dofetilide on Transmural Dispersion of Repolarization in Ventriculum. A Computer Modeling Study

    Publication Year: 2011 , Page(s): 43 - 53
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    Dofetilide is a class-Ill drug that inhibits the rapid component of the delayed potassium current (IKr). Experimental studies have shown that the different layers of ventricular muscle present differences in action potential duration (APD) and different responses to class III agents. It has been suggested that it contributes to APD heterogeneity in the ventricles. However, in vivo studies suggest that the strong cellular coupling reduces APD dispersion in intact heart. The aim of this paper is to study the effect of dofetilide on the action potentials (APs) in isolated ventricular cells and on APD dispersion in a strand of ventricular tissue. A mathematical model of dofetilide effects on IKr has been developed and incorporated into the Luo-Rudy dynamic model of ventricular AP. Our results show that dofetilide induces in midmyocardium cells a faster time-course inhibition of IKr than in endocardial or epicardial cells, and periods of instability with beat-to-beat APs variability. This behavior could favor temporal dispersion of repolarization between the different cells. The results also indicate that although dofetilide increases, the transmural gradient of APD in the ventricular wall, early after depolarizations (EADs) did not appear even under strong uncoupling conditions. However, reduced repolarization reserve favors the induction of EADs, even under normal coupling conditions. View full abstract»

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  • Identification of Electroencephalographic Arousals in Multichannel Sleep Recordings

    Publication Year: 2011 , Page(s): 54 - 63
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (423 KB) |  | HTML iconHTML  

    Electroencephalographic arousals are defined as abrupt shifts in electroencephalogram (EEG) frequency during sleep. Occurrence of arousals results in fragmented sleep, being one of the most important causes of daytime sleepiness among sleep disorders. Detection of arousals requires a polysomnographic (PSG) recording to be made during the patient's sleep. The resulting PSG is then analyzed offline by the physician. This is a time-consuming task, hence, automation of this process is pursued. The analysis, which involves the correlation of various events in time occurring among the different channels, in conjunction with the complexity of the related biomedical signals, makes this task also difficult to achieve in the computer algorithm. In this paper, we present a method for the detection of EEG arousals working on multichannel PSGs. The algorithm detects arousals using the information available through two EEG channels and the electromyography. A signal-processing technique is first proposed for the analysis of biomedical signals and extraction of relevant information. Individual events are detected from the signals and subsequently are related in time. Finally, a classification phase carries out the final decision on the presence of the event. Classifiers based on Fisher's linear and quadratic discriminants, support vector machines and artificial neural networks are compared at this phase. Experiments conducted on 20 patients reported a sensitivity and specificity respectively of 0.86 and 0.76 in the detection of the arousal events. View full abstract»

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  • Extended Noninvasive Fetal Monitoring by Detailed Analysis of Data Measured With Phonocardiography

    Publication Year: 2011 , Page(s): 64 - 70
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (417 KB) |  | HTML iconHTML  

    This paper presents a complex heuristic method for the evaluation of fetal heart sounds, applying simultaneously several algorithms, where the autocorrelation technique has been completed with the wavelet transform and the matching pursuit methods. In this way, a more reliable heart rate variability can be achieved and further parameters of the cardiac operation can be assessed in addition to the conventional cardiotocographic examination. This also comprises those parameters, which can be investigated only with long-term or continuous monitoring, and those, which rely on a very accurate estimation of the heart rate variability. The proposed method provides a way for assessing fetal heart murmurs, which is a completely new possibility for monitoring the well-being of the fetus. View full abstract»

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  • Phase-Interpolated Averaging for Analyzing Electroencephalography and Magnetoencephalography Epochs

    Publication Year: 2011 , Page(s): 71 - 80
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (690 KB) |  | HTML iconHTML  

    Stimulus-locked averages of electroencephalography (EEG) and magnetoencephalography (MEG) epochs reveal characteristic waveforms. EEG/MEG generation models to have reconstruct such waveforms have been recently proposed. These models assume that evoked, phase-modulated, and amplitude-modulated activities occur solely or simultaneously. We propose a two-stage stimulus-locked averaging method, called phase-interpolated averaging, to investigate the EEG/MEG generation process. First, virtual EEG/MEG epochs, which would be obtained as if instantaneous phases for each time sampling point were on a phase-grid, are interpolated from actually measured EEG/MEG epochs. Then, the virtual EEG/MEG epochs are discrete Fourier transformed. A simulation revealed that the zeroth Fourier term revealed the evoked activity, the first Fourier term revealed the amplitude-modulated activity, and the condition number of the interpolation reflected the phase-modulated activity. On the basis of these facts, a preliminary EEG analysis implied that the evoked activity is much smaller than what would be expected by using conventional averaging, the evoked and phase-modulated activities simultaneously occur, and the amplitude-modulated activity occasionally associates with the evoked and phase-modulated activities. To the best of our knowledge, this is the first time that these three activities have been shown to coexist by actually separating them. View full abstract»

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  • Acoustical Modeling of Swallowing Mechanism

    Publication Year: 2011 , Page(s): 81 - 87
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB) |  | HTML iconHTML  

    In this paper, a mathematical modeling of the swallowing sound generation is presented. To evaluate the model, its application on swallowing disorder (dysphagia) diagnosis is discussed. As a starting point, a simple linear time invariant model is assumed to represent the pharyngeal wall and tissue excited by a train of impulses. The modeling is approached by two different assumptions. In one approach, it is assumed that the impulse train, representing the neural activities to trigger swallow, is the same for both groups of control and dysphagic, and it is the pharyngeal model that accounts for the difference between the two groups. On the other hand, in the second approach, it is assumed that the pharyngeal response is the same for both groups, but the neural activities to initiate the swallow are different between the two groups. The results show that the second approach complies better with the physiological characteristics of swallowing mechanism as it provides a much better discrimination between the swallowing sounds of control and dysphagic groups of this study. Though, it should be noted that our dysphagic group subjects were cerebral palsy and stroke patients. Hence, the model accounting for initiation of neural activities is reasonable to show better results. View full abstract»

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  • Automatic Optic Disc Detection From Retinal Images by a Line Operator

    Publication Year: 2011 , Page(s): 88 - 94
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1043 KB) |  | HTML iconHTML  

    Under the framework of computer-aided eye disease diagnosis, this paper presents an automatic optic disc (OD) detection technique. The proposed technique makes use of the unique circular brightness structure associated with the OD, i.e., the OD usually has a circular shape and is brighter than the surrounding pixels whose intensity becomes darker gradually with their distances from the OD center. A line operator is designed to capture such circular brightness structure, which evaluates the image brightness variation along multiple line segments of specific orientations that pass through each retinal image pixel. The orientation of the line segment with the minimum/maximum variation has specific pattern that can be used to locate the OD accurately. The proposed technique has been tested over four public datasets that include 130, 89, 40, and 81 images of healthy and pathological retinas, respectively. Experiments show that the designed line operator is tolerant to different types of retinal lesion and imaging artifacts, and an average OD detection accuracy of 97.4% is obtained. View full abstract»

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  • A Classification Tree Approach for Cardiac Ischemia Detection Using Spatiotemporal Information From Three Standard ECG Leads

    Publication Year: 2011 , Page(s): 95 - 102
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (155 KB) |  | HTML iconHTML  

    The accurate noninvasive diagnosis of cardiac ischemia remains a great challenge. To this end, the ECG is the main source of information, and personal health systems may now embed intelligence for enabling any citizen to self-record an ECG anywhere at any time. Our objective is to find a decision-support approach that makes best use of these resources. A new classification tree based on conditions combinations competition (T-3C) is proposed for building a multibranch tree of combined decision rules, and its performance is compared to usual methods based either on discriminant analysis or on classification trees. Moreover, we assessed with these methods, the diagnosis content for ischemia detection of the spatiotemporal ECG information that can be retrieved either from the standard 12-lead ECG or from only the three orthogonal leads subset (I, II, and V2), easy to set-up in self-care. The diagnostic accuracy of 14 decision-making strategies was compared for ischemia detection induced by angioplasty on a test set from a study population of 90 patients. The best performance is obtained with the T-3C algorithm on three-lead ECG, reaching 98% of sensitivity and of specificity, thus exceeding 23% of the diagnostic accuracy of the recommended and currently used standard ECG criteria. View full abstract»

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  • An Automated Hirschberg Test for Infants

    Publication Year: 2011 , Page(s): 103 - 109
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    A novel automated method to measure eye misalignment in infants is presented. The method uses estimates of the Hirschberg ratio (HR) and angle Kappa (the angle between the visual and optical axis) for each infant to calculate the angle of eye misalignment. The HR and angle Kappa are estimated automatically from measurements of the direction of the optical axis and the coordinates of the center of the entrance pupil and corneal reflexes in each eye when infants look at a set of images that are presented sequentially on a computer monitor. The HR is determined by the slope of the line that describes the direction of the optical axis as a function of the distance between the center of the entrance pupil and the corneal reflexes. The peak of the distribution of possible angles Kappa during the image presentation determines the value of angle Kappa. Experiments with five infants showed that the 95% limits of agreement between repeated measurements of angle Kappa are 0.61. The maximum error in the estimation of eye alignment in orthotropic infants was 0.9 with 95% limits of agreement between repeated measurements of 0.75. View full abstract»

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  • Depolarization Changes During Acute Myocardial Ischemia by Evaluation of QRS Slopes: Standard Lead and Vectorial Approach

    Publication Year: 2011 , Page(s): 110 - 120
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1003 KB) |  | HTML iconHTML  

    Diagnosis and risk stratification of patients with acute coronary syndromes can be improved by adding information from the depolarization phase (QRS complex) to the conventionally used ST-T segment changes. In this study, ischemia-induced changes in the main three slopes of the QRS complex, upward (XUS) and downward (XDS) slopes of the R wave as well as the upward (ITS) slope of the terminal S wave, were evaluated as to represent a robust measure of pathological changes within the depolarization phase. From ECG recordings both in a resting state (control recordings) and during percutaneous coronary intervention (PCI)-induced transmural ischemia, we developed a method for quantification of IUS, IDS, and ITS that incorporates dynamic ECG normalization so as to improve the sensitivity in the detection of ischemia-induced changes. The same method was also applied on leads obtained by projection of QRS loops onto their dominant directions. We show that IUS, IDS, and ITS present high stability in the resting state, thus providing a stable reference for ischemia characterization. Maximum relative factors of change (RI) during PCI were found in leads derived from the QRS loop, reaching 10.5 and 13.7 times their normal variations in the control for IUS and IDS, respectively. For standard leads, the relative factors of change were 6.01 and 9.31. The ITS index presented a similar behavior to that of IDS. The timing for the occurrence of significant changes in IUS and IDS varied with lead, ranging from 30 s to 2 min after initiation of coronary occlusion. In the present ischemia model, relative IDS changes were smaller than ST changes in most leads, however with only modest correlation between the two indices, suggesting they present different information about the ischemic process. We conclude- - that QRS slopes offer a robust tool for evaluating depolarization changes during myocardial ischemia. View full abstract»

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  • Driver Drowsiness Classification Using Fuzzy Wavelet-Packet-Based Feature-Extraction Algorithm

    Publication Year: 2011 , Page(s): 121 - 131
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB) |  | HTML iconHTML  

    Driver drowsiness and loss of vigilance are a major cause of road accidents. Monitoring physiological signals while driving provides the possibility of detecting and warning of drowsiness and fatigue. The aim of this paper is to maximize the amount of drowsiness-related information extracted from a set of electroencephalogram (EEG), electrooculogram (EOG), and electrocardiogram (ECG) signals during a simulation driving test. Specifically, we develop an efficient fuzzy mutual-information (MI)- based wavelet packet transform (FMIWPT) feature-extraction method for classifying the driver drowsiness state into one of predefined drowsiness levels. The proposed method estimates the required MI using a novel approach based on fuzzy memberships providing an accurate-information content-estimation measure. The quality of the extracted features was assessed on datasets collected from 31 drivers on a simulation test. The experimental results proved the significance of FMIWPT in extracting features that highly correlate with the different drowsiness levels achieving a classification accuracy of 95%-97% on an average across all subjects. View full abstract»

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  • A New Spatiotemporal Filtering Method for Single-Trial Estimation of Correlated ERP Subcomponents

    Publication Year: 2011 , Page(s): 132 - 143
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1185 KB) |  | HTML iconHTML  

    A novel spatiotemporal filtering method for single trial estimation of event-related potential (ERP) subcomponents is proposed here. Unlike some previous works in ERP estimation, the proposed method is able to estimate temporally correlated ERP subcomponents such as P3a and P3b. A new cost function is, therefore, defined which can deflate one of the correlated subcomponents. The method is applied to both simulated and real data and has shown to perform very well even in low signal-to-noise ratio situations. In addition, the method is compared to spatial principal component analysis and its superiority has been confirmed by using simulated signals. The approach can be especially useful in mental fatigue analysis where the relative variability of P300 subcomponents is the key factor in detecting the level of fatigue. View full abstract»

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  • Volitional Control of a Prosthetic Knee Using Surface Electromyography

    Publication Year: 2011 , Page(s): 144 - 151
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (710 KB) |  | HTML iconHTML  

    This paper presents a method for providing volitional control of a powered knee prosthesis during nonweight-bearing activity such as sitting. The method utilizes an impedance framework, such that the joint can be programmed with a given stiffness and damping that reflects the nominal impedance properties of an intact joint. Volitional movement of the knee joint is commanded via the stiffness set-point angle of the joint impedance, which is commanded by the user as a function of the measured surface electromyogram (EMG) from the hamstring and quadriceps muscles of the residual limb. Rather than using the respective EMG measurements from these muscles to directly command the flexion or extension set point of the knee, the presented approach utilizes a combination of quadratic discriminant analysis and principal component analysis to align the user's intent to flex or extend the knee joint with the pattern of measured EMG. The approach was implemented on three transfemoral amputees, and their ability to control knee movement was characterized by a set of knee joint trajectory tracking tasks. Each amputee subject also performed the same set of trajectory tracking tasks with his sound side (intact) knee joint. The average root mean square trajectory tracking errors of the prosthetic knee employing the EMG-based volitional control and the intact knee of the three subjects were 6.2° and 5.2°, respectively. View full abstract»

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  • Estimation of Lung's Air Volume and Its Variations Throughout Respiratory CT Image Sequences

    Publication Year: 2011 , Page(s): 152 - 158
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (917 KB) |  | HTML iconHTML  

    A respiratory image-sequence-segmentation technique is introduced based on a novel image-sequence analysis. The proposed technique is capable of segmenting the lung's air and its soft tissues followed by estimating the lung's air volume and its variations throughout the image sequence. Accurate estimation of these two parameters is very important in many applications related to lung disease diagnosis and treatment systems (e.g., brachytherapy), where the parameters are either the variables of interest themselves or are dependent/independent variables. The concept of the proposed technique involves using the image sequence's combined histogram to obtain a reasonable initial guess for the lung's air segmentation thresholds. This is followed by an optimization process to find the optimum threshold values that best satisfy the lung's air mass conservation and tissue incompressibility principles. These threshold values are consequently applied to estimate the lung's air volume and its variations throughout respiratory Computed Tomography (CT) image sequences. Ex vivo experiments were conducted on porcine left lungs in order to demonstrate the performance of the proposed technique. The proposed method was initially validated using a breath-hold CT image sequence with known air volumes inside the lung, where results show that the proposed technique outperforms single-histogram-based methods. This was followed by demonstrating the proposed technique's application in a 4-D-CT respiratory sequence, where the air volume inside the lung was unknown. Consistency of the obtained results in the latter experiment with tissue near incompressibility principle was validated. The results indicate a very good ability of the proposed method for estimating the lung's air volume and its variations in a respiratory image sequence. View full abstract»

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  • In Vivo Micro-Image Mosaicing

    Publication Year: 2011 , Page(s): 159 - 171
    Cited by:  Papers (11)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1736 KB) |  | HTML iconHTML  

    Recent advances in optical imaging have led to the development of miniature microscopes that can be brought to the patient for visualizing tissue structures in vivo. These devices have the potential to revolutionize health care by replacing tissue biopsy with in vivo pathology. One of the primary limitations of these microscopes, however, is that the constrained field of view can make image interpretation and navigation difficult. In this paper, we show that image mosaicing can be a powerful tool for widening the field of view and creating image maps of microanatomical structures. First, we present an efficient algorithm for pairwise image mosaicing that can be implemented in real time. Then, we address two of the main challenges associated with image mosaicing in medical applications: cumulative image registration errors and scene deformation. To deal with cumulative errors, we present a global alignment algorithm that draws upon techniques commonly used in probabilistic robotics. To accommodate scene deformation, we present a local alignment algorithm that incorporates deformable surface models into the mosaicing framework. These algorithms are demonstrated on image sequences acquired in vivo with various imaging devices including a hand-held dual-axes confocal microscope, a miniature two-photon microscope, and a commercially available confocal microendoscope. View full abstract»

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  • Automated Analysis of Fluorescence Lifetime Imaging Microscopy (FLIM) Data Based on the Laguerre Deconvolution Method

    Publication Year: 2011 , Page(s): 172 - 181
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    In fluorescence lifetime imaging microscopy (FLIM), fluorescence time decay at each pixel of the imaged sample are measured. Every recorded fluorescence decay corresponds to the time convolution of the instrument response with the intrinsic fluorescence impulse response function (IRF), from which the sample fluorescence lifetime is determined. To estimate the IRF, the instrument response thus needs to be deconvolved from the recorded fluorescence decay. We have recently introduced a novel FLIM time-deconvolution method based on the linear expansion of the fluorescence decays on an orthonormal Laguerre basis. Since this method allows simultaneous estimation of the IRFs at all pixels, it performs at least two orders of magnitude faster than standard algorithms. In its original implementation, however, the Laguerre basis, determined by the Laguerre parameter , is selected using a heuristic approach. Here, we present an automated implementation, whereby the Laguerre parameter is treated as a free parameter within a nonlinear least squares optimization scheme. The new implementation combines the unmatched inherent computational speed of the Laguerre deconvolution method with a systematic model selection approach. This method will thus facilitate applications of FLIM requiring automatic estimation of the spatial distribution of fluorescence lifetimes, such as in in vivo tissue FLIM imaging. View full abstract»

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  • Computer-Assisted Planning and Navigation for Corrective Distal Radius Osteotomy, Based on Pre- and Intraoperative Imaging

    Publication Year: 2011 , Page(s): 182 - 190
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    Malunion after a distal radius fracture is very common and if symptomatic, is treated with a so-called corrective osteotomy. In a traditional distal radius osteotomy, the radius is cut at the fracture site and a wedge is inserted in the osteotomy gap to correct the distal radius pose. The standard procedure uses two orthogonal radiographs to estimate the two inclination angles and the dimensions of the wedge to be inserted into the osteotomy gap. However, optimal correction in 3-Dspace requires restoring three angles and three displacements. This paper introduces a new technique that uses preoperative planning based on 3-D images. Intraoperative 3-D imaging is also used after inserting pins with marker tools in the proximal and distal part of the radius and before the osteotomy. Positioning tools are developed to correct the distal radius pose in six degrees of freedom by navigating the pins. The method is accurate (derr <; 1.2 mm, φerr <; 0.9°, mTRE = 1.7 mm), highly reproducible (SEd <; 1.0 mm, SEφ ≤ 1.4°, SEmTRE = 0.7 mm), and allows intraoperative evaluation of the end result. Small incisions for pin placement and for the osteotomy render the method minimally invasive. View full abstract»

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Aims & Scope

IEEE Transactions on Biomedical Engineering contains basic and applied papers dealing with biomedical engineering. Papers range from engineering development in methods and techniques with biomedical applications to experimental and clinical investigations with engineering contributions.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering