IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Modeling and monitoring of blood perfusion in burn skin has been presented in this study. A non invasive Laser speckle contrast imaging (LSCI) system is presented here for monitoring different flow conditions in a burn layer simulated capillary phantom. Speckle contrast variations with respect to changes in burn depth and blood perfusion rate have been studied in this work. © 2011 Springer-Verlag.

Department of Applied Mechanics

IFMBE Proceedings

Laser speckle contrast imaging for perfusion monitoring in burn tissue phantoms

Imaging of tissue perfusion is a vital tool in assessing the status of various diseases that are reflected in the microcirculation. Different techniques developed for imaging microcirculation as well as assessing red blood cell (RBC) concentration are lacking quantitative flow information, whole field imaging capability and non invasiveness. This paper reports on a whole field, non invasive laser speckle imaging technique to quantitatively assess the capillary flow variations and scatterer concentration using microcirculation phantoms. A capillary phantom has been fabricated on two perspex sheets of 12mm thickness each. The flow channels of depth 0.7 and 2mm were machined in the sheets and blood mimicking phantom solution of desired concentration was pumped using a syringe infusion pump (RH-SY10, Ravel Hitecks, India) to get the desired flow rate. The phantom was illuminated with a He Ne laser (ThorLabs) and the resulting speckle pattern was captured using a CCD camera and frame grabber card and the images were analysed using the developed algorithm. The experimental set up is shown in Fig.1. © 2011 IEEE.

2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011

Laser speckle contrast imaging for assessing flow velocities and scatterer concentration in capillary phantoms

The objective of telemedicine is to monitor and treat patients at home (more generally, at any location outside the hospital), under remote supervision of clinical specialists; telemedicine aims to limit or avoid inpatient care, which in turn should help to reduce the workload of clinicians and the costs of health care. Telemedicine requires autonomous monitoring and treatment, with little or no direct intervention from patients or clinicians. To be practical, monitoring and treatment systems need to be user-friendly on a long-term basis: The devices should be mobile, wearable, and operable on batteries. Consequently, telemedicine involves a wide variety of engineering challenges, from communications security and low-power hardware design, to adaptive signal processing; in this brief paper, we address the challenges related to signal processing. For the sake of definiteness, we consider telemedicine for applications in neurology, e.g., for treatment of epilepsy patients or patients with sleep disorders; we focus on electroencephalograms (EEG) recorded from the scalp or brain surface. Copyright © 2011 Organizers.

ISOB 2011 - Proceedings of the 1st International Symposium ISOB 2011 - Proceedings of the 1st International Symposium on Bioengineering

Signal processing for telemedicine: Key challenges

Microcirculation is essential for the proper supply of oxygen and nutritive substances to the biological tissue and the removal of waste products of metabolism. The determination of blood flow in the capillaries is therefore of great interest to clinicians. A comparison has been carried out using the developed non-invasive, non-contact and whole field laser speckle contrast imaging (LSCI) based technique and as well as a commercially available laser Doppler blood flowmeter (LDF) to evaluate blood flow at the finger tip and elbow and is presented here. The LSCI technique gives more quantitative information on the velocity of blood when compared to the perfusion values obtained using the LDF. Measurement of blood flow in capillaries can be of great interest to clinicians in the diagnosis of vascular diseases of the upper extremities.

World Academy of Science, Engineering and Technology

Non-invasive capillary blood flow measurement: Laser speckle and laser doppler

Untiring cardiac activity keeps human being to perform activities from birth to death. Cardiac dysfunction is associated with a variety of cardiovascular conditions that lead to heart failure. These cardio vascular diseases (CVD) are responsible for more than 5 million deaths each year. A major group of CVD involves disturbances in the normal cardiac rhythm (Cardiac Arrhythmias) due to failure in the coordination among contraction of cardiac muscles. Among several types of cardiac arrhythmias, ventricular reentrant arrhythmia is being more dangerous. Recent theoretical and experimental studies have stressed the importance of modeling of reentrant arrhythmia. This presentation discusses the ventricular reentrant arrhythmia using computational models of cardiac ventricular cell from cellular level to tissue level. © 2010 IEEE.

International Conference on Systems in Medicine and Biology, ICSMB 2010 - Proceedings

Effect of sodium channel parameters on reentrant arrhythmia: A computational study

In this paper, a two-stage coder based near-lossless compression of Electroencephalogram&nbsp;(EEG) is discussed. It consists of wavelet based lossy coding layer (until bitplane n d ) followed by entropy coding of the wavelet domain residuals. L  ∞ -error bound is fixed in wavelet domain and the corresponding time-domain absolute error variation is studied. Studies show that intermediate demarcating bit-planes&nbsp;(n d ) register a higher compression and gives a nearly constant time-domain error. Both the normal and epileptic EEG registered a comparable compression performance.

Department Of Civil Engineering

International Conference on Business Administration and Information Processing

Wavelet-Domain L  ∞ -Constrained Two-Stage Near-Lossless EEG Coder

The use of auditory models in cochlear implant speech processing strategies aims to improve cochlear implantee's perception of speech. Current speech processing strategies for cochlear implants use an IIR filter bank which decomposes the audio signals into multiple frequency bands each associated with one electrode. This paper describes a 16-channel non-uniformly spaced, high stop band attenuation (≅ -60dB) finite impulse response (FIR) filter bank model for cochlear implants and how speech intelligibility is evaluated as a function of various parameters in cochlear implant processors. The design has the advantages of higher stop band attenuation and linear phase frequency response. The filter bank implemented is successfully tested using speech signals extracted from TIMIT database and their band energies are calculated which are useful in estimating the stimulation pulse level to be generated and presented to the cochlear electrodes. © 2010 IEEE.

Signal analysis by using FIR filter banks in cochlear implant prostheses

An efficient preprocessing technique of arranging an electroencephalogram (EEG) signal in matrix form is proposed for real-time lossless EEG compression. The compression algorithm consists of an integer lifting wavelet transform as the decorrelator with set partitioning in hierarchical trees as the source coder. Experimental results show that the preprocessed EEG signal gave improved rate-distortion performance, especially at low bit rates, and less encoding delay compared to the conventional one-dimensional compression scheme. © 2010 The Institution of Engineering and Technology.

Electronics Letters

Efficient preprocessing technique for real-time lossless EEG compression

In this paper, a method of Electrocardiographic (ECG) signal denoising during Magnetic Resonance Imaging (MRI) is proposed. In MR environment ECG signals will get corrupted by flow artifacts and hence reduces its diagnostic value. The proposed method focuses on removal of flow artifacts from multi-channel ECG signals, thereby improving its diagnostic quality. The standard or instantaneous independent component analysis (ICA) model is used with a reference signal to eliminate the flow artifacts. The performance of method is evaluated using MGH/MF multiparameter database with simulated flow artifacts. The diagnostic quality of filtered ECG is evaluated with different quality measures. In future, the performance of the method is to be studied on ECGs recorded during the MRI examination. © 2009 IEEE.

GENERAL

ACT 2009 - International Conference on Advances in Computing, Control and Telecommunication Technologies

ICA based flow artifact Removal from ECG during MRI

This paper presents probabilistic fracture-mechanics analysis of linear-elastic cracked structures subjected to mixedmode (modes I and II) loading conditions using fractal finite element method (FFEM). The method involves FFEM for calculating fracture response characteristics; statistical models of uncertainties in load, material properties, and crack geometry; and the first-order reliability method for predicting probabilistic fracture response and reliability of cracked structures. The sensitivity of fracture parameters with respect to crack size, required for probabilistic analysis, is calculated using continuum shape sensitivity analysis. Numerical examples based on mode-I and mixedmode problems are presented to illustrate the proposed method. The results show that the predicted failure probability based on the proposed formulation of the sensitivity of fracture parameter is in good agreement with the Monte Carlo simulation results. Since all gradients are calculated analytically, reliability analysis of cracks can be performed efficiently using FFEM.

Journal of Structural Engineering (Madras)

Probabilistic fracture mechanics by fractal finite element method

In this paper, a new signal processing method for suppression of Magnetohydrodynamic (MHD) artifacts on single channel Electrocardiogram (ECG) during cardiac Magnetic Resonance Imaging (MRI) is proposed. The singular value decomposition (SVD) is performed on data in time-frequency domain to separate two signal components. The performance of the method is evaluated using simulated signals for different heart rate variations and MR system dependent parameters such as, magnetic field strength and sampling frequency. In future, the performance of the method is to be studied on real signals acquired during the MRI scan. © 2009 IEEE.

IEEE Region 10 Annual International Conference, Proceedings/TENCON

Suppression of MHD artifacts on single channel ECG during cardiac MRI

Advanced digital imaging technology in medical domain demands efficient and effective DICOM image compression for progressive image transmission and picture archival. Here a compression system, which incorporates sensitivities of HVS coded with SPIHT quantization, is discussed. The weighting factors derived from luminance CSF are used to transform the wavelet subband coefficients to reflect characteristics of HVS in best possible manner. Mannos et al. and Daly HVS models have been used and results are compared. To evaluate the performance, Eskicioglu chart metric is considered. Experiment is done on both Monochrome and Color Dicom images of MRI, CT, OT, and CR, natural and benchmark images. Reconstructed image through our technique showed improvement in visual quality and Eskicioglu chart metric at same compression ratios. Also the Daly HVS model based compression shows better performance perceptually and quantitatively when compared to Mannos et el. model. Further "bior4.4" wavelet filter provides better results than "db9" filter for this compression system. Results give strong evidence that under common boundary conditions; our technique achieves competitive visual quality, compression ratio and coding/decoding time, when compared with jpeg2000 (kakadu). © 2007.

European Journal of Radiology

HVS scheme for DICOM image compression: Design and comparative performance evaluation

In this paper, we describe a group delay-based signal processing technique for the analysis and detection of hypernasal speech. Our preliminary acoustic analysis on nasalized vowels shows that, even though additional resonances are introduced at various frequency locations, the introduction of a new resonance in the low-frequency region (around 250 Hz) is found to be consistent. This observation is further confirmed by a perceptual analysis carried out on vowel sounds that are modified by introducing different nasal resonances, and an acoustic analysis on hypernasal speech. Based on this, for subsequent experiments the focus is given only to the low-frequency region. The additive property of the group delay function can be exploited to resolve two closely spaced formants. However, when the formants are very close with considerably wider bandwidths as in hypernasal speech, the group delay function also fails to resolve. To overcome this, we suggest a band-limited approach to estimate the locations of the formants. Using the band-limited group delay spectrum, we define a new acoustic measure for the detection of hypernasality. Experiments are carried out on the phonemes /a/, /i/, and /u/ uttered by 33 hypernasal speakers and 30 normal speakers. Using the group delay-based acoustic measure, the performance on a hypernasality detection task is found to be 100% for /a/, 88.78% for /i/ and 86.66% for /u/. The effectiveness of this acoustic measure is further cross-verified on a speech data collected in an entirely different recording environment. © 2007 IEEE.

IEEE Transactions on Biomedical Engineering

Acoustic analysis and detection of hypernasality using a group delay function

Cardiac arrhythmias are mainly due to failure in the coordination among contraction of cardiac muscle. Among several types of arrhythmias, we focused on ventricular reentrant arrhythmia because it is more dangerous arrhythmia. With the help of detailed biophysical model of human ventricular cell, the role of sodium ion concentration and calcium currents on single and one-dimensional array of cells in establishing arrhythmias are studied. Two simulation studies have been made. First study showed the effect of variation in sodium ion concentration and calcium current on single cell behavior. In the next study, onedimensional array of cell is coupled via gap junction conductance and it is observed that there is change in propagation of action potentials (i.e. action potential duration, notch in AP and flow of ionic currents among cells) due to the variations in ion concentration as well as calcium currents are well studied. The effect of drugs and some external influence (tension, stress in cardiac system) in real environment causes abnormalities in cardiac electrical activity due to the changes in ionic concentration. This motivated to study how variation in ionic concentration leads to arrhythmia by simulation. © 2006 Research Publishing Services.

ICBPE 2006 - Proceedings of the 2006 International Conference on Biomedical and Pharmaceutical Engineering

A simulation study of arrhythmia using computational model

Based on 2D Doppler echocardiography a non-invasive automated method for assessing the severity of Aortic Regurgitation (AR) is explained in this paper. Using GE ultrasound machine equipped with 1.7MHz to 15MHz phased array transducers. Continuous Wave (CW) color Doppler echocardiographic images of aortic valve were obtained from Frontier Life Line Hospital, Chennai, India. Doppler index is extracted by applying image processing techniques. Proposed algorithm automatically detects Peak velocity envelope of the spectral Doppler ultrasound tracings for calculating Pressure Half Time (PHT) available in a single screen frame. Measurements extracted automatically from the maximal velocity envelope are compared with measurements obtained manually where PHT for severity assessment of AR show strong positive correlation (r=0.950313). Present work provides a novel automated tool for extraction of clinical parameters from 2D Doppler images and assesses the severity of AR thus overcoming the short comings of the manual technique. ©2006 IEEE.

IST 2006 - Proceedings of the 2006 IEEE International Workshop on Imagining Systems and Techniques

Automated assessment of aortic regurgitation using 2D doppler echocardiogram

The objective is to increase the number of selections in brain computer interfaces (BCI) by recording and analyzing the steady state visual evoked potential response to dual stimulation. A BCI translates the VEP signals into user commands. The frequency band from which stimulation frequency can be selected is limited for SSVEP. This paper discusses a method to increase the number of commands by using a suitable combination of frequencies for stimulation. A biopotential amplifier based on the driven right leg circuit (DRL) is used to record 60 s epochs of the SSVEP (Oz-A1) on 15 subjects using simultaneous overlapped stimulation (6, 7, 12, 13 and 14 Hzs and corresponding half frequencies). The power spectrum of each recording is obtained by frequency domain averaging of 400 ms SSVEPs and the spectral peaks were normalized. The spectral peaks of the combination frequencies of stimulation are predominant compared to individual stimulating frequencies. This method increases the number of selections by using a limited number of stimulating frequencies in BCI. For example, six selections are possible by generating only three frequencies. © 2006 IOP Publishing Ltd.

Physiological Measurement

A novel multiple frequency stimulation method for steady state VEP based brain computer interfaces

In the present work the role of a speech recognition system in the assessment of dysarthric speech is studied. Initially a continuous speech recognition system is developed for the assessment of dysarthric speech. The performance of the continuous speech recognition system on the assessment of dysarthric speech is found to be dis-satisfactory due to greater number of insertions. Analysis conducted on duration of phoneme and speech rate confirms the fact that the more number of insertions in the recognizer output is due to lower speech rate of dysarthric speakers. To overcome the problem with the continuous speech recognition system an isolated-style speech recognition system is developed. The performance of this system on the assessment is compared with the Frenchay dysarthric assessment (FDA) scores provided with the Nemours speech corpus. From the performance of the isolated-style speech recognition system it is observed that apart from the articulatory problems, some of the speakers are affected with velopharyngeal incompetence also and is analyzed with group delay function based acoustic measure for the detection of hypernasality on dysarthric speech. © 2006 IEEE.

Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings

Assessment of dysarthric speech and an analysis on velopharyngeal incompetence

Arrhythmia refers to any change from the normal sequence of electrical impulses, causing abnormal heart rhythms. With the help of well-known Beeler - Reuter mathematical model of a cardiac cell, we demonstrate that some of the clinically observed manifestations of arrhythmia property can be simulated. In our simulation study a 60×60 network of cells is considered. The cells are coupled through resistive element. These resistive elements are similar to gap junction in real cardiac tissue. An input stimulus is presented in addition to ionic current to generate action potential continuously, since ventricle cells are not oscillatory. The input stimulus is presented in a group of cells at the left most corner of the grid of cells at specific instant of time. The selection of duration and amplitude of input stimulus plays a vital role. The presentation of input stimulus makes a regular cardiac rhythm traveling from left top most corner to right bottom corner in the grid. External signals are applied in the grid of cells to disturb a regular rhythmic pattern to simulate arrhythmia condition and leads to generation of spiral waves. This situation is clinically identified as re-entrant arrhythmia. The external signals are Gaussian in nature having a frequency same as that frequency of action potential in that region. It is observed that the location of presentation of external signal leads to different kinds of abnormalities. This above study was performed using nominal initial values for all the variables. It is further observed that increase in sodium ion conductance from nominal value does not disturb the regular rhythmic pattern even with the application of external Gaussian signal. This shows an initial step in identifying the role of sodium ions in arrhythmias. Also we have studied the similar simulation study with 90×90 grids of cells.

World University root node

World Congress on Medical Physics and Biomedical Engineering

A Simulation Study on the Effect of Ionic Mechanism Underlying Arrhythmias

Objectives: We sought to quantify the left ventricle systolic dysfunction by a geometric index from two-dimensional (2D) echocardiography by implementing an automated fuzzy logic edge detection algorithm for the segmentation. Background: The coronary injuries have repercussions on the left ventricle producing changes on wall contractility, the shape of the cavity, and as a whole changes on the ventricular function. Methods: 2D echocardiogram and M-mode recordings were performed over the control group and those with the dysfunctions. From 2D recordings, individual frames were extracted for at least five cardiac cycles and then segmentation of left ventricle was done by automated fuzzy systems. In each frame, the volumes are measured and a geometric index, eccentricity ratio (ER), was derived. The endocardial fractional shortening (FS), midwall fractional shortening (mFS), and the relative wall thickness (RWT) were also measured in each case. Results: Depressed value of endocardial FS (20.39 ± 5.43 vs 34.28 ± 9.36, P = 0.0046), mFS (33 ± 8.3 vs 52.5 ± 11.7, P = 0.0047), and the RWT (0.337 ± 0.096 vs 0.525 ± 0.119, P = 0.0002) was observed with dysfunction. ER measured at end-diastole (2.86 ± 0.703 vs 4.14 ± 0.38) and end-systole (3.14 ± 0.79 vs 5.48 ± 0.74) was found to be decreased in the dysfunction group and more significant at the end-systole (P = 0.00017 vs 6.6E-06). Conclusion: This work concludes that the regional and global left ventricle systolic dysfunction can be assessed by the ER measured at end-diastole and end-systole from 2D echocardiogram and may contribute to the high rate of cardiovascular disorders. © 2006, the Authors.

Echocardiography

Quantitative evaluation of left ventricle performance from two dimensional echo images

In this study, solid, stable, and cost-effective optical phantoms of scalp-skull, white matter and grey matter are developed by inverse method. To begin with, to obtain a range of optical parameters, absorption and reduced scattering coefficients (μa and μ′s, respectively), 20 homogeneous phantoms were made of paraffin wax by using optically contrast black and highly scattering white colouring materials in different combination. By comparing the measured reflectance values for each phantom got from the four channel reflectometer with that obtained from steady-state diffusion equation, the values of μa and μ′s were determined. Next, phantoms which exhibit specific optical properties of scalp-skull, white and grey matter are developed iteratively by comparing actual reflectance measurements got by adjusting the colour concentration with the predicted reflectance values from the diffusion equation. This is done as follows: to obtain μa of 0.04 mm -1 for scalp-skull, 9.5 mg of black dye per 100 ml of wax added since more attenuation of light occurs in bone tissue. To obtain a μ′s 6.0 mm-1 for white matter in brain tissue, 190 mg of white dye per 100 ml of wax was used to facilitate more scatter of light. The colour concentrations of phantoms were then adjusted to obtain the predetermined values of optical parameters for scalp-skull, grey and white matter. © Springer-Verlag 2005.