Biomedical subjects

M Ramasubba Reddy

Publications and source records attributed to M Ramasubba Reddy.

5 recordsLinked to original sources

PubMed2006

Quantitative evaluation of left ventricle performance from two dimensional echo images.

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.

Adult↗

PubMed2005

Brain tissue phantoms for optical near infrared imaging.

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 (mu(a) and mu(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 mu(a) and mu(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 mu(a) 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 mu(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.

Animals↗

PubMed2005

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

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 (O(z)-A(1)) 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.

Adult↗

PubMed2005

Neural network based approach for anomaly detection in the lungs region by electrical impedance tomography.

In this paper, we have shown a simple procedure to detect anomalies in the lungs region by electrical impedance tomography. The main aim of the present study is to investigate the possibility of anomaly detection by using neural networks. Radial basis function neural networks are used as classifiers to classify the anomaly as belonging to the anterior or posterior region of the left lung or the right lung. The neural networks are trained and tested with the simulated data obtained by solving the mathematical model equation governing current flow through the simulated thoracic region. The equation solution and model simulation are done with FEMLAB. The effect of adding a higher number of neurons to the hidden layer can be clearly seen by the reduction in classification error. The study shows that there is interaction between the size (radius) and conductivity of anomalies and for some combination of these two factors the classification error of neural networks will be very small.

Computer Simulation↗

PubMed2005

Detection of left ventricle systolic dysfunction from shape deformity.

Coronary artery disease producing ischemic cardiomyopathy is the most frequent cause of left ventricular systolic dysfunction. Non-ischemic cardiomyopathies can also produce systolic dysfunction; they may be inherited as genetic disorders or occur sporadically. These coronary injuries have repercussions on the left ventricle producing changes on wall contractility, the shape of the cavity and also changes on ventricular function. This study is focused on the 2D echocardiograms of the left ventricle. Apical two chamber and four chamber view recordings were performed on normal and systolic dysfunction subjects. Individual frames were extracted for at least five cardiac cycles. After pre-processing these images, segmentation of the left ventricle was performed by Fuzzy systems. Then the volumes were measured by single and biplane methods along with the perimeter, short axis length and long axis length in each frame, from which the two indices Sphericity Index (SI) and Normalized Eccentricity Index (NEI) was determined. It was found that the diastolic phase is short in the case of systolic dysfunction, and its volume variation is not uniform as in the normal case. Also, in the case of systolic dysfunction, the span of either the long or short axis length variation is less than 0.5 cm. This depicts that akinesis is in the corresponding direction; the value of SI is less than 2 for systolic dysfunction. A sharp peak is seen at each systole point in the NEI plot and also its variation is smooth in subjects having LVEF > 45%, which is not the case for dysfunction.

Algorithms↗