Qualification: 
Ph.D, MPhil, MSc
k_gayathri@cb.amrita.edu

Dr. Gayathri K. currently serves as Assistant Professor (Sr. Gr.) at Department of Mathematics, School of Engineering, Coimbatore Campus. Her areas of research include Fluid Mechanics. She has also completed PGDCA.

Publications

Publication Type: Journal Article

Year of Publication Title

2019

Gayathri K. and Dr. Shailendhra K., “MRI and Blood Flow in Human Arteries: Are There Any Adverse Effects?”, Cardiovasc Eng Technol, vol. 10, no. 2, pp. 242-256, 2019.[Abstract]


PURPOSE: To explore if there are any adverse effects on blood flow in human beings when they are exposed to high or ultra high intensity magnetic fields in MRI, by investigating both qualitatively and quantitatively the effects of such fields on the velocity of blood and medically significant hemodynamic wall parameters such as wall shear stress (WSS), oscillatory shear index (OSI) and relative residence time (RRT) in four human large arteries.

METHODS: Blood flow in an artery is approximated as a flow through a uniform circular tube with rigid porous walls and the well-known McDonalds model is employed by using pressure gradient waveforms reported in the medical literature.

RESULTS: No significant change in the above parameters is observed up to 3T in all these arteries except a discernible change in the velocity and RRT in the pulmonary artery. Very significant changes are noticed in the above parameters beyond 8T in the pulmonary artery. The common hypothesis that low WSS and high OSI co-locate is not acceptable.

CONCLUSIONS: Our results suggest that the clinical consequences are to be carefully considered before exposing human beings to ultra high field MRI. It may not be appropriate to conclude anything about the effect of magnetic field on blood flow in human beings based on experimental studies on animals, which is one of the reasons for the contradicting reports found in the literature. A slip condition at the wall which is appropriate to hemodynamics is yet to be developed.

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2018

Gayathri K. and Dr. Shailendhra K., “A mathematical modelling on the effect of high intensity magnetic fields on pulsatile blood flow in human arteries”, International Journal of Bioinformatics Research and Applications (IJBRA), , vol. 14, no. 1/2, 2018.[Abstract]


An attempt is made to investigate whether the static magnetic field (SMF) employed in magnetic resonance imaging (MRI) have any adverse effect on the hemodynamic wall parameters in large arteries or not. With the intention of addressing the controversy in the safety issues during MRI exposure, haemodynamics and pathology of large arteries, such as brachial, femoral and pulmonary artery, are compared by varying the intensity of SMF from high to ultrahigh. To be more medically accurate physiological pressure gradient waveforms taken from cardiology literature were digitised and adequate number of harmonics were extracted in order to represent them as Fourier series. All the medically relevant parameters related to endothelial functioning are significantly affected during the time of exposure to ultrahigh intensity SMF, irrespective of the fact whether the artery is closer or away from the heart. In such fields, the fluctuation of Wall Shear Stress (WSS) vector in pulmonary artery is too severe as inferred from oscillatory shear index (OSI) values. The common hypothesis that low WSS and high OSI colocate is not acceptable both in the absence and the presence of magnetic field. It is also inferred that relative residence time can be considered as a single robust metric to predict the pathogenesis of vascular diseases when OSI is moderate. It is felt that more research is necessary, especially to clarify many existing contradictory results in this regard. The controversial reports in the literature of SMF motivated us to mathematically investigate the possible adverse effects of ultrahigh SMFs on pulsatile blood flow in large human arteries and find the maximum intensity of SMF up to which the blood flow and other medically relevant parameters are not significantly affected.

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2018

Gayathri K. and Dr. Shailendhra K., “Mathematical investigation of aetiology and pathogenesis of atherosclerosis in human arteries”, International Journal of Bioinformatics Research and Applications (IJBRA), vol. 14, no. 1/2, 2018.[Abstract]


To understand the role of medically significant hemodynamic wall parameters in the pathogenesis of vascular diseases, pulsatile blood flow in large human arteries of systemic, pulmonary and coronary circulation is investigated by mathematical modelling. To be medically realistic, the pressure gradient waveforms reported in the cardiology literature for the arteries considered are digitised and developed in Fourier series (McDonald's model). Three objectives of the article are to (i) compare qualitatively and quantitatively the pulsatile blood flow between the parallel plate and circular geometry, (ii) compare the hemodynamic wall parameters in the three major circulations mentioned above to gain new medical or physiological insights and (iii) understand if slip at the wall has significant influence on the hemodynamic wall parameters. Our model is reliable since the results obtained here through exact solutions are in great agreement with those reported in the medical literature. New insights gained from our study, documented here for the first time in the hemodynamic literature, are as follows: parallel plate geometry approximation is not reliable quantitatively; larger the radius (Womersley number), larger is the value of relative residence time and hence, higher the probability for vascular diseases; none of the commonly employed interface conditions are suitable for the hemodynamic studies. Comparing our results with earlier studies, we recommend that future research should focus on developing an interface condition exclusively for haemodynamics. We support the recent understanding that low wall shear stress and high oscillatory shear index need not co-locate. We have rendered new physiological insight for this result.

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Publication Type: Conference Proceedings

Year of Publication Title

2016

V. Thiagarajan, Purushothaman, R. K., ,, Dr. Shailendhra K., and Gayathri K., “Pulsatile blood flow through large arteries with BJR slip condition”, 2016 International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT). IEEE, Chennai, India, 2016.[Abstract]


Hemodynamics in large human arteries, both in systemic and pulmonary circulation, is analysed. To the best of our knowledge, in pulsatile flow, this is the first theoretical study elaborating on hemodynamic factors such as Wall Shear Stress, Oscillatory Shear Index, Relative Residence Time and their effects on the pathogenesis of atherosclerosis by employing BJR slip at the lumen-wall interface, which takes into account the finite wall thickness of the artery. Also, the physiological pressure gradient waveform taken from the medical literature is modeled realistically by using McDonald's model. All the results reported are in good agreement with the data given in the available medical literature. Our model can predict the biological response of the artery in the normal/abnormal flow regime in a much better way, if the data fixed are subject specific. Our results confirm that low WSS and high OSI need not co-locate and also, explain the significances of OSI and RRT in the formation of atherosclerosis. Further, it emphasizes the need for the appropriate slip condition at the lumen-wall interface in the context of blood flow.

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