Limits...
Effect of non-linearity in predicting Doppler waveforms through a novel model.

Gayasen A, Dua SK, Sengupta A, Nagchoudhuri D - Biomed Eng Online (2003)

Bottom Line: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model.Both these results are established clinical facts.Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology, New Delhi, India. gayasen@cse.psu.edu

ABSTRACT

Background: In pregnancy, the uteroplacental vascular system develops de novo locally in utero and a systemic haemodynamic & bio-rheological alteration accompany it. Any abnormality in the non-linear vascular system is believed to trigger the onset of serious morbid conditions like pre-eclampsia and/or intrauterine growth restriction (IUGR). Exact Aetiopathogenesis is unknown. Advancement in the field of non-invasive doppler image analysis and simulation incorporating non-linearities may unfold the complexities associated with the inaccessible uteroplacental vessels. Earlier modeling approaches approximate it as a linear system.

Method: We proposed a novel electrical model for the uteroplacental system that uses MOSFETs as non-linear elements in place of traditional linear transmission line (TL) model. The model to simulate doppler FVW's was designed by including the inputs from our non-linear mathematical model. While using the MOSFETs as voltage-controlled switches, a fair degree of controlled-non-linearity has been introduced in the model. Comparative analysis was done between the simulated data and the actual doppler FVW's waveforms.

Results & discussion: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model. It is observed that the dicrotic notch disappears and the S/D ratio decreases as the pregnancy matures. Both these results are established clinical facts. Effects of blood density, viscosity and the arterial wall elasticity on the blood flow velocity profile were also studied. Spectral analysis on the output of the model (blood flow velocity) indicated that the Total Harmonic Distortion (THD) falls during the mid-gestation.

Conclusion: Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health. Effects of the blood density, the viscosity and the elasticity changes on the blood FVW are simulated. Future works are expected to concentrate mainly on improving the load with respect to varying non-linear parameters in the model. Heart rate variability, which accounts for the vascular tone, should also be included. We also expect the model to initiate extensive clinical or experimental studies in the near future.

Show MeSH

Related in: MedlinePlus

Proposed MOSFET model
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC222923&req=5

Figure 2: Proposed MOSFET model

Mentions: The model is based upon the transmission line model described in [6]. We proposed the mathematical model for uteroplacental artery, which contributes to the load at the end of the transmission line [4]. Various inputs used in the model representing the non-linear parameters such as elastic parameters, viscosity, wall density, womersley parameters are taken from the known experimental and histopathological studies and are further modified for specific conditions by using standard formula [4]. Based on the accumulated knowledge, the entire system has been simplified to develop a novel MOSFET model. MOSFET is the ideal choice for this model, because (i) it exhibits the desired non-linear current-voltage characteristics, (ii) simulation models of MOSFET are easily available and (iii) MOSFETs are easy to fabricate with state of the art technology. A schematic representation of the proposed model is shown in Fig. 2. All circuit elements in the transmission line model that vary with pregnancy time are replaced by some kind of MOSFET-based active structure (Appendix). These elements are shown as boxes in Fig. 2. The model consists of the following components.


Effect of non-linearity in predicting Doppler waveforms through a novel model.

Gayasen A, Dua SK, Sengupta A, Nagchoudhuri D - Biomed Eng Online (2003)

Proposed MOSFET model
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222923&req=5

Figure 2: Proposed MOSFET model
Mentions: The model is based upon the transmission line model described in [6]. We proposed the mathematical model for uteroplacental artery, which contributes to the load at the end of the transmission line [4]. Various inputs used in the model representing the non-linear parameters such as elastic parameters, viscosity, wall density, womersley parameters are taken from the known experimental and histopathological studies and are further modified for specific conditions by using standard formula [4]. Based on the accumulated knowledge, the entire system has been simplified to develop a novel MOSFET model. MOSFET is the ideal choice for this model, because (i) it exhibits the desired non-linear current-voltage characteristics, (ii) simulation models of MOSFET are easily available and (iii) MOSFETs are easy to fabricate with state of the art technology. A schematic representation of the proposed model is shown in Fig. 2. All circuit elements in the transmission line model that vary with pregnancy time are replaced by some kind of MOSFET-based active structure (Appendix). These elements are shown as boxes in Fig. 2. The model consists of the following components.

Bottom Line: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model.Both these results are established clinical facts.Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electrical Engineering, Indian Institute of Technology, New Delhi, India. gayasen@cse.psu.edu

ABSTRACT

Background: In pregnancy, the uteroplacental vascular system develops de novo locally in utero and a systemic haemodynamic & bio-rheological alteration accompany it. Any abnormality in the non-linear vascular system is believed to trigger the onset of serious morbid conditions like pre-eclampsia and/or intrauterine growth restriction (IUGR). Exact Aetiopathogenesis is unknown. Advancement in the field of non-invasive doppler image analysis and simulation incorporating non-linearities may unfold the complexities associated with the inaccessible uteroplacental vessels. Earlier modeling approaches approximate it as a linear system.

Method: We proposed a novel electrical model for the uteroplacental system that uses MOSFETs as non-linear elements in place of traditional linear transmission line (TL) model. The model to simulate doppler FVW's was designed by including the inputs from our non-linear mathematical model. While using the MOSFETs as voltage-controlled switches, a fair degree of controlled-non-linearity has been introduced in the model. Comparative analysis was done between the simulated data and the actual doppler FVW's waveforms.

Results & discussion: Normal pregnancy has been successfully modeled and the doppler output waveforms are simulated for different gestation time using the model. It is observed that the dicrotic notch disappears and the S/D ratio decreases as the pregnancy matures. Both these results are established clinical facts. Effects of blood density, viscosity and the arterial wall elasticity on the blood flow velocity profile were also studied. Spectral analysis on the output of the model (blood flow velocity) indicated that the Total Harmonic Distortion (THD) falls during the mid-gestation.

Conclusion: Total harmonic distortion (THD) is found to be informative in determining the Feto-maternal health. Effects of the blood density, the viscosity and the elasticity changes on the blood FVW are simulated. Future works are expected to concentrate mainly on improving the load with respect to varying non-linear parameters in the model. Heart rate variability, which accounts for the vascular tone, should also be included. We also expect the model to initiate extensive clinical or experimental studies in the near future.

Show MeSH
Related in: MedlinePlus