A novel method of artery stenosis diagnosis using transfer function and support vector machine based on transmission line model: A numerical simulation and validation study

https://doi.org/10.1016/j.cmpb.2016.03.005Get rights and content

Highlights

  • A calculation method of transfer function (TF) was proposed by a TLM model of human artery tree.

  • The effects of artery stenosis on the TF were simulated and discussed by a series of simulation.

  • A novel method of artery stenosis diagnosis was proposed and validated by TF and SVM.

  • The accuracies of the method for moderate and serious stenosis were 87% and 99%, respectively.

  • The proposed method is a theoretically feasible method for diagnosis of artery stenosis.

Abstract

Background and objective

Transfer function (TF) is an important parameter for the analysis and understanding of hemodynamics when arterial stenosis exists in human arterial tree. Aimed to validate the feasibility of using TF to diagnose arterial stenosis, the forward problem and inverse problem were simulated and discussed.

Methods

A calculation method of TF between ascending aorta and any other artery was proposed based on a 55 segment transmission line model (TLM) of human artery tree. The effects of artery stenosis on TF were studied in two aspects: stenosis degree and position. The degree of arterial stenosis was specified to be 10–90% in three representative arteries: carotid, aorta and iliac artery, respectively. In order to validate the feasibility of diagnosis of artery stenosis using TF and support vector machine (SVM), a database of TF was established to simulate the real conditions of artery stenosis based on the TLM model. And a diagnosis model of artery stenosis was built by using SVM and the database.

Results

The simulating results showed the modulus and phase of TF were decreasing sharply from frequency 2 to 10 Hz with the stenosis degree increasing and displayed their unique and nonlinear characteristics when frequency is higher than 10 Hz. The diagnosis results showed the average accuracy was above 76% for the stenosis from 10% to 90% degree, and the diagnosis accuracies of moderate (50%) and serious (90%) stenosis were 87% and 99%, respectively. When the stenosis degree increased to 90%, the accuracy of stenosis localization reached up to 94% for most of arteries.

Conclusions

The proposed method of combining TF and SVM is a theoretically feasible method for diagnosis of artery stenosis.

Introduction

Artery stenosis is one kind of arterial disease in human cardiovascular system caused by the lesion of artery wall or congenital dysplasia disease, which usually occurs in the large and middle-sized arteries, such as carotid, cerebral, coronary and renal arteries [1], [2]. This disease directly affects the normal operation of relevant organs, causes organ insufficiency or degradation, and results in serious consequences: stroke, myocardial infarction, renal function loss, etc [3], [4]. Therefore, the early detection of arterial stenosis is very important for reducing the high morbidity and mortality caused by the kind disease.

The diagnosis technologies of artery stenosis mainly include digital subtraction angiography (DSA), transcranial Doppler (TD), computed tomography angiography (CTA), magnetic resonance angiography (MRA), etc [5], [6], [7]. Although these powerful technologies have advanced greatly, disadvantages still exist for each procedure. For example, DSA is an invasive method, though it is considered to be a gold standard; TD has low accuracy for the detection of stenosis of small arteries; CTA exposes patients to X-ray radiation and cannot completely prevent allergy to iodinated contrast agents; MRA is expensive. Moreover, pieces of equipment used in these technologies are mainly applied in hospitals and are not suitable for large area screenings. Therefore, a non-invasive, portable and simple technology has to be developed as a valuable complement to current methods, which is urgently needed for the large area screening of early artery stenosis [8], [9], [10].

The pulse-wave-based analysis method is a potential portable and noninvasive diagnosis technology of artery stenosis. Some useful parameters have been proposed based on this method, such as ankle brachial index (ABI) [11], pulse wave velocity (PWV) [12], transfer function (TF) [13], input impedance [14]. ABI is only used to detect the arterial stenosis of lower extremity, but not to detect the arterial stenosis of upper extremity, chest, abdomen, etc. Input impedance has been demonstrated numerically to be a valuable and useful parameter for the prediction of the artery stenosis in the human artery tree [15]. However, it is difficult to measure or calculate the input impedance of human arterial tree in clinic trials [14], [16]. The measurement or calculation of TF is easier than input impedance and also represents the mechanical and geometrical features of human arterial tree like input impedance. Because it is not affected by the blood pressure and flow waveform, TF has been successfully applied to noninvasively measure central blood pressure by using blood pressure waveform of radial or brachial artery, and achieved some good clinical results [17], [18].

Some researches have demonstrated there is a relation between TF and stenosis to some extent. Rajani [19] validated the central blood pressure and TF changed when some stenosis exist in human arterial tree. Gong [20] and Reinhard [21] evaluated the validity of the transfer function analysis in the assessment of human cerebral autoregulation in patients with carotid or basilar artery stenosis. Chao [22] conducted a study on comparisons of the baroreflex sensitivity and heart rate variability in patients with carotid stenosis and normal controls by using the method of TF analysis. Although a few valuable results and conclusions were obtained, the mathematical relation or model between TF and stenosis has not been established. In order to discover the potential of pulse-wave-based method for stenosis diagnosis, it is worthwhile to study the relation or modeling between of them.

In this paper, two aspects were mainly discussed: (1) A calculating method of TF was firstly proposed based on our previously presented transmission line model of 55 segment human arterial tree [23]. Then, one discussed the effects of arterial stenosis degree and position on the TF between ascending artery and carotid artery, radial artery and tibial artery. (2) Support vector machine (SVM) [24], [25], [26], [27], a machine learning method based on statistics, was introduced into the diagnosis of artery stenosis with TF as the feature vector of SVM model, and was validated by numerical simulation experiments. In the experiments, firstly, we built a database of samples using the transmission line model of human artery tree. Secondly, TF for each sample was calculated by a serial multiplication algorithm. Finally, two prediction models, one for stenosis existence, other for stenosis localization, were built by SVM and TF, and used to predict artery stenosis. The effects of the degree and position of artery stenosis on the prediction accuracy were discussed.

Section snippets

Arterial tree

The schematic diagram of the human arterial tree of this study is shown in Fig. 1. The original physiology data of the arterial tree was compiled by Noordergraaf et al. [28], and subsequently modified by Westerhof et al. [29], Avolio [30], Stergiopulos et al. [31], Wang and Parker [32], Liang et al. [33], and Alastruey and Parker et al. [34]. The arterial model of this study is based upon Stergiopuloss version of data that has 55 segments. The detail vascular dimensions and elastic constants

Transfer function of 55 segment human arterial tree without stenosis

In normal case, there is no stenosis in 55 segment human arterial tree. Transfer function between any two points in arterial tree can be calculated by using Eqs. (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13). Generally, the TF between ascending aorta and other artery is the hot spot of research, such as radial artery, carotid artery and tibial artery. Fig. 2 showed the normal modulus and phase of TF in low frequency domain between the No. 1 ascending aorta to the No. 11

Conclusion

Based on the 55 segment human arterial tree, the effect of arterial stenosis on the modulus and phase of TF were discussed. In generally, the rule can be concluded as following four points: (1) for different arterial stenosis, the modulus of TF between any two points has a big difference, but the difference of phase is less obvious than the modulus; (2) when the stenosis occurs inside the path of two points for calculating the TF, there is a good correlation between the peak of modulus and the

Acknowledgements

This research is funded by the National Natural Science Foundation of China (grant no. 61501070) and Chongqing Natural Science Foundation (grant no. cstc2014jcyjA10040). This research is funded by Doctoral Scientific Research Foundation of Chongqing University of Technology (grant no. 2012ZD40).

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