Jian Xing Wu

Synchronizing chaotification with support vector machine and wolf pack search algorithm for estimation of peripheral vascular occlusion in diabetes mellitus

Abstract This study proposes a method for the estimation of peripheral vascular occlusion (PVO) in diabetic foot using a support vector machine (SVM) classifier with the wolf pack search (WPS) algorithm. The long-term presence of elevated blood sugar levels commonly results in peripheral neuropathy, peripheral vascular disease, nephropathy, and retinopathy in patients with Type 2 diabetes mellitus. Patients with PVO disease have decreased walking capability and life quality in diabetes mellitus and poor peripheral circulation of PVO causes morbidity like infection and amputation of the legs or feet of diabetics. This progressively vascular occlusion is often ignored by the patients and primary care physicians in early stage. Therefore, a reliable method of diagnostic assistance is crucial for early diagnosis and monitoring of PVO and prevention of amputation. Photoplethysmography (PPG) is a non-invasive technique for detecting blood volume changes in peripheral vascular bed. Literature indicates that the pulse transit time increases and waveform shape changes increase in PPG of the vascular occlusion. PPG pulses of feet gradually become asynchronous due to the different speed of deteriorating patency and collateral circulation in the peripheral arteries. We utilized synchronizing chaotification to compare the bilateral similarity and asymmetry of PPG signals, and applied SVM to estimate three degrees of PVO. Among 33 subjects tested, this classification technique could recognize various butterfly motion patterns representing severities successfully including normal condition, lower-degree disease, and higher-degree disease. The proposed method has potential for providing diagnostic assistance for PVO of diabetics and other high-risk populations, with efficiency and higher accuracy.

Chaos synchronization detector combining radial basis network for estimation of lower limb peripheral vascular occlusive disease

Early detection of lower limb peripheral vascular occlusive disease (PVOD) is important to prevent patients from getting disabled claudication, ischemic rest pain and gangrene. This paper proposes a method for the estimation of lower limb PVOD using chaos synchronization (CS) detector with synchronous photoplethysmography (PPG) signal recorded from the big toes of both right and left feet for 21 subjects. The pulse transit time of PPG increases with diseased severity and the normalized amplitudes decreases in vascular disease. Synchronous PPG pulses acquired at the right and left big toes gradually become asynchronous as the disease progresses. A CS detector is used to track bilateral similarity or asymmetry of PPG signals, and to construct various butterfly motion patterns. Artificial neural network (ANN) was used as a classifier to classify and assess the PVOD severity. The results demonstrated that the proposed method has great efficiency and high accuracy in PVOD estimation.

A novel bipolar pulse generator for high-frequency ultrasound system

Pulse generator is the critical component in all ultrasound systems for driving a piezoelectric transducer to medical or nondestructive testing (NDT) applications. The transducer in ultrasound system was driven by a pulse train generator, which delivers high-voltage bipolar or unipolar pulse train. Several recent papers have discussed both the importance and the design of unipolar and bipolar pulse generator for ultrasound applications. Bipolar voltage pulse has lower unwanted DC and low-frequency component could decrease the leakage current. Also, its peak-to-peak pulse voltage could achieve twice of the voltage rating of the coaxial cable connecting the generator and the transducer. In current commercial ultrasound systems, bipolar pulse generators are commonly used; however, it still had some disadvantages like longer pulse length, which limited the driving frequency and affect the signal performance. This paper purposed a novel design of bipolar pulse generator based on a novel dual P-N channel MOSFET and FPGA timing control. It could produce multi-cycle pulses with center frequency over 50 MHz and shorter pulse length. This design also preserved the low-cost advantage compared to other commercial design of bipolar pulse generator. It is suitable for high-frequency ultrasound Doppler and B-mode imaging applications.

Dynamic analysis with a fractional-order chaotic system for estimation of peripheral arterial disease in diabetic foot

Lower-extremity peripheral arterial disease (PAD) is caused by narrowing or occlusion of vessels in patients like type 2 diabetes mellitus, the elderly and smokers. Patients with PAD are mostly asymptomatic; typical early symptoms of this limb-threatening disorder are intermittent claudication and leg pain, suggesting the necessity for accurate diagnosis by invasive angiography and ankle-brachial pressure index. This index acts as a gold standard reference for PAD diagnosis and categorizes its severity into normal, low-grade and high-grade, with respective cut-off points of ≥0.9, 0.9–0.5 and <0.5. PAD can be assessed using photoplethysmography as a diagnostic screening tool, displaying changes in pulse transit time and shape, and dissimilarities of these changes between lower limbs. The present report proposed photoplethysmogram with fractional-order chaotic system to assess PAD in 14 diabetics and 11 healthy adults, with analysis of dynamic errors based on various butterfly motion patterns, and color relational analysis as classifier for pattern recognition. The results show that the classification of PAD severity among these testees was achieved with high accuracy and efficiency. This noninvasive methodology potentially provides timing and accessible feedback to patients with asymptomatic PAD and their physicians for further invasive diagnosis or strict management of risk factors to intervene in the disease progression.

Bilateral photoplethysmography for arterial steal detection in arteriovenous fistula using a fractional-order decision-making quantizer

As inflow and outflow stenoses worsen, both flow resistance and pressure increase in the stenotic vascular access. During dialysis, when blood flow decreases, it may retrograde from the peripheral artery through the palmar arch to the arterial anastomosis site. Arterial steal syndrome (ASS) causes distal hypoperfusion, resulting in hand ischemia or extremity pain and edema. Hence, this study proposes the bilateral photoplethysmography (PPG) for ASS detection in arteriovenous fistulas. The decision-making quantizer utilizes the fractional-order feature extraction method and a non-cooperative game (NCG) framework to evaluate the ASS risk level. Bilateral asynchronous PPG signals have significant differences in the rise time and amplitude in relation to the degree of stenosis. The fractional-order self-synchronization error formulation is a feature extraction method used to quantify bilateral differences in blood flow changes between the dexter and sinister PPG signals. The NCG model as a method of decision-making is then employed to evaluate the ASS risk level. Using an acoustic Doppler measurement, the resistive (Res) index is also used to evaluate the vascular access stenosis at the arterial anastomosis site. In contrast with alternative methods including the high-sensitivity C-reactive protein level or Res index, our experimental results indicate that the proposed decision-making quantizer is more efficient in preventing ASS during hemodialysis treatment.

Quantitative ultrasound method for assessing stress?strain properties and the cross-sectional area of Achilles tendon

The Achilles tendon is one of the most commonly observed tendons injured with a variety of causes, such as trauma, overuse and degeneration, in the human body. Rupture and tendinosis are relatively common for this strong tendon. Stress–strain properties and shape change are important biomechanical properties of the tendon to assess surgical repair or healing progress. Currently, there are rather limited non-invasive methods available for precisely quantifying the in vivo biomechanical properties of the tendons. The aim of this study was to apply quantitative ultrasound (QUS) methods, including ultrasonic attenuation and speed of sound (SOS), to investigate porcine tendons in different stress–strain conditions. In order to find a reliable method to evaluate the change of tendon shape, ultrasound measurement was also utilized for measuring tendon thickness and compared with the change in tendon cross-sectional area under different stress. A total of 15 porcine tendons of hind trotters were examined. The test results show that the attenuation and broadband ultrasound attenuation decreased and the SOS increased by a smaller magnitude as the uniaxial loading of the stress–strain upon tendons increased. Furthermore, the tendon thickness measured with the ultrasound method was significantly correlated with tendon cross-sectional area (Pearson coefficient = 0.86). These results also indicate that attenuation of QUS and ultrasonic thickness measurement are reliable and potential parameters for assessing biomechanical properties of tendons. Further investigations are needed to warrant the application of the proposed method in a clinical setting.

Multiple-site hemodynamic analysis of doppler ultrasound with an adaptive color relation classifier for arteriovenous access occlusion evaluation

This study proposes multiple-site hemodynamic analysis of Doppler ultrasound with an adaptive color relation classifier for arteriovenous access occlusion evaluation in routine examinations. The hemodynamic analysis is used to express the properties of blood flow through a vital access or a tube, using dimensionless numbers. An acoustic measurement is carried out to detect the peak-systolic and peak-diastolic velocities of blood flow from the arterial anastomosis sites (A) to the venous anastomosis sites (V). The ratio of the supracritical Reynolds (Resupra) number and the resistive (Res) index quantitates the degrees of stenosis (DOS) at multiple measurement sites. Then, an adaptive color relation classifier is designed as a nonlinear estimate model to survey the occlusion level in monthly examinations. For 30 long-term follow-up patients, the experimental results show the proposed screening model efficiently evaluates access occlusion.

Development of a FPGA-based quantitative ultrasound system for assessing stress-strain properties of Achilles tendon

Achilles tendon (AT) is the most fragile and vulnerable part in human body. Stress-strain properties and shape changing such as cross-sectional area variations of this tendon are important biomechanical properties used clinically for assessing and monitoring surgical repair or postoperative healing progress. However, so far, there are few methods for non-invasively, precisely and quantitatively assessing in vivo AT mechanism. In this study, we develop a quantitative ultrasound system (QUS) based on FPGA aiming at estimating stress-strain properties of AT via evaluating the broadband ultrasound attenuation (BUA) parameter upon different levels of applied stress on the AT. Twenty fresh ATs of hind porcine trotters were procured from a local abattoir, and were preloaded for 30 cycles with a cyclic loading ranging from 0 to 300 N. The loading force pulled along the tendon fibers, and the changes of AT cross-sectional area were acquired by ultrasound transducer implemented in the palmardorsal direction which was perpendicular to the tendon fibers. BUA has been widely used to estimate the broadband ultrasonic attenuation (dB MHz-1) by calculating the slope of a linear regression fit to the attenuation against frequency plot within a frequency range. The tendons were then strained from 1 to 400 N with single steps of 50 N, and the measurements were repeated for ten times following calculating the average slope of BUA to reduce the interference of noise. Results showed that as the tendon tissue was stretched orthogonally to the beam axis, BUA coefficient decreased linearly with increasing stress (R-square =0.89). This indicated that the BUA coefficient is a potentially useful parameter for quantitative characterization of ATs. The FPGA system proposed for measuring tendon thickness using QUS technique is an easy and objective method to precisely evaluate the tissue thickness, providing a new way for AT to implement high-speed online diagnosis.

Estimation of arteriovenous fistula stenosis by FPGA based Doppler flow imaging system

Arteriovenous fistula (AVF) is a vascular access and very import in hemodialysis that is a treatment for patients suffering from end-stage renal disease. Stenosis is considered the major cause of dysfunction of AVF. Despite the relatively low thrombosis rates of AVF, surveillance programs are necessary for detection of stenosis. However, conventional Doppler ultrasound cannot facilitate the risk assessment of AVF, such as insufficient resolution. The objective of this study was to develop an estimation system using FPGA based color relational analysis (CRA) method for AVF stenosis on hemodialysis patients by quantitative Doppler ultrasound, which provides not only the degrees of stenosis (DOS), but also anatomical locations and blood flow physiology information for clinical physicians, lowing the risk arising from treatment. In this paper we proposed a method based on hemodynamic analysis with dimensionless numbers to capture and further quantify the feature values of Doppler ultrasound extracted from intraluminal blood flow. The ratio of the supracritical Reynolds (Resupra) number and the resistive (Res) index were calculated via the peak-systolic and peak-diastolic velocities of blood flow from the arterial anastomosis sites (A) to the venous anastomosis sites (V) to quantitate the DOS at multiple measurement sites. After that, the results were mapped with a CRA classifier to real-time display the DOS. The examination results from thirty long-term dialysis patients showed that this proposed method performed well in DOS and occlusion site detection, with >95% of accuracy. This study confirmed the CRA method is a potential candidate method to effectively evaluate the AVF caused by long-term dialysis or vascular disease. The proposed system provides useful information with better accuracy and convenience for clinical examination.

BILATERAL PPG SYSTEM WITH AR AND VAN DER POL SCREENING METHODS FOR PAD ESTIMATION IN HEMODIALYSIS PATIENTS

Peripheral arterial disease (PAD) is highly encountered in hemodialysis patients. The rate of cardiovascular disease-associated hospitalization and mortality among those PAD patients is higher than nonPAD subjects. Early detection of PAD could prevent peripheral limbs problems such as numbness, limp, and amputations, especially in hemodialysis patients’ foot. The ankle brachial index (ABI) is a widely used tool for PAD screening; however it has many clinical limitations and is not suitable for the patients with vascular sclerosis. Therefore, the aim of the present study is to develop a bilateral photoplethysmography (PPG) system with Van der Pol (VDP) Oscillator detector based on Burg autoregressive (AR) method for PAD estimation. The proposed system could track the bilateral symmetry or asymmetry of PPG signals and classify the grade of PAD in hemodialysis patients. The test results from 32 patients showed that the proposed system has high accuracy of classification (over 90%) for hemodialysis patients.