Particle swarm optimization solution for roll-off control in radiofrequency ablation of liver tumors: Optimal search for PID controller tuning.

The study investigates the efficacy of a bioinspired Particle Swarm Optimization (PSO) approach for PID controller tuning in Radiofrequency Ablation (RFA) for liver tumors. Ex-vivo experiments were conducted, yielding a 9th order continuous-time transfer function. PSO was applied to optimize PID parameters, achieving outstanding simulation results: 0.605% overshoot, 0.314 seconds rise time, and 2.87 seconds settling time for a unit step input. Statistical analysis of 19 simulations revealed PID gains: Kp (mean: 5.86, variance: 4.22, standard deviation: 2.05), Ki (mean: 9.89, variance: 0.048, standard deviation: 0.22), Kd (mean: 0.57, variance: 0.021, standard deviation: 0.14) and ANOVA analysis for the 19 experiments yielded a p-value ≪ 0.05. The bioinspired PSO-based PID controller demonstrated remarkable potential in mitigating roll-off effects during RFA, reducing the risk of incomplete tumor ablation. These findings have significant implications for improving clinical outcomes in hepatocellular carcinoma management, including reduced recurrence rates and minimized collateral damage. The PSO-based PID tuning strategy offers a practical solution to enhance RFA effectiveness, contributing to the advancement of radiofrequency ablation techniques.

Evaluation of infrared thermography with a portable camera as a diagnostic tool for peripheral arterial disease of the lower limbs compared with color Doppler ultrasonography.

Introduction: We aimed to evaluate whether infrared thermography (IRT) with a portable camera is a useful tool for diagnosing or screening peripheral arterial disease of the lower limbs (PAD-LL) when compared with the traditional method of color Doppler ultrasonography. Material and methods: The study enrolled 90 volunteers: 45 who were diagnosed with PAD-LL (PAD-LL group) and 45 who did not have a diagnosis of PAD-LL (control group). The diagnosis was made using color Doppler ultrasonography, and the results were compared with those of IRT. Results: The IRT-based procedure evaluated in this study had a sensitivity of 97.62% and a specificity of 91.67% for PAD-LL diagnosis compared to color Doppler ultrasonography. The method was limited for diagnosing PAD-LL manifesting above the knees (suprapopliteal PAD-LL). Our results also suggest that the ankle-brachial index is an important predictor of PAD-LL, with a sensitivity of 91.17% and a specificity of 75% at a value of ≤ 0.9. Current or previous smoking habits, higher body mass index, and the presence of diabetes mellitus were significantly elevated in the PAD-LL group. Conclusions: Our results indicate that IRT is an efficient and low-cost method for screening and diagnosing PAD-LL, particularly infrapopliteal PAD-LL manifesting below the knees. However, further studies are required to establish the validity of this technique.

Acute Limb Ischemia After Self-Injection of Crushed Morphine Tablets into the Radial Artery: Role of Infrared Thermography in the Assessment of Tissue Perfusion.

BACKGROUND This article presents a case involving complications after intentional injection of crushed tablets into the arterial circulation, its diagnosis, and the treatment adopted. The diagnosis process illustrates the potential of techniques based on thermal imaging as tools to assess tissue perfusion. Inadvertent intravenous injection of crushed tablets is more common, but there are few reports on arterial circulation, and no studies were found on the self-injection of crushed morphine tablets, particularly into the radial artery. CASE REPORT A 51-year-old man with alcoholism and a history of illegal drug usage intentionally self-injected 3 crushed morphine tablets into his right radial artery. The patient progressed with compartment syndrome, requiring decompressive fasciotomy of the right forearm and ischemia of the right fingers, which were amputated. He presented with rhabdomyolysis and required dialysis. The patient agreed to full heparinization, corticotherapy, and the use of nitroglycerin and prostaglandin E1. Due to the progression of the necrotic area, the patient underwent proximal phalanx excision and surgical reconstruction of the right-hand remnant. CONCLUSIONS The injection of morphine tablets into circulation caused severe complications, which led to the excision of the proximal phalanx and the surgical reconstruction of the remnant of the right hand. In the present case, infrared thermography proved to be an effective method in assessing tissue perfusion.

Validation study of the use of the HRVCAM software for the evaluation of heart rate and heart rate variability at rest.

Aims: The existing instruments for assessing heart rate (HR) and heart rate variability (HRV) require contact area. This is difficult to obtain from specific groups of patients and from those moving. The aim of this study was to validate the use of the HRVCam software for measuring HR and HRV in healthy adults. Methods and results: The HR and HRV variables were evaluated in terms of time and frequency using a webcam and Polar® S810i. The Shapiro-Wilk test was used to test the normality of the data, and the Pearson's correlation coefficient (r) was used to identify the possible correlation between the two instruments. The size of the effect was calculated based on a generalized linear model, and the Bland-Altman plots were used to analyse the agreement between the methods. The level of significance for all analyses was set at P < 0.05. We evaluated 102 participants, of whom 52% were men; 83.3% were aged between 18 and 29.9 years; and 84.3% were single. Conclusion: There was a good agreement and moderate to strong correlations among all analysed variables. The biases were low, except for the low frequency/high frequency measures. Moreover, the difference between the samples was small to moderate. The results of this study corroborate the use of HRVCam for measuring HR and HRV.

Use of electromyographic signals for characterization of voluntary coughing in humans with and without spinal cord injury-A systematic review.

INTRODUCTION: Individuals with spinal cord injury (SCI) frequently have an ineffective cough ability due to dysfunctions in expiratory muscles. In such cases, several articles have reported the occurrence of residual muscular activity in muscles that are accessory to coughing. The knowledge about this activity may be useful for building cough assistance devices. The goal of this review is to investigate and to describe the electromyographic signals generated during voluntary coughing in healthy people and in patients with SCI. METHODS: Two researchers performed, blindly and independently, a systematic review of the following databases: PubMed, PEDro, LILACS, and Science Direct. We conducted the searches using descriptors in English, Portuguese, and Spanish, with no limitations regarding the publication year. The review included articles describing experiments performed in humans and with the use of electromyographic signals in the analysis of voluntary coughing. RESULTS: Among the 156 initially found articles, only nine had results that described the study of electromyographic signals associated with voluntary coughing. The results showed evidence that, during voluntary coughing, electromyographic signals are generated both in expiratory and accessory muscles in healthy subjects. In individuals with SCI below the 5th cervical level (C5), the electromyographic signal appeared only in the clavicular portion of the pectoralis major, especially in the explosive cough phase. CONCLUSION: Our evaluation of the current literature shows that, according to the analysed studies, the electromyographic signals are more pre-eminent in the expiratory phase of the pectoralis major, during voluntary cough of individuals with SCI (C5-T12).

Characterization of the Cicatrization Process in Diabetic Foot Ulcers Based on the Production of Reactive Oxygen Species.

The present study aims at evaluating the correlation between the free radical formation and the healing action of lower limbs' ulcers in a randomized controlled trial with the use of an adhesive derived from natural latex associated with a light-emitting diode (LED) circuit. The sample consists of 15 participants with lower limb lesions divided into three groups: group 1 case (5 participants) received the proposed dressing system adhesive of the natural latex associated with the LED circuit; group 2 control (5 participants) received the dressings at home performed by nurses according to and established by the clinic of wounds (treated with calcium alginate or silver foam); and group 3 (5 participants) also received the dressing in their homes with the use of the dressing adhesive derived from the natural latex associated with the LED circuit. The collected data were analyzed qualitatively and quantitatively by electron paramagnetic resonance for determination of free radical formation. Kruskal-Wallis statistical test was used to evaluate the effect of treatment on the lower limb's ulcer cicatrization process and its correlation with free radical. The results obtained corroborated the hypothesis about the reduction of the quantity of these molecules in the end of treatment related to the healing wound.

Motor unit action potential conduction velocity estimated from surface electromyographic signals using image processing techniques.

In surface electromyography (surface EMG, or S-EMG), conduction velocity (CV) refers to the velocity at which the motor unit action potentials (MUAPs) propagate along the muscle fibers, during contractions. The CV is related to the type and diameter of the muscle fibers, ion concentration, pH, and firing rate of the motor units (MUs). The CV can be used in the evaluation of contractile properties of MUs, and of muscle fatigue. The most popular methods for CV estimation are those based on maximum likelihood estimation (MLE). This work proposes an algorithm for estimating CV from S-EMG signals, using digital image processing techniques. The proposed approach is demonstrated and evaluated, using both simulated and experimentally-acquired multichannel S-EMG signals. We show that the proposed algorithm is as precise and accurate as the MLE method in typical conditions of noise and CV. The proposed method is not susceptible to errors associated with MUAP propagation direction or inadequate initialization parameters, which are common with the MLE algorithm. Image processing -based approaches may be useful in S-EMG analysis to extract different physiological parameters from multichannel S-EMG signals. Other new methods based on image processing could also be developed to help solving other tasks in EMG analysis, such as estimation of the CV for individual MUs, localization and tracking of innervation zones, and study of MU recruitment strategies.

Electromyographic study in 5 muscles during an isometric fatiguing protocol.

In this study, 12 healthy men aging 22.8 ± 2.2 years old were submitted to a protocol of isometric resistance to fatigue contemplating elbow flexion on three different angles: 45°, 90° and 135°. The objective was to study electromyographic median frequency (MDF) in the following muscles: i) Biceps Brachialis Long Head (BBL), Brachioradialis (BRD), Flexor Digitorum Superficialis (FDS), Triceps Brachialis Long Head (TBL), and Extensor Digitorum (ED). It was verified that, for all muscles, including the muscles that act in opposition to the contraction, fatigue presence was verified by the decrease of MDF value.

Evaluating different combinations of feature selection algorithms and cost functions applied to iPCA tuning in myoelectric control systems.

A myoelectric control system extracts information from electromyographic (EMG) signals and uses it to control different types of prostheses, so that people who suffered traumatisms, paralysis or amputations can use them to execute common movements. Recent research shows that the addition of a tuning stage, using the individual component analysis (iPCA), results in improved classification performance. We propose and evaluate a set of novel configurations for the iPCA tuning, based on a biologically inspired optimization procedure, the artificial bee colony algorithm. This procedure is implemented and tested using two different cost functions, the traditional classification error and the proposed correlation factor, which involves lower computational effort. We compare the tuned system's performance, in terms of correct classifications, to that of a system tuned using two standard algorithms, the sequential forward selection and the sequential floating forward selection. The statistical analyses of the results don't find a significant difference among the classification performances associated with the search algorithms (p < 0.01). On the other hand, they establish a significant difference among the classification performances related to the cost functions (p < 0.02).

On the behavior of surface electromyographic variables during the menstrual cycle.

The goal of this work is to study the behavior of electromyographic variables during the menstrual cycle. Ten female volunteers (24.0 ± 2.8 years of age) performed fatiguing isometric contractions, and electromyographic signals were measured on the biceps brachii in four phases of the menstrual cycle. Adaptations of classical algorithms were used for the estimation of the root mean square (RMS) value, absolute rectified value (ARV), mean frequency (MNF), median frequency (MDF), and conduction velocity (CV). The CV estimator had a higher (p = 0.002) rate of decrease at the end of the follicular phase and at the end of the luteal phase. The MDF (p = 0.002) and MNF (p = 0.004) estimators had a higher rate of decrease at the beginning of the follicular phase and at the end of the luteal phase. No significant differences between phases of the menstrual cycle were detected with the ARV and RMS estimators (p > 0.05). These results suggest that the behavior of the muscles in women presents different characteristics during different phases of the menstrual cycle. In particular, women were more susceptible to fatigue at the end of the luteal phase.

Electromyographic evaluation of muscle recovery after isometric fatigue.

Despite growing interest in the behavior of electromyographic signals during muscle fatigue, few studies investigate fatigue recovery. In this work, we use surface electromyographic signals to determine the recovery time after isometric fatigue of the biceps brachii muscle in 90° flexion of the non-dominant elbow. Sixty volunteers were arranged into six experimental groups. Experiments were performed in three stages: reference phase (REF), fatigue resistance phase (RES), and recovery phase (REC). An isometric exercise was performed during the RES stage. The time interval between the RES and REC stages was different for each experimental group: 1, 2, 4, 8, 24 and 48 hours. Surface electromyographic signals were acquired during each phase, and the following electromyographic variables were calculated for each phase: median frequency (MDF), root mean squared (RMS) value, and maximum voluntary contraction (MVC). The REF data were compared with the REC data using a paired Wilcoxon test. The results show that the MVC is recovered 2 hours after the exercise. The MDF seems not to be fully recovered after 48 hours, but displays an apparent recovery trend.

Evaluation of a mobile electrode for electrical stimulation of the perineal muscle.

This work evaluates the effectiveness of a new type of electrode for functional electrical stimulation of the perineal muscle in women. The new electrode is shaped like a pen, with an active stimulation electrode located on its tip. The goals of the study are to (i) demonstrate that stimulation using the new device results in increased muscle strength; and (ii) compare the performance of the new device with that of a traditional (fixed) electrode. Eight women were evaluated, following a blind study protocol. The preliminary results suggest that stimulation with the new electrode achieves better results than stimulation with traditional electrodes, as higher increases in strength were observed in the group that used the mobile electrode.

Improved segmentation of echocardiographic images using fusion of images from different cardiac cycles.

In this work, an algorithm for the detection of the left ventricular border in two-dimensional long axis echocardiographic images is presented. In its preprocessing stage, images fusion was applied to a sequence of images composed of three cardiac cycles. This method exploits the similarity of corresponding frames from different cycles and produces contrast enhancement in the left ventricular boundary. This result improves the performance of the segmentation stage which is based on watershed transformation. The obtained left ventricle border is quantitatively and qualitatively compared with contours manually segmented by a cardiologist, and with results obtained using seven different techniques from the literature.

Fusion of electromyographic signals with proprioceptive sensor data in myoelectric pattern recognition for control of active transfemoral leg prostheses.

This paper presents a myoelectric knee joint angle estimation algorithm for control of active transfemoral prostheses, based on feature extraction and pattern classification. The feature extraction stage uses a combination of time domain and frequency domain methods (entropy of myoelectric signals and cepstral coefficients, respectively). Additionally, the methods are fused with data from proprioceptive sensors (gyroscopes), from which angular rate information is extracted using a Kalman filter. The algorithm uses a Levenberg-Marquardt neural network for estimating the intended knee joint angle. The proposed method is demonstrated in a normal volunteer, and the results are compared with pattern classification methods based solely on electromyographic data. The use of surface electromyographic signals and additional information related to proprioception improves the knee joint angle estimation precision and reduces estimation artifacts.

Probabilistic finite element analysis of radiofrequency liver ablation using the unscented transform.

The main limitation of radiofrequency (RF) ablation numerical simulations reported in the literature is their failure to provide statistical results based on the statistical variability of tissue thermal-electrical parameters. This work developed an efficient probabilistic approach to hepatic RF ablation in order to statistically evaluate the effect of four thermal-electrical properties of liver tissue on the uncertainty of the ablation zone dimensions: thermal conductivity, specific heat, blood perfusion and electrical conductivity. A deterministic thermal-electrical finite element model of a monopolar electrode inserted in the liver was coupled with the unscented transform method in order to obtain coagulation zone confidence intervals, probability and cumulative density functions. The coagulation zone volume, diameter and length were 10.96 cm(3), 2.17 cm and 4.08 cm, respectively (P < 0.01). Furthermore, a probabilistic sensitivity analysis showed that perfusion and thermal conductivity account for >95% of the variability in coagulation zone volume, diameter and length.

Effect of variable heat transfer coefficient on tissue temperature next to a large vessel during radiofrequency tumor ablation.

BACKGROUND: One of the current shortcomings of radiofrequency (RF) tumor ablation is its limited performance in regions close to large blood vessels, resulting in high recurrence rates at these locations. Computer models have been used to determine tissue temperatures during tumor ablation procedures. To simulate large vessels, either constant wall temperature or constant convective heat transfer coefficient (h) have been assumed at the vessel surface to simulate convection. However, the actual distribution of the temperature on the vessel wall is non-uniform and time-varying, and this feature makes the convective coefficient variable. METHODS: This paper presents a realistic time-varying model in which h is a function of the temperature distribution at the vessel wall. The finite-element method (FEM) was employed in order to model RF hepatic ablation. Two geometrical configurations were investigated. The RF electrode was placed at distances of 1 and 5 mm from a large vessel (10 mm diameter). RESULTS: When the ablation procedure takes longer than 1-2 min, the attained coagulation zone obtained with both time-varying h and constant h does not differ significantly. However, for short duration ablation (5-10 s) and when the electrode is 1 mm away from the vessel, the use of constant h can lead to errors as high as 20% in the estimation of the coagulation zone. CONCLUSION: For tumor ablation procedures typically lasting at least 5 min, this study shows that modeling the heat sink effect of large vessels by applying constant h as a boundary condition will yield precise results while reducing computational complexity. However, for other thermal therapies with shorter treatment using a time-varying h may be necessary.

An instrument to measure the convective heat transfer coefficient on large vessels.

Hepatocellular carcinoma is one of the most common malignancies worldwide. During radiofrequency hepatic ablation, the tumor is heated by means of radiofrequency energy. The heating causes necrosis of the malignant tumor. Thus, if the procedure is successful it can cure the patient. Studies have shown that recurrences occur after the treatment and these recurrences frequently take place next to the hepatic artery and portal vein. The recurrences occur due to the high convective loss on these vessels. This work proposed, developed and tested an instrument for the measurement of the convective heat transfer coefficient (h) in large vessels. Moreover, this work developed a mechanical simulator and validated an equation developed by Consiglieri et al, which analytically determines the value of h. The instrument was tested using a mechanical simulator that reproduces the flow conditions and the geometry of large vessels in the liver. A flow velocity of 0.2 m/s was simulated in order to mock the typical flow at the portal vein. The average value of h using the experimental apparatus was 2130+/-40 W.m(-2).K(-1) (mean+/-SD). The results showed that the error of the proposed method is approximately 22%. This work showed that the instrument can be used for measuring h in vitro and that the Consiglieri's equation can be used to determine the convective heat transfer coefficient on large vessels.

Development of a microcontrolled bioinstrumentation system for active control of leg prostheses.

This article describes the design of a microcontrolled bioinstrumentation system for active control of leg prostheses, using 4-channel electromyographic signal (EMG) detection and a single-channel electrogoniometer. The system is part of a control and instrumentation architecture in which a master processor controls the tasks of slave microcontrollers, through a RS-485 interface. Several signal processing methods are integrated in the system, for feature extraction (Recursive Least Squares), feature projection (Self Organizing Maps), and pattern classification (Levenberg-Marquardt Neural Network). The acquisition of EMG signals and additional mechanical information could help improving the precision in the control of leg prostheses.

Gender differences in muscle fatigue of the biceps brachii and influences of female menstrual cycle in electromyography variables.

Several studies report gender differences in response to fatigue. Most results suggest that females have higher muscle endurance than males. Possible explanations lie on differences in muscle mass, substrate utilization, muscle morphology and neuromuscular activation. One relevant aspect not always considered is the hormonal fluctuations during the female menstrual cycle. The present work observed eighteen healthy and untrained adults (eight males, 26.9 +/- 4.0 yr and ten females, 24.0 +/- 2.8 yr) performing fatiguing isometric contractions to evaluate both the influence of menstrual cycle and gender differences in fatigability. Surface electromyographic signals were recorded from the biceps brachii using a linear electrode array of eight electrodes during 90 seconds at 40% of maximal voluntary contraction. Root mean square (RMS), mean frequency (MNF) the conduction velocity (CV) values were estimated using windows of 0.5 seconds. Female subjects showed overall lower fatigability, demonstrated by the lower mean CV decrease (1.494) compared to males (1.787). However, in periods of high decreases in hormones concentrations in females (the end of both the follicular and luteal phases), higher CV decreases were observed (1.921 and 2.183). These results indicate the need of considering the effects of hormonal fluctuations in females when observing gender effects on muscle fatigue.

Compression of electromyographic signals using image compression techniques.

Despite the growing interest in the transmission and storage of electromyographic signals for long periods of time, few studies have addressed the compression of such signals. In this article we present an algorithm for compression of electromyographic signals based on the JPEG2000 coding system. Although the JPEG2000 codec was originally designed for compression of still images, we show that it can also be used to compress EMG signals for both isotonic and isometric contractions. For EMG signals acquired during isometric contractions, the proposed algorithm provided compression factors ranging from 75 to 90%, with an average PRD ranging from 3.75% to 13.7%. For isotonic EMG signals, the algorithm provided compression factors ranging from 75 to 90%, with an average PRD ranging from 3.4% to 7%. The compression results using the JPEG2000 algorithm were compared to those using other algorithms based on the wavelet transform.