Simulation of Ultrasound RF Signals Backscattered from a 3D Model of Pulsating Artery Surrounded by Tissue.

Arterial stiffness is an independent predictor of cardiovascular events. The motion of arterial tissues during the cardiac cycle is important as a mechanical deformation representing vessel elasticity and is related to arterial stiffness. In addition, arterial pulsation is the main source of endogenous tissue micro-motions currently being studied for tissue elastography.

Main Uncertainties in the RF Ultrasound Scanning Simulation of the Standard Ultrasound Phantoms.

Ultrasound echoscopy technologies are continuously evolving towards new modalities including quantitative parameter imaging, elastography, 3D scanning, and others. The development and analysis of new methods and algorithms require an adequate digital simulation of radiofrequency (RF) signal transformations. The purpose of this paper is the quantitative evaluation of RF signal simulation uncertainties in resolution and contrast reproduction with the model of a phased array transducer.

Endogenous motion of liver correlates to the severity of portal hypertension.

Background: Degree of portal hypertension (PH) is the most important prognostic factor for the decompensation of liver cirrhosis and death, therefore adequate care for patients with liver cirrhosis requires timely detection and evaluation of the presence of clinically significant PH (CSPH) and severe PH (SPH). As the most accurate method for the assessment of PH is an invasive direct measurement of hepatic venous pressure gradient (HVPG), the search for non-invasive methods to diagnose these conditions is actively ongoing.

Aim: To evaluate the feasibility of parameters of endogenously induced displacements and strain of liver to assess degree of PH.

Diagnostic Ability of Radiofrequency Ultrasound in Parkinson's Disease Compared to Conventional Transcranial Sonography and Magnetic Resonance Imaging.

We aimed to estimate tissue displacements' parameters in midbrain using ultrasound radiofrequency (RF) signals and to compare diagnostic ability of this RF transcranial sonography (TCS)-based dynamic features of disease affected tissues with conventional TCS (cTCS) and magnetic resonance imaging (MRI) while differentiating patients with Parkinson's disease (PD) from healthy controls (HC). US tissue displacement waveform parametrization by RF TCS for endogenous brain tissue motion, standard neurological examination, cTCS and MRI data collection were performed for 20 PD patients and for 20 age- and sex-matched HC in a prospective manner. Three logistic regression models were constructed, and receiver operating characteristic (ROC) curve analyses were applied.

Ultrasonic Assessment of the Medial Temporal Lobe Tissue Displacements in Alzheimer's Disease.

We aim to estimate brain tissue displacements in the medial temporal lobe (MTL) using backscattered ultrasound radiofrequency (US RF) signals, and to assess the diagnostic ability of brain tissue displacement parameters for the differentiation of patients with Alzheimer's disease (AD) from healthy controls (HC). Standard neuropsychological evaluation and transcranial sonography (TCS) for endogenous brain tissue motion data collection are performed for 20 patients with AD and for 20 age- and sex-matched HC in a prospective manner. Essential modifications of our previous method in US waveform parametrization, raising the confidence of micrometer-range displacement signals in the presence of noise, are done.

Exposure to total 36-hr sleep deprivation reduces physiological and psychological thermal strain to whole-body uncompensable passive heat stress in young adult men.

Total sleep deprivation (TSD) is associated with endothelial dysfunction and a consequent decrease in vascular reactivity and increase in peripheral vascular resistance. These effectors compromise the body's ability to thermoregulate in hot and cold stress conditions. We investigated heat-unacclimated young adult men (26 ± 2 years) to determine whether 36 hr of TSD compared to an 8 or 4-hr sleep condition, would suppress the responses of the autonomic system (body rectal temperature [T ], heart rate [HR], root mean square of successive interbeat intervals, physiological strain, blood pressure [BP], circulating blood catecholamines, sweating rate and subjective sensations) to whole-body uncompensable passive heat stress in traditional Finnish sauna heat (T  = 80-90°C, rh = 30%).

Quantification of Endogenous Brain Tissue Displacement Imaging by Radiofrequency Ultrasound.

The purpose of this paper is a quantification of displacement parameters used in the imaging of brain tissue endogenous motion using ultrasonic radiofrequency (RF) signals. In a preclinical study, an ultrasonic diagnostic system with RF output was equipped with dedicated signal processing software and subject head-ultrasonic transducer stabilization. This allowed the use of RF scanning frames for the calculation of micrometer-range displacements, excluding sonographer-induced motions.

Current Directions in the Auricular Vagus Nerve Stimulation I - A Physiological Perspective.

Electrical stimulation of the auricular vagus nerve (aVNS) is an emerging technology in the field of bioelectronic medicine with applications in therapy. Modulation of the afferent vagus nerve affects a large number of physiological processes and bodily states associated with information transfer between the brain and body. These include disease mitigating effects and sustainable therapeutic applications ranging from chronic pain diseases, neurodegenerative and metabolic ailments to inflammatory and cardiovascular diseases.

Investigation of Radiofrequency Ultrasound-Based Fibrotic Tissue Strain Imaging Method Employing Endogenous Motion.

Objectives: The paper presents the results of an initial clinical study, which were obtained using the strain elastography imaging method based on radio frequency ultrasound signal analysis.

Methods: The technique employs endogenous motion of the liver induced by beating heart and vascular pulsatility as an excitation source of tissue microdisplacement. The potential for fibrotic tissue characterization was demonstrated using a clinical data set of radio frequency ultrasound signals (23 healthy controls, 21 subjects with hepatitis, and 16 subjects with liver cirrhosis).

Algorithm for diabetes risk evaluation from past gestational diabetes data.

Gestational diabetes mellitus (GDM) is defined as glucose intolerance that is diagnosed in pregnancy period, leading to possible complications for both mother and fetus during pregnancy. The aim of this study was to build an objective method to evaluate diabetes mellitus (DM) risk from past GDM data recorded 15 years ago and find a short list of most informative indicators. The dataset consists of demographic, lifestyle, clinical, genetic and pregnancy related information recorded 15 years ago.

Transcranial Ultrasonographic Image Analysis System for Decision Support in Parkinson Disease.

Objectives: Transcranial ultrasonography (US) is a relatively new neuroimaging modality proposed for early diagnostics of Parkinson disease (PD). The main limitation of transcranial US image-based diagnostics is a high degree of subjectivity caused by low quality of the transcranial images. The article presents a developed image analysis system and evaluates the potential of automated image analysis on transcranial US.

Noninvasive Evaluation of Portal Hypertension Using a Supervised Learning Technique.

Portal hypertension (PHT) is a key event in the evolution of different chronic liver diseases and leads to the morbidity and mortality of patients. The traditional reliable PHT evaluation method is a hepatic venous pressure gradient (HVPG) measurement, which is invasive and not always available or acceptable to patients. The HVPG measurement is relatively expensive and depends on the experience of the physician.

Computer-Aided Segmentation of the Mid-Brain in Trans-Cranial Ultrasound Images.

This paper presents a novel and rapid method developed for semi-automated segmentation of the mid-brain region in B-mode trans-cranial ultrasound (TCS) images. TCS is a relatively new neuroimaging tool having promising application in early diagnosis of Parkinson's disease. The quality of TCS images is much lower compared with the ultrasound images obtained during scanning of the soft tissues; the structures of interest in TCS are difficult to extract and to evaluate.

Detection of occult paroxysmal atrial fibrillation.

This work introduces a novel approach to the detection of brief episodes of paroxysmal atrial fibrillation (PAF). The proposed detector is based on four parameters which characterize RR interval irregularity, P-wave absence, f-wave presence, and noise level, of which the latter three are determined from a signal produced by an echo state network. The parameters are used for fuzzy logic classification where the decisions involve information on prevailing signal quality; no training is required.

Microbubble sonodestruction rate as a metric to evaluate sonoporation efficiency.

Objectives: The efficiency of sonoporation is directly related to microbubble cavitation and can be dependent on the microbubble sonodestruction rate. The objective of this study was to investigate whether the rate of microbubble sonodestruction can be used as a parameter to develop an implicit dosimetric method for sonoporation efficiency evaluation.

Methods: To evaluate the rate of microbubble sonodestruction as a function of the ultrasound (US) peak negative ultrasound pressure, 12-MHz diagnostic US was used in the B-scan mode.

Ensemble empirical mode decomposition based feature enhancement of cardio signals.

This paper presents an application of ensemble empirical mode decomposition method for enhancement of specific biological signal features. The application for two types of cardiological signals is presented in this article. Detection of fiducial points is a routine task for analyzing these signals.

An echo state neural network for QRST cancellation during atrial fibrillation.

A novel method for QRST cancellation during atrial fibrillation (AF) is introduced for use in recordings with two or more leads. The method is based on an echo state neural network which estimates the time-varying, nonlinear transfer function between two leads, one lead with atrial activity and another lead without, for the purpose of canceling ventricular activity. The network has different sets of weights that define the input, hidden, and output layers, of which only the output set is adapted for every new sample to be processed.

Algorithms and results of eye tissues differentiation based on RF ultrasound.

Algorithms and software were developed for analysis of B-scan ultrasonic signals acquired from commercial diagnostic ultrasound system. The algorithms process raw ultrasonic signals in backscattered spectrum domain, which is obtained using two time-frequency methods: short-time Fourier and Hilbert-Huang transformations. The signals from selected regions of eye tissues are characterized by parameters: B-scan envelope amplitude, approximated spectral slope, approximated spectral intercept, mean instantaneous frequency, mean instantaneous bandwidth, and parameters of Nakagami distribution characterizing Hilbert-Huang transformation output.

Automated segmentation of transcranial sonographic images in the diagnostics of Parkinson's disease.

Images captured during routine clinical transcranial sonography (TCS) examination are of a low resolution, so can be confusing for diagnostic evaluations. Manual segmentation of brain structures (areas of the midbrain and substantia nigra (SN)) that are of special interest cause inter-observer and intra-observer variability, thus restricting the reliability of Parkinson disease (PD) diagnostics. This paper presents a new technique for automated segmentation applicable to low resolution sonographic images, and particularly to brain structures related to PD.

Specificity of transcranial sonography in parkinson spectrum disorders in comparison to degenerative cognitive syndromes.

Background: Hyperechogenicity of the substantia nigra (SN+), detected by transcranial sonography (TCS), was reported as a characteristic finding in Parkinson's disease (PD), with high diagnostic accuracy values, when compared mainly to healthy controls or essential tremor (ET) group. However, some data is accumulating that the SN + could be detected in other neurodegenerative and even in non-neurodegenerative disorders too. Our aim was to estimate the diagnostic accuracy of TCS, mainly focusing on the specificity point, when applied to a range of the parkinsonian disorders, and comparing to the degenerative cognitive syndromes.

Adjustment of ultrasound exposure duration to microbubble sonodestruction kinetics for optimal cell sonoporation in vitro.

Cell sonoporation enables the delivery of various exogenous molecules into the cells. To maximize the percentage of reversibly sonoporated cells and to increase cell viability we propose a model for implicit dosimetry for adjustment of ultrasound (US) exposure duration. The Chinese hamster ovary cell suspension was supplemented with microbubbles (MB) and exposed to US, operating at the frequency of 880kHz, with a 100% duty cycle and with an output peak negative pressure (PNP) of 500kPa for durations ranging from 0.

A comparison of conductive textile-based and silver/silver chloride gel electrodes in exercise electrocardiogram recordings.

Background: The goal of this study was to compare disposable silver/silver chloride and reusable conductive textile-based electrodes in electrocardiogram (ECG) signal monitoring during physical activity.

Materials And Methods: The reusable electrodes were produced using thin silver-plated nylon 117/17 2-ply conductive thread (Statex Productions & Vertriebs GmbH, Bremen, Germany) sewed with a sewing machine on a chest belt. The disposable and reusable electrodes were compared in vivo according to ECG signal baseline drift, broadband electrode noise properties, and influence of electrode area to ECG signal morphology and frequency content.

Model based investigation of retinal vessel tortuosity as a function of blood pressure: preliminary results.

Tortuosity is one of parameters which describe a state of the eye fundus blood vessels. Tortuosity can be estimated from the detected vessels in optical fundus images. The increase in vessel tortuosity was observed in eyes of patients with advanced background diabetic retinopathy, papilloedema, even in some completely healthy eyes (in this case tortuosity does not change in time).

Backscattered ultrasound from contrast microbubbles: effects of tissue and bubble interaction.

The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast microbubbles is a complex physical process. Our model driven approach is used to gain better knowledge of the different processes involved in the generation of the backscattered contrast echo. It can be divided into three separable stages: linear and nonlinear wave propagation in tissue, the resulting echo from the pulse interaction with the contrast microbubble, and the propagation of the scattered echo.