Multichannel Pulsed Doppler Signal Processing for Vascular Measurements in Mice

The small size, high heart rate and small tissue displacement of a mouse require small sensors that are capable of high spatial and temporal tissue displacement resolutions and multichannel data acquisition systems with high sampling rates for simultaneous measurement of high fidelity signals. We developed and evaluated an ultrasound-based mouse vascular research system (MVRS) that can be used to characterize vascular physiology in normal, transgenic, surgically altered and disease models of mice. The system consists of multiple 10/20 MHz ultrasound transducers, analog electronics for Doppler displacement and velocity measurement, signal acquisition and processing electronics and personal computer based software for real-time and off-line analysis. In vitro testing of the system showed that it is capable of measuring tissue displacement as low as 0.1 μm and tissue velocity (μm/s) starting from 0. The system can measure blood velocities up to 9 m/s (with 10 MHz Doppler at a PRF of 125 kHz) and has a temporal resolution of 0.1 milliseconds. Ex vivo tracking of an excised mouse carotid artery wall using our Doppler technique and a video pixel tracking technique showed high correlation (R² = 0.99). The system can be used to measure diameter changes, augmentation index, impedance spectra, pulse wave velocity, characteristic impedance, forward and backward waves, reflection coefficients, coronary flow reserve and cardiac motion in murine models. The system will facilitate the study of mouse vascular mechanics and arterial abnormalities resulting in significant impact on the evaluation and screening of vascular disease in mice. (E-mail: areddy@bcm.edu)     

Simultaneous Multichannel Cardiac Mapping Systems

There is much current interest in simultaneous multichannel cardiac mapping. In this paper we give recommendations for the construction of a cardiac mapping system. Because the field of cardiac mapping is relatively young, optimum mapping techniques and all possible applications have not yet been developed. Therefore, the mapping system should be flexible and it should have many capabilities. The system should be digital; if variable gains are used, the amplifiers should be programmable and controlled by a microprocessor. It should be possible to analyze previous recordings and acquire additional recordings simultaneously. The mapping system should be able to record continuously for at least tens of minutes and preferably for hours. The recorded data stream should be a self-contained unit, holding all important electrophysiologic information as well as the recorded electrode signals. The programs should be written in C under a UNIX operating system. A minimum of 64 channels should be used for epicardial or endocardial mapping and a minimum of 128 channels for three-dimensional intramural mapping. The leakage current requirements for multichannel mapping systems are too stringent and should be re-evaluated. The major limitation to progress in cardiac mapping is neither the hardware nor the software; it is the electrode: its construction, its placement, its fixation, and the interpretation of its recordings.     

A perspective on the usefulness of computers in nuclear medicine

Summary A computer system in clinical nuclear medicine has a wide variety of operations which it can perform. These range from simple data acquisition and tabulation to elaborate temporal and spatial reconstructions. Simultaneous recording of physiological data has also expanded the number of nuclear medical studies possible. The multiple-gated cardiac equilibrium analysis is the primary example of this format which has evolved rapidly with the availability of inexpensive central memory. Decreasing size and cost of processor units recently have led to the development of multiple processor systems. In some cases, the peripheral devices have a microprocessor already built in. The total cost of the computer system is essentially dictated by the number of peripheral devices.     

Multichannel SEMG in clinical gait analysis: a review and state-of-the-art

Background

Application of surface electromyography (SEMG) to the clinical evaluation of neuromuscular disorders can provide relevant “diagnostic” contributions in terms of nosological classification, localization of focal impairments, detection of pathophysiological mechanisms, and functional assessment.

Methods

The present review article elaborates on: (i) the technical aspects of the myoelectric signals acquisition within a protocol of clinical gait analysis (multichannel recording, surface vs. deep probes, electrode placing, encumbrance effects), (ii) the sequence of procedures for the subsequent data processing (filtering, averaging, normalization, repeatability control), and (iii) a set of feasible strategies for the final extraction of clinically useful information.

Findings

Relevant examples of SEMG application to functional diagnosis are provided.

Interpretation

Emphasis is given to the key role of SEMG along with kinematic and kinetic analysis, for non-invasive assessment of relevant pathophysiological mechanisms potentially hindering the gait function, such as changes in passive muscle–tendon properties (peripheral non-neural component), paresis, spasticity, and loss of selectivity of motor output in functionally antagonist muscles.     

Evaluation of a portable prototype to analyze heart rate variability

Power spectrum analysis of heart rate fluctuations provide a quanitative noninvasive means of assessing the functioning of the cardiovascular control system.Until now the equipment used to study heart rate variability (HRV) have been complicated systems utilized mostly in research centers. Simpler systemsare needed for routine clinical application. We have evaluated, through clinical practice, the usefulness of prototype equipment which allows acquisition and analysis of ECG signals by a portable electrocardiograph and a personal computer in which sophisticated software is installed.We performed one hundred forty-five recordings in twenty-two patients admitted to ICU. With this technique two different predictive patterns were detected: one concerning survivors, the other concerning nonsurvivors.Reliability, portability, simplicity and quality results are the main advantages of the system. The disadvantage is that it is difficult to perform HRV analysis in patients with ECG arrhythmia. This is because the program does not allow the choice of an arrhythmia-free section of the tachoram to analyze.     

The cost of nurse-sensitive adverse events

OBJECTIVE: The aim of this study was to describe the methodology for nursing leaders to determine the cost of adverse events and effective levels of nurse staffing. BACKGROUND: The growing transparency of quality and cost outcomes motivates healthcare leaders to optimize the effectiveness of nurse staffing. Most hospitals have robust cost accounting systems that provide actual patient-level direct costs. These systems allow an analysis of the cost consumed by patients during a hospital stay. By knowing the cost of complications, leaders have the ability to justify the cost of improved staffing when quality evidence shows that higher nurse staffing improves quality. METHODS: An analysis was performed on financial and clinical data from hospital databases of 3,200 inpatients. The purpose was to establish a methodology to determine actual cost per case. Three diagnosis-related groups were the focus of the analysis. Five adverse events were analyzed along with the costs. RESULTS: A regression analysis reported that the actual direct cost of an adverse event was dollars 1,029 per case in the congestive heart failure cases and dollars 903 in the surgical cases. There was a significant increase in the cost per case in medical patients with urinary tract infection and pressure ulcers and in surgical patients with urinary tract infection and pneumonia. The odds of pneumonia occurring in surgical patients decreased with additional registered nurse hours per patient day. CONCLUSION: Hospital cost accounting systems are useful in determining the cost of adverse events and can aid in decision making about nurse staffing. Adverse events add costs to patient care and should be measured at the unit level to adjust staffing to reduce adverse events and avoid costs.     

Improving MEG source localizations: an automated method for complete artifact removal based on independent component analysis

The major limitation for the acquisition of high-quality magnetoencephalography (MEG) recordings is the presence of disturbances of physiological and technical origins: eye movements, cardiac signals, muscular contractions, and environmental noise are serious problems for MEG signal analysis. In the last years, multi-channel MEG systems have undergone rapid technological developments in terms of noise reduction, and many processing methods have been proposed for artifact rejection. Independent component analysis (ICA) has already shown to be an effective and generally applicable technique for concurrently removing artifacts and noise from the MEG recordings. However, no standardized automated system based on ICA has become available so far, because of the intrinsic difficulty in the reliable categorization of the source signals obtained with this technique. In this work, approximate entropy (ApEn), a measure of data regularity, is successfully used for the classification of the signals produced by ICA, allowing for an automated artifact rejection. The proposed method has been tested using MEG data sets collected during somatosensory, auditory and visual stimulation. It was demonstrated to be effective in attenuating both biological artifacts and environmental noise, in order to reconstruct clear signals that can be used for improving brain source localizations.     

Velocity measurements using a single transmitted linear frequency-modulated chirp

Velocity measurement is a challenge for a variety of remote sensing systems such as ultrasonic and radar scanners. However, current Doppler-based techniques require a comparatively long data acquisition time. It has been suggested to use coded signals, such as linear frequency-modulated signals (chirp), for ultrasonic velocity estimation by extracting the needed information from a set of several sequential coded pulses. In this study, a method for velocity estimation using a single linear frequency-modulated chirp transmission is presented and implemented for ultrasonic measurements. The complex cross-correlation function between the transmitted and reflected signals is initially calculated. The velocity is then calculated from the phase of the peak of the envelope of this cross-correlation function. The suggested method was verified using computer simulations and experimental measurements in an ultrasonic system. Applying linear regression to the data has yielded very good correlation (r = 0.989). With the suggested technique, higher frame rates of velocity mapping can be potentially achieved relative to current techniques. Also, the same data can be utilized for both velocity mapping and image reconstruction.     

Improved Recovery of High Frequency P Wave Energy by Selective P Wave Averaging

Most signal averaging processes used for cardiac signals align successive waveforms using a template matching process. In addition to achieving accurate temporal alignment of the signals, this operation m ust also ensure that the signal average comprises signals of the same morphology. For P wave signal averaging, systems designed for QRS complex averaging are often used, with the template acquisition window shifted to include the P wave. Theoretically, with this technique, variations in P wave morphology could reduce the high frequency content of the signal. We tested this hypothesis by comparing the performance of a selective P wave averaging system with a conventional system, based on template matching by cross-correlation over a fixed acquisition window, on identical P wave recordings from 15 subjects. The selective system identifies variations in P wave morphology and generates up to five candidate templates for averaging. Subsequently, the most frequently matched template over a 100-beat sample is used for averaging. Only P waves with the same morphology as this template are averaged. Selective averaging mainly increased the measured high frequency P wave energy, without affecting P wave duration after high pass filtering at 40 Hz, (Duration: 157(4)ms selective vs 155(4) nonselective. Energy 80–150 Hz: 1.77(0.28)μV².s selective vs 1.61(0.3)μV².s non selective, P < 0.01). These observations confirm that non-selective P wave averaging can reduce apparent P wave energy, especially at high frequency. Before meaningful studies of the value of frequency domain analysis of the P wave can be performed, it is important that signal averaging systems of sufficient fidelity are utilized.     

Designing informed game-based rehabilitation tasks leveraging advances in virtual reality

Purpose: This paper details a brief history and rationale for the use of virtual reality (VR) technology for clinical research and intervention, and then focuses on game-based VR applications in the area of rehabilitation. An analysis of the match between rehabilitation task requirements and the assets available with VR technology is presented. Key messages and implications: Low-cost camera-based systems capable of tracking user behavior at sufficient levels for game-based virtual rehabilitation activities are currently available for in-home use. Authoring software is now being developed that aims to provide clinicians with a usable toolkit for leveraging this technology. This will facilitate informed professional input on software design, development and application to ensure safe and effective use in the rehabilitation context. Conclusion: The field of rehabilitation generally stands to benefit from the continual advances in VR technology, concomitant system cost reductions and an expanding clinical research literature and knowledge base. Home-based activity within VR systems that are low-cost, easy to deploy and maintain, and meet the requirements for "good" interactive rehabilitation tasks could radically improve users' access to care, adherence to prescribed training and subsequently enhance functional activity in everyday life in clinical populations. [Box: see text].     

Designing microarray phantoms for hyperspectral imaging validation

The design and fabrication of custom-tailored microarrays for use as phantoms in the characterization of hyperspectral imaging systems is described. Corresponding analysis methods for biologically relevant samples are also discussed. An image-based phantom design was used to program a microarrayer robot to print prescribed mixtures of dyes onto microscope slides. The resulting arrays were imaged by a hyperspectral imaging microscope. The shape of the spots results in significant scattering signals, which can be used to test image analysis algorithms. Separation of the scattering signals allowed elucidation of individual dye spectra. In addition, spectral fitting of the absorbance spectra of complex dye mixtures was performed in order to determine local dye concentrations. Such microarray phantoms provide a robust testing platform for comparisons of hyperspectral imaging acquisition and analysis methods.     

Method of detecting tissue contact for fiber-optic probes to automate data acquisition without hardware modification

We present a novel algorithm to detect contact with tissue and automate data acquisition. Contact fiber-optic probe systems are useful in noninvasive applications and real-time analysis of tissue properties. However, applications of these technologies are limited to procedures with visualization to ensure probe-tissue contact and individual user techniques can introduce variability. The software design exploits the system previously designed by our group as an optical method to automatically detect tissue contact and trigger acquisition. This method detected tissue contact with 91% accuracy, detected removal from tissue with 83% accuracy and reduced user variability by > 8%. Without the need for additional hardware, this software algorithm can easily integrate into any fiber-optic system and expands applications where visualization is difficult.OCIS codes: (170.1610) Clinical applications, (060.2310) Fiber optics, (120.1880) Detection, (230.3120) Integrated optics devices, (170.6510) Spectroscopy, tissue diagnostics     

A decision table and rule based interpretation system for epileptic discharges

The representation of the various features of waveforms and their correlations, in EEG recording for the diagnosis of different diseases have been carried out by many researchers due to the impact of knowledge based on expert systems development tools and techniques.The realisation of these system requires a specific hardware and software tool for its implementation, which may be a costly affair. The design and development of low cost effective system for the diagnosis of epileptic patients have benn reported in this paper. Two different and linked (at certain stage) approaches (i) decision tabel; (ii) rule based system have been followed to model the reasoning processes of physician in the diagnosis. In the decision table the features of specific waveforms of EEG are represented in the tabular form. The features are obtained from a 8086 microprocessor based data acquisition system. The rule based system is designed with IF and THEN form of rules using Turbo-Prolog as programming language tool and is implemented on low cost PC-AT. The results obtained are at an intermediate stage of data processing by decision tables and at the final stage being carried out by rule based model.The performance of the system is evaluated by recording of EEG of some epileptic patients. The results obtained are comparable and to a certain extend appreciable in the opinion of the physician.     

基于PCI总线的磁共振成像数据采集卡设计

目的为小型磁共振成像装置设计专用的高速数据采集卡.方法采用高速模数转换器ADS 804对MRI复数模拟信号进行数字化采样,用静态存储器(SRAM)暂存这数字化信号数据.扫描完一幅图像数据后再把数据从SRAM读入计算机.对模数转换器ADC和静态存储器SRAM的所有逻辑控制信号包括写入ADC的地址均由现场可编程器件FPGA产生.对FPGA读、写和对AD的读出均使用并行总线,由PCI 9052总线控制器进行控制.结果用甚高速硬件描述语言Foundation 3.1软件对FPGA进行设计,并对其产生的控制逻辑电路进行了功能仿真模拟,得到了可行的结果.结论用硬件描述语言VHDL对FPGA进行数字逻辑电路设计是很方便的,修改纠错也很容易.     

Clinical application of magnetocardiography

Magnetocardiography is a noninvasive contactless method to measure the magnetic field generated by the same ionic currents that create the electrocardiogram. The time course of magnetocardiographic and electrocardiographic signals are similar. However, compared with surface potential recordings, multichannel magnetocardiographic mapping (MMCG) is a faster and contactless method for 3D imaging and localization of cardiac electrophysiologic phenomena with higher spatial and temporal resolution. For more than a decade, MMCG has been mostly confined to magnetically shielded rooms and considered to be at most an interesting matter for research activity. Nevertheless, an increasing number of papers have documented that magnetocardiography can also be useful to improve diagnostic accuracy. Most recently, the development of standardized instrumentations for unshielded MMCG, and its ease of use and reliability even in emergency rooms has triggered a new interest from clinicians for magnetocardiography, leading to several new installations of unshielded systems worldwide. In this review, clinical applications of magnetocardiography are summarized, focusing on major milestones, recent results of multicenter clinical trials and indicators of future developments.     

Compression systems for hearing aids and cochlear prostheses

Audio and speech compression systems have suffered several characteristic deficiencies. Single-channel compression systems cannot compress wideband signals without suffering from either spectral distortion or the inability to respond quickly to fast transients. When the input signal contains noise in addition to the desired speech signal, single-channel systems unnecessarily attenuate speech information. Single-channel compressors cannot compress the input signal differentially as a function of frequency. Multichannel compressors are capable of different levels of compression as a function of frequency. However, standard multichannel compressors unnecessarily attenuate important information about the shape of the short-term speech spectrum. This has resulted in poorer speech perception when using standard multichannel systems as compared with single-channel compression systems. A more general form of multichannel compression can emphasize information about the shape of the short-term speech spectrum. Susceptibility to many forms of noise is also reduced with such multichannel systems. Spectral distortion and undesired rapid overshoots and undershoots of signal level, characteristic of many single- and multi-channel systems, can be substantially reduced with such systems.     

Role-player expectations regarding the education of nursing research

This article reports on role player expectations regarding the education of nursing research. The importance of the role player expectations are two-fold: firstly as a factor in the external environment influencing and guiding the formulation phase of the development of standards and secondly, due to the clear indications of problems regarding nursing research in the nursing profession in literature. The role player expectations were elicited using a qualitative, exploratory and contextual design. The role player population included nurse educators, nurses in managerial, clinical and research positions, students and the medical profession. The data was gathered using the na?ve sketches and qualitative data analysis was done using Morse & Field's approach (1996:103-107) in combination with Tesch's data analysis approach as cited by Creswell (1994:154-156). Sixty initial categories were narrowed down to six final categories, which are the research learning programme, personnel, students, departmental policies, funding and support systems. The role player expectations were elicited as part of a research study aiming tot develop a self-evaluation system for quality assurance in nursing research and as such, the role player expectations plays a pivotal role in the development of standards for the self-evaluation system.     

Comparing Teacher and Student Use and Preference of Two Methods of Augmentative and Alternative Communication: Picture Exchange and a Speech-Generating Device

Handheld computing technologies such as the iPad®, which can be adapted to function as a speech-generating device, has led to an influx of evolutions comparing modalities of Augmentative and Alternative Communication systems (AAC) in the acquisition of a mand (i.e., request) repertoire in children with autism and related developmental disabilities. While these studies have consistently yielded results indicating equal acquisition across picture-based systems (PE) and the SGD, they have demonstrated a primary preference for the SGD. The purpose of this study was to extend such research by comparing not only student acquisition and preference, but also stakeholder fidelity of use and preference. Using an alternating treatment design, teachers and paraprofessionals were instructed to conduct mand training trials using both a PE system and an iPad® Mini with the application Proloqu2Go? as a SGD, with seven school aged children with a diagnosis of autism or downs syndrome. Following 10-weeks of data collection, the student participants were exposed to a device preference assessment and teachers completed a social validity questionnaire to assess preference. The results were consistent with previous research indicating equal acquisition and fidelity of use across both devices; but a general preference for the iPad® based SGD.