Sixty-four channel wearable acquisition system for long-term surface electromyogram recording with electrode arrays

The use of mono- and bi-dimensional electromyogram (EMG) electrode arrays for the assessment of the neuromuscular system can provide an insight into muscle physiology not achieved with classical bipolar surface EMG. Among the advantages of multichannel EMG detection, there is a) the possibility of estimating muscle fibre conduction velocity, even during motor tasks, and b) the possibility to increase the number of detection points on a muscle, improving the performance of pattern-based EMG decomposition methods. For these reasons, the development and use of multi-channel surface EMG devices and techniques were chosen as the primary goals within the European RTD Project ‘Neuromuscular assessment in the elderly worker’ (NEW). The specific requirements of Project NEW called for the availability of a user-friendly, small-sized EMG acquisition system for field use, suitable for multichannel EMG recording using electrode arrays from one or more muscles. A market survey established that none of the commercially available EMG acquisition systems featured all the desired specifications, nor could they be easily adapted for specific use. The paper describes the design of an innovative acquisition system for long-term multichannel EMG recording fulfilling these requirements and comprising adhesive electrode arrays for artifact-free EMG acquisition during work activity and a portable, user-friendly, battery-powered acquisition system for multichannel EMG recording and storage on a removable PCMCIA card. The system has been used extensively within Project NEW for laboratory and field tests and can find applications in other fields of basic and applied research, including ergonomics, occupational and sports medicine.     

Neuromagnetic functional Localization: Principles,state of the art,and perspectives

The neuromagnetic method has been providing impressive results in the understanding of the functions and of some pathologies of the human brain. The possibility of achieving three-dimensional source localization represents a fundamental step forward in the study of the organization of cortical areas, in that of focal disorders and, in general, in the investigation of brain information processing. The development of large multichannel systems to achieve real time functional localization is being carried on in several countries and the first prototypes are already operating for a full assessment of the benefits of the technique. The use of time-varying magnetic pulses provides the opportunity for non-invasive stimulation of the central nervous system toward the achievement of functional imaging of the motor cortices.     

Split-focused ultrasound transducer with multidirectional heating for breast tumor thermal surgery

This study investigated the feasibility of using a split-focused ultrasound transducer to perform thermal surgery on breast tumors, based on a multidirectional heating scheme. The transducer is a square section of a sphere with a radius of 10 cm. The transducer was tilted such that its acoustic beam was 45 degrees relative to the rib surface, and its focal zone was arranged by a shift of 6 mm away from the center of the planning target volume. The multifocus switching technique was employed to enhance the heating efficiency. When a single transducer was used, the transducer sonicated from a certain position for a given duration, and then rotated sequentially to continue the heating. Computer simulations and in vitro phantom experiments have been studied for this heating system. Both simulation and experimental results demonstrated that the system based on a multidirectional heating scheme is capable of generating a proper thermal lesion within 8 min. Meanwhile, from the simulation results, the rib heating was effectively alleviated by tilting the transducer to induce the total reflection at the muscle/bone interface. While using multiple ultrasound transducers, an appropriate arrangement was designed to have the same configuration of acoustic beams as is used for a single-transducer strategy. The simulation results from the four-transducer strategy indicated that the heating results could be further improved. This study revealed that it is very promising to have an appropriate arrangement of a single split-focused ultrasound transducer with mechanical rotation, or to have multiple split-focused transducers that use multidirectional heating for breast tumor thermal therapy.     

Resonance frequency analysis of implants in the guinea pig model: influence of boundary conditions and orientation of the transducer

The goal of this study was to identify the parameters that must be controlled during in vivo resonance frequency measurements with a custom Osstell transducer for custom implants in the guinea pig animal model. A numerical study and in vitro measurements were performed to determine the influence of the boundary conditions as well as the transducer orientation on the resonance frequency measured by the custom Osstell transducer. In the reported guinea pig model, the type of boundary condition, the orientation of the transducer (parallel or perpendicular to the long axis of the bone) and the length of the modelled bone have a large influence on the resonance frequency values. This implies that a follow-up in time of the stability of an implant requires the boundary conditions applied to the bone in which the implant is installed as well as the orientation of the transducer to be highly repeatable. Applying controlled boundary conditions during in vivo measurements had a highly positive influence on the repeatability of the Osstell measurements. This improves the possibility of the technique to measure changes in the implant-bone interface during healing of the implant.     

In vivo three-dimensional photoacoustic imaging based on a clinical matrix array ultrasound probe

We present an integrated photoacoustic and ultrasonic three-dimensional (3-D) volumetric imaging system based on a two-dimensional (2-D) matrix array ultrasound probe. A wavelength-tunable dye laser pumped by a Q-switched Nd:YAG laser serves as the light source and a modified commercial ultrasound imaging system (iU22, Philips Healthcare) with a 2-D array transducer (X7-2, Philips Healthcare) detects both the pulse-echo ultrasound and photoacoustic signals. A multichannel data acquisition system acquires the RF channel data. The imaging system enables rendering of co-registered 3-D ultrasound and photoacoustic images without mechanical scanning. The resolution along the azimuth, elevation, and axial direction are measured to be 0.69, 0.90 and 0.84 mm for photoacoustic imaging. In vivo 3-D photoacoustic mapping of the sentinel lymph node was demonstrated in a rat model using methylene blue dye. These results highlight the clinical potential of 3-D PA imaging for identification of sentinel lymph nodes for cancer staging in humans.     

A technique for the accurate measurement of cardiac ventricular pressures in chronic animals

Accurate ventricular pressure measurements are essential in many experimental procedures. However, obtaining this information in the chronic animal is either very expensive or plagued with uncertainties. This paper describes a method for implanting a chronic ventricular catheter which permits the repeated insertion into the left ventricle of a miniature pressure transducer. Since only one such transducer is required it reduces expense and as the transducer is not chronically implanted, it permits repeated calibration, thus eliminating the uncertainty of transducer drift. This procedure has been used successfully in chronically prepared dogs and promises to be a useful technique in working with conscious animals.     

New system for recording ambulatory blood pressure in man

A new perfusion and transducer unit for ambulatory blood-pressure recording is described, followed by reports of both the laboratory evaluation of the unit and experience with its clinical use. The major change from earlier systems is the perfusion system, now based on an electrically driven ‘delta’ pump. Pressure is measured by a semiconductor strain-gauge pressure transducer. Laboratory evaluation has shown that the transducer with associated tubing and cannulae has a satisfactory frequency response, considerably better than that of the recording system normally used. Both quantitatively and qualitatively there was a very close correspondence between signals obtained from the entire Oxford system (including recording and replay) and signals obtained directly by means of a catheter-tip transducer. Small, but consistent, signal drifts attributable to battery behaviour are described. The system appears remarkably insensitive to temperature variations within the range of expected ambient temperatures. Delta pump performance is satisfactory, producing essentially constant perfusion rates. Clinically, the system has been used for the recording of ambulatory blood pressures in 110 patients for periods up to 72 h with satisfactory results. Reliability appears good, with minimal artefacts atributable to the equipment. This transducer and perfusion system appears to be fully satisfactory and considerably more reliable than the earlier designs.     

A novel photoacoustic tomography based on a time-resolved technique and an acoustic lens imaging system

A novel photoacoustic (PA) tomographic method, which is based on a time-resolved technique and an acoustic lens imaging system, is presented in this paper. A YAG laser operating at 532 nm with a 7 ns pulse width and 10 mJ optical pulse is employed as the excitation source to irradiate the tissue. PA signals generated from the tissue are imaged onto a multi-element linear array transducer with an acoustic lens. A 64 electronic switch is efficiently used for changing the parallel PA signals into a series. The proposed method directly provides PA images without any complex reconstruction algorithms. With the time-resolved technique, tomographic imaging can be achieved successfully. The results show that the images agree well with the original samples.     

Developments for recording lumbosacral evoked potentials

Detailed measurement of lumbosacral evoked potentials is usually only feasible using sophisticated, multichannel neurophysiological equipment. This paper describes the recording technique, and the additional equipment developed for use with a high-quality two-channel recording system, the Dantec Neuromatic 2000M, to facilitate the routine measurement of these potentials. The characteristic feature is a microprocessor based control unit, which allows switching of multiple input channels prior to preamplification and detects the electrocardiogram to trigger the stimulus with a variable time delay.     

Free of speckle ultrasonic imaging of soft tissue with account of second harmonic signal

The Born approximation deconvolved inverse scattering imaging technique is an alternative to the conventional pulse-echo method. This novel technique deconvolves the incident pulse from the reflected pulse, and uses the resulting impulse response to produce an image of the acoustic impedance distribution. It is applicable mainly to structures that resemble a layered medium. The images captured by this method prove to have improved resolution and are free of speckle. With this method one can use ultrasound of lower frequencies than would be required by the pulse-echo method to achieve the same resolution. To provide further improvement of images the second harmonic signals can be employed. Here we describe the deconvolved inverse scattering imaging technique with account of the second harmonic signal. For this purpose the hybrid transducer by Krautkramer Branson Co., which consists of a cylindrical 5 MHz transducer wrapped in an annulus-shaped 2.5 MHz transducer, has been used. The phantom and soft tissue were imaged and in both cases the account of the second harmonic reflection data provides an improvement of the image quality.     

Integration of optical fiber light guide,fluorescence detection system,and multichannel disposable microfluidic chip

A combination of fluorescence detection and microfluidic technology provides promising applications in life sciences. A prototype of an integrated fluorescence detection system and optical fiber light guide on a laminate-based multichannel microfluidic chip has been developed and tested. A blue LED, plastic optical fiber, photodiode, Mylar and PMMA, and fluorescein and BSA-FITC were used as an excitation source, light coupler and guide, detector, microfluidic substrate and sample, respectively. The results show that the system is capable of detecting weak fluorescence emission from a fluorescein solution at concentration down to 0.01 ng/ml, and gives linear response. The results were also reproducible, and no cross-talk between adjacent channels was observed. The test using BSA as a model analyte demonstrates its feasibility for on-chip immunosensor applications. The performance and applications can be developed further. This prototype can be used as a platform to develop a simple and compact bio-fluorescence detection system integrated with an inexpensive and disposable multichannel microfluidic chip for biomedical devices.     

Ultrasonic characterization of cancellous bone using apparent integrated backscatter

Apparent integrated backscatter (AIB) is a measure of the frequency-averaged (integrated) backscattered power contained in some portion of a backscattered ultrasonic signal. AIB has been used extensively to study soft tissues, but its usefulness as a tissue characterization technique for cancellous bone has not been demonstrated. To address this, we performed measurements on 17 specimens of cancellous bone over two different frequency ranges using a 1 MHz and 5 MHz broadband ultrasonic transducer. Specimens were obtained from bovine tibiae and prepared in the shape of cubes (15 mm side length) with faces oriented along transverse (anterior, posterior, medial and lateral) and longitudinal (superior and inferior) principal anatomic directions. A mechanical scanning system was used to acquire multiple backscatter signals from each direction for each cube. AIB demonstrated highly significant linear correlations with bone mineral density (BMD) for both the transverse (R2 = 0.817) and longitudinal (R2 = 0.488) directions using the 5 MHz transducer. In contrast, the correlations with density were much weaker for the 1 MHz transducer (R2 = 0.007 transverse, R2 = 0.228 longitudinal). In all cases where a significant correlation was observed, AIB was found to decrease with increasing BMD.     

Measuring Upper and Lower Airway Resistance During Sleep with the Forced Oscillation Technique

The forced oscillation technique (FOT) is a non-invasive technique to monitor airway obstruction in those with asthma. The aim of this study was to design and validate a system to use FOT during sleep, both with and without bi-level positive airway pressure (BPAP), and to separate upper airway resistance from lower. 8 Hz pressure oscillations were supplied, over which the subject breathed, pressure and flow measurements were then used to calculate impedance. A phase-shift induced by the pressure transducer tubing was characterized, and FOT resistance was compared to steady flow resistance both with and without BPAP. A Millar catheter was used to measure pressure at the epiglottis, allowing the separation of upper from lower airway resistance. A phase shift of −0.010 s was calculated for the pressure transducer tubing, and the average error between FOT and steady flow resistance was −0.2 ± 0.2 cmH₂O/L/s without BPAP and 0.4 ± 0.2 cmH₂O/L/s with BPAP. The system was tested on three subjects, one healthy, one with obstructive sleep apnea, and one with asthma. The FOT was well tolerated and resistance was separated into upper and lower airway components. This setup is suitable for monitoring both upper and lower airway obstruction during sleep in those with and without asthma.     

DNA场效应管传感器的分子设计

为满足临床医学基因诊断的需要,本研究以场效应管为基本传感器,并在栅区构建单链核苷酸敏感栅,实现对目的基因快速、定点、在体检测。本文介绍了ＤＮＡ场效应管传感器的敏感机理和定量依据,并就传感器结构、自组装单分子膜技术、杂交指示剂、多道测量技术等进行设计和探讨。     

Finite element analysis of imposing femtonewton forces with micropipette aspiration

A novel technique of imposing femtonewton forces with micropipette aspiration [i.e., the extended micropipette aspiration technique (EMAT)] is proposed, and an axisymmetric finite element analysis of this technique is provided. The EMAT is experimentally based upon a micropipette manipulation system and is theoretically based upon hydrodynamics. Any spherical object such as a human neutrophil or a latex bead can be employed as the force transducer, so cell–cell interactions can be directly studied. Our computational analysis shows that femtonewton forces can indeed be imposed. The force magnitude is sensitive to the radius of the micropipette and the micropipette-transducer distance, but it is much less sensitive to other parameters including the radius of the transducer, the substrate curvature, and the thickness of the micropipette wall. Combining the EMAT and the previously developed micropipette aspiration technique will allow us to impose an unprecedented range of forces, from a few femtonewtons to a few hundred piconewtons on single molecules or receptor-ligand bonds. © 2002 Biomedical Engineering Society. PAC2002: 8780Fe, 8715La, 0270Dh, 8715Aa     

Development of a microprocessor-based adaptive technique for blood pressure measurements

The paper introduces a new microprocessor-based adaptive technique for the indirect measurement of the systolic and diastolic pressure in humans. The technique is based upon a statistically consistent relationship between the amplitude of the pulsative pressure waveform at the systolic and diastolic points and the amplitude of pulse signals detected when the artery is fully occluded. An adaptive measurement philosophy has been implemented in the design of an electronic analog-digital sphygmomanometer which, in addition to a pressure transducer, contains suitable electronic instrumentation for processing and displaying the electronic signals. A dedicated microprocessor is used to store statistical relations and control the operation of the device. Verification of overall system accuracy is accomplished via direct comparison with manual auscultatory measurements. Clinical testing of a prototype indicates satisfactory performance; measurement errors are maintained well within proposed standards for automated sphygmomanometers.     

基于虚拟仪器技术的聚焦超声换能器电声转换效率自动测试系统

聚焦超声换能器是超声治疗设备的核心部件,电声转换效率是衡量其性能重要指标之一,实际工作中常以电声转换特性来确定治疗系统的工作频率和驱动参数,这对其测试系统的准确性、效率和便捷性提出很高的要求。为此,构建一套自动测试系统,采用基于定向耦合器的电功率计来测量换能器的输入电功率;运用辐射力天平测量换能器输出声功率;基于虚拟仪器技术开发上位机自动测试软件,实时采集和处理测量数据。基于所开发的自动测试系统,测试换能器在不同频率和驱动功率下的电声转换效率,采用变异系数对系统的稳定性进行分析,并与人工测试方法作对照。结果表明,测试系统具有较好的准确性,且单次测试时间可缩短5倍以上,在驱动功率分别为10、20和30 W情况下,自动测试系统(变异系数分别为4.06%、4.31%、4.65%)比人工测试(变异系数分别为4.14%、4.69%、5.83%)更稳定,满足测试系统应用需求。     

生理学教学实验用微机数据采集系统的研制

基于ＰＣ机的通用生物医学信号数据采集及处理系统研制成功产应用于生理学及电生理学的教学实验。该系统具有多通道数据采集，曲线刷新显示、参数测算、信号处理、存储和及打印输出等功能。实现了多道生理信号的无笔描枋。作者介绍该系统的硬件组成和软件设计方法，并给出部分实验内容和结果。     

Photoacoustic imaging with deconvolution algorithm

The impulse response of the ultrasonic transducer used for detection is crucial for photoacoustic imaging with high resolution. We demonstrate a reconstruction method that allows the optical absorption distribution of a sample to be reconstructed without knowing the impulse response of the ultrasonic transducer. A convolution relationship between photoacoustic signals measured by an ultrasound transducer and optical absorption distribution is developed. Based on this theory, the projection of the optical absorption distribution of a sample can be obtained directly by deconvolving the recorded PA signal originating from a point source out of that from the sample. And a modified filtered back projection algorithm is used to reconstruct the optical absorption distribution. We constructed a photoacoustic imaging system to validate the reconstruction method and the experimental results demonstrated that the reconstructed images agreed well with the original phantom samples. The spatial resolution of the system reaches 0.3 mm.     

Applicators for generating ultrasound-induced hyperthermia in neoplastic tumours and for use in ultrasound physiotherapy

Ultrasound in the low megahertz frequency range is used by physiotherapists to treat a variety of conditions. The treatments reduce swelling, reduce pain and increase movement at joints. Ultrasound is now also beginning to be used to treat malignant tumours. The tumours are heated to temperatures between 42 degrees and 45 degrees C, producing cellular damage, the extent of which is determined by the duration and number of treatments and 'concurrent' treatments by chemo and x-ray therapy. In the light of the results of computer simulation, we discuss in this paper: (a) The properties of a five-element divergent transducer array to treat large superficial neoplastic tumours. The field distribution measured by the Sarvazyan method will be described and also compared with that of computer simulation. The benefits of frequency wobbling will also be discussed. (b) The possibility of employing a multiple field applicator for use by physiotherapists to obviate the need for continuous movement of a small transducer of area approximately 5 cm2 over the affected area.