In vivo measurement of fundus pulsations by laser interferometry

A new noninvasive interferometric technique is described that yields information about the hemodynamic conditions at the fundus. Typical results as obtained from normal subjects are presented and briefly discussed. There is a typical position-dependent time course of the blood pulse induced dilatation of the fundus tissue.     

In vivo measurement of swine endocardial convective heat transfer coefficient

We measured the endocardial convective heat transfer coefficient h at 22 locations in the cardiac chambers of 15 pigs in vivo. A thin-film Pt catheter tip sensor in a Wheatstone-bridge circuit, similar to a hot wire/film anemometer, measured h. Using fluoroscopy, we could precisely locate the steerable catheter sensor tip and sensor orientation in pigs' cardiac chambers. With flows, h varies from 2500 to 9500 W/m2 x K. With zero flow, h is approximately 2400 W/m2 x K. These values of h can be used for the finite element method modeling of radiofrequency cardiac catheter ablation.     

In vivo measurement of tumor conductiveness with the magnetic bioimpedance method

A noninvasive electromagnetic method has been developed that can effectively measure the in-vivo conductivity difference between rat tumor lines having a low and high metastatic potential. These tumor lines are used in the study of human prostate tumor.     

In vivo measurement of frequency characteristics of phase velocityof bone with bending vibration

The authors propose a new method of measuring the frequency characteristics of phase velocity along a bone for bending vibration modes to diagnose its mechanical characteristics. By introducing a simple model of a distributed-constant network, the phase velocity is determined for each frequency from the spatial distribution of velocity along a radius bone surface which is measured by the ultrasonic Doppler method     

In vivo measurement of the oxygen saturation of retinal vessels in healthy volunteers

A new method for the spatially resolved measurement of the oxygen saturation of retinal vessels is described. Imaging spectrometry was used for both measurements of transmission and reflectance spectra of whole blood in cuvettes as well as for fundus reflectance spectra. A model was developed for the calculation of the oxygen saturation, valid in the wavelength range between 510 nm and 586 nm, in that the internal reflectance is constant and only the transmitted light depends on layer thickness and hematocrit. Altogether 265 measurements were performed in different number at 30 eyes. In each measurement, the oxygen saturation was simultaneously determined for 193 locations along a line of 1.5 mm at the fundus. The mean oxygen saturation in retinal arteries was (92.2 +/- 4.1)% and (57.9 +/- 9.9)% in retinal veins. The mean retinal arterio-venous difference of the oxygen saturation was (35.1 +/- 9.5)%. The venous oxygen saturation depended on distance from the optic disc. The measured mean of the arterio-venous difference of the oxygen saturation corresponded well to the value of the brain (34%). The utilization of oxygen in the temporal quadrants (inferior: 39.4 +/- 10.4%) is significantly (p = 0.05) higher than in the nasal quadrants (inferior: 31.3 +/- 6.7%).     

In vitro and in vivo measurement for biological applications using micromachined probe

We developed a small-sized micromachined probe for the measurement of biological properties using microelectromechanical systems (MEMS) technology. We also experimentally showed the suitability of the micromachined probe for biological applications through in vivo, as well as in vitro measurements of various types of tissue. We measured the permittivities of 0.9% saline and the muscle and fat of pork using the micromachined probe after liquid calibration. The measured permittivities of 0.9% saline and pork agreed well with both the expected values of the Cole-Cole equation along with the measured values obtained through the use of a 1-mm-diameter open-ended coaxial probe. We also performed in vivo measurements of breast cancer tissue implanted in an athymic nude mouse to show the suitability of the small-sized micromachined probe for practical biological applications. Through the obtained data, the capability of the micromachined probe of distinguishing different tissue types from one another was shown. The actual aperture size of the micromachined probe is only 240 /spl mu/m /spl times/ 70 /spl mu/m and, therefore, we can extract the biological information from very small biological tissues and drastically decrease the invasiveness of this method through the implementation of the small probe created through the use of MEMS technology.     

In vivo micro-image mosaicing

Recent advances in optical imaging have led to the development of miniature microscopes that can be brought to the patient for visualizing tissue structures in vivo. These devices have the potential to revolutionize health care by replacing tissue biopsy with in vivo pathology. One of the primary limitations of these microscopes, however, is that the constrained field of view can make image interpretation and navigation difficult. In this paper, we show that image mosaicing can be a powerful tool for widening the field of view and creating image maps of microanatomical structures. First, we present an efficient algorithm for pairwise image mosaicing that can be implemented in real time. Then, we address two of the main challenges associated with image mosaicing in medical applications: cumulative image registration errors and scene deformation. To deal with cumulative errors, we present a global alignment algorithm that draws upon techniques commonly used in probabilistic robotics. To accommodate scene deformation, we present a local alignment algorithm that incorporates deformable surface models into the mosaicing framework. These algorithms are demonstrated on image sequences acquired in vivo with various imaging devices including a hand-held dual-axes confocal microscope, a miniature two-photon microscope, and a commercially available confocal microendoscope.     

In vivo measurement of 3-D skeletal kinematics from sequences ofbiplane radiographs: Application to knee kinematics

Current noninvasive or minimally invasive methods for evaluating in vivo knee kinematics are inadequate for accurate determination of dynamic joint function due to limited accuracy and/or insufficient sampling rates. A three-dimensional (3-D) model-based method is presented to estimate skeletal motion of the knee from high-speed sequences of biplane radiographs. The method implicitly assumes that geometrical features cannot be detected reliably and an exact segmentation of bone edges is not always feasible. An existing biplane radiograph system was simulated as two separate single-plane radiograph systems. Position and orientation of the underlying bone was determined for each single-plane view by generating projections through a 3-D volumetric model (from computed tomography), and producing an image (digitally reconstructed radiograph) similar (based on texture information and rough edges of bone) to the two-dimensional radiographs. The absolute 3-D pose was determined using known imaging geometry of the biplane radiograph system and a 3-D line intersection method. Results were compared to data of known accuracy, obtained from a previously established bone-implanted marker method. Difference of controlled in vitro tests was on the order of 0.5 mm for translation and 1.4 degrees for rotation. A biplane radiograph sequence of a canine hindlimb during treadmill walking was used for in vivo testing, with differences on the order of 0.8 mm for translation and 2.5 degrees for rotation.     

In vivo and real-time measurement of magnetic nanoparticles distribution in animals by scanning SQUID biosusceptometry for biomedicine study

Magnetic nanoparticles have been widely applied to biomagnetism, such as drug deliver, magnetic labeling, and contrast agent for in vivo image, etc. To localize the distribution of these magnetic particles in living organism is the first important issue to confirm the effects of magnetic nanoparticles and also evaluate the possible untoward effects. In this study, a scanning high T(c) rf-SQUID superconducting quantum interference devices (SQUIDs) biosusceptometry, composed of static SQUID unit and scanning coil sets, is developed for biomedicine study with the advantages of easy operation and unshielded environment. The characteristics tests showed that the system had the low noise of 8 pT/Hz at 400 Hz and the high sensitivity with the minimum detectable magnetization around 4.5 × 10(-3) EMU at distance of 13 mm. A magnetic nanoparticle detection test, performed by ex vivo scanning of the magnetic fluids filled capillary under swine skin for simulation of blood vessels in living bodies, confirmed that the system is feasible for dynamic tracking of magnetic nanoparticles. Based on this result, we performed further studies in rats to clarify the dynamic distribution of magnetic nanoparticle in living organism for the pharmacokinetics analysis like drug delivers, and propose the possible physiological metabolism of intravenous magnetic nanoparticles.     

In vivo measurement of the brain and skull resistivities using an EIT-based method and realistic models for the head

In vivo measurements of equivalent resistivities of skull (rho(skull)) and brain (rho(brain)) are performed for six subjects using an electric impedance tomography (EIT)-based method and realistic models for the head. The classical boundary element method (BEM) formulation for EIT is very time consuming. However, the application of the Sherman-Morrison formula reduces the computation time by a factor of 5. Using an optimal point distribution in the BEM model to optimize its accuracy, decreasing systematic errors of numerical origin, is important because cost functions are shallow. Results demonstrate that rho(skull)/rho(brain) is more likely to be within 20 and 50 rather than equal to the commonly accepted value of 80. The variation in rho(brain)(average = 301 omega x cm, SD = 13%) and rho(skull)(average = 12230 omega x cm, SD = 18%) is decreased by half, when compared with the results using the sphere model, showing that the correction for geometry errors is essential to obtain realistic estimations. However, a factor of 2.4 may still exist between values of rho(skull)/rho(brain) corresponding to different subjects. Earlier results show the necessity of calibrating rho(brain) and rho(skull) by measuring them in vivo for each subject, in order to decrease errors associated with the electroencephalogram inverse problem. We show that the proposed method is suited to this goal.     

Ultrasonic in vivo measurement of ocular surface expansion

Our aim was to ascertain whether the ultrasonic measurement of longitudinal corneal apex displacements carried out in a proper headrest is a credible method of ocular pulse (OP) detection. To distinguish between longitudinal movements of the eye globe treated as a rigid body and ocular surface expansion caused by the variations of the eye-globe volume, two ultrasound distance sensors were applied to noninvasively measure displacements of cornea and sclera. The same sensors were used to examine the influence of the anterio-posterior movements of a fixed head on the registration of corneal apex pulsation. In both experiments, ECG signals were synchronically recorded. Time, spectral, and coherence analyses obtained for four healthy subjects showed that the ocular surface expansion due to pulsatile ocular blood flow (POBF) is the main component of longitudinal corneal displacement. Ocular surface pulsation is always affected by the head movement. However, there exist some unique properties of signals, which help to distinguish between head and eye movements. A rigid headrest and a bite bar are required to stabilize the head during OP measurement. Ultrasonic technique enables noninvasive and accurate in vivo measurement of corneal pulsation, which could be of interest for indirectly estimating intraocular pressure propagation and POBF component.     

In vivo mechanical behavior of intra-abdominal organs

For realistic surgical simulation in a virtual environment, in vivo material properties of biological tissues are required for simulating the deformations and the reaction forces from the tool-tissue interactions. In this paper, the in vivo static and dynamic mechanical behavior of the liver and lower esophagus of pigs were presented both in linear and nonlinear regions under compressive and shear indentations. A robotic device was programmed to function as a mechanical stimulator with a 2-mm flat-tipped cylindrical probe attached to its tip. A series of ramp and hold stimuli, as well as sinusoidal indentation stimuli, were delivered to the organs and reaction forces were measured. The conditions for these indentation stimuli were designed such that they were similar to conditions in an operating room. Experiments were also carried out on the organs for ex vivo and in vitro conditions. Results show that the breathing and pulse rate significantly affect the measured force responses of the organs. From the obtained force-displacement relationships, steady-state impedances as well as dynamic impedances of both organs were calculated. The results also show that in vivo steady-state impedance of the lower esophagus is significantly higher than that of the liver. The in vivo steady-state response of the liver, however, exhibits a greater degree of nonlinearity than that of the lower esophagus. The in vivo steady-state response of the lower esophagus in the three orthogonal directions also indicates that the lower esophagus is not significantly anisotropic. The impedance of both organs under sinusoidal indentations (0-5 Hz) are fairly similar each other. Magnitudes of the impedance over the stimulus frequencies are fairly constant. The impedance phase angles decrease over the range of stimulus frequencies applied. Comparison of the measurements obtained from the in vivo, ex vivo, and in vitro experiments shows that the mechanical properties of the biological tissues change significantly after the death of the animal. The tissues generally become stiffer and exhibit greater nonlinearity. The degree of change in their mechanical properties is dependent on the amount of time after the death of the animal. These data can be further utilized in the computing of the material parameters of tissue models for laparoscopic surgery simulators as well as open surgery simulators.     

In vivo high-frequency ultrasonic characterization of human dermis

The aim of this study is in vivo skin tissue characterization of young and old human cutaneous tissues by estimating the slope of the attenuation coefficient. The method used is the centroid algorithm with a second-order autoregressive model to perform the spectral analysis. Backscattered signals are acquired with a 40-MHz transducer fixed on a three-dimensional robot. Diffraction phenomena are eliminated via an axial translation of the transducer that allows the acquisition of the signal in the focal zone. The slope of the attenuation coefficient is estimated on phantoms of known attenuation, in order to validate the method. Preliminary measurements of the slope of the attenuation coefficient are subsequently performed in the echographic mode on abdominal human skin samples in vitro at 40 MHz. After assessing the reproducibility of the measurement of the attenuation coefficient slope in human dermis at 40-MHz in vivo, this is carried out on the volar face of the forearm of 150 healthy subjects aged 14-85 yr. The values measured range from 0.7 to 3.6 dB/cm.MHz. The main result of this study is the decrease with advancing age of the attenuation coefficient slope, which may reflect structural modifications of human dermis with age.     

In vivo measurement of the brain and skull resistivities using an EIT-based method and the combined analysis of SEF/SEP data

Results of "in vivo" measurements of the skull and brain resistivities are presented for six subjects. Results are obtained using two different methods, based on spherical head models. The first method uses the principles of electrical impedance tomography (EIT) to estimate the equivalent electrical resistivities of brain (rhobrain), skull (rhoskull) and skin (rhoskin) according to. The second one estimates the same parameters through a combined analysis of the evoked somatosensory cortical response, recorded simultaneously using magnetoencephalography (MEG) and electroencephalography (EEG). The EIT results, obtained with the same relative skull thickness (0.05) for all subjects, show a wide variation of the ratio rhoskull/rhobrain among subjects (average = 72, SD = 48%). However, the rhoskull/rhobrain ratios of the individual subjects are well reproduced by combined analysis of somatosensory evoked fields (SEF) and somatosensory evoked potentials (SEP). These preliminary results suggest that the rhoskull/rhobrain variations over subjects cannot be disregarded in the EEG inverse problem (IP) when a spherical model is used. The agreement between EIT and SEF/SEP points to the fact that whatever the source of variability, the proposed EIT-based method 相似文献   

手势控制的LED变形灯设计

针对LED灯具互动性差,造型单一的现状,设计一种基于手势控制的LED吊灯。该设计以STM32为控制核心,包括无线WiFi模块、手势识别模块、灯光控制模块和电机驱动模块。所设计的LED吊灯具有手势控制和手机APP控制两种控制模式,具备亮度调节、色温调节、颜色变换等功能。灯罩的展开与闭合,改变灯具的照明角度,实现变形的效果。该设计通过WiFi技术接入家庭局域网,实现灯具的网络化、智能化。     

In situ measurement of misalignment errors in free-space opticalinterconnects

A nonobtrusive technique for measuring misalignment errors in multistage free-space optical interconnects is proposed. The technique makes use of dedicated microoptics to relay higher order dedicated alignment beams generated by an optical power supply onto alignment detectors located on the periphery of a smart pixel chip. An implementation of this technique for measuring lateral (x-y) misalignment error in a multistage optical backplane demonstrator is then presented. Performance parameters are analyzed and future directions such as photonic extensions to electronic boundary scan standards are suggested     

In situ measurement of an image during lithographic exposure

This letter describes a method which can directly observe the aerial image of a lithographic exposure tool. Submicrometer resist structures, doped with a laser dye, are swept through the lithographic image as fluorescence is monitored. Experimental aerial image profiles are reported for a 5X reduction lens at varying focus parameters. The location of the fluorescent structures with respect to the image can be accurately determined to yield real-time overlay information.     

In vivo Doppler shift measurements using multimode fiber-opticcatheters

A new fiber-optic catheter for in vivo blood-flow measurements has been developed. The catheter is designed to measure blood flow in both the forward (toward the catheter tip) and reverse (away from the catheter tip) flow directions. It consists of two multimode optical fibers with core diameter of 50 μm and cladding diameter of 125 μm. One fiber transmits the laser beam into blood and the other receives the backscattered light from the erythrocytes within the probe volume. In the flow experiment, it was found that the flow within the boundary layer is indeed laminar and, hence, the relationship between the Doppler shift frequencies and the flow velocities is linear, thereby making the linear calibration possible for predicting the free stream flow velocity. Plots of the maximum shift frequency (frequency at which the Doppler spectrum disappeared into the noise spectrum) against the flow velocities are found to be more linear in both the forward and reverse flow directions than that of the dominant shift frequency (frequency with the highest amplitude). These results were reaffirmed by the numerical flow simulation along the catheter side wall     

In situ measurement of thermomechanical effects and properties inthin-film polymers

Results of in situ measurements of the thermomechanical properties of polyimides used in the microelectronic packaging industry are presented. During the formation of polymer layers and their subsequent use, there are several thermomechanical effects which can affect the electronic packages performance. Specifically, thermal loading of the structure results in elastic and inelastic effects such as relaxation. The time and temperature dependent relaxation behavior of polyimides in multilayer structures were investigated to determine their thermomechanical properties. Both a numerical model and experimental analysis were used to determine the curvature change of multilayer structures during manufacturing. The numerical model, which is based on Maxwell's model, characterizes the stress relaxation behavior of thermoplastics. The changes in stress over time for quartz-polyimide-aluminum and quartz-polyimide-germanium heterostructures were obtained. From these observations, the relaxation time constant, activation energy, and viscosity-to-shear-modulus ratio were determined for the polyimide     

基于红外热成像的在体呼吸监测方法

人体红外辐射及温度特性与呼吸等生理活动密切相关。针对远程监测需要,提出了一种基于面部红外图像分析的在体呼吸监测方法。为了提高红外热成像中鼻孔区域识别及跟踪精度,研究了基于Harris角点法的提取方法,及基于光流场方法的特征跟踪识别方法;分析对比了不同环境中在体呼吸信号时频特征及统计参数。实验结果表明,本文提出的方法可以准确监测在体呼吸信号,分析呼吸模式变化,为红外热成像方法在临床医学的应用提供了参考。