Synchronous Data Acquisition Research Articles

Angle‐independent measure of motion for image‐based gating in 3D coronary angiography

The role of three-dimensional (3D) image guidance for interventional procedures and minimally invasive surgeries is increasing for the treatment of vascular disease. Currently, most interventional procedures are guided by two-dimensional x-ray angiography, but computed rotational angiography has the potential to provide 3D geometric information about the coronary arteries. The creation of 3D angiographic images of the coronary arteries requires synchronization of data acquisition with respect to the cardiac cycle, in order to minimize motion artifacts. This can be achieved by inferring the extent of motion from a patient's electrocardiogram (ECG) signal. However, a direct measurement of motion (from the 2D angiograms) has the potential to improve the 3D angiographic images by ensuring that only projections acquired during periods of minimal motion are included in the reconstruction. This paper presents an image-based metric for measuring the extent of motion in 2D x-ray angiographic images. Adaptive histogram equalization was applied to projection images to increase the sharpness of coronary arteries and the superior-inferior component of the weighted centroid (SIC) was measured. The SIC constitutes an image-based metric that can be used to track vessel motion, independent of apparent motion induced by the rotational acquisition. To evaluate the technique, six consecutive patients scheduled for routine coronary angiography procedures were studied. We compared the end of the SIC rest period (rho) to R-waves (R) detected in the patient's ECG and found a mean difference of 14 +/- 80 ms. Two simultaneous angular positions were acquired and rho was detected for each position. There was no statistically significant difference (P = 0.79) between rho in the two simultaneously acquired angular positions. Thus we have shown the SIC to be independent of view angle, which is critical for rotational angiography. A preliminary image-based gating strategy that employed the SIC was compared to an ECG-based gating strategy in a porcine model. The image-based gating strategy selected 61 projection images, compared to 45 selected by the ECG-gating strategy. Qualitative comparison revealed that although both the SIC-based and ECG-gated reconstructions decreased motion artifact compared to reconstruction with no gating, the SIC-based gating technique increased the conspicuity of smaller vessels when compared to ECG gating in maximum intensity projections of the reconstructions and increased the sharpness of a vessel cross section in multi-planar reformats of the reconstruction.

Weekly observations on dispersal and sink pathways of the terrigenous flux of the Ganga–Brahmaputra in the Bay of Bengal during NE monsoon

The analyses of 64 sequential satellite images (October 1999–March 2001) of Indian Remote Sensing Satellite IRS— P4 ocean color monitor (OCM) (bands around 490, 555, and 670 nm) for total suspended matter (TSM), synchronous sea truth data acquisition, and salinity variations have been used to construct dispersal pathways of the surficial fluvial flux into the northern Bay of Bengal during the NE monsoon. From the spatial extent of the plumes of TSM (160–120 km) during October of 1999 and2000, off the mouth of the Himalayan rivers the Ganga andthe Brahmaputra (G–B), it is deduced that fluvial flux does not diminish concurrently with the termination of the southwest (SW) monsoon, as suggestedby time-series trap experiments in the northern bay. During the NE monsoon, the G–B plumes move north to south initially off the mouth, and thereafter advects SW alongshore in the form of coastal sediment plumes, reducing the salinity of the coastal waters along the entire northern bay during October–December. We have observed a strong relation between enhanced episodic discharges of the Ganga–Brahmaputra (G–B) and augmented coastal turbidity during weekly events. It is also observed that even during such short (weekly) events of very high pulse of TSM discharge by the G–B system, the fluvial fluxes do not advect offshore into the deeper regions of the northcentral bay, but are transportedalongshore andd istributedalong the shelf. Our results, therefore, suggest that the reduced recovery of the fluxes in the sediments traps subsequent to the SW monsoon are not linearly related to the magnitude of fluvial flux of the G–B, but stems from the prevalent dispersal patterns. r 2005 Elsevier Ltd. All rights reserved.

Dynamic Field Mapping for Obtaining the Current Distribution in High-Temperature Superconducting Tapes

The magnetic field profile on the surface of Bi-2223/Ag tapes has been dynamically measured across the width of the samples. The experimental technique uses a Hall-probe array with 7 sensors connected to a multiple channel lock-in amplifier especially programmed for fast and synchronous data acquisition measurements. The speed of the system is high enough to measure real-time profiles with 7 probes and 50 Hz sine current through the sample. A numerical method to estimate the current distribution inside the tapes using the measured field profile data is proposed. The inverse problem has been solved using certain assumptions on the current distribution in the superconductor. Validation of the results has been done by comparison with finite element method simulations.

Online-offline laser ultrasonic quality inspection tool for multilayer ceramic capacitors - part II

The adoption of surface mount technology has provided many competitive advantages for the electronics industry. Smaller, lighter, and more efficient packages create better products for consumers, but new manufacturing problems are created through the adoption of new technology. Inspection and verification systems are employed to prevent known defective parts from reaching consumers, but not all future reliability problems can be identified through traditional inspection methods. In multilayer ceramic capacitors (MLCCs), flex cracks can be created during manufacturing. However, traditional online and offline inspection methods have been unable to consistently identify these defects. The location and orientation of the cracks, perpendicular to the printed wiring board (PWB) and obscured by the MLCCs end metallization for solder connection, makes detection using immersion ultrasound or x-ray inspection difficult. The metallization occludes the ability of these methods to image the defect. Therefore, a new inspection technique is required to identify these defects. A laser-generated ultrasonic system has been designed and constructed to meet the need of a noncontact, nondestructive, fast, and accurate system for identifying defects in a laboratory environment, as well as on the manufacturing fine. The system consists of a pulsed infrared laser that excites samples of both an 0805, 10 /spl mu/F, 6.3 V, X5R and an 0603, X5R, 6.3 V, 1 /spl mu/F, MLCC, both having square cross sections, into small-amplitude structural vibration after attachment to the PWB through the process of laser-generated ultrasound. An interferometer, sampled with a synchronized data acquisition system, records the structural impulse response of the MLCC. Monitoring the impulse response for changes indicates changes in the structure of the device. Several MLCC samples were prepared and mounted on PWBs, and some of them were intentionally flexed until a loss of insulation resistance was recorded, indicating the presence of a flex crack. Measurements were taken on the as-manufactured and flexed-to-failure samples. The test results contained in part I were obtained with 0805 MLCC samples with rectangular cross sections, which are less stiff than MLCCs with square cross sections. These results indicated potential for success using the method described here to identify flex cracks. These results indicated potential for success using the method described here to identify flex cracks. The current results also indicate that the laser ultrasonic system could be used to detect flex cracks in 0805 MLCCs with a square cross section and in the smaller 0603 package configuration with a square cross section. Classification of the capacitors requires a reduction in the variance of the error ratio values, so an average of the values computed in comparison with each of the reference devices is implemented.

The Data-Acquisition System of the GOL-3 Facility

Using the upgrading of the measuring system of the GOL-3 plasma facility as an example, the structure of hardware and software environment developed for data-acquisition systems of large pulse electrophysical plants is considered. The equipment is built into 3U-size 19-inch subracks. The control computers are connected to the measuring equipment via standard network facilities (Ethernet-10/100 interface and TCP/IP protocol). At present, we have begun making basic diagnostic measurements using the ADC1250/32 multichannel synchronous data-acquisition systems.

Elastographic imaging using a handheld compressor.

Elastography is an emerging imaging modality that allows noninvasive imaging of tissue stiffness changes and stiffness values associated with pathology or as a result of therapy. However, many currently-used systems for elastography rely on a fixed geometry transducer and compressor system for imaging. This configuration is disadvantageous for imaging difficult-to-reach regions that are currently accessible with conventional ultrasound. In this paper, we describe a handheld, portable stepper motor controlled system for elastography. This system may reduce motion and jitter errors that are prevalent in completely 'freehand elastography' that employs hand-induced compressions using the transducer. The latter also requires collection of large amounts of data and use of strain estimation algorithms that may not be sensitive to phase changes or use additional preprocessing to minimize decorrelation effects. The stepper motor controlled handheld system provides controlled compressions and synchronized data acquisition. Our technique yields elastograms of a low-contrast phantom that have contrast levels and contrast-to-noise ratios that are comparable to those obtained with a fixed geometry system.

Development of a Special Multi-Wavelength Pyrometer for Temperature Distribution Measurements in Rocket Engines

Previously a fast multi-wavelength pyrometer was developed in a collaboration between the Harbin Institute of Technology of China and Rome University of Italy. The main features of the instrument include the use of a dispersing prism and a photodiode array to cover the entire spectral band. Following this experience, a new type of six-target eight-wavelength pyrometer for solid propellant rocket engine plume temperature distribution measurements has been developed. The instrument can record the radiation fluxes of eight wavelengths for six different uniformly distributed points on the target surface, which are well defined by holes on a field stop. The fast pyrometer with a specially designed synchronous data acquisition system can assure that the recorded thermal radiation fluxes of different spectral regions are at the same time and the same true temperature, even with dramatically changed targets.

Full-scale study of conical vortices and roof corner pressures

A full-scale synchronized data acquisition system was set up on the roof of the experimental building at the Texas Tech University Wind Engineering Research Field Laboratory to simultaneously collect approaching wind data, conical vortex images, and roof corner suction pressure data. One-second conditional sampling technique has been applied in the data analysis, which makes it possible to separately evaluate the influencing effects of the horizontal wind angle of attack, <TEX>${\theta}$</TEX>, and the vertical wind angle of attack, <TEX>${\varphi}$</TEX>. Results show a clear cause-and-effect relationship between the incident wind, conical vortices, and the induced roof-corner high-suction pressures. The horizontal wind angle of attack, <TEX>${\theta}$</TEX>, is shown to be the most significant factor in influencing the overall vortex structure and the suction pressures beneath. It is further revealed that the vertical wind angle of attack, <TEX>${\varphi}$</TEX>, plays a critical role in generating the instantaneous peak suction pressures near the roof corner.

Novel apparatus and methods for performing remotely controlled particle-solid interaction experiments at CERN

Recent atomic physics studies involving ultrarelativistic Pb ions required solid target positioners, scintillators, and a sophisticated data acquisition and control system placed in a remote location at the CERN Super Proton Synchrotron near Geneva, Switzerland. The apparatus, installed in a high-radiation zone underground, had to (i) function for months, (ii) automatically respond to failures such as power outages and particle-induced computer upsets, and (iii) communicate with the outside world via a telephone line. The heart of the apparatus developed was an Apple Macintosh-based CAMAC system that answered the telephone and interpreted and executed remote control commands that (i) sensed and set targets, (ii) controlled voltages and discriminator levels for scintillators, (iii) modified data acquisition hardware logic, (iv) reported control information, and (v) automatically synchronized data acquisition to the CERN spill cycle via a modem signal and transmitted experimental data to a remote computer. No problems were experienced using intercontinental telephone connections at 1200 baud. Our successful “virtual laboratory” approach that uses off-the-shelf electronics is generally adaptable to more conventional bench-type experiments.

Laser Doppler techniques for the combined measurement of inlet flow and valve motion in IC engines

A measurement methodology and a test set-up for the experimental investigation of internal combustion engines are presented. This system is based on a laser Doppler anemometer and a laser Doppler vibrometer which measure in a co-ordinated or simultaneous mode both the velocity of the intake flow and the motion of the inlet poppet valve. A synchronized data acquisition procedure allows the use of two optical instruments to analyse the effects of valve jumps and bounces on the inlet flow field. At high rpm, anomalous valve behaviour may appear. Fluid velocity measurements are taken inside the cylinder and the manifold of a motored automotive engine head at different rpm, up to a speed at which anomalous valve behaviour regularly occurs. Velocity data are processed in both time and frequency domains. This measurement system also represents a valuable tool to study resonance phenomena in ducts.

Study of the influence of clock instabilities in synchronized data acquisition systems

The influence of clock jitter (for example, phase noise) in synchronized measurement systems (signal generator + data acquisition) on the quality of the measurements is studied. Explicit expressions for the measurement errors are derived for sinusoidal phase noise. These expressions can be used to specify the required clock stability of data acquisition systems.

A real-time electrical impedance tomograph.

Electrical properties of tissues in the human body can be imaged using a technology known as Electrical Impedance Tomography. In this modality, sinusoidal electrical currents are applied to the body using electrodes attached to the skin, and voltages that are developed on the electrodes are measured. Using these data, a reconstruction algorithm computes the conductivity and permittivity distributions within the body. This paper describes the reconstruction algorithm, image display algorithm, and hardware of a real-time Electrical Impedance Tomograph known as the Real-Time Imaging System. The reconstruction algorithm, executed by a commercially available coprocessor board that resides in a 386-based personal computer, is a modification of the Newton's One Step Error Reconstructor (NOSER) that minimizes algorithm execution time by precomputing many quantities. The image display algorithm, also executed by the coprocessor board, maps the output of the reconstruction algorithm into an image which is displayed using a video graphics board. The architecture of the system and execution times of algorithms implemented by the system are discussed. Using the continuous data acquisition mode of the Real-Time Imaging System, data from the thorax of a normal human subject were collected. Admittivity changes in the chest, as a result of respiration and the cardiac cycle, are presented. Data that were collected from the leg of a normal subject are shown which demonstrate capabilities of the triggered data acquisition mode of the system, allowing data acquisition synchronization with an electrocardiogram.

A self-contained floating spherical probe for the measurement of volume electric fields

A self-contained, electrically floating, spherical electric field probe which is capable of measuring DC electric fields in volume regions has been developed. The spatial field variation must occur on a length scale larger than the sphere diameter. The sphere floats to the local potential existing in its absence, perturbing the ambient field in a precisely known way, thus providing a means to measure volume fields without ambiguous perturbations. The sphere is also capable of measuring its own collected charge which can be used to infer the polarity and magnitude of ions or other space charge in the probe vicinity. The 15 cm diameter aluminum sphere contains six miniature 800 Hz vibrating capacitor sensors, a synchronous detection data acquisition system with A/D converter, and a digital fm transmitter operating at 50 MHz. Data is sent at 1200 baud to a nearby receiver and computer for interpretation and processing. The sensor data, processed in real time, provide values of ambient field magnitude and collected sphere charge. The probe can measure fields as low as 50 V/m and can operate for several hours on one set of batteries.

Application of a 3000-gate GaAs array in the development of a gigahertz digital test system

The characterization of a high-speed GaAs LSi gate array and its personalization as the central control chip for a gigahertz-rate digital test system are described. The array is a 1020-configurable-cell, 3000-gate device that utilizes a commercially available enhancement/depletion (E/D) mode IC process. The development and experimental evaluation of an array personalization designed to characterize all logic macros, the array speed-power performance, and a simple MSI arithmetic element are described. The results of the evaluation of this first design were used to design a digital tester control chip for use at clock rates of up to 1 GHz. Issues in the design of a digital tester are outlined, and the architectural features of a modular tester providing synchronous data acquisition, high-speed RAM control, and pattern generation are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In vivo measurements of relaxation process in the human liver by MRI. The role of respiratory gating/triggering

In vivo estimation of relaxation processes in the liver by magnetic resonance imaging (MRI) may be helpful for characterization of various pathological conditions in the liver. However, such measurements may be significantly hampered by movement of the liver with the respiration. The effect of synchronization of data acquisition to the respiratory cycle on measured T 1- and T 2-relaxation curves was studied in normal subjects, patients with diffuse liver disease, and patients with focal liver pathology. Multi spin echo sequences with five different repetition times were used. The measurements were carried out with and without respiratory gating/triggering. In the healthy subjects as well as in the patients with diffuse liver diseases respiratory synchronization did not alter the obtained relaxation curves. However, in the patients with focal pathology the relaxation curves were significantly different, when respiratory synchronization was employed. The results indicate that respiratory synchronization is only necessary for estimation of relaxation processes in the liver with focal pathology.

Inhomogeneous interactions in rotating solids

According to selective averaging theory, the time-independent and time-dependent terms of inhomogeneous interactions in the NMR of rotating solids can experimentally be observed selectively by synchronous data acquisition. The general behaviors of inhomogeneous interactions in rotating solids are discussed, with the quadrupolar interaction of a nucleus with spin I described by 2 I “effective chemical shifts.” The asymptotic behavior of inhomogeneous interactions in the case of off-magic-angle spinning is also discussed and is seen to lead to a new and accurate method of spinning-angle measurement.

Real‐Time lethality Evaluation During the Flame Sterilization of Canned Foods

A pilot‐scale flame sterilizer was interfaced to a microcomputer for real‐time thermal process evaluation of individual cans. The computerized system used a photodetector system to synchronize data acquisition at predetermined monitoring sites. Infrared sensors were used to measure can temperatures. Also, a method to measure can surface temperature was developed for infrared sensor calibrations. Foil thermocouples were found to be the most accurate and reliable for surface temperature measurements. However, a thin gauge wire thermocouple attached to the inside of the can end surface was a more practical and economical method for sensor calibration.

Microcomputer-Based Synchronous Multichannel Data Acquisition System

Most of the multichannel data acquisition systems invariably use a sequential data conversion method. Thus, the sampling instants of the analog signals are dispersed in time. However, synchronous sampling is desirable when the data are required for system indentification studies, or when fast data conversion of a large number of analog channels is involved. A cost-effective technique is proposed here for a microcomputer-based 8-channel synchronous data acquisition system. The software routine for complete data conversion and storing the values in RAM takes only 93 /s=u/s of CPU time, when used with a single-board microcomputer SDK-85. As the A/D converters (ADC's) are operated in a memory mapped mode, the system can be expanded almost indefinitely. The circuit can handle ADC's of 12-bit resolution as well.