Transducer Location Research Articles

Clinical evaluation of the InnerSpace fibreoptic intracranial pressure monitoring device

Objective : The aim of this study is the clinical evaluation of the intraparenchymal ICP monitor InnerSpace OPX 100. Methods : Sixty four Inner Space OPX 100 transducers in 51 patients with severe head injury 42, intracranial spontaneous bleeding 6 or hypoxia 3 were studied. The transducer was placed in the frontal white matter. Thirty nine patients received one catheter, eleven patients two catheters and one patient three catheters. The study period ranged from 10 hours-25 days; total study time was 421.5 days mean duration 6.6 days. Results : In nine cases 14.1 an inadequate location of the ICP transducer was found, but the accuracy of the measurement was not influenced. Dislocation of the transducer occurred in eight cases 12.5 due to inadequate handling. A failed transducer was observed in four cases 6.3 because of a damaged optical fibre 1 or inadequate handling 3. In one patient 1.9 a minor local infection developed. In eleven cases 17 a haematoma around the ICP sensor was observed. Six haematomas were small; five haematomas were larger than 1cm in diameter. In two patients a large frontal haematoma developed after exchange of the transducer. Operative evacuation was necessary in both cases. Zero shift was below 2mmHg in all catheters. Conclusion : It is concluded that the InnerSpace intraparenchymal ICP monitor is a reliable device: the rate of catheter related intracerebral haematomas, however, is not acceptable. This could be improved by a better fixation of the catheter in the burr hole in order to avoid micromovements of the transducer.

Magnetic compatibility of magnetic induction transducers with a moving object

Different technical solutions are proposed to solve the problem of magnetic compatibility of magnetic induction transducers with a moving object. The solutions are based on measuring the difference between magnetic induction vectors due to the object and the external magnetic field at selected points in space and by finding the Poisson parameters of the object at the transducer location.

Methodical approach to the experimental acoustic-emission evaluation of the crack resistance of structural materials

We develop a general approach to the determination of the characteristics of crack resistance of structural materials by the method of acoustic emission. This approach includes the procedure of selection of acoustic signals from cracks and the proper choice of the most efficient parameters of acoustic signals, the operating frequency of the receiving circuit of an acoustic-emission device, and the location of an acoustic-emission transducer. It is shown that, in the process of propagation of a crack, acoustic radiation is directed and the frequency band of emitted acoustic signals becomes narrower in the stage of subcritical crack growth.

Toroidal geometry: Novel three-dimensional intracardiac imaging with a phased-array transducer

Recent advances in small, linear-array transducers have opened new avenues for three-dimensional image acquisition from an intracardiac approach. The purpose of this study was to introduce a novel method of image acquisition using toroidal geometry, explore its fidelity of reproduction of three-dimensional cardiac anatomy, and determine whether a whole-heart scan is achievable. Acquisition was accomplished through 360-degree incremental rotation of a rigid endoscope with a side-mounted ultrasound transducer. The procedure was first tested with the use of a gelatin model to define far-field slice resolution with 1.8-degree rotational increments. Comparison of three-dimensional scans of cardiac specimens with corresponding photographs confirmed that toroidal geometry can provide a high-quality display of structures from all sides. We conclude that whole-heart three-dimensional scanning from within the cardiac chambers is possible with toroidal geometry. The quality of depicted anatomy depends on transducer location within the heart, distance from the transducer, density of slices, and image resolution. The potential of intracardiac three-dimensional ultrasound imaging includes detailed spatial evaluation of cardiac morphology, determination of appropriate placement of investigative or therapeutic devices (catheters, closure devices, etc.), and assessment of cardiac function. (J Am Soc Echocardiogr 1997;10:493-8.)

OPTIMIZATION OF AN ACTIVE NOISE CONTROL SYSTEM USING SPHERICAL HARMONICS EXPANSION OF THE PRIMARY FIELD

The design of an active noise control system involves several steps. One of the most important is to find the best locations of the control sources and error sensors according to the primary source distribution and its spectrum. Thus the first step in this optimization problem is to obtain an analytical expression for the primary sound field. In this work this was done by using a spherical harmonics expansion, determined on the basis of measurements of the primary field. It is shown how, by using such an expansion, a method can be developed for optimizing the transducer locations for the case of free field radiation of a period general primary source. Finally it is shown how this measurement database can be used to choose a good compromise between the number and the locations of the error sensors.

A study of the quantitative and qualitative impact of catheter shaft angulation in a mechanical intravascular ultrasound system

Nonuniform rotation of mechanical intravascular ultrasound transducers may give rise to a geometric distortion of the ultrasound image known as the rotation angle artefact. This investigation studied the influence of different degrees and combinations of catheter shaft angulation on image morphology and the quantitative impact of the artefact using a circular perspex phantom and 3.5 F, 30 MHz Boston Scientific “Sonicath” catheters connected to a Hewlett Packard Sonos intravascular scanner. Major and minor diameters, cross-sectional area and circumference of the phantom lumen were measured and a “distortion index” calculated. Visually apparent geometric distortion was graded from 1 (absent) to 4 (severe). As expected, eccentric transducer location was associated much more frequently with identifiable distortion (70%) than was a concentric location (6%). Greater distortion occurred with increasing degrees of catheter shaft angulation, and was more pronounced in images from older catheters. The lumen area measurements in images in which no artefact was identified were accurate to within ±10% in 97% of cases, compared to only 81% of cases when an artefact was noted. The quantitative accuracy of an image in which geometric distortion is identified is thus not reliable. The direction of the quantitative error cannot be confidently predicted in any given case, although the mean lumen area tends to increase as the grade of distortion increases.

In-flight imaging of transverse gas jets injected into compressible crossflows

The development of and results from an airborne flight-test experiment to study nonreacting gas jets injected transversely into subsonic and slightly supersonic crossflows is presented. Freestream/crossflow Mach numbers in the study ranged from 0.6 to 1.2, and planar laser-induced fluorescence imaging of an iodine-seeded nitrogen jet was used to visualize the jet flow. Time-dependent images were obtained with a high-speed intensified video camera synchronized to the laser pulse rate. The entire experimental assembly was configured compactly inside a unique flight-test fixture mounted under the fuselage of NASA Dryden's F-104G research aircraft, which served as a flying wind tunnel. Recorded transverse gas jet images were then digitized to allow analysis of jet trajectory, spreading, and mixing characteristics. Comparisons of experimental results with model predictions in this transonic crossflow regime show reasonable agreement. Nomenclature AJ = cross-sectional area of jet nozzle at exit A6 = cross-sectional area of jet nozzle at transducer location; see Fig. 4 Mj = jet exit Mach number

Pathogenesis of acute ischemic mitral regurgitation in three dimensions

Changes in the geometric and intravalvular relationships between subunits of the ovine mitral valve were measured before and after acute posterior wall myocardial infarction in three dimensions by means of sonomicrometry array localization. In 13 sheep, nine sonomicrometer transducers were attached around the mitral anulus and to the tip and base of each papillary muscle. Five additional transducers were placed on the epicardium. Snares were placed around three branches of the circumflex coronary artery. One to 2 weeks later, echocardiograms, dimension measurements, and left ventricular pressures were obtained before and after the coronary arteries were occluded. Data were obtained from seven sheep. Coronary occlusion infarcted 32% of the posterior left ventricle and produced 2 to 3+ mitral regurgitation by Doppler color flow mapping. Multidimensional scaling of dimension measurements obtained from sonomicrometry transducers produced three-dimensional spatial coordinates of each transducer location throughout the cardiac cycle before and after infarction and onset of mitral regurgitation. After posterior infarction, the mitral anulus enlarges asymmetrically along the posterior anulus, and the tip of the posterior papillary muscle moves 1.5 ± 0.3 mm closer to the posterior commissure at end-systole. The posterior papillary muscle also elongates 1.9 ± 0.3 mm at end-systole. The left ventricle enlarges asymmetrically and ventricular torsion along the long axis changes. The development of postinfarction mitral regurgitation appears to be the consequence of multiple small changes in ventricular shape and contractile deformation and in the spatial relationships of mitral valvular subunits. (J T HORAC C ARDIOVASC S URG 1995;109:684-93)

Usefulness of dobutamine echocardiography in distinguishing severe from nonsevere valvular aortic stenosis in patients with depressed left ventricular function and low transvalvular gradients

The safety of dobutamine echocardiography in coronary artery disease is well established. 27 This study shows that dobutamine can be given safely to patients with AS during noninvasive hemodynamic monitoring. The small number of patients in this study preclude assessment of the effect of dobutamine echocardiography on outcome. A large prospective study is indicated. Although the continuity equation does not contain a flow-dependent constant, its limitations include underestimation of LV outflow diameter and failure to properly align the Doppler beam. 18 However, even if errors in velocity measurement occurred, directional changes should be valid since the transducer locations were identical at baseline and dobutamine infusion.

Fluid Pressures in Partially Liquid-Filled Horizontal Cylindrical Vessels Undergoing Impact Acceleration

An experimental investigation has been carried out to study the fluid pressures in partially liquid-filled vessels when they are suddenly accelerated by impact along the longitudinal axis. The experiments were conducted with three horizontal cylindrical tanks of different length-to-diameter ratios of L/D = 6.0, 3.5, 2.0. The tanks were filled with water at ambient pressure and temperature and were accelerated using a large steel impact hammer. Internal tank wall pressures caused by the acceleration were measured with transient pressure transducers. Six types of pressure-time histories have been observed and results indicated that the pressure profile changes with fill level and transducer location. The peak pressures on the end of the tank are strongly affected by the fill level and the tank length-to-diameter ratio L/D. A modal change in the behavior of liquid movement has been found around fill level h/D = 0.95. For fill levels h/D above 0.95, the pressure in the tanks acted like either a water hammer or an accelerated fluid column, depending on the duration of the impact relative to the pressure wave transit time. For the fill levels with h/D below 0.95, liquid sloshing activity was involved and the pressure at the end of the tank was a function of the liquid dynamic pressure. This modal change also caused the location of maximum peak pressure to move from the impact end of the tank to the tank top. In some cases the pressure on the tank top was two times larger than that at the tank impact end. The maximum pressure observed from the tests was on the top of the tank. This modal change may have some significance in some transportation applications.

Laboratory and model simulations of a LNAPL spill in a variably-saturated sand, 1. Laboratory experiment and image analysis techniques

A two-dimensional, multiphase flow experiment was conducted in the laboratory. The saturation distribution of a lighter than water non-aqueous-phase liquid (LNAPL) as it migrated through a variably-saturated sand medium was determined using image analysis techniques. The pressures in the water and LNAPL phases were measured using hydrophilic and hydrophobic porous cups connected to a series of pressure transducers and a data acquisition system. The LNAPL inflow and water outflow were also recorded. A series of capillary pressure-saturation experiments were conducted for each two-phase system. The capillary pressures recorded by the pressure transducers were used to calculate the pphase saturations based on a fully hysteretic capillary pressure-saturation algorithm. The static equilibrium capillary pressure-saturation relationships proved to be invalid immediately ahead of the LNAPL front. The capillary pressure-saturation relationship appeared to be dynamic for short periods of time as the LNAPL front arrived at each transducer location. The presence of an entrapped air phase as the LNAPL migrated through the unsaturated zone clearly affected the migration of the LNAPL and the maximum LNAPL saturation reached in the sand medium.

RECOMMENDATIONS FOR STANDARDS IN TRANSTHORACIC TWO‐DIMENSIONAL ECHOCARDIOGRAPHY IN THE DOG AND CAT*

Recommendations are presented for standardized imaging planes and display conventions for two‐dimensional echocardiography in the dog and cat. Three transducer locations (“windows”) provide access to consistent imaging planes: the right parasternal location, the left caudal (apical) parasternal location, and the left cranial parasternal location. Recommendations for image display orientations are very similar to those for comparable human cardiac images, with the heart base or cranial aspect of the heart displayed to the examiner's right on the video display. From the right parasternal location, standard views include a long‐axis four‐chamber view and a long‐axis left ventricular outflow view, and short‐axis views at the levels of the left ventricular apex, papillary muscles, chordae tendineae, mitral valve, aortic valve, and pulmonary arteries. From the left caudal (apical) location, standard views include long‐axis two‐chamber and four‐chamber views. From the left cranial parasternal location, standard views include a long‐axis view of the left ventricular outflow tract and ascending aorta (with variations to image the right atrium and tricuspid valve, and the pulmonary valve and pulmonary artery), and a short‐axis view of the aortic root encircled by the right heart. These images are presented by means of idealized line drawings. Adoption of these standards should facilitate consistent performance, recording, teaching, and communicating results of studies obtained by two‐dimensional echocardiography.

Unsteady blade pressures on a propfan - Predicted and measured compressibility effects

The effect of compressibility on unsteady blade pressures is studied by solving the 3D Euler equations. The operation of the eight-bladed SR7L propfan at 4.75 deg angle of attack was considered. Euler solutions were obtained for three Mach numbers, 0.6, 0.7, and 0.8 and the predicted blade pressure waveforms were compared with flight data. In general, the effect of Mach number on pressure waveforms are correctly predicted. The change in pressure waveforms are minimal when the Mach number is increased from 0.6 to 0.7. Increasing the Mach number from 0.7 to 0.8 produces significant changes in predicted pressure levels. The predicted amplitudes, however, differ from measurements at some transducer locations. Also the predicted appearance of a shock in the highly loaded portion of the blade revolution is not indicated by the measurements. At all the three Mach numbers, the measured (installed propfan) pressure waveforms show a relative phase lag compared to the computed (propfan alone) waveforms due to installation effects. Measured waveforms in the blade tip region show nonlinear variations which are not captured by the present numerical procedure.

Standard penetration test energy measurements using a system based on the personal computer: Discussion

where c is the longitudinal wave speed in the rods; E is Young's modulus of the rods; A is the cross-sectional area of the rods; K , and K2 are theoretical correction factors to account for the load cell position in the rods and the finite length of the drill rods, respectively; Kc is a wave speed correction factor, and F(t) is the measured force-time history. The integration is carried out over the duration of the impact compression pulse, At, which is approximately 2Lrlc, where L' is the total length of the drill rods and sampler below the transducer location. This force integration method was proposed by Schmertmann and Palacios (1979) and has been adopted in the ASTM Standard D4633-86 (ASTM 1986) and in the International Reference Test procedure for SPT energy measurement (International Society of Soil Mechanics and Foundation Engineering (ISSMFE) 1988). The main feature of the proposed SPT energy measurement system is the use of bonded strain gauges, which has several practical advantages. Strain gauges are relatively cheap compared with the piezoelectric load cell, and they do not introduce a change in cross-sectional area of the rod. The PC-based system also displays the force-time history in real time, which allows the operator to view the force wave trace for every blow. The authors show applications of the new system to three projects involving the SPT and one project involving the Becker hammer test (BHT; more commonly known as the Becker penetration test, BPT). The energy results presented in the paper are interesting, but several conclusions drawn by the authors are not supported by considerations of wave mechanics principles. In addition, the application of the force integration method to the BHT is not appropriate. The authors' SPT and BHT energy data are explored in more detail in this discussion.

Recommendations for standards in transthoracic two-dimensional echocardiography in the dog and cat. Echocardiography Committee of the Specialty of Cardiology, American College of Veterinary Internal Medicine.

Recommendations are presented for standardized imaging planes and display conventions for two-dimensional echocardiography in the dog and cat. Three transducer locations ("windows") provide access to consistent imaging planes: the right parasternal location, the left caudal (apical) parasternal location, and the left cranial parasternal location. Recommendations for image display orientations are very similar to those for comparable human cardiac images, with the heart base or cranial aspect of the heart displayed to the examiner's right on the video display. From the right parasternal location, standard views include a long-axis four-chamber view and a long-axis left ventricular outflow view, and short-axis views at the levels of the left ventricular apex, papillary muscles, chordae tendineae, mitral valve, aortic valve, and pulmonary arteries. From the left caudal (apical) location, standard views include long-axis two-chamber and four-chamber views. From the left cranial parasternal location, standard views include a long-axis view of the left ventricular outflow tract and ascending aorta (with variations to image the right atrium and tricuspid valve, and the pulmonary valve and pulmonary artery), and a short-axis view of the aortic root encircled by the right heart. These images are presented by means of idealized line drawings. Adoption of these standards should facilitate consistent performance, recording, teaching, and communicating results of studies obtained by two-dimensional echocardiography.

Initial experience and potential applications of multiplane transesophageal echocardiography

Transesophageal echocardiography (TEE) has become an accepted diagnostic cardiac ultrasound technique. The approach provides new, clinically relevant information in a large variety of diseases of the heart and great vessels. 1,2 Indications for TEE are further developing, and the safety of the method has been documented. 3 However, most studies describing the value of TEE were performed using monoplane transducers that enable multiple but exclusively horizontal images. Biplane transesophageal echocardiographic probes, enabling both transverse and longitudinal image planes, provide additional anatomic details, particularly concerning such vertically oriented structures as the superior vena cava, interatrial septum, ascending aorta, left atrial appendage, mitral valve and left ventricle in a long-axis view. 4–9 Most biplane probes use 2 separate transducer arrays mounted proximally and distally at the tip of the endoscope, so that adjustment of the position of the probe is needed when scan planes are changed. The matrix probe 4 enables synchronous side-by-side biplane imaging from 1 transducer location, but has a reduced frame rate and a limited number of transducer elements per plane. Recently, prototype multiplane transesophageal echocardiographic probes were made available; these enable stepwise examination of an area of interest by minute rotation of the scan plane through 180 °, using a fixed transducer position in the esophagus. This report describes our initial experience with multiplane TEE and discusses potential clinical applications.

A wafer scale visual-to-thermal converter

Wafer scale transducer arrays (WSTA's) containing multitransducer arrays combined with processing circuits are produced using a combination of CMOS technology, silicon micromachining, and laser interconnection techniques. A prototype wafer scale visual-to-thermal converter is being developed to convert a visual scene to thermal scene with the same resolution. The basic array is composed of transducer pixels, which combine photodetectors and thermal emitters as transducers together with signal conditioning and control circuitry, enabling 75%-50% local redundancy of system components. Unlike digital WSI designs, the WSTA redundancy approach is driven by regularity in transducer location and emphasizes local over global transducer sparing even when considering cluster defects. For WSTA, testing of functioning cells for WSI must be supplemented by compensating the transducer nonuniformities across the array.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Chapter 30 Synergies and strategies underlying normal and vestibulary deficient control of balance: implication for neuroprosthetic control

Future developments of neuroprosthetic control will probably permit locomotion and posture to be maintained without the aid of crutches and will therefore require some form of balance control. Three fundamental questions will arise. First, the question of the location of imbalance-sensing transducers must be assessed. Secondly, the synergy, which is the relative amplitude and timing of muscle activity, and/or the strategy of joint torques required to re-establish a stable posture for different types of balance disturbances must be addressed. Thirdly, the control laws that map either trunk muscle activity or imbalance-sensing transducer outputs into multi-joint postural control of standing by paraplegic individuals must be generated. The most appropriate means of gathering the relevant information applicable to neuroprosthetic control systems is through the detailed analysis of normal and non-normal human models. In order to gain such detailed insights into normal balance control and its dependence on head angular and linear accelerations, the synergy and strategy of balance corrections in normal subjects or patients with vestibular deficits were investigated for two types of support surface perturbation, a dorsiflexion rotation (ROT) and a rearward translation (TRANS). These experimentally induced perturbations to upright stance were adjusted to cause equal amplitudes of ankle dorsiflexion, thus providing additional information about the role of lower leg proprioception on balance control. Synergies defined on the basis of peak cross-correlations of each recorded muscle's EMG to that of the largest muscle response were significantly different for TRANS and ROT. Translation synergies consisted of a sequential coactivation at several levels (soleus and abdominals some 30 msec before hamstrings, and trapezius some 15 msec before paraspinals), whereas the sequential activation of paraspinals and tibialis anterior dominated the balance synergy to ROT. Likewise, response strategies, defined using cross-correlations of joint torques, differed. That for TRANS was organised as a multi-link strategy with neck torques leading those of all other joints by 40 msec or more; hip joint lead ankle torques by 30 msec. That for ROT was organised around hip and ankle torques without a major correlation to neck torques. Vestibulary deficient subjects developed weaker synergies with respect to subjects with normal balance systems under eyes-open conditions and there was no clear synergy with eyes closed. Consequently, hip torques were delayed some 180 msec with respect to ankle torques, and correlations to neck torques were completely out of phase under eyes-closed conditions. Fundamental changes in TRANS synergies and strategies also occurred in vestibulary deficient subjects for eyes-open and eyes-closed conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Electromagnetic midsagittal articulometer systems for transducing speech articulatory movements

This paper describes two electromagnetic midsagittal articulometer (EMMA) systems that were developed for transducing articulatory movements during speech production. Alternating magnetic fields are generated by transmitter coils that are mounted in an assembly that fits on the head of a speaker. The fields induce alternating voltages in a number of small transducer coils that are attached to articulators in the midline plane, inside and outside the vocal tract. The transducers are connected by fine lead wires to receiver electronics whose output voltages are processed to yield measures of transducer locations as a function of time. Measurement error can arise with this method, because as the articulators move and change shape, the transducers can undergo a varying amount of rotational misalignment with respect to the transmitter axes; both systems are designed to correct for transducer misalignment. For this purpose, one system uses two transmitters and biaxial transducers; the other uses three transmitters and single-axis transducers. The systems have been compared with one another in terms of their performance, human subjects compatibility, and ease of use. Both systems can produce useful midsagittal-plane data on articular movement, and each one has a specific set of advantages and limitations. (Two commercially available systems are also described briefly for comparison purposes). If appropriate experimental controls are used, the three-transmitter system is preferable for practical reasons.

Multiplane Transesophageal Echocardiography

Multiplane transesophageal echocardiography is a new exciting development in echocardiography. We examined the methodology and echo-anatomic correlations of multiplane transesophageal echocardiography and its clinical applications in 100 patients. We used a 5-MHz phased array multiplane (OmniPlane) transesophageal probe. In this instrument, the transducer array can be steered through 180 degrees from any transducer location. This provides a vast assembly of imaging planes, allowing for detailed visualization of all dimensions of cardiac anatomy. This report presents our observations on the echocardiographic anatomy seen in various image planes and the unique clinical potential of multiplane transesophageal echocardiography in the diagnostic assessment of cardiovascular disorders. This technique appears to provide incremental diagnostic information that enhances the interpretative ability. Less esophageal probe manipulation is required with consequent decrease in patient discomfort. We conclude that multiplane transesophageal echocardiography enhances the versatility of transesophageal examination and offers many new avenues for developments such as three-dimensional echocardiography.