Broadband Transducers Research Articles

Pulse duration, frequency band, and sweep direction effects on crosstalk in wideband backscattering measurements.

Multiple broadband transducers are typically used to cover both a wide frequency range and fill in gaps resulting from sampling with multiple narrowband echosounders. Synchronized operation of these echosounders is preferred in many cases. Simultaneous operation of multiple broadband echosounders, even when using non-overlapping primary bands, can result in cross-channel interferences caused by nonlinear generation of sound and can contaminate backscattered signal. Decreasing the transmit power of channels with lower frequencies has been demonstrated as an effective technique for reducing the level of crosstalk. Reducing the transmit power inherently decreases the signal energy. Hence, the reduction in crosstalk also reduces signal-to-noise ratio and consequently observation range. Increasing the broadband pulse duration is an alternative to compensate for the reduced signal energy from lower transmit power. This paper examines the effects of increasing pulse duration on crosstalk through numerical modeling and field experiments. Raising the transmit power amplifies the higher-harmonic level more than the main band, while extending the pulse duration increases the levels of both main-band and higher harmonics the same amount. Additionally, the study explores the influence of frequency band and sweep direction on crosstalk.

Optimizing electromechanical properties of KNN-based piezoelectric ceramics through regulation of lattice distortion

With the rapid development of broadband transducers, there is an increasing demand for enhanced electromechanical properties in lead-free piezoelectric ceramics. In this study, the strategies to enhance the electrical properties of ceramics were explored by doping BaZrO3 into 0.96(K0.48Na0.52)Nb0.96Sb0.04O3-0.04(Bi0.5Ag0.5)ZrO3 ceramics, inducing lattice distortion (c/a) and regulating the phase structure. The ceramics doped with 1.5 mol% BaZrO3 demonstrate excellent electrical performance, with a piezoelectric coefficient (d33) of 545 pC/N, a relative dielectric constant (εr) of 4126, and an electromechanical coupling factor (kp) of 54.1 %. The reduced c/a ratio and rhombohedral-orthorhombic-tetragonal phase structure reduce the polarization energy barrier and promote the ordered arrangement of ferroelectric dipoles, thereby enhancing the comprehensive performance of the ceramics. Lastly, the electrical impedance of ceramics is studied in detail and reveals the main conduction mechanism in the microscopic region. This research provides new insights into optimizing the electrical properties of ceramics through microstructural manipulation and demonstrates the potential application of KNN-based ceramics in high performance piezoelectric transducers.

Special anatomy series. Imaging inner ear structures with high-frequency ultrasound: Application to physical rehabilitation space medicine.

The objective of this paper is to document the feasibility of image acquisition, image optimization, and sonographic appearance of the exposed anatomic windows of cadaveric inner ear dissection for purposes of potential future clinical evaluation as part of the developing area of physical and rehabilitation space medicine. Cadaveric dissection of the inner ear was conducted with the goal of exposing areas relevant to vestibular balance. Middle and inner ear structures of 3 human cadavers were imaged with multiple broadband transducers, including emphasis with higher frequency transducers. The images were best optimized with 17 MHz and 22 MHz small footprint transducers. High-frequency ultrasound (US) images of the semicircular canals, vestibular and facial nerves, and utricles with reflected otoliths (otoconia) were obtained and reported in this article. Detailed visualization of both the vestibular nerve and facial nerve was accomplished, including identification of fascicular architecture. In addition, US reflection from the otoliths contained within the utricle was identified with sufficient clarity to provide surface measurements. Bony acoustic landmarks of the middle ear bones were identified by scanning externally from the tympanic membrane, including the dynamic movement of the bones with manual manipulation. US visualization has the potential to be an effective imaging modality to monitor potential changes to the otolith's size throughout extended space flight. To our knowledge, no prior study has reported US images of human inner ear structures.

Nonlinear Frequency Mixing Ultrasound Imaging of Nanoscale Contrast Agents.

Nanoscale ultrasound contrast agents show promise as alternatives for diagnostics and therapies due to their enhanced stability and ability to traverse blood vessels. Nonetheless, their reduced size limits echogenicity. This study introduces an enhanced nanobubble frequency mixing ultrasound imaging method, by capitalizing on their nonlinear acoustic response to dual-frequency excitation. A single broadband transducer (L12-3v) controlled by a programmable ultrasound system was used to transmit a dual-frequency single-cycle wavefront. The frequency mixing effect enabled simultaneous transducer capture of nanobubble-generated sum and difference frequencies in real time without the need for additional hardware or post-processing, by substituting the single-frequency wavefront in a standard contrast harmonic pulse inversion imaging protocol, with the dual-frequency wavefront. Optimization experiments were conducted in tissue mimicking phantoms. Among the dual-frequency combinations that were tested, the highest contrast was obtained using 4&8 MHz. The nanobubble contrast improved with increased mechanical index, and achieved a maximal contrast improvement of 8.4 ± 0.5 dB compared to 4 MHz pulse inversion imaging. In imaging of a breast cancer tumor mouse model, after a systemic nanobubble injection, the contrast was improved by 3.4 ± 1.7, 4.8 ± 1.8, and 6.3 ± 1.6 dB for mechanical indices of 0.04, 0.08, and 0.1, respectively. Nonlinear frequency mixing significantly improved the nanobubble contrast, which facilitated their imaging in-vivo. This study offers a new avenue to enhance ultrasound imaging utilizing nanobubbles, potentially leading to advancements in other diagnostic applications.

Assessment of sulphur content in nitrile rubber through ultrasonic measurement

ABSTRACT Ultrasonic testing is a popular non-destructive method for characterising engineering materials and detecting their properties. Diverse quantities of sulphur are incorporated into an uncured rubber compound, which is subsequently cured under specific pressure and heat conditions to attain the desired properties in the final product. The present work represents a quantitative estimation of sulphur content for cured NBR (Nitrile Butadiene Rubber) samples by an ultrasonic approach. The experiments have been conducted using cured NBR samples with varying sulphur content, ranging from 0% to 1.34%. Ultrasonic pulse behaviour at different temperatures (30°C to 160°C) has been observed using an ultrasonic setup which has been developed in-house. A-scan data is obtained at a sampling rate of 80 MHz using an 18 mm diameter broadband transducer with a 1 MHz central frequency. The ultrasonic longitudinal velocity (ULV) of rubber is determined from A-scan data using time-of-flight, and sulphur content has a significant impact on the ULV. At a temperature of 160°C, the ultrasonic longitudinal velocity (ULV) is measured at 1262 m/s for a sample with 0.62% sulphur content, and at 1321 m/s for a sample with 1.34% sulphur content.

Biaxial Excitation and Reception Method Applied to Ultrasound Imaging.

The biaxial method consists of the utilization of orthogonal electric fields in single-element piezoceramics both in transmission and reception. This study demonstrates the application of the biaxial method to broadband transducers. We developed a three-element biaxial transducer array to demonstrate the feasibility of biaxial method in imaging applications. Finite element analysis was used to model the response of a single transducer element. An electric characterization was performed at each transducer element to determine their driving frequency. Each transducer was driven at 6.25 MHz and tested in different phases to determine the phase that produced the maximum pressure amplitude and shortest pulsewidth. Both simulations and experimental results showed that the acoustic pressure and half-pulsewidth followed a sinusoidal response as a function of the difference in phase applied to the lateral electrodes, as it has been described in our previous work. An imaging test was performed by placing a 0.36-mm diameter nylon wire 20 mm away from the transducer while driving and receiving each element with different combinations of conventional and biaxial driving. By applying a biaxial rephasing at the receiving electrodes during the data analysis, we obtained a maximum reduction in the axial resolution from 4.6 to 1.3 mm and signal-to-noise ratio (SNR) improvements from 15.2 to 24.4 dB, when compared to conventional driving.

Assessment of sulfur content in nitrile rubber through ultrasonic measurement

ABSTRACT Ultrasonic testing is a popular non-destructive method for characterising engineering materials and detecting their properties. Diverse quantities of sulphur are incorporated into an uncured rubber compound, which is subsequently cured under specific pressure and heat conditions to attain the desired properties in the final product. The present work represents a quantitative estimation of sulphur content for cured NBR (Nitrile Butadiene Rubber) samples by an ultrasonic approach. The experiments have been conducted using cured NBR samples with varying sulphur content, ranging from 0% to 1.34%. Ultrasonic pulse behaviour at different temperatures (30°C to 160°C) has been observed using an ultrasonic setup which has been developed in-house. A-scan data is obtained at a sampling rate of 80 MHz using an 18 mm diameter broadband transducer with a 1 MHz central frequency. The ultrasonic longitudinal velocity (ULV) of rubber is determined from A-scan data using time-of-flight, and sulphur content has a significant impact on the ULV. At a temperature of 160°C, the ultrasonic longitudinal velocity (ULV) is measured at 1262 m/s for a sample with 0.62% sulphur content, and at 1321 m/s for a sample with 1.34% sulphur content.

Venous Pseudoaneurysms: Sonographic Presentation, Correlation with Other Diagnostic Imaging Techniques, and Supported by the Literature

Objective: The objective of this study is to demonstrate the sonographic and computed tomographic features of venous pseudoaneurysms and show the difference between true and false venous aneurysms and arterial pseudoaneurysms. Likewise, it was important to provide a historical context based on a literature review of vascular aneurysms and pseudoaneurysms, emphasizing venous pseudoaneurysms. Materials and Methods: Clinical cases are presented for context, and the vascular examinations were performed utilizing a General Electric (GE) Logiq Fortis or Logiq S8 scanners with a broad-band linear-array transducer (L2-9). Computed tomography (CT) with contrast was performed on a GE Revolution Maxima 64-slice CT scanner with 100 mL Omnipaque-350 as a contrast agent. The three-dimensional (3D) axial, sagittal, and coronal reconstructions were made with the Philips IntelliSpace software. Levels of evidence are provided based on a literature search of relevant publications using the National Library of Medicine, PubMed, and Google Books. Results: Different types of venous pseudoaneurysms, venous aneurysms, and arterial pseudoaneurysm diagnosed by duplex sonography and CT were presented. An extensive historical and literature review was conducted based on publications from the 18th to 21st centuries. Conclusion: Venous pseudoaneurysms are uncommon. Most of them are iatrogenic and are usually found as a complication of repetitive venipuncture in patients receiving hemodialysis with arteriovenous fistulas. In rare cases, venous pseudoaneurysms occur spontaneously.

Target strength measurements of individual sub-Arctic krill have frequency-dependent differences from scattering model predictions.

Target strength (TS) is commonly used to convert acoustic backscatter from marine organisms to numerical abundance estimates. Shipboard, tank-based TS measurements were made on four sub-Arctic krill species (Euphausia pacifica, Thysanoessa spinifera, Thysanoessa inermis, and Thysanoessa raschii) from the eastern Bering Sea and Gulf of Alaska at discrete frequencies between 42 and 455 kHz. These measurements were compared to scattering model predictions parameterized with data from the same (when possible) individual krill. Statistically significant differences between modeled and experimental estimates at 42, 45, 120, and 131 kHz exceeded 2 dB on average. Variability in the signal-to-noise ratio, animal length, and measurements from two separate narrowband and broadband transducer pairs (at those frequencies) did not account for these differences. Scattering predictions at 120 and 131 kHz were consistent with the expected transition from Rayleigh-to-geometric scattering where models become increasingly sensitive to orientation and body shape variability. Disagreement between modeled and measured TS may be due to using scattering models developed for, and validated on, larger krill (i.e., Euphausia superba) rather than smaller species of krill. Acoustic surveys of smaller (15-30 mm) krill may require further validation of both the generalizability and parameterization of applied scattering models.

Coupling coefficient analysis of composite bar: A new idea for the design of multi-resonant longitudinal transducer

Multi-resonant longitudinal transducers are widely used in sonar technology by exciting multiple resonant modes to extend the operating bandwidth. However, the existing design methods of multi-resonant longitudinal transducers lack unified and effective theoretical guidance, and usually require extensive parameter searches and calculations, so it is not universal and difficult to popularize. Based on the one-dimensional longitudinal vibration theory, the mode analysis and harmonic analysis of the single piezoelectric bar and the composite bar are carried out, and the physical mechanism of the modes not being excited is revealed. Then, starting with the original definition of electromechanical coupling coefficient, the effective coupling coefficients of the composite bar at different resonant modes are given. Finally, a method to adjust the relative strength of resonant modes is proposed based on the relationship between dynamic conductance and effective coupling coefficient. In this paper, electromechanical coupling coefficient is taken as the core factor of transducer design, which holds the key point and provides a new idea for the design of multi-resonant longitudinal broadband transducers.

A new in-situ method to estimate fish target strength reveals high variability in broadband measurements

Fish Target Strength (TS) is a requirement for estimating abundance from surveys of pelagic fish using echosounders. This paper describes a novel in-situ method to estimate TS as a function of fish body length (L), according to the standard equation TS = 20 log (L) +b20, where b20 is the species-specific factor to be estimated. We made measurements of TS with a broadband scientific echosounder, which is becoming the new tool of choice in fisheries acoustics due to its enhanced signal-to-noise ratio, and higher range resolution and the ability to measure the frequency response. A split-beam 38 kHz broadband transducer was pole-mounted on a small boat in the fjords of Nuuk, Greenland. With the boat stationary, individual Atlantic cod Gadus morhua were detected as echotraces, caught with a fishing line, measured in length and then released. Video footage, from a camera attached to the line, was inspected to verify a single individual was attracted to the lure and caught. Fish echotrace tracking techniques were applied to estimate the tilt of the fish from each acoustic sample and the measured TS was adjusted accordingly with the use of a Kirchhoff-Approximation scattering model. The b20 parameter was estimated by linear regression. This method combines the benefits of associating TS from single fish of known length, which is typical of ex-situ methods, with the in-situ advantages of measuring TS of an undisturbed fish in its natural environment. Results yielded a b20 of − 65.6 dB ( ± 0.83 dB C.I.), which is within the range of previously published values for Atlantic cod measured with narrowband systems. Large variability of TS was observed within fish tracks (average s.d. of 5.55 dB). This is the first description of TS for Atlantic cod with broadband equipment. The high variability could not be attributed to variation in fish length nor tilt angle. Other physiological and behavioural aspects were also discarded. It is possible that this may be an intrinsic property of broadband acoustics, which indicates a need for re-evaluating TS to length relationships as fisheries science moves towards the wider application of broadband acoustics.

Excitation mechanism and application of continuous-order mode for one-dimensional thickness vibration.

The main method to expand the operating bandwidth of the transducer is by exciting multi-order vibration modes, which develop from the earliest excitation of odd-order modes to the excitation of multi-order continuous modes. However, no detailed theoretical characterization of the excitation mechanism and electroacoustic properties of continuous-order modes has been given. In this paper, the excitation mechanism of continuous-order modes for one-dimensional thickness vibration is studied in detail. From the perspective of analytical characterization, the mathematical and physical conditions of mode excitation are analyzed and extended to continuous-order modes. Partial 1-3 piezocomposite consists of two parts; one part is complete lead zirconate-titanate and the other part is 1-3 composite, which is helpful for exciting continuous-order modes. Based on the excitation mechanism of continuous-order modes, a design method of broadband transducer used of partial 1-3 piezocomposite is proposed, and large bandwidth and good pulse response are obtained. The excitation mechanism of continuous-order modes proposed in this paper provides an idea for the theoretical analysis and design of multi-resonant broadband transducers.

Design and Optimization of High-Power and Low-Frequency Broadband Transducer with Giant Magnetostrictive Material.

The applications of sensors in the aerospace industry are mostly concentrated in the middle and high frequencies, and low-frequency sensors often face the problems of low power and short working bandwidth. A lightweight, thin, high-power, low-frequency broadband transducer based on giant magnetostrictive material is designed. The design and optimization processes of the core components are introduced and analyzed emphatically. The finite element simulation results are validated by the PSV-100 laser vibration meter. Three basic configurations of the work panel are proposed, and the optimal configuration is determined by modal, acoustic, and vibration coupling analyses. Compared with the original configuration, it is found that the lowest resonant frequency of the optimal configuration is reduced by 24.6% and the highest resonant frequency within 2000 Hz is 1744.9 Hz, which is 54.2% higher than that of the original configuration. This greatly improves the vibration power and operating frequency range of the transducer. Then, the honeycomb structure is innovatively applied to the work panel, and it is verified that the honeycomb structure has a great effect on the vibration performance of the work panel. By optimizing the size of the honeycomb structure, it is determined that the honeycomb structure can improve the vibration power of the work panel to its maximum value when the distance between the half-opposite sides of the hexagon is H = 3.5 mm. It can reduce the resonant frequency of the work panel; the lowest resonant frequency is reduced by 12.8%. At the same time, the application of a honeycomb panel structure can reduce the weight of the transducer.

Cumulative dyslipidaemia from mid-adolescence through young adulthood with carotid intima-media thickness progression: a 9-year longitudinal study

Abstract Background Carotid intima-media thickness (cIMT) progression was recently established as a predictor of cardiovascular events among adults. To date, a single cIMT measure has largely been used as a marker of preclinical atherosclerotic changes in the young population and dyslipidaemia has been associated with single measured cIMT. The longitudinal relationship between dyslipidaemia and repeated measure of cIMT in a large apparently healthy young population remains unknown. Purpose To investigate the longitudinal associations of total cholesterol (TC), non–high-density lipoprotein cholesterol (non–HDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride, and low-density lipoprotein cholesterol (LDL-C) with cIMT progression in adolescence. Methods We studied 1779 British 15-year-olds (50% females) followed up for 9 years. TC, triglyceride, and HDL-C were measured in line with standard protocols at ages 15, 17, and 24 years, respectively. LDL-C and non-HDL-C were estimated. Lipid phenotypes were categorized based on the 2011 National Heart, Lung, and Blood Institute classification into normal (reference), elevated, and dyslipidaemia. cIMT from the right and left common carotid arteries at 17 years was assessed by ultrasound using a linear 12-MHz transducer and cIMT from the right and left common carotid arteries at 24 years was measured using an ultrasound machine (CardioHealth Panasonic and a 13.5 MHz linear array broadband transducer (probe; centre frequency 9.0 MHz). We conducted linear mixed-effect model analyses and adjusted for sex, age, high sensitivity C-reactive protein, glucose, insulin, total fat mass, lean mass, heart rate, systolic blood pressure, diastolic blood pressure, sedentary time, light physical activity, moderate to vigorous physical activity, family history of cardiometabolic disease, socioeconomic status, pubertal attainment, and smoking status, in addition to lipid covariates such as HDL-C, LDL-C, or triglyceride depending on the predictor. However, TC and non-HDL-C analyses were not adjusted for lipids. Results Participants mean (SD) age in years at different time points were 15.43 (0.29), 17.69 (0.31), and 24.53 (0.72). Persistently elevated TC: effect estimate 0.026 mm [95% CI 0.004 to 0.049; p=0.024], elevated non–HDL-C: 0.033 mm [0.009 to 0.056; p=0.007], and elevated LDL-C: 0.035 mm [0.003 to 0.067); p=0.034], from 15 through 24 years were cumulatively associated with the 7-year cIMT progression. Persistent borderline-low HDL-C: −0.027 mm [−0.050 to −0.005; p=0.019] and very-low HDL-C: −0.035 mm [−0.057 to −0.013; p=0.002] levels were associated with cIMT progression. Triglyceride was not associated with cIMT progression. Conclusion These findings suggest that elevated lipids from mid-adolescence through young adulthood were associated with the progression of carotid wall thickening, a marker of preclinical atherosclerosis. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Cultural Foundation

Cumulative hyperinsulinemia, hyperglycaemia, and insulin resistance from mid-adolescence through young adulthood with carotid intima-media thickness progression: a 9-year longitudinal study

Abstract Background In a recent meta-analysis of randomized clinical trials conducted among adults, carotid intima-media thickness (cIMT) progression was established as a predictor of cardiovascular morbidity and mortality. However, due to the paucity of hard outcomes among adolescents and young adults, a single cIMT measure has largely been used as a marker of preclinical atherosclerotic changes. The repeated measure of cIMT in the young population is scarce thus a knowledge gap exists on the associations of metabolic indices with cIMT progression. Purpose To investigate the associations of cumulative fasting plasma glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) with cIMT progression in adolescence. Methods We studied 1779 British 15-year-olds (50% females) followed up for 9 years. Fasting insulin and glucose were measured in line with standard protocols at ages 15, 17, and 24 years, respectively. HOMA-IR was computed for each time point. Metabolic indices were age and sex-specifically dichotomized as ≥75%, indicating high category and <75% indicating moderate or reference category. cIMT from the right and left common carotid arteries at 17 years was assessed by ultrasound using a linear 12-MHz transducer (Vivid7, GE Medical, Chicago, Illinois) and cIMT from the right and left common carotid arteries at 24 years was measured using an ultrasound machine (CardioHealth Panasonic and a 13.5 MHz linear array broadband transducer (probe; centre frequency 9.0 MHz). We conducted linear mixed-effect model analyses and adjusted for statistically significant determinants of cIMT progression, viz: sex, age, high sensitivity C-reactive protein, insulin or glucose, dual-energy Xray absorptiometry measured total fat mass and lean mass, systolic blood pressure, diastolic blood pressure, smoking status, and ActiGraph measured sedentary time and light physical activity. Covariates were repeatedly measured. Results Participants mean (SD) age in years at different time points were 15.43 (0.29), 17.69 (0.31), and 24.53 (0.72). Cumulative high exposures to glucose: effect estimate 0.009 mm [95% CI −0.003 to 0.021; p=0.130], insulin: 0.002 mm [−0.030 to 0.013; p=0.704], and HOMA-IR: 0.003 mm [−0.009 to 0.016; p=0.608] from 15 to 24 years of age were not associated with the 7-year cIMT progression after full covariate adjustments. Sex-based analyses were consistent with the group analyses in both males and females. Conclusion These findings suggest that hyperinsulinemia, hyperglycaemia, and elevated insulin resistance from mid-adolescence through young adulthood may not be associated with progressive carotid wall thickening during late adolescence through young adulthood. Future studies investigating the role of other metabolic indices such as cumulative elevated lipid exposures on cIMT progression in the young population are warranted. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Cultural Foundation

Temporal causal longitudinal associations of high-sensitivity C-reactive protein with carotid intima-media thickness progression in adolescents: the ALSPAC birth cohort study

Abstract Background The causal role of high-sensitivity C-reactive protein (hsCRP) in the evolution of preclinical cardiovascular disease remains unclear. A previous longitudinal study concluded that hsCRP measured in childhood was not associated with a single measure of carotid intima-media thickness (cIMT) assessed at mid-adulthood. The use of hsCRP samples stored for 25 years prior to analysis might have confounded this previous findings. In the young population of adolescents and young adults no study has investigated whether elevated hsCRP temporally precedes higher cIMT or if bi-directional associations exist, due to the lack of repeated measures of cIMT. Purpose To examine the temporal causal longitudinal associations between repeated measures of cIMT and hsCRP in a young population. Methods We studied 3862 adolescents, aged 17.7 years, followed-up for 7 years, from Avon Longitudinal Study of Parents and Children, birth cohort, UK. Fasting plasma hsCRP was assessed at age 17.7 and 24.5-year clinic visits. cIMT from the right and left common carotid arteries at 17 years was assessed by ultrasound using a linear 12-MHz transducer (Vivid7, GE Medical, Chicago, Illinois) and cIMT from the right and left common carotid arteries at 24 years was measured using an ultrasound machine (CardioHealth Panasonic and a 13.5 MHz linear array broadband transducer (probe; centre frequency 9.0 MHz). We conducted autoregressive cross-lagged structural equation model path analyses to untangle temporal and bi-directional associations. We adjusted for sex, time in years between ages 17.7 and 24.5 years, age, low-density lipoprotein cholesterol, insulin, triglyceride, high-density lipoprotein cholesterol, fasting plasma glucose, systolic blood pressure, heart rate, dual-energy Xray absorptiometry measured total fat mass and lean mass, ActiGraph measured moderate to vigorous physical activity at 15.5 years, smoking status, and family history of cardiovascular and metabolic diseases. Results Among 3862 adolescents (55.5% female), median (IQR) hsCRP values at 17.7 and 24.5 years were 0.56 (0.98) mg/L and 0.84 (1.62) mg/L, respectively. The median (IQR) cIMT values at 17.7 and 24.5 years were 0.48 (0.05) mm and 0.54 (0.09) mm, respectively. Higher hsCRP at age 17.7 years was associated with cIMT [Standardized β = 0.062, standard error = 0.004, p=0.035] at age 24.5 years. However, higher cIMT at age 17.7 years was not associated with higher hsCRP [β = −0.014, standard error = 0.284, p=0.523] at 24.5 years. Conclusion These findings in the largest adolescent population to date suggest that higher inflammation in adolescence temporally precede higher carotid thickness 7 years later and there was no bi-directional relationship. Clinical and public health interventions targeted at reducing low-grade inflammation to potentially attenuate the development of atherosclerotic cardiovascular disease in the young population are warranted. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Cultural Foundation

Frequency dependence of the ultrasonic power reflected from the water-tissue interface of human cancellous bone in vitro.

Numerous studies have performed in vitro ultrasonic measurements of cancellous bone in water to develop techniques for ultrasonic bone assessment. Because cancellous bone is a highly porous medium, ultrasonic reflections at the water-bone interface may be frequency dependent. The goal of this study was to investigate the effect of porosity on the frequency dependence of the reflected power. Ultrasonic measurements were performed in a water tank at room temperature on 15 specimens of cancellous bone prepared from the proximal end of 9 human femurs using single element, broadband transducers with center frequencies of 3.5, 5, 7.5, and 10 MHz. Power spectra of pulses reflected from the water-specimen interface were corrected for the frequency response of the measurement system to obtain the reflected power in decibels R^dB(f). To suppress random phase cancellation effects, R^dB(f) was averaged over multiple sites on multiple specimens. A frequency dependence of R^dB(f) was observed in the 2.6-10 MHz range. The frequency dependence was moderate, with a maximum change of less than 6 dB over the entire frequency range. R^dB(f) was greatest for low porosity specimens. The frequency averaged intensity reflection coefficient ranged from 7.4 × 10^-4 to 7.8 × 10^-3 for high and low porosity specimen groups, respectively.

Application of Koopman operator theory to the control of nonlinear bubble dynamics

Microbubbles are widely used in biomedicine for ultrasound contrast imaging and are a promising vehicle for targeted drug and gene delivery. The ability to control the oscillations of bubbles through the applied ultrasound can improve the effectiveness of these treatments, for example, by enhancing the acoustic echo or inciting bubble rupture at precise locations. Koopman operator theory has gained interest in the past decade as a framework for rigorously transforming nonlinear dynamics on the state space into linear dynamics on abstract function spaces, which preserves the underlying nonlinear dynamics of the system. These spaces can be approximated purely through machine learning and data-driven methodologies, which then enables the application of classical linear control strategies to strongly nonlinear systems. Here, we use a Koopman linear quadratic regulator (LQR) to control the nonlinear dynamics of spherical bubbles, as described by the well-known Rayleigh-Plesset equation, with two novel objectives: (1) stabilization of the bubble at a nonequilibrium radius and (2) simple harmonic oscillation at amplitudes large enough to incite nonlinearities. Control is implemented through both broadband and single-frequency transducers that are modulated by the Koopman LQR controller. We repeat these results using Koopman model predictive control (MPC), which allows for the implementation of constraints. This work is a step towards controlling nonspherical shape modes of encapsulated microbubbles.

Two-dimensional mapping of the ultrasonic attenuation and speed of sound in brain

Brain is inhomogeneous due to its composition of different tissue types (gray and white matter), anatomical structures (e.g. thalamus and cerebellum), and cavities in the brain (ventricles). These inhomogeneities lead to spatial variations in the ultrasonic properties of the organ. The goal of this study is to characterize the spatial variation of the speed of ultrasound and frequency slope of attenuation in fixed sheep brain. 1-cm-thick slices of tissue from the coronal, sagittal and transverse cardinal planes were prepared from 12 brains. Ultrasonic measurements were performed using broadband transducers with center frequencies of 3.5, 5.0, 7.5 and 10 MHz. By mechanically scanning the transducers over the specimens, two-dimensional maps of the speed of sound (SOS) and frequency slope of attenuation (FSA) were produced. Measured values for the spatial mean and standard deviation of FSA ranged between 0.59 and 0.81 dB/cm·MHz and 0.29–0.60 dB/cm·MHz, respectively, depending on the specimen and transducer frequency. Measured values for the spatial mean and standard deviation of SOS ranged from 1532–1541 m/s and 10–14 m/s, respectively. Detailed, two-dimensional maps of FSA and SOS were produced, representing the first such characterization of the spatial variation of the ultrasonic properties of normal mammalian brain.

Evaluating the Frequency of Infertility in Retroverted Versus Anteverted Uterus Using Ultrasound

Aim: To evaluate the frequency of infertility in retroverted versus anteverted uterus using ultrasound. Methods: The descriptive cross-sectional study was performed in total number of 380 patients using non-probability sampling technique. The study was conducted in the Department of Radiology, Tahir Medical Complex, Haroonabad in 6 months of duration. Married women of all age groups with anteverted and retroverted uterus were included in this study while all unmarried females were excluded from this study. The ultrasound was performed using VOLISON 730 with 3.5 MHz linear array broadband transducer on grayscale while patient positioning was supine. Results: Total 386 woman were enrolled and the mean age of the patient was 25 years with a range of 21-30±3.26 years. Out of 386 woman anteverted uterus was found in 134(34.7%) and anteflexed uterus was found in 2(0.5%). On the other hand, retroverted uterus was found in 86(22.3%) women and retroflex uterus was found and none of the women. Among 386 women, 142(36.8%) were nulliparous (P0), 107(27.7%) were primiparas (P1), 108(28%) were multiparas (P2) and 29(7.5%) were grand multiparas (P3). Primary fertility was diagnosed in 142(36.8%) women while secondary infertility was diagnosed in 244(63.2%). Conclusion: Secondary infertility was seen more frequently in anteverted uterus as compared with retroverted uterus. Keywords: Infertility, Ultrasound, Uterus.