Ultrasound Sensor Research Articles

Multimodal photoacoustic and optical coherence tomography scanner using an all optical detection scheme for 3D morphological skin imaging

A noninvasive, multimodal photoacoustic and optical coherence tomography (PAT/OCT) scanner for three-dimensional in vivo (3D) skin imaging is described. The system employs an integrated, all optical detection scheme for both modalities in backward mode utilizing a shared 2D optical scanner with a field-of-view of ~13 × 13 mm2. The photoacoustic waves were detected using a Fabry Perot polymer film ultrasound sensor placed on the surface of the skin. The sensor is transparent in the spectral range 590-1200 nm. This permits the photoacoustic excitation beam (670-680 nm) and the OCT probe beam (1050 nm) to be transmitted through the sensor head and into the underlying tissue thus providing a backward mode imaging configuration. The respective OCT and PAT axial resolutions were 8 and 20 µm and the lateral resolutions were 18 and 50-100 µm. The system provides greater penetration depth than previous combined PA/OCT devices due to the longer wavelength of the OCT beam (1050 nm rather than 829-870 nm) and by operating in the tomographic rather than the optical resolution mode of photoacoustic imaging. Three-dimensional in vivo images of the vasculature and the surrounding tissue micro-morphology in murine and human skin were acquired. These studies demonstrated the complementary contrast and tissue information provided by each modality for high-resolution 3D imaging of vascular structures to depths of up to 5 mm. Potential applications include characterizing skin conditions such as tumors, vascular lesions, soft tissue damage such as burns and wounds, inflammatory conditions such as dermatitis and other superficial tissue abnormalities.

Iterative motion compensation algorithm for heart rate detection with ultrasound data.

Noncontact active ultrasound sensors can be used to detect human physiological signals such as respiration and heart rate using Doppler processing. Target motion such as a person swaying can reduce the performance of these algorithms. To mitigate the effect of target motion or respiration on estimating the heart rate, we developed an iterative motion compensation algorithm. We low pass filter the demodulated data, estimate the motion of the target, and then compensate the data for the slow moving motion. This procedure can be repeated at different cutoff frequencies for different scenarios. Now, standard Doppler processing techniques can be used to analyze the motion compensated data. The algorithm was tested on people standing in a laboratory illuminated with a 40-KHz continuous-wave ultrasound sensor. Results for estimating the respiration rate and heart rate will be presented.

Passive mapping for imaging thermal lesions in tissue.

Passive acoustic mapping, a method of mapping sources of high‐frequency ultrasound emissions during focused ultrasound treatment, has been tested in ex vivo ox liver. The method uses an array of ultrasound sensors placed coaxially with a focused therapeutic ultrasound transducer. The ultrasound emissions received during treatment are first filtered and then beamformed to produce reconstructions of either broadband or harmonic source intensity within the tissue during the application of focused ultrasound. At pressure amplitudes in excess of the inertial cavitation threshold, passive mapping of broadband emissions is found to provide a good indication of the location and size of the lesion, while mapping of harmonic emissions adequately describes the location and onset of boiling. The results for different treatment parameters across several liver samples will be presented. Alternative methods of postprocessing the passively received data for improved spatiotemperoral resolution and signal‐to‐noise ratio will also be introduced and compared. These methods are being developed to characterize cavitation activity in order to give estimates of cavitation energy, tissue heating, and temperature during therapeutic ultrasound exposures, to ultimately enable prediction of cell death during treatment.

Inline Analyzing of Industrial Crystallization Processes by an Innovative Ultrasonic Probe Technique

AbstractThe mean particle size and suspension density of industrial ammonium sulfate and urea crystals were measured by a single ultrasound sensor in a saturated solution at only one frequency. The information on ultrasound velocity and attenuation were combined and related to characteristic properties of the solid phase of suspensions. By model identification, a correlation between the measured signals and mean particle size as well as suspension density were evaluated and verified by additional experiments. The measurements with different particle size fractions and different suspension densities up to 40 wt‐% were carried out isothermally. The approach of coupled ultrasound velocity and attenuation provides a simple technique for inline process control on the liquid and solid state of a suspension process like solution crystallization only by a single measurement device.

On coverage issues in directional sensor networks: A survey

The coverage optimization problem has been examined thoroughly for omni-directional sensor networks in the past decades. However, the coverage problem in directional sensor networks (DSN) has newly taken attraction, especially with the increasing number of wireless multimedia sensor network (WMSN) applications. Directional sensor nodes equipped with ultrasound, infrared, and video sensors differ from traditional omni-directional sensor nodes with their unique characteristics, such as angle of view, working direction, and line of sight (LoS) properties. Therefore, DSN applications require specific solutions and techniques for coverage enhancement. In this survey article, we mainly aim at categorizing available coverage optimization solutions and survey their problem definitions, assumptions, contributions, complexities and performance results. We categorize available studies about coverage enhancement into four categories. Target-based coverage enhancement, area-based coverage enhancement, coverage enhancement with guaranteed connectivity, and network lifetime prolonging. We define sensing models, design issues and challenges for directional sensor networks and describe their (dis)similarities to omni-directional sensor networks. We also give some information on the physical capabilities of directional sensors available on the market. Moreover, we specify the (dis)advantages of motility and mobility in terms of the coverage and network lifetime of DSNs.

Ultrasound transducers based on ferroelectret materials

Ferroelectret materials can be utilized to set up electroacoustic transducers. The materials offer both, a rather large bandwidth and a high piezoelectric strain constant. Due to its cellular structure, the material is flexible and exhibits an excellent matching to air. Therefore, this polymer is appropriate for many sound as well as ultrasound transducer applications. Our research is concentrated on the simulation based design and characterization of ultrasound transducers. In this contribution, we present a finite element based modeling of the cellular structured ferroelectret materials. In particular, a microscopic as well as a macroscopic model is discussed. We fabricate single element and array transducers based on ferroelectret materials, namely the so-called EMFi (Electro- Mechanical-Film) material. To show the applicability of ferroelectret materials for ultrasound transducers, different applications in air and water are presented. An emitter-receiver-unit is introduced which is utilized in an artificial bat head and allows the functional reproduction of the biosonar system found in bats. Moreover, a robust sensor array consisting of 16 single elements (4x4) is studied. With the aid of this sensor array, cavitation effects in ultrasonic cleaning systems can be investigated on the specimen's surface, which is not possible with common ultrasound sensors, e.g., hydrophones.

Development of Fall Detection System Using Ultrasound Sensors

This paper proposes a sensing system for detecting bather's fall. The fall detection system uses ultrasound sensors installed on the ceiling of bathroom to measure the distance between sensor and a bather. The merits of utilizing ultrasound sensor are easy installation and easy use. Moreover the apparatus has an advantage of enhancing the privacy of bathers and having robustness against humidity. In order to detect bather's fall, the proposed system uses the following two methods: status detection and behavior detection. The function of status detection is to estimate bather's postures such as standing and sitting by monitoring the highest part of bather's body. Meanwhile, the function of behavior detection is to grasp the speed of bather's vertical movement by monitoring the change of distance between sensor and the bather. The system estimates the occurrence of bather's fall when the distance changes suddenly. As a result of experiment with some subjects, the system was possible to detect bather's falling behavior with high accuracy.

Broadband optical ultrasound sensor with a unique open-cavity structure

High-resolution ultrasound imaging requires quality sensors with wide bandwidth and high sensitivity, as shown in a wide range of applications, including intravascular imaging of cardiovascular diseases. However, piezoelectric technology, the current dominant approach for hydrophone fabrication, has encountered many technical limitations in the high-frequency range. Using optical techniques for the detection of high-frequency ultrasound signals has attracted much recent attention. One of the most studied approaches is based on a Fabry-Pérot interferometer, consisting of an optical cavity sandwiched between two mirrors. This technique offers promising sensitivity and bandwidth, and a potential alternative to piezoelectric polyvinylidene fluoride (PVDF) hydrophones. We propose an innovative optical ultrasound sensor using only a single mirror in a total-internal-reflection configuration. Besides retaining the advantages of Fabry-Pérot interferometer-based ultrasound sensors, this unique design provides a bandwidth of at least 160 MHz, a potential decrease in fabrication cost, and an increase in signal fidelity.

Performance testing of collision-avoidance system for power wheelchairs

The Drive-Safe System (DSS) is a collision-avoidance system for power wheelchairs designed to support people with mobility impairments who also have visual, upper-limb, or cognitive impairments. The DSS uses a distributed approach to provide an add-on, shared-control, navigation-assistance solution. In this project, the DSS was tested for engineering goals such as sensor coverage, maximum safe speed, maximum detection distance, and power consumption while the wheelchair was stationary or driven by an investigator. Results indicate that the DSS provided uniform, reliable sensor coverage around the wheelchair; detected obstacles as small as 3.2 mm at distances of at least 1.6 m; and attained a maximum safe speed of 4.2 km/h. The DSS can drive reliably as close as 15.2 cm from a wall, traverse doorways as narrow as 81.3 cm without interrupting forward movement, and reduce wheelchair battery life by only 3%. These results have implications for a practical system to support safe, independent mobility for veterans who acquire multiple disabilities during Active Duty or later in life. These tests indicate that a system utilizing relatively low cost ultrasound, infrared, and force sensors can effectively detect obstacles in the vicinity of a wheelchair.

Transradial Prosthesis: Artificial Vision for Control of Prehension

We present a practical system for controlling the prehension of a transradial prosthesis. The system is mounted on the artificial hand and comprises simple hardware and software that are convenient for real-time implementation. The hardware consists of a standard web camera and an ultrasound distance sensor. The control algorithm mimics biological mechanisms for the control of grasping and uses the measured distance to the target object and the method of computer vision to estimate the object's size and orientation. Based on these estimates, the algorithm outputs the following commands for the control of prehension: (i) the type of grasp and the aperture size appropriate for the target object; and (ii) the angle through which the wrist should be rotated (pronation/supination) in order to properly position the hand for the grasp. We have tested the system's performance with different targets (planar geometric shapes, real-life objects) under static conditions (i.e., when the system is stationary) and dynamic conditions (i.e., when the system moves toward the target). The size estimation was more accurate in the static experiments (error < 36%). Importantly, the system showed to be very robust with respect to the estimation errors, and the correct control commands were generated in most of the tested cases. The presented system is only one component of the hand controller, related strictly to the prehension phase of grasping. The final solution is envisioned as a combination of the presented system, inertial sensors (hand orientation), and a myoelectric control (triggering).

Design and Testing of an Ultrasound System for Targeted Spraying in Orchards

The research aims to demonstrate the basic system elements of a prototype automated orchard sprayer, which can deliver pesticide spray selectively with respect to the characteristics of the targets. The contour of the apple tree canopy was detected by ultra sound sensors Prowave 400EP14D and appropriate electronics. Ultra sound signal was processed by a personal computer and fed in real-time to spraying nozzles which open and close in relation to the canopy structure. The current project focuses on developing the system components for spraying an individual tree. The evaluation was performed in field experiments by detecting deposits on leaves and water sensitive papers (WSP). The demonstrated concept of precise application of pesticide sprays supports a decrease in the amount of delivered spray, thereby reducing both costs and environmental pollution by plant protection products.

Possibility of Using Acoustic Techniques for Dough Processing Evaluation

Ultrasonic techniques have become developed and are widely used in many various fields of engineering and basic science. The development and optimization of industrial food processes requires a modern rapid non-destructive measuring technique for giving information about the useful fundamental and empirical properties of the product. This information provide better understanding of the processes that will consistently ensure a predefined quality at the end of manufacturing process therefore, led the industry to improve their conformity with manufacturing regulation. In this work, the developed non-invasive system showed the possibility of calculating the solid/non-solid density of dough, void fraction and complex moduli in dough, based on a two layer neural network that combine the acoustics impedance and energy of an ultrasonic signals passing through the dough specimens. A system of a low frequency ultrasound sensor devoted to this study for characterization of wheat flour–water system. The ultrasonic velocity measurements and attenuation was linearly related to the water contents of the tested dough samples. Several numerical models were constructed to test and validate the ultrasonic-velocity measurement system. The test and validation showed agreements with the achieved results with 1.88%.maximum error in the ultrasonic-velocity.

Daylight integrated illumination control of LED systems based on enhanced presence sensing

Light emitting diodes (LEDs) are considered to become the dominant source of illumination in the future, offering long life times, energy efficiency and flexible tunability. The flexibility of adapting LED parameters offers multiple degrees of freedom in designing LED based lighting systems. In this paper, we consider energy-efficient illumination control design of LED based lighting systems in office spaces. Our goal is to determine the optimum dimming levels of the LED sources so as to minimize the power consumption while rendering (i) uniform illumination at a given illumination level in workspace regions that are occupied, and (ii) a minimum illumination level of lower value in unoccupied regions, while taking daylight distribution over the workspace plane into account. In order to determine occupant locations, we present an ultrasound array sensor solution with enhanced presence detection capability. We further propose a method to estimate and disaggregate illumination contributions of daylight and the different LED sources at the workspace plane. The performance of our proposed control solution is evaluated under different occupancy scenarios.

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.

Ultrasonic Sensitivity of Strain-Insensitive Fiber Bragg Grating Sensors and Evaluation of Ultrasound-Induced Strain

In conventional ultrasound detection in structures, a fiber Bragg grating (FBG) is glued on or embedded in the structure. However, application of strain to the structure can influence the sensitivity of the FBG toward ultrasound and can prevent its effective detection. An FBG can work as a strain-insensitive ultrasound sensor when it is not directly glued to the monitored structure, but is instead applied to a small thin plate to form a mobile sensor. Another possible configuration is to affix an FBG-inscribed optical fiber without the grating section attached to the monitored structure. In the present study, sensitivity to ultrasound propagated through an aluminum plate was compared for a strain-insensitive FBG sensor and an FBG sensor installed in a conventional manner. Strains induced by ultrasound from a piezoelectric transducer and by quasi-acoustic emission of a pencil lead break were also quantitatively evaluated from the response amplitude of the FBG sensor. Experimental results showed that the reduction in the signal-to-noise ratio for ultrasound detection with strain-insensitive FBG sensors, relative to traditionally-installed FBG sensors, was only 6 dB, and the ultrasound-induced strain varied within a range of sub-micron strains.

Measurement of melanoma thickness – comparison of two methods: Ultrasound versus morphology

The aim of our study was to investigate the association between non-invasive ultrasound examination and morphologic test results in the measurement of cutaneous melanoma thickness influencing surgical treatment strategy. Our prospective clinical study has been conducted in the Clinic of Plastic and Reconstructive Surgery of Kaunas University of Medicine Hospital (KUMH) since January 2004 until October 2008. A total of 100 patients with a clear clinical diagnosis of stage I-II cutaneous melanoma were enrolled in this study. Melanoma depth was measured using a linear 14-MHz frequency ultrasound sensor (Toshiba Xario XG). Surgically removed fragments of skin-subcutaneous tissue were fixated using 10% formalin solution in the operating theatre, and sent to KUMH Clinic of Pathological Anatomy. The most informative sections were analysed for tumour thickness, according to Breslow, as well as tumour type, vascular and lymphatic invasion and dissemination. A comparative data analysis of melanoma thickness measured by ultrasound (T) preoperatively and histologically estimated cutaneous melanoma (CM) thickness according to Breslow (pT) using the Bland-Altman method was performed. Higher mean difference of melanoma thickness (60 μm) between T and pT measurements was found when tumour thickness matched pT1 and pT2 categories. In cases of CM depth exceeding 2mm, mean difference of measurements between CM thickness determined by ultrasound and histological examination was lower (30 μm). Data regression analysis showed that correlation between T and pT measurements was lower when CM was thinner (1-2 mm) (Pearson's correlation coefficient, r: 0.283). In cases of thicker melanoma (>2 mm), strong and statistically significant (p<0.0001) correlation (r: 0.869) was observed. Correlation between melanoma thickness measured using a linear 14-MHz frequency ultrasound sensor and histologically estimated melanoma thickness according to Breslow was lower if melanoma was thinner (1-2 mm). However, in cases of thicker melanoma (>2 mm), very strong correlation between measurements was observed.

Research of Deformation Process Control of Generator’s Retaining Rings on Hydraulic Bulging Strengthening Technology

The hydraulic bulging strengthening technology is a kind of strengthening technology of large generator’s retaining ring. In the right punch working angle and sealing pressure of equipment, the ring billet is deformed uniformly by high pressure water. The experiment in 5MN oil-hydraulic machine proves that the ring billet is deformed uniformly while the punch working angle is 60° and the pressure between the punch and the rings is 1MN. When the internal and external diameter deformation of the ring billet is 8.5% and 14.0%, the external generatrices of the ring are nearly line. The ring billet is 1/5 of 300MW18-18 steel retaining ring. It may improve productivity to measure real-time thickness of the ring billet with ultrasound sensors and control pressure of the oil-hydraulic machine and ultra-high pressure pump with 80c51.

MiroSurge—Advanced User Interaction Modalities in Minimally Invasive Robotic Surgery

This paper presents MiroSurge, a telepresence system for minimally invasive surgery developed at the German Aerospace Center (DLR), and introduces MiroSurge's new user interaction modalities: (1) haptic feedback with software-based preservation of the fulcrum point, (2) an ultrasound-based approach to the quasi-tactile detection of pulsating vessels, and (3) a contact-free interface between surgeon and telesurgery system, where stereo vision is augmented with force vectors at the tool tip. All interaction modalities aim to increase the user's perception beyond stereo imaging by either augmenting the images or by using haptic interfaces. MiroSurge currently provides surgeons with two different interfaces. The first option, bimanual haptic interaction with force and partial tactile feedback, allows for direct perception of the remote environment. Alternatively, users can choose to control the surgical instruments by optically tracked forceps held in their hands. Force feedback is then provided in augmented stereo images by constantly updated force vectors displayed at the centers of the teleoperated instruments, regardless of the instruments' position within the video image. To determine the centerpoints of the instruments, artificial markers are attached and optically tracked. A new approach to detecting pulsating vessels beneath covering tissue with an omnidirectional ultrasound Doppler sensor is presented. The measurement results are computed and can be provided acoustically (by displaying the typical Doppler sound), optically (by augmenting the endoscopic video stream), or kinesthetically (by a gentle twitching of the haptic input devices). The control structure preserves the fulcrum point in minimally invasive surgery and user commands are followed by the surgical instrument. Haptic feedback allows the user to distinguish between interaction with soft and hard environments. The paper includes technical evaluations of the features presented, as well as an overview of the system integration of MiroSurge.

Design and Experiment Research of a Non-Contact Optical Fiber F-P Ultrasound Sensor for Detecting Surface Defects

Laser ultrasound technology has many advantages such as being non-contact, nondestructive, fast, accurate and low cost. Therefore it is usually used as an effective way to detect and characterize small surface or subsurface breaking cracks. The optical fiber F-P sensor is adapted to laser ultrasound detection field because it can detect ultrasound signals non-contact. But the optical fiber F-P sensor deviates from working point easily because of machining error and external factors in practical applications. It leads to output signal attenuation and the decreasing of signal noise ratio. On this problem, an optical fiber F-P sensing system based on two wavelength quadrature-shifted demodulation technique is designed. The mathematical model of sensing system is established. Differential Evolution Algorithm is introduced to establish the optimal model of sensing system for the first time. The structure of sensing system is optimized designed. The non-contact laser ultrasound experimental devices based on optical fiber F-P senor are established for detecting surface defects. The experimental results show this sensor can detect surface defects effectively. It has higher sensitivity and larger signal-to-noise ratio.

12b 50 MS/s 0.18 µm CMOS ADC with highly linear input variable gain amplifier

A 12b 50 MS/s 0.18 µm CMOS ADC with a highly linear variable gain amplifier (VGA) for medical ultrasound and CCD image sensor applications is presented. The proposed four-step pipeline ADC optimises power and chip area at target specifications while the front-end VGA, based on a conventional approximated log function, employs a merged capacitor switching scheme to improve the VGA gain linearity. The proposed input VGA shows a linearity error less than 0.013 dB in a gain range from −3 to 0 dB by a 0.2 dB step. The measured prototype ADC with an active die area of 1.09 mm2 shows a maximum SNDR and SFDR of 62.6 and 73.1 dB, respectively, and consumes 28.1 mW at 1.8 V and 50 MS/s.