Ultrasound Reflection Research Articles

Press-fit joints study by multiangle ultrasonic sounding method

In the article the authors consider the problem and the way of press-fit joints quality quantitative estimation with an ultrasonic echo-impulse method. It is shown that the reflection coefficient is the general characteristics of press-fit joint quality rather its load carrying capacity defined by the maximum rotation moment transmitted by the press-fit joint, because it is bound with the normal stresses appearing on the joint surfaces. The equation for calculation of the coefficient of ultrasound reflection from the interference area of a joint by echo-impulse amplitudes measured from the quill cylinder and from a joint is received. Peculiarities of the research procedure are accentuated and described. The peculiarities allow receiving exact estimation of press-fit joints quality by a non-destructive method either on the localized areas of the interference or the estimation of an averaged value around the joint during multiangle study of the object on different directions in the definite ultrasonic sounding plane. Special attention is paid by the authors to the possibility and practicability of automation of the process of control on the basis of the multiangle ultrasonic sounding method in order to improve the joint quality studying process.

A Bilateral Constrained Image Reconstruction Method Using Electrical Impedance Tomography and Ultrasonic Measurement

Electrical Impedance Tomography (EIT) reconstructs the conductivity distribution in a sensing area through an array of boundary electrodes and has received increasing attention in bio-impedance measurement. To provide accurate image reconstruction of irregular conductivity distribution in large sensing area, we propose an efficient and accurate bilateral constrained dual modality reconstruction algorithm using EIT and ultrasonic measurement, where the EIT pre-reconstruction helps to select the time of flight (TOF) time window and the ultrasound reflection information of boundary points contributes to joint iterative reconstruction. In the simulations and phantom experiments selecting abdomen tumor as the object of interest, the proposed method successfully reconstructed the small inclusions. Quantitatively, the proposed bilateral constrained method has improved the reconstruction performance in terms of boundary preservation and robustness compared with single modality EIT and ultrasonic algorithms.

Discrimination of thoracic spine from muscle based on their difference in ultrasound reflection and scattering characteristics

Medical ultrasound is often used to specify the puncture position during epidural anesthesia. However, visualization of the thoracic spine is difficult because of the complex structure, i.e., it is difficult to determine whether the thoracic spine or muscle is depicted. Therefore, this study aims to distinguish bone from muscle tissue using the differences in reflection and scattering characteristics of ultrasound. We experimentally investigated the difference in signals received from bone and muscle. We proposed a new parameter utilizing the ratio of the amplitude of the received signals averaged in a wide range around the ideal delay line and that only along the ideal delay line, to emphasize the bone. First, we confirmed the difference in signals received from bone and muscle tissue by basic experiments. We also investigated the difference by in vitro experiments using chicken thigh and in vivo experiments in humans. In both experiments, the proposed method succeeded to clearly depict bone, suppressing the depiction of muscle, compared with conventional B-mode imaging. Using the difference in the characteristics of reflection from bone and scattering from muscle tissue, we could distinguish bone from muscle tissue with the proposed method.

Electrical resonance/antiresonance characterization of NDT transducer and possible optimization of impulse excitation signals width and their types

This work presents an experimental method for obtaining the best excitation pulse type and width for optimal driving of an industrial non-destructive testing (NDT) ultrasound transducer by using its electrical impedance parameters as input. Within the optimization method, a classic low-voltage frequency sweeping signal and two different types of high-voltage impulse excitation signals (unipolar and bipolar), with different pulse widths, are used for the electromechanical characterization of the transducer. The optimization of the excitation signal is verified by measuring the voltage, current and electrical power of the excitation and received signals obtained by ultrasound pulse reflection from two cracks (2 mm and 3 mm) in a stainless-steel block. Additionally, the influence of the output electrical impedance of the power amplifier on the optimal transfer of electrical power from the amplifier to the loading (the NDT transducer on the block) and vice versa is also discussed in this work. The optimum working point for the ultrasound NDT transducer, regarding the impulse excitation type and its pulse width, is a bipolar impulse excitation with the width and amplitude calculated from maximum values of the measured voltage, electric current and power generated in the transducer receive mode by the reflected ultrasound signals.

A Lagrange-Newton Method for EIT/UT Dual-Modality Image Reconstruction.

An image reconstruction method is proposed based on Lagrange-Newton method for electrical impedance tomography (EIT) and ultrasound tomography (UT) dual-modality imaging. Since the change in conductivity distribution is usually accompanied with the change in acoustic impedance distribution, the reconstruction targets of EIT and UT are unified to the conductivity difference using the same mesh model. Some background medium distribution information obtained from ultrasound transmission and reflection measurements can be used to construct a hard constraint about the conductivity difference distribution. Then, the EIT/UT dual-modality inverse problem is constructed by an equality constraint equation, and the Lagrange multiplier method combining Newton-Raphson iteration is used to solve the EIT/UT dual-modality inverse problem. The numerical and experimental results show that the proposed dual-modality image reconstruction method has a better performance than the single-modality EIT method and is more robust to the measurement noise.

ABSCESO DEL PSOAS PEDIÁTRICO, MANEJO CONSERVADOR: REPORTE DE CASO


 
 
 El absceso del psoas es una entidad clínica rara, de difícil diagnóstico en edad pediátrica, con presentación ambigua, retrasando así el diagnós- tico y tratamiento. Pueden ser primarios o secundarios, siendo los primarios unilaterales en el 98%, alrededor del 70% de los casos se han reportado en el grupo de edad de 10-17 años, 75% en el sexo masculino. Únicamente en 20% de los casos se identifica el factor causal. Con incidencia anual de doce en países desarrollados. Se presenta caso de masculino de 15 años, procedente de Juticalpa Olancho, con anteceden- te de apendicectomía hace 10 años, inicia con dolor abdominal de 22 días de evolución, localizado en hipocondrio derecho, de intensidad progresiva. Posteriormente, claudicación y fiebre, fue llevado a clínica privada y manejado con analgésico sin mejoría. Evaluado nuevamente en clínica privada donde indican realizar ultrasonido abdominal que reporto masa heterogénea en corredera paracólica derecha, considerar absceso del psoas y referencia a Hospital Materno Infantil, Tegucigalpa. Al ingreso febril, con dolor a la palpación profunda en hipocondrio derecho y dificultad de extender miembro inferior derecho por dolor. Los exámenes laboratoriales eran compatibles con proceso infeccioso y el USG abdominal confirmó el diagnostico. Con evolución clínica satisfactoria y ultrasonido control reflejo reducción de la colección a 9ml por lo que se omitió la TAC.
 Palabras clave
 Absceso del Psoas, Dolor Abdominal, Leucocitosis, Diagnóstico por Imagen, Claudicación Intermitente
 
 

Role of modern imaging techniques for the in vivo diagnosis of lichen planus.

Lichen planus (LP) is a chronic inflammatory skin disease that can sometimes affect mucosal surfaces, with unknown pathogenesis, even though it appears to be an autoimmune disease. The diagnosis of lichen planus is usually based on histopathological examination of the lesions. Nowadays, the classical invasive diagnostic methods are replaced by modern non-invasive techniques. In this review, we present the main non-invasive imaging methods (dermoscopy, reflectance confocal microscopy, optical coherence tomography, ultrasound and diffuse reflection spectrophotometry) used in the diagnosis and therapeutic monitoring of lichen planus. Dermoscopy is a non-invasive method initially used for diagnosis of pigmented tumors but now is used also for inflammatory and infectious skin diseases. In lichen planus, the dermoscopy increases the accuracy of diagnosis, avoids skin biopsies commonly used and can be useful in the therapeutic monitoring by repeated investigation at different stages of treatment. Reflectance confocal microscopy (RCM) is a novel non-invasive imaging technique that is prevalently used for the diagnosis of skin tumors and inflammatory skin diseases. This technology has been mostly employed for bedside, real-time microscopic evaluation of psoriasis, lichen planus, contact dermatitis, revealing specific confocal features to support clinical diagnosis and assist with patient management. Optical coherence tomography (OCT) is an emergent imaging technique, developed over the last decade, based on the interaction of the infrared radiation (900–1,500 nm) and the living tissues. A limited information exists on the benefits of OCT technology for the in vivo diagnosis of LP but could be a useful auxiliary tool in the in vivo differential diagnosis, especially in clinical equivocal settings like mucosal lesions, and in monitoring the response to treatment. Our review shows the possibility of using modern imaging techniques for the in vivo diagnosis and also for evaluation of the treatment response.

A fast method for simulating ultrasound image from patient-specific CT data

Abstract Introduction and problem statement Ultrasound imaging is one of the most preferred modalities for image-guided procedures owing to its low-cost, non-ionizing nature, and real-time capability. However, its interpretation is complex, and hence considerable research has gone into developing methods that can help improve the interpretation of ultrasound images. One such solution is to use ultrasound simulation tools that can generate patient-specific ultrasound images from image data obtained from other modalities during pre-planning stage. Use of such tools can aid the user to have enough practice before the actual image-guided procedure. In this regard, ultrasound simulation from CT data has gained much interest over the past few years. Methodology One of the most recent ways of simulating ultrasound images from CT is to combine the ultrasound echo reflection image, the transmission intensity map, and the scatter image of the region of interest from the CT image. However, the scatter image is simulated using Field II program, which is computationally very intensive. In this paper, we propose combining the traditional convolution method for scatter map generation along with ray tracing approaches to simulate an ultrasound image. The methodology is tested on CT data from Visible Human Project (VHP) in simulations and validated on multi-modality tissue-mimicking phantom in vitro. Simulation is done for a curvilinear array transducer at 2.5 MHz frequency and an imaging depth of 180 mm. Results and conclusion The results obtained from simulation suggests that using convolution method reduces the computation time significantly, from almost 2.4 h to about 17 s for a chosen region of interest in VHP data of dimensions 180 mm x 60 mm x 1 mm without affecting the image quality. In case of in-vitro phantom, the computation time is reduced from almost 3 h to about 10 s for a chosen region of interest of dimensions 180 mm x 60 mm x 1.25 mm. Thus, convolution method may be preferred over Field II for generating ultrasound scatter image since the method provides a comparable image to that of real-time images, but takes only significantly less computation time.

To local reconstruction from the spherical mean Radon transform

The article suggests a new approach using the so-called consistency method for the inversion of the spherical mean Radon transform in 2D with detectors on a line. We present a new iterative formula which gives an algorithm to recover an unknown function supported completely on one side of a line L from its spherical means over circles centered on the line L. Our reconstruction formula has the benefit of being local. Such an inversion is required in problems of thermo- and photo-acoustic tomography, ultrasound reflection tomography, radar imaging, and a few other.

An augmented Lagrangian trust region method for inclusion boundary reconstruction using ultrasound/electrical dual-modality tomography

The ultrasound/electrical dual-modality tomography utilizes the complementarity of ultrasound reflection tomography (URT) and electrical impedance tomography (EIT) to improve the speed and accuracy of image reconstruction. Due to its advantages of no-invasive, no-radiation and low-cost, ultrasound/electrical dual-modality tomography has attracted much attention in the field of dual-modality imaging and has many potential applications in industrial and biomedical imaging. However, the data fusion of URT and EIT is difficult due to their different theoretical foundations and measurement principles. The most commonly used data fusion strategy in ultrasound/electrical dual-modality tomography is incorporating the structured information extracted from the URT into the EIT image reconstruction process through a pixel-based constraint. Due to the inherent non-linearity and ill-posedness of EIT, the reconstructed images from the strategy suffer from the low resolution, especially at the boundary of the observed inclusions. To improve this condition, an augmented Lagrangian trust region method is proposed to directly reconstruct the shapes of the inclusions from the ultrasound/electrical dual-modality measurements. In the proposed method, the shape of the target inclusion is parameterized by a radial shape model whose coefficients are used as the shape parameters. Then, the dual-modality shape inversion problem is formulated by an energy minimization problem in which the energy function derived from EIT is constrained by an ultrasound measurements model through an equality constraint equation. Finally, the optimal shape parameters associated with the optimal inclusion shape guesses are determined by minimizing the constrained cost function using the augmented Lagrangian trust region method. To evaluate the proposed method, numerical tests are carried out. Compared with single modality EIT, the proposed dual-modality inclusion boundary reconstruction method has a higher accuracy and is more robust to the measurement noise.

Multimodal ultrasound computer-assisted tomography: An approach to the recognition of breast lesions

The research here presented aims at developing a new, promising method for the imaging diagnostics of breast lesions – ultrasound tomography (UST). A currently implemented device enables the reconstruction three complementary images for each coronal breast section. Based on in vivo breast examination, the authors developed an approach to breast diagnostics which employs ultrasound transmission and reflection tomography imaging. The obtained transmission images of ultrasound speed distribution show good correlation of glandular tissue areas with their visualization on MRI images. The results also allow a prediction that the implemented UST device offering fusion of reconstructed images may contribute to achieving a new standard for breast cancer diagnostics through non-invasive, fast and cheap screening tests.

A Marchenko equation for acoustic inverse source problems.

From acoustics to medical imaging and seismology, one strives to make inferences about the structure of complex media from acoustic wave observations. This study proposes a solution that is derived from the multidimensional Marchenko equation, to learn about the acoustic source distribution inside a volume, given a set of observations outside the volume. Traditionally, this problem has been solved by backpropagation of the recorded signals. However, to achieve accurate results through backpropagation, a detailed model of the medium should be known and observations should be collected along a boundary that completely encloses the volume of excitation. In practice, these requirements are often not fulfilled and artifacts can emerge, especially in the presence of strong contrasts in the medium. On the contrary, the proposed methodology can be applied with a single observation boundary only, without the need of a detailed model. In order to achieve this, additional multi-offset ultrasound reflection data must be acquired at the observation boundary. The methodology is illustrated with one-dimensional synthetics of a photoacoustic imaging experiment. A distribution of simultaneously acting sources is recovered in the presence of sharp density perturbations both below and above the embedded sources, which result in significant scattering that complicates the use of conventional methods.

Dual modality electrical impedance and ultrasound reflection tomography to improve image quality

Abstract Electrical impedance tomography (EIT) is relatively new. It is a verypromising technique to be developed especially in the medical field. The advantages of EIT are that it is non-ionizing, simple, and portable and that it produces a high contrast image. Unfortunately, this modality does not have the capability to generate a highresolution image. Almost all imaging modalities has both advantages and disadvantages. Combining one modality with another is hence expected to cover the weaknesses of each other. The problem is how to develop the concepts, measurement systems and algorithm of dual modalities, particularly electrical and acoustical. The electrical modality can produce high contrast and the acoustical modality can produce high resolution. Combination of these will enhance the image resolution of EIT. High image resolution from the ultrasound reflection tomography is used as the prior information to improve the image resolution of the EIT. Finite Element Model (FEM) can be arranged by non-uniform elements, which are adapted to the boundary. Element models with higher density are arranged at the boundaries to obtain improvements of resolution and the model elements with lower density arranged at other locations to reduce the computational cost. The dual modality EIT with Ultrasound Reflection (EIT-UR) can produce high resolution and contrast image. The resolution improvement can also accelerate the convergence of the Newton-Raphson reconstruction methods.

Acoustic field structure simulation in quasi-collinear acousto-optic cells with ultrasound beam reflection

Ultrasound wave reflection from one of the crystal faces is the convenient way to arouse the acoustic beam with a desired propagation direction in acousto-optic cells with collinear and quasi-collinear interaction geometries. The reflection process effects on the ultrasound field amplitude and phase structure. The method to simulate the reflected finite ultrasound beam structure in the case of acoustically anisotropic media is presented in this paper. The investigation is carried on the example of two quasi-collinear acousto-optic cells fabricated on the base of tellurium dioxide crystal. The cells have special geometry that allows to obtain extremely long acousto-optic interaction length and to achieve unprecedented spectral resolution. The influence of reflection process in the acousto-optic diffraction characteristics was also examined.

A numerical study of ultrasonic response of random cortical bone plates

A probabilistic study on ultrasound wave reflection and transmission from cortical bone plates is proposed. The cortical bone is modeled by an anisotropic and heterogeneous elastic plate sandwiched between two fluids and has randomly varied elastic properties in the thickness direction. A parametric stochastic model is proposed to describe the elastic heterogeneity in the plate. Reflection and transmission coefficients are computed via the semi-analytical finite element (SAFE) method. The effect of material heterogeneity on reflected and transmitted waves is investigated from a probabilistic point of view. The parametric study highlights effects of the uncertainty of material properties on the reflection and transmission coefficients by varying the frequency, angle of incidence and bone thickness.

Ultrasonic nondestructive characterization of mortars by the width of the resonances

In this work, we study the width of the resonances of the ultrasound waves reflection coefficient backscattered by a plane structure of the mortar. We establish the relationship between this width with two parameters which are widely used in non-destructive characterization of cementitious materials namely the velocity and attenuation. Monitoring the hydration of three solutions of mortars produced with different sizes of sand grains shows that the experimental results confirmed the theoretical predictions. Linear correlations are established between the width of resonance and the two ultrasonic parameters.

An In Vitro Assay for Sonothrombolysis Based on the Spectrophotometric Measurement of Clot Thickness.

For improved thrombolysis therapy based on ultrasound irradiation, researchers and practitioners would strongly benefit from an easy and efficient in vitro assay system of thrombolysis activity involving irradiated ultrasound. For the present study, we designed a new in vitro sonothrombolysis assay system using a sheet-type clot. We designed a cell for clot assay, and we confirmed that this clot cell did not significantly intervene in the acoustic field. Using human plasma, we made a sheet-type clot in the cell. Clot thicknesses at 100 points along 4 directions were measured photometrically at a rate of approximately 4 points/s. The sonothrombolysis effects at 13 levels of ultrasonic intensity were obtained with only one sheet-type clot. With this method, we used a clinically oriented probe at 0.7 and 0.3 W/cm2 to confirm that sonothrombolysis took place. We successfully established a new, easy, and efficient method for conducting in vitro sonothrombolysis assays. This method involves little intervention of either ultrasound reflection or standing waves in the clot cell. We believe that this new assay method is very useful for fundamental analyses of ultrasound's thrombolysis effects.

Alternative methods to visual and radiographic examinations for approximal caries detection.

A shift in caries prevalence from occlusal surfaces to approximal surfaces has been demonstrated by epidemiological studies. Two recent meta-analyses evaluated the performance of visual examination and radiography for carious lesion detection, and reported low sensitivity but high specificity for early approximal caries detection. This suggests that the conventional methods have a higher risk of failing to detect approximal lesions. Consequently, in caries susceptible populations, there is a risk of progression of non-cavitated lesions to irreversible tooth destruction before the lesions are detected. This paper aims to review the performance of unconventional and novel methods for approximal caries detection. In vitro and in vivo studies identified through a MEDLINE search using keywords such as caries detection, approximal caries detection, light fluorescence and dental caries, and transillumination and dental caries were reviewed. The unconventional methods known to be used for approximal caries detection and included in this review are: cone beam computed tomography, fiber-optic trans-illumination, digital imaging fiber optic trans-illumination, near-infrared digital imaging transillumination, optical coherence tomography, laser fluorescence, ultrasound, and LED reflection and refraction.

Research on Mud Flow Rate Measurement Method Based on Continuous Doppler Ultrasonic Wave

In deep-water drilling processes, the flow rate of drilling mud inside an annular pipe is significant judgment data for early kick detection. On the basis of the continuous-wave Doppler ultrasound, this paper proposes a new detection method of nonoriented continuous-wave Doppler ultrasound. The method solves the problem of the ultrasound having great attenuation in mud and not receiving effective signals by using a continuous ultrasound. Moreover, this method analyzes the nonoriented characteristics of ultrasound reflection on principle and proposes the detection of ultrasound Doppler frequency shift by detecting Lamb wave, which releases the detection of oil-based mud flow rate in a nonintrusive annular pipe. The feasibility of the method is verified through theoretical analysis and numerous experiments on a gas kick simulation platform. The measurement result has reached a flow accuracy approximating to the intrusive flow meter.

Porosity predicted from ultrasound backscatter using multivariate analysis can improve accuracy of cortical bone thickness assessment.

A rapidly growing area of interest in quantitative ultrasound assessment of bone is to determine cortical bone porosity from ultrasound backscatter. Current backscatter analyses are based on numerical simulations, while there are no published reports of successful experimental measurements. In this study, multivariate analysis is applied to ultrasound reflections and backscatter to predict cortical bone porosity. The porosity is then applied to estimate cortical bone radial speed of sound (SOS) and thickness using ultrasound backscatter signals obtained at 2.25 and 5 MHz center frequencies from cortical bone samples (n = 43) extracted from femoral diaphyses. The study shows that the partial least squares regression technique could be employed to successfully predict (R2 = 0.71-0.73) cortical porosity. It is found that this multivariate approach can reduce uncertainty in pulse-echo assessment of cortical bone thickness from 0.220 to 0.045 mm when porosity based radial SOS was applied, instead of a constant value from literature. Upon further validation, accurate estimation of cortical bone porosity and thickness may be applied as a financially viable option for fracture risk assessment of individuals.