An Ultrasonic Adaptive Beamforming Method and Its Application for Trans-Skull Imaging of Certain Types of Head Injuries; Part II: Reception Mode and Adaptive Imaging.

Objective: Background theory and a new algorithm for single-point adaptive focusing in transmission mode through ultrasonic barriers via one-dimensional phased arrays were reported in part I. In this paper the algorithm is further extended and implemented into a full adaptive beamforming process, including complete transmission and reception modes.

Methods: Corrected time delay patterns, adapted to the local acoustical and geometrical properties of the barrier, are calculated and applied in both modes.

Using machine learning to automate ultrasound-based classification of butt-fused joints in medium-density polyethylene gas pipes.

Polyethylene (PE) pipes are widely used in gas distribution. Their joints are prone to various flaws and are the most problematic part of the pipeline, so the infrastructure industry requires an effective inspection technique. Butt-fusion (BF) is the most common method of joining PE pipes.

High-resolution quantitative acoustic microscopy of cutaneous carcinoma and melanoma: Comparison with histology.

Background: The increased incidence rate of skin cancers during the last decades is alarming. One of the significant difficulties in the histopathology of skin cancers is appearance variability due to the heterogeneity of diseases or tissue preparation and staining process. This study aims to investigate whether the high-resolution acoustic microscopy has the potential for identifying and quantitatively classifying skin cancers.

Accurate 3-D Profile Extraction of Skull Bone Using an Ultrasound Matrix Array.

The present study investigates the feasibility, accuracy, and precision of 3-D profile extraction of the human skull bone using a custom-designed ultrasound matrix transducer in Pulse-Echo. Due to the attenuative scattering properties of the skull, the backscattered echoes from the inner surface of the skull are severely degraded, attenuated, and at some points overlapped. Furthermore, the speed of sound (SOS) in the skull varies significantly in different zones and also from case to case; if considered constant, it introduces significant error to the profile measurement.

Ultrasonic imaging of static objects through an aberrating layer using harmonic phase conjugation approach.

The main goal of this study is to develop a new image reconstruction approach for the ultrasonic detection of small objects (comparable to or smaller than the ultrasonic wavelength) behind an aberrating layer. Instead of conventional pulse-echo experimental setup we used through transmission, as the backscattered field after going twice through the layer becomes much weaker than the through-transmitted field. The proposed solution is based on the Harmonic Phase Conjugation (HPC) technique.

An Ultrasonic-Adaptive Beamforming Method and Its Application for Trans-skull Imaging of Certain Types of Head Injuries; Part I: Transmission Mode.

A new adaptive beamforming algorithm for imaging via small-aperture 1-D ultrasonic-phased arrays through composite layered structures is reported. Such structures cause acoustic phase aberration and wave refraction at undulating interfaces and can lead to significant distortion of an ultrasonic field pattern produced by conventional beamforming techniques. This distortion takes the form of defocusing the ultrasonic field transmitted through the barrier and causes loss of resolution and overall degradation of image quality.

An ultrasonic array technique for material characterization of plate samples.

An ultrasonic system with a linear array for characterization of a layered specimen placed in immersion liquid parallel to the aperture of the array is considered. To estimate the longitudinal and transverse wave velocities as well as the thickness and density of the specimen, it is proposed to decompose the spatio-temporal data recorded by the array in a spectrum of plane pulse waves. Based on fitting the developed wave model of the system to the experimental data, it is shown that the relative delays and amplitudes of the spectral responses can be used for the estimation of the velocities and thickness of the layer and its density.

Assessment of gingival thickness using an ultrasonic dental system prototype: A comparison to traditional methods.

Knowledge of periodontal anatomy is essential when performing surgical and non-surgical procedures in the field of oral healthcare. Gingival thickness (GT) is often assessed for this purpose. A dental system prototype was recently developed for quantitative, non-invasive GT assessment by high-frequency (HF) ultrasound.

Advantages and limitations of using matrix pencil method for the modal analysis of medical percussion signals.

Although clinical percussion remains one of the most widespread traditional noninvasive methods for diagnosing pulmonary disease, the available analysis of physical characteristics of the percussion sound using modern signal processing techniques is still quite limited. The majority of existing literature on the subject reports either time-domain or spectral analysis methods. However, Fourier analysis, which represents the signal as a sum of infinite periodic harmonics, is not naturally suited for decomposition of short and aperiodic percussion signals.

Estimating the parameters of audible clinical percussion signals by fitting exponentially damped harmonics.

Used for centuries in the clinical practice, audible percussion is a method of eliciting sounds by tapping various areas of the human body either by finger tips or by a percussion hammer. Despite its advantages, pulmonary diagnostics by percussion is still highly subjective, depends on the physician's skills, and requires quiet surroundings. Automation of this well-established technique could help amplify its existing merits while removing the above drawbacks.

Enamel thickness measurement with a high frequency ultrasonic transducer-based hand-held probe for potential application in the dental veneer placing procedure.

This study presents a novel approach to measure the enamel thickness potentially applicable to the veneer placing procedure. All experiments have been carried out on the extracted human teeth, using a high frequency ultrasonic transducer (50 MHz, Sonix, Springfield, VA, USA). The enamel thickness measurement results obtained with high positional accuracy by a scanning acoustic microscope (Tessonics AM1103, Windsor, ON, Canada) were compared with the measurements conducted in a hand-held mode by using the same transducer placed in a custom fixture.

Acoustic imaging of thick biological tissue.

Up to now, biomedical imaging with ultrasound for observing a cellular tissue structure has been limited to very thinly sliced tissue at very high ultrasonic frequencies, i.e., 1 GHz.

A study of the adhesion between dental cement and dentin using a nondestructive acoustic microscopy approach.

Objectives: The goal of the present study was to investigate the potential for acoustic microscopy techniques to characterize the cement-dentin interface in restored teeth.

Methods: Special flat-parallel specimens and whole extracted teeth with restorations were scanned using a high-frequency (50 MHz) focused ultrasonic transducer. Visual acoustic images (B- and C-scans) of the cement-dentin interface were obtained nondestructively, analyzed and compared with optical images taken after the samples were cut along the scanning axis.

Pulse-echo NDT of adhesively bonded joints in automotive assemblies.

A new method for the detection of void-disbonds at the interfaces of adhesively bonded joins is considered. Based on a simple plane wave model, the output waveform is presented as a sum of two responses associated with the reflection of the ultrasonic wave at the first metal-adhesive interface and the second metal-adhesive interface, respectively. The strong response produced by the wave reverberating in the first metal sheet is eliminated through comparison between the pulse-echo signal measured at the area under the test and reference waveform recorded for the bare first metal sheet outside of the joint.

Application of a nonlinear boundary condition model to adhesion interphase damage and failure.

In an earlier paper [J. Sadler, B. O'Neill, and R.

A one-dimensional numerical model of acoustic wave propagation in a multilayered structure of a resistance spot weld.

A one-dimensional model of acoustic wave propagation in a multilayered structure of a spot weld is developed. The inhomogeneity of the material properties due to the thermal inhomogeneity is included in the equation of motion. The model enables us to deal with arbitrary spatial distributions of Lamé constants and density.

Ultrasonic wave propagation across a thin nonlinear anisotropic layer between two half-spaces.

Boundary conditions and perturbation theory are combined to create a set of equations which, when solved, yield the reflected and transmitted wave forms in the case of a thin layer of material that is perfectly bonded between two isotropic half-spaces. The set of perturbed boundary conditions is created by first using the fully bonded boundary conditions at each of the two interfaces between the thin layer and the half-spaces. Then, by restricting the layer's thickness to be much smaller than an acoustic wavelength, perturbation theory can be used on these two sets of boundary equations, producing a set of equations which effectively treat the thin layer as a single interface via a perturbation term.

New data on histology and physico-mechanical properties of human tooth tissue obtained with acoustic microscopy.

Quantitative evaluation of human tooth structural elements, revealed in acoustic images, has been carried out. It has been shown that tissue elements with different acoustic impedances differed in acoustic images by intensity of grey color, and also feature with different longitudinal sound velocities (C(L)). In the layer of mantle dentin, C(L) is 7% to 8% lower than in bulk dentin, and in the layer of dentin around the pulp chamber, C(L) is 15% lower.