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.

Imaging results of multi-modal ultrasound computerized tomography system designed for breast diagnosis.

Nowadays, in the era of common computerization, transmission and reflection methods are intensively developed in addition to improving classical ultrasound methods (US) for imaging of tissue structure, in particular ultrasound transmission tomography UTT (analogous to computed tomography CT which uses X-rays) and reflection tomography URT (based on the synthetic aperture method used in radar imaging techniques). This paper presents and analyses the results of ultrasound transmission tomography imaging of the internal structure of the female breast biopsy phantom CIRS Model 052A and the results of the ultrasound reflection tomography imaging of a wire sample. Imaging was performed using a multi-modal ultrasound computerized tomography system developed with the participation of a private investor.

Recognition of external object features in gas media using ultrasound transmission tomography.

The paper presents and analyzes a new way of recognizing external object features (shape, size, location) in gas media using ultrasound transmission tomography (UTT) with parallel-ray-projection scanning geometry. The concept of UTT in a gas medium is close to classical tomography, however because of the nature of the measurement environment, visualizing the internal structure of solid objects is difficult; whereas it is possible to image their external features: their shape, size and spatial location. The paper presents the results of examining the shape, size and location of different objects in the air in the form of tomographic images, obtained in parallel-ray-projection geometry, using a specially elaborated research setup for UTT.

Multi-parameter ultrasound transmission tomography of biological media.

Using a specially elaborated computer software and research setup, within the scope of this paper, projection and tomographic calculations (simulation) and real measurements of biological media by means of ultrasound were carried out, and the images of different parameters of the ultrasonic wave run through biological objects were obtained. The images were analyzed from the point of view of the precision of representation of the structures and visualization of different features of these structures. On the basis of the results obtained it can be said that such a complex multi-parameter ultrasound transmission tomography (MUTT) is best suited for diagnosing early stages of tumors in tissues, and especially women's breast tumors, because of the structure of this organ and its possible scanning in vivo from many directions.

The ultrasonic probe for the investigating of internal object structure by ultrasound transmission tomography.

The main component of every device used for investigating internal object structure by Ultrasound Transmission Tomography (UTT) is a special ultrasonic probe. This paper presents the structure of model multielement ring probe for examining objects using this method in divergent ray projection geometry. The probe is made up of 1024 rectangular separate piezoelectric transducers working at frequency f=1.

Three-dimensional reconstruction of biological objects' internal structure heterogeneity from the set of ultrasonic tomograms.

The paper presents the method of the three-dimensional reconstruction of biological objects' internal structure heterogeneity based on the ultrasonic examination of a woman's breast biopsy phantom. The phantom is made of quasi-homogeneous dense gel in which drops of lesions, characterized by fixed sizes and two different acoustic impedances, were dipped at random. For the purpose of this research a special measurement setup was elaborated, enabling a non-invasive in vitro imaging of biological objects' internal structure in cross-sections for fixed levels, by means of ultrasound transmission tomography (UTT) using the parallel-ray projection geometry of scanning.

Applying spectrum analysis and cepstrum analysis to examine the cavitation threshold in water and in salt solution.

The paper presents the way of determining the cavitation threshold by means of classical spectral analysis and proposes the usage of cepstrum analysis in examining the cavitation phenomenon. Cepstrum analysis enables a more lucid interpretation of signals generated in the cavitation process than the universally used Fourier analysis. This refers above all to evaluating the relationship between particular frequencies as well as frequency groups.

Ultrasonic transducers working in the air with the continuous wave within the 50-500 kHz frequency range.

Transmitting and receiving ultrasonic waves in the air requires high standards of both the transmitters and the receivers of these waves. The paper presents the results of measurements of ultrasonic signals generated by ultrasonic transducers of mean power working with the continuous wave, designed for operating in the air at the frequencies between 50 and 500 kHz. The characteristic feature of these transducers is their high effectiveness and sensitivity, which are necessary for working in the transmission system.

Influence of the thickness of multilayer matching systems on the transfer function of ultrasonic airborne transducer.

The effective ultrasonic energy radiation into the air of piezoelectric transducers requires using multilayer matching systems with accurately selected acoustic impedances and the thickness of particular layers. This problem is of particular importance in the case of ultrasonic transducers working at a frequency above 1 MHz. Because the possibilities of choosing material with required acoustic impedance are limited (the counted values cannot always be realised and applied in practice) it is necessary to correct the differences between theoretical values and the possibilities of practical application of given acoustic impedances.

Influence of acoustic impedance of multilayer acoustic systems on the transfer function of ultrasonic airborne transducers.

In different solutions of ultrasonic transducers radiating acoustic energy into the air there occurs the problem of the proper selection of the acoustic impedance of one or more matching layers. The goal of this work was a computer analysis of the influence of acoustic impedance on the transfer function of piezoceramic transducers equipped with matching layers. Cases of resonance and non-resonance matching impedance in relation to the transfer function and the energy transmission coefficient for solid state-air systems were analysed.