The possibility of acoustic wave propagation in optical waveguides creates new prospects for simultaneous transmission of laser beams and ultrasonic waves. Combined laser-ultrasonic technology could be useful in e.g. surgical treatment. The article presents the results of experimental studies of transmission of ultrasonic wave in optical fibres, the core of which is doped by 7.5% of TiO2, using a sandwich-type transducer. It also presents amplitude characteristics of an ultrasonic signal propagated in the optical fibre. Authors studied the effect which the length of the fibre has on the achieved output signal amplitudes. They presented the relation of the output signal amplitude from a capacitive sensor to the power applied to the sandwich-type transducer. The obtained results were compared with the results produced when using an optical fibre with a core doped by 3% of GeO2, in order to select optical fibre suitable for simultaneous transmission of ultrasonic waves and laser rays.
There exist some possibilities for simultaneous delivery of laser radiation and ultrasounds of low frequency and high intensity: introducing ultrasound oscillations in the optical fiber by the rigid connection of the fiber to the vibrating element and non-contact influence of the ultrasonic wave on the laser beam. The article presents the results of Matlab simulations and experimental studies of influence of the ultrasonic wave on the laser beam. A role of the air gap, and its influence on laser-ultrasonic transmission in optical fiber was examined. Advantages and disadvantages of both solutions of interaction of ultrasonic and optical waves in, e.g., surgical applications are discussed.
This paper presents and analyses the results of a simulation of the acoustic field distribution in sectors of a 1024-element ring array, intended for the diagnosis of female breast tissue with the use of ultrasonic tomography. The array was tested for the possibility to equip an ultrasonic tomograph with an additional modality - conventional ultrasonic imaging with the use of individual fragments (sections) of the ring array. To determine the acoustic field for sectors of the ring array with a varying number of activated ultrasonic transducers, a combined sum of all acoustic fields created by each elementary transducer was calculated. By the use of MATLAB software, a unique algorithm was developed, for a numerical determination of the distribution of pressure of an ultrasonic wave on any surface or area of the medium generated by the concave curvilinear structure of rectangular ultrasound transducers with a geometric focus of the beam. The analysis of the obtained results of the acoustic field distribution inside the ultrasonic ring array used in tomography allows to conclude that the optimal number of transducers in a sector enabling to obtain ultrasound images using linear echographic scanning is 32 ≤ n ≤ 128, taking into account that due to an increased temporal resolution of ultrasonic imaging, this number should be as low as possible.
The following paper presents an idea of minimising the number of connections of individual piezoelectric transducers in a row-column multielement passive matrix system used for imaging of biological media structure by means of ultrasonic projection. It allows to achieve significant directivity with acceptable input impedance decrease. This concept was verified by designing a model of a passive ultrasonic matrix consisting of 16 elementary piezoceramic transducers, with electrode attachments optimised by means of electronic switches in rows and columns. Distributions of acoustic field generated by the constructed matrix model in water and results of the calculations conformed well.
This article presents the results of experimental studies of simultaneous transmission of ultrasonic waves and laser signals in optical fibers by the use of both the optical single mode and multimode fiber couplers. This work was aimed, among other things, at the study of the way the acoustic energy affects a laser beam. The light wave was guided into one of the coupler's arms. The optical power applied to one input of the coupler is separated into two coupler outputs according to the rate determined by the coupling coefficient. Only an ultrasonic wave generated by a sandwich type transducer is applied to the other arm of the coupler. In this experiment, as in case of the light wave, the acoustic power is separated into both the outputs. One can observe the interaction of both the waves on the two outputs - a modulation of the light wave by means of the ultrasonic wave is possible. The output signal was detected using a PIN diode and an optical power meter (OPM). Temporary courses were observed on an oscilloscope screen. The simultaneous transmission of ultrasounds and optical radiation in optical fibers can be used in the construction of medical equipment.
The following work presents the idea of constructing a digitally controlled active piezoceramic transducer matrix for ultrasonic projection imaging of biological media in a similar way as in case of roentgenography (RTG). Multielement ultrasonic probes in the form of flat matrices of elementary piezoceramic transducers require attaching a large number of electrodes in order to activate the individual transducers. This paper presents the idea of minimising the number of transducer connections in an active row-column matrix system. This idea was verified by designing a model of a matrix consisting of 16 ultrasonic transducers with electrode attachments optimised by means of electronic switches in rows and columns and miniature transistor switches in the nodes of the matrix allowing to activate selected transducers. The results of measurements and simulations of parameters of the designed matrix show that it is suitable to be used in projection imaging of biological media as a sending probe. In to use the matrix as a universal sending or receiving probe, it was suggested to add further switches that would eliminate the undesired effect of crosstalks in case of switches used for toggling the transducers in the nodes of the matrix.
Ultrasonic projection imaging is similar to X-ray radiography. Nowadays, ultrasonic projection methods have been developed in the set-up of multi-element flat arrays with miniature transducers, where one of the array acts as a transmitter and the other one is a receiver. In the paper, a new method of the projection imaging using a 1024-element circular ultrasonic transducer array is presented. It allows the choice of a projection scanning plane for any angle around a studied object submerged in water. Fast acquisition of measurement data is achieved as a result of parallel switching of opposite transmitting and receiving transducers in the circular array and vertical movement of the array. The algorithm equalizing the length of measurement rays and the distances between them was elaborated for the reconstruction of projection images. Projection research results of breast phantom obtained by means of the elaborated measurement set-up and compared with mammography simulations (acquired through overlapping of X-ray tomographic images) show that ultrasonic projection method presented in this paper (so-called ultrasonic mammogra-phy) can be applied to the woman's breast and be used as a diagnosis for an early detection of cancerous lesions. It can, most of all, be used as an alternative or complementary method to standard mammography, which is harmful because of ionizing radiation and invasive due to the mechanical compression of tissue.
The work presents the results of experimental study on the possibilities of determining the source of an ultrasonic signal in two-dimensional space (distance, horizontal angle). During the research the team used a self-constructed linear array of MEMS microphones. Knowledge in the field of sonar systems was utilized to analyse and design a location system based on a microphone array. Using the above mentioned transducers and broadband ultrasound sources allows a quantitative comparison of estimation of the location of an ultrasonic wave source with the use of broadband modulated signals (modelled on bats' echolocation signals) to be performed. During the laboratory research the team used various signal processing algorithms, which made it possible to select an optimal processing strategy, where the sending signal is known.
This paper presents a solution that utilises ultrasonic technology to allow monitoring snow layer thickness or water level based on measurement from air. It describes the principle of operation of a measurement device using three methods of compensating for changing external factors affecting appliance’s precision. Block diagram of the device is also provided. In order to verify the proposed solutions, the research team tested the device in laboratory and operating conditions. The results obtained this way make it possible to select a configuration of device operation depending on the required measurement precision and limitations associated with installing the system for actual operation.
The paper presents an analysis of the results of ultrasound transmission tomography (UTT) imaging of the internal structure of a breast elastography phantom used for biopsy training, and compares them with the results of CT, MRI and, conventional US imaging; the results of the phantom examination were the basis for the analysis of UTT method resolution. The obtained UTT, CT and MRI images of the CIRS Model 059 breast phantom structure show comparable (in the context of size and location) heterogeneities inside it. The UTT image of distribution of the ultrasound velocity clearly demonstrates continuous changes of density. The UTT image of derivative of attenuation coefficient in relation to frequency is better for visualising sharp edges, and the UTT image of the distribution of attenuation coefficient visualises continuous and stepped changes in an indirect way. The inclusions visualized by CT have sharply delineated edges but are hardly distinguishable from the phantom gel background even with increased image contrast. MRI images of the studied phantom relatively clearly show inclusions in the structure. Ultrasonography images do not show any diversification of the structure of the phantom. The obtained examination results indicate that, if the scanning process is accelerated, ultrasound transmission tomography method can be successfully used to detect and diagnose early breast malignant lesions. Ultrasonic transmission tomography imaging can be applied in medicine for diagnostic examination of women’s breasts and similarly for X-ray computed tomography, while eliminating the need to expose patients to the harmful ionising radiation.