Search Results

You are looking at 1 - 10 of 27 items for

  • Author: Andrzej Nowicki x
Clear All Modify Search
Open access

Janusz Wójcik, Jerzy Litniewski and Andrzej Nowicki

Abstract

A trabecular bone consists of trabeculae whose mechanical properties differ significantly from the surrounding marrow, therefore an ultrasonic wave propagating within the bone structure is strongly scattered. The aim of this paper was to evaluate the contribution of the first, second and higher order scattering (multiple scattering) into the total scattering of ultrasound in a trabecular bone. The scattering due to the interconnections between thick trabeculae, usually neglected in trabecular bone models, has been also studied. The basic element in our model of the trabecular bone was an elastic cylinder with a various finite-length and diameter as well as orientation. The applied model was taking into account variation of both, elements size and their spatial configuration. The field scattered on the bone model was evaluated by solving numerically the integral form of the generalized Sturm-Liouville equation describing a scalar wave in inhomogeneous and lossy media. For the scattered fields calculated numerically the effective cross-sections were determined. The influence of absorption on the scattering coefficients was demonstrated. The results allowed to conclude that within the frequency range from 0.5 to 1.5 MHz contribution of the second order scattering to the effective backscattering cross-section is at least 500 times lower than that due to the first order scattering. It was noticed that for a frequency higher than 1.5 MHz fast growth of the backscattering (reflection) coefficients, calculated for the second order scattering, occurs.

Open access

Andrzej Nowicki, Anna Szwed and Ryszard Laskowski

Depression and Anxiety Before and After Breast Amputation in Women

Breast cancer is the most frequent malignancy in women. The diagnosis of neoplastic disease produces or deepens anxiety and depression in a patient.

The aim of the study was to assess the influence of surgery and socio-demographic factors on the level of anxiety and depression in women suffering from breast cancer.

Material and methods. 50 women (30-71 years old, mean age 54.7 years) with breast cancer were enrolled into the study. They were assessed two times - before and after surgery. To evaluate the level of depression BECK scale was used. It consists of 21 points that determine the level of depression. HAD scale containing seven descriptions of a patient's status was used to assess the level of anxiety.

Results. Most of patients (17(34%) women had vocational education. More than half of the analyzed women were free of depression both before and after surgery, 50 % and 60% respectively. 2% of all women had extremely deep depression preoperatively. A normal and high level of anxiety before surgery was felt by 21 (42%) and 21 (42%) women respectively.

A high level of anxiety was found in 15 patients (30%) postoperatively. The level of depression after surgery decreased in 32 women and psychological status was deteriorated in 9 patients according to BECK scale. The level of anxiety after surgery decreased in 30 patients and deteriorated in 8 cases according to HAD scale. The intensity of anxiety decreased after surgical treatment. The most intensive increase in depression was observed in women with secondary education (51 points) before surgery and 35 points in women with vocational education after surgery. The highest level of anxiety before surgical treatment was found in women with secondary as well as vocational education (21 points). Whereas the highest level of anxiety after surgery was observed in patients with secondary education. (21 points). The hardest depression was observed in working patients (51 points) preoperatively and they still had the hardest depression (35 points) postoperatively, too. The level of anxiety was highest in working women both preoperatively and postoperatively (21 points). The most intensive depression before surgery was observed in women at middle social status (35 points) and this tendency was observed also after surgery. The level of anxiety before surgery was the highest in women with good and middle social status (21 points). After surgery it was the highest in patients with middle social status (21 points). The most intensive depression before surgical treatment was found in patients between 51 and 60 years old (51 points). The hardest depression after surgery was observed in women between 41 and 50 years old (35 points). The highest level of anxiety was felt by patients between 41 and 50 and between 51 and 60 years old (21 points) preoperatively and in women between 51 and 60 years old (21 points) postoperatively.

Conclusions. The intensity of depression and anxiety in women with breast cancer decreased significantly after mastectomy. Patients with university education had lower levels of anxiety and depression both before and after surgery. Working women with average social status had the highest levels of anxiety and depression both before and after surgical treatment. The age of a patient did not influence significantly on the levels of anxiety and depression both before and after surgery.

Open access

Ziemowit Klimonda, Jerzy Litniewski and Andrzej Nowicki

Abstract

The pathological states of biological tissue are often resulted in attenuation changes. Thus, information about attenuating properties of tissue is valuable for the physician and could be useful in ultrasonic diagnosis. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The attenuation estimation method based on the echoes mean frequency changes due to tissue attenuation dispersion, is presented. The Doppler IQ technique was adopted to estimate the mean frequency directly from the raw RF data. The Singular Spectrum Analysis technique was used for the extraction of mean frequency trends. These trends were converted into attenuation distribution and finally the parametric images were computed. In order to reduce variation of attenuation estimates the spatial compounding method was applied. Operation and accuracy of attenuation extracting procedure was verified by calculating the attenuation coefficient distribution using the data from the tissue phantom (DFS, Denmark) with uniform echogenicity while attenuation coefficient underwent variation.

Open access

Eugeniusz Kozaczka, Adam Kawalec and Andrzej Nowicki

Open access

Ziemowit Klimonda, Jerzy Litniewski and Andrzej Nowicki

Abstract

The attenuating properties of biological tissue are of great importance in ultrasonic medical imaging. Investigations performed in vitro and in vivo showed the correlation between pathological changes in the tissue and variation of the attenuation coefficient. In order to estimate the attenuation we have used the downshift of mean frequency (fm) of the interrogating ultrasonic pulse propagating in the medium. To determine the fm along the propagation path we have applied the fm estimator (I/Q algorithm adopted from the Doppler mean frequency estimation technique). The mean-frequency shift trend was calculated using Single Spectrum Analysis. Next, the trends were converted into attenuation coefficient distributions and finally the parametric images were computed. The RF data were collected in simulations and experiments applying the synthetic aperture (SA) transmit-receiving scheme. In measurements the ultrasonic scanner enabling a full control of the transmission and reception was used. The resolution and accuracy of the method was verified using tissue mimicking phantom with uniform echogenicity but varying attenuation coefficient.

Open access

Piotr Karwat, Ziemowit Klimonda, Michał Sęklewski, Marcin Lewandowski and Andrzej Nowicki

Abstract

Ultrasonic methods of human body internal structures imaging are being continuously enhanced. New algorithms are created to improve certain output parameters. A synthetic aperture method (SA) is an example which allows to display images at higher frame-rate than in case of conventional beam-forming method.

Higher computational complexity is a limitation of SA method and it can prevent from obtaining a desired reconstruction time. This problem can be solved by neglecting a part of data. Obviously it implies a decrease of imaging quality, however a proper data reduction technique would minimize the image degradation.

A proposed way of data reduction can be used with synthetic transmit aperture method (STA) and it bases on an assumption that a signal obtained from any pair of transducers is the same, no matter which transducer transmits and which receives. According to this postulate, nearly a half of the data can be ignored without image quality decrease.

The presented results of simulations and measurements with use of wire and tissue phantom prove that the proposed data reduction technique reduces the amount of data to be processed by half, while maintaining resolution and allowing only a small decrease of SNR and contrast of resulting images.

Open access

Ihor Trots, Andrzej Nowicki, Marcin Lewandowski and Yuriy Tasinkevych

Abstract

Synthetic aperture (SA) technique is a novel approach to present day commercial systems and has previously not been used in medical ultrasound imaging. The basic idea of SA is to combine information acquired simultaneously from all directions over a number of emissions and to reconstruct the full image from these data.

The paper presents the multi-element STA (MSTA) method for medical ultrasound imaging. The main difference with the STA approach is the use of a few elements in the transmit mode in contrast to a single element aperture. This allows increasing the system frame rate, decreasing the number of emissions, and provides the best compromise between the penetration depth and lateral resolution. Besides, a modified MSTA is proposed with a corresponding RF signal correction in the receive mode, which accounts for the element directivity property.

In the experiments a 32-element linear transducer array with 0.48 mm inter-element spacing and a burst pulse of 100 ns duration were used. Two elements wide transmission aperture was used to generate an ultrasound wave covering the full image region. The comparison of 2D ultrasound images of a tissue mimicking phantom obtained using the STA and MSTA methods is presented to demonstrate the benefits of the second one.

Open access

Sylwia Dahms and Andrzej Nowicki

Open access

Yuriy Tasinkevych, Ihor Trots, Andrzej Nowicki and Marcin Lewandowski

Abstract

The paper presents the optimization problem for the multi-element synthetic transmit aperture method (MSTA) in ultrasound imaging applications. The optimal choice of the transmit aperture size is made as a trade-off between the lateral resolution, penetration depth and the frame rate. Results of the analysis obtained by a developed optimization algorithm are presented. The maximum penetration depth and lateral resolution at given depths are chosen as optimization criteria. The results of numerical experiments carried out in MATLAB® using synthetic aperture data of point reflectors obtained by the FIELD II simulation program are presented. The visualization of experimental synthetic aperture data of a tissue mimicking phantom and in vitro measurements of the beef liver performed using the SonixTOUCH Research system are also shown.

Open access

Tamara Kujawska, Wojciech Secomski, Kazimierz Krawczyk and Andrzej Nowicki

Abstract

Many therapeutic applications of pulsed focused ultrasound are based on heating of detected lesions which may be localized in tissues at different depths under the skin. In order to concentrate the acoustic energy inside tissues at desired depths a new approach using a planar multi-element annular array transducer with an electronically adjusted time-delay of excitation of its elements, was proposed. The 7-elements annular array transducer with 2.4 MHz center operating frequency and 20 mm outer diameter was produced. All its elements (central disc and 6 rings) had the same radiating area. The main purpose of this study was to investigate thermal fields induced in bovine liver in vitro by pulsed focused ultrasonic beams with various acoustic properties and electronically steered focal plane generated from the annular array transducer used. The measurements were performed for the radiating beams with the 20 mm focal depth. In order to maximize nonlinear effects introducing the important local temperature rise, the measurements have been performed in two-layer media comprising of a water layer, whose thickness was specific for the transducer used and equal to 13 mm, and the second layer of a bovine liver with a thickness of 20 mm. The thickness of the water layer was determined numerically as the axial distance where the amplitude of the second harmonics started to increase rapidly. The measurements of the temperature rise versus time were performed using a thermocouple placed inside the liver at the focus of the beam. The temperature rise induced in the bovine liver in vitro by beams with the average acoustic power of 1W, 2 W and 3 W and duty cycle of 1/5, 1/15 and 1/30, respectively, have been measured. For each beam used the exposure time needed for the local tissue heating to the temperature of 43°C (used in therapies based on ultrasonic enhancement of drug delivery or in therapies involving stimulation of immune system by enhancement of the heat shock proteins expression) and to the temperature of 56°C (used in HIFU therapies) was determined. Two sets of measurements were done for each beam considered. First, the thermocouple measurement of the temperature rise was done and next, the real-time monitoring of dynamics of growth of the necrosis area by using ultrasonic imaging technique, while the sample was exposed to the same acoustic beam. It was found that the necrosis area becomes visible in the ultrasonic image only for beams with the average acoustic power of 3 W, although after cutting the sample the thermo ablated area was visible with the naked eye even for the beams with lower acoustic power. The quantitative analysis of the obtained results allowed to determine the exposure time needed to get the necrosis area visible in the ultrasonic image.