Papers by Andrzej Nowicki
Archives of Acoustics
The brain is subject to damage, due to ageing, physiological processes and/or disease. Some of th... more The brain is subject to damage, due to ageing, physiological processes and/or disease. Some of the damage is acute in nature, such as strokes; some is more subtle, like white matter lesions. White matter lesions or hyperintensities (WMH) can be one of the first signs of micro brain damage. We implemented the Acoustocerebrography (ACG) as an easy to use method designed to capture differing states of human brain tissue and the respective changes. Aim: The purpose of the study is to compare the efficacy of ACG and Magnetic Resonance Imaging (MRI) to detect WMH in patients with clinically silent atrial fibrillation (AF). Methods and results: The study included 97 patients (age 66.26 ± 6.54 years) with AF. CHA2DS2-VASc score (2.5 ±1.3) and HAS BLED (1.65 ± 0.9). According to MRI data, the patients were assigned into four groups depending on the number of lesions: L0-0 to 4 lesions, L5-5 to 9 lesions, L10-10 to 29 lesions, and L30-30 or more lesions. Authors found that the ACG method clearly differentiates the groups L0 (with 0-4 lesions) and L30 (with more than 30 lesions) of WMH patients. Fisher's Exact Test shows that this correlation is highly significant (p < 0.001). Conclusion: ACG is a new, easy and cost-effective method for detecting WMH in patients with atrial fibrillation. The ACG measurement methodology should become increasingly useful for the assessment of WMH.
Archives of Acoustics
Objectives: In the article we describe the new, high frequency, 20 MHz scanning/Doppler probe des... more Objectives: In the article we describe the new, high frequency, 20 MHz scanning/Doppler probe designed to measure the flow mediated dilation (FMD) and shear rate (SR) close to the radial artery wall. Methods: We compare two US scanning systems, standard vascular modality working below 12 MHz and high frequency 20 MHz system designed for FMD and SR measurements. Axial resolutions of both systems were compared by imaging of two closely spaced food plastic foils immersed in water and by measuring systolic/diastolic diameter changes in the radial artery. The sensitivities of Doppler modalities were also determined. The diagnostic potential of a high frequency system in measurements of FMD and SR was studied in vivo, in two groups of subjects, 12 healthy volunteers and 14 patients with stable coronary artery disease (CAD). Results: Over three times better axial resolution was demonstrated for a high frequency system. Also, the sensitivity of the external single transducer 20 MHz pulse Doppler proved to be over 20 dB better (in terms of a signal-to-noise ratio) than the pulse Doppler incorporated into the linear array. Statistically significant differences in FMD and FMD/SR values for healthy volunteers and CAD patients were confirmed, p-values < 0.05. The areas under Receiver Operating Characteristic (ROC) curves for FMD and FMD/SR for the prediction CAD had the values of 0.99 and 0.97, respectively. Conclusions: These results justify the usefulness of the designed high-frequency scanning system to determine the FMD and SR in the radial artery as predictors of coronary arterial disease.
Archives of Acoustics, 1984
Journal of Cosmetics, Dermatological Sciences and Applications, 2013
The purpose of the research was to evaluate the role of high frequency ultrasound in monitoring a... more The purpose of the research was to evaluate the role of high frequency ultrasound in monitoring and efficacy assessment of anti-cellulite treatments. A group of 66 women used 3 different types of anti-cellulite treatments; additionally a placebo group (n = 18) was created. The µ-Scan ultrasound device with a 35 MHz mechanical probe was used for the examinations. The following parameters were subjected to the ultrasound evaluation: epidermis thickness, dermis thickness, dermis echogenicity, the length and area of subcutaneous tissue bands projecting into the dermis (dermis-hypodermis junction), as well as the presence/absence of edema within the dermis. As a result of anti-cellulite treatment, the length and area of dermis-hypodermis junction significantly decreased, and dermis echogenicity significantly increased. Ultrasound imaging made it possible to evaluate the efficacy of the applied treatments. The high frequency ultrasound is a useful imaging technique for the application in aesthetic dermatology and cosmetology.
Ultrasonic Transducers, 2012
Research Square (Research Square), Apr 29, 2024
Background: In the range of acoustic pressures used in ultrasound imaging, the waves propagating ... more Background: In the range of acoustic pressures used in ultrasound imaging, the waves propagating in tissue are distorted due to the nonlinear properties of the tissue. The adipose tissue exhibits up to 2 times greater nonlinear behavior than other tissue. In general, the nonlinear property of the media is addressed by using the B/A nonlinearity parameter measured in transmission mode and requiring wide band reception systems. Method: We propose a new simple approach for estimating the non-linear properties of tissue. The proposed method involves the use of several waves transmissions with significantly different acoustic pressures and recording the echoes only in the fundamental frequency band. The set of images of "linear" tissues (B/A=0) will differ only in amplitude proportional to the amplitude of the transmitted wave. Therefore, the ratios of the echoes' amplitudes recorded for the sequence of low and high pressure transmission, after compensating for different transmit acoustic pressures, should be close to one. If there are areas in the imaging space with B/A0, the amplitude ratios will differ from one and this value should increase with increasing nonlinearity coefficient of the imaged tissue. The research was carried out in three steps. In the first step of the evaluation, the amplitude of the first and higher harmonics in water and in vegetable oil was measured for various sound pressures. Sound pressures were measured using a needle hydrophone at a depth of 1 cm up to 6 cm from the face of the ultrasonic head. In the second part the echoes from the thread phantom in water and sunflower oil were analyzed. Finally, we studied the backscattered ultrasound measurements from the sample of beef liver with oil mimicking fatty tissue. Results: We have introduced a simple non-linearity index (NLI) in the form of the quotient of the backscattered signals amplitudes EP1 and EP2 for two different transmitted pressures, after compensating for the transmitted pressures, NLI=EP1/EP2.
Archives of Acoustics
Quantitative ultrasound has been widely used for tissue characterization. In this paper we propos... more Quantitative ultrasound has been widely used for tissue characterization. In this paper we propose a new approach for tissue compression assessment. The proposed method employs the relation between the tissue scatterers' local spatial distribution and the resulting frequency power spectrum of the backscattered ultrasonic signal. We show that due to spatial distribution of the scatterers, the power spectrum exhibits characteristic variations. These variations can be extracted using the empirical mode decomposition and analyzed. Validation of our approach is performed by simulations and in-vitro experiments using a tissue sample under compression. The scatterers in the compressed tissue sample approach each other and consequently, the power spectrum of the backscattered signal is modified. We present how to assess this phenomenon with our method. The proposed in this paper approach is general and may provide useful information on tissue scattering properties.
The work describes the use of a synthetic transmit aperture (STA) with a single element transmitt... more The work describes the use of a synthetic transmit aperture (STA) with a single element transmitting and all elements receiving in medical ultrasound imaging. STA technique is a novel approach to today-s commercial systems, where an image is acquired sequentially one image line at a time that puts a strict limit on the frame rate and the amount of data needed for high image quality. The STA imaging allows to acquire data simultaneously from all directions over a number of emissions, and the full image can be reconstructed. In experiments a 32-element linear transducer array with 0.48 mm inter-element spacing was used. Single element transmission aperture was used to generate a spherical wave covering the full image region. The 2D ultrasound images of wire phantom are presented obtained using the STA and commercial ultrasound scanner Antares to demonstrate the benefits of the SA imaging.
Streaming velocity depends on intensity and absorption of ultrasound in the media. In some cases,... more Streaming velocity depends on intensity and absorption of ultrasound in the media. In some cases, such as ultrasound scattered on blood cells at high frequencies, or the presence of ultrasound contrast agents, scattering affects the streaming speed. The velocities of acoustic streaming in a blood-mimicking starch suspension in water and Bracco BR14 contrast agent were measured. The source of the streaming was a plane 20MHz ultrasonic transducer. Velocity was estimated from the averaged Doppler spectrum. The single particle driving force was calculated as the integral of the momentum density tensor components. For different starch concentrations, the streaming velocity increased from 8.9 to 12.5mm/s. This corresponds to a constant 14% velocity increase for a 1 g/l increase in starch concentration. For BR14, the streaming velocity remained constant at 7.2mm/s and was independent of the microbubbles concentration. The velocity was less than in reference, within 0.5mm/s measurement error. Theoretical calculations showed a 16% increase in streaming velocity for 1 g/l starch concentration rise, very similar to the experimental results. The theory has also shown the ability to reduce the streaming velocity by low-density scatterers, as was experimentally proved using the BR14 contrast agent.
Ultrasonics, 2022
In this paper, we propose a novel deep learning method for joint classification and segmentation ... more In this paper, we propose a novel deep learning method for joint classification and segmentation of breast masses based on radio-frequency (RF) ultrasound (US) data. In comparison to commonly used classification and segmentation techniques, utilizing B-mode US images, we train the network with RF data (data before envelope detection and dynamic compression), which are considered to include more information on tissue's physical properties than standard B-mode US images. Our multi-task network, based on the Y-Net architecture, can effectively process large matrices of RF data by mixing 1D and 2D convolutional filters. We use data collected from 273 breast masses to compare the performance of networks trained with RF data and US images. The multi-task model developed based on the RF data achieved good classification performance, with area under the receiver operating characteristic curve (AUC) of 0.90. The network based on the US images achieved AUC of 0.87. In the case of the segmentation, we obtained mean Dice scores of 0.64 and 0.60 for the approaches utilizing US images and RF data, respectively. Moreover, the interpretability of the networks was studied using class activation mapping technique and by filter weights visualizations.
Preceding atherosclerosis is an endothelial dysfunction. Therefore there is a growing interest in... more Preceding atherosclerosis is an endothelial dysfunction. Therefore there is a growing interest in the application of non-invasive clinical tools to assess endothelial function. Commercially available ultrasound machines can measure flow-mediated vasodilatation of the brachial artery using maximum 10-12 MHz linear probes. The higher the probe frequency, the better the axial resolution. Recently, a new technology of piezoelectric transducers based on PZT thick film technology has been developed in Meggitt (Denmark) as a response to a call for devices working at higher frequencies. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducers, resulting in an increase in match filtering encoding output by a factor of 1.4-1.5 and finally resulting in a signal to noise gain of the same order. The introduction of a high frequency 25-30 MHz ultrasound scanner to measure radial artery diameter after reactive hyperemia opens a new window for more precise imaging of endothelial function.
The aim of this work was to use the streaming phenomena to assist clot dissolution in blood vesse... more The aim of this work was to use the streaming phenomena to assist clot dissolution in blood vessel. Such treatment is called sonothrombolysis. Acoustic streaming is a steady flow in a fluid driven by the acoustic wave propagating in a lossy medium. It is a non-linear effect and it depends on ultrasound intensity, and sound absorption in the media. The source of ultrasound was a flat piezoceramic disc generating long pulses at 1 MHz frequency and 0.2 W/cm ITA acoustical intensity. The streaming was generated in a vessel simulating free space, and next repeated in a multi-well cell culture plate, and in the limited space inside the 8 mm diameter silicone tube positioned perpendicular to the ultrasonic beam. The tube was filled with a mixture of water, glycerol, and starch, so with acoustic properties similar to blood. The streaming velocity was recorded either by the Siemens Acuson Antares ultrasonic scanner operating in the color Doppler mode at 8.9 MHz, or by the custom built 20 MHz...
Ultrasound is the most widely used medical imaging modality. T he majority of ultrasound systems ... more Ultrasound is the most widely used medical imaging modality. T he majority of ultrasound systems operate at frequencies in the I to 5 MHz range and form images using a hand-held transducer that is external to the body. It is capable of provid ing real-time information about tissue structure and blood flow in the heart and larger vessels. Unfortunately, in smaller vessels and capillaries blood detection is not possib le due to the low signal strength of blood, tissue motion effects, and limited resol ution (-0.5-1 mm). It is the blood volume in small capillaries, monitored as a
Archives of Acoustics, 2014
This study was concerned with a membrane, pdvf foil and double-screened hydrophone, manufactured ... more This study was concerned with a membrane, pdvf foil and double-screened hydrophone, manufactured by Sonic Technologies, USA. Using the producer's data in the form of discrete data, power functions, describing the input impedance and the sensitivity of the hydrophone, depending on the frequency, were found. This made it possible to represent the measuring system in the form of a equivalent circuit containing a pressure source, a transformer which converted the acoustic pressure into the electric intensity (the hydrophone sensitivity), the hydrophone impendance, an additional coaxial cable and the input receiver impedance. The impacts of the receiver impedance and that of the additional cable on the accuracy of measurements of the acoustic pressure using a hydrophone were subsequently investigated. As an example, an ultrasonographic measurement using the hydrophone in question was cited.
Propagation of ultrasonic waves in the tissue is sensitive to the alternation of tissue compositi... more Propagation of ultrasonic waves in the tissue is sensitive to the alternation of tissue composition and structure.. This paper presents the classification of healthy skin and skin lesions (basal cell carcinoma (BCC)) based on statistic parameters of the envelope of echosignal. The statistics of envelope of the ultrasonic signal was modeled using Rayleigh and non-Rayleigh (the K-distribution) statistics. Furthermore the characteristic parameter of K-distribution, the effective number of scaterrers (M) was investigated. Comparison of the results obtained for region of the skin where the BCC was diagnosed and the regions of healthy skin has shown differences in the values of M parameter. These results indicate that this parameter has the potential for extracting information useful for characterizing skin lesions. INTRODUCTION
Ultrasonic imaging is a well-established technique in medicine. However, in most conventional app... more Ultrasonic imaging is a well-established technique in medicine. However, in most conventional applications of clinical ultrasonic scanners only the peak amplitude echogenicity is used to create the image. Moreover, signal envelope detection destroys potentially useful information about frequency dependence of acoustic properties of tissue comprised in RF backscattered echoes. We have explored the possibility of developing the method of imaging the distribution of the acoustic attenuation in tissue. We expect that the method will help in localization of the pathological states of tissue including tumors and diffuse liver diseases. The spatial resolution and precision of the method are crucial for medical diagnosis, hence the synthetic aperture technique was applied for ultrasonic data collection. The final goal of the presented project is to develop reliable diagnostic tool, which could be implemented in standard USG systems, as the new visualization mode.
Nowadays there are new modalities in ultrasound imaging allowing better characterization of tissu... more Nowadays there are new modalities in ultrasound imaging allowing better characterization of tissue regions with different stiffness. We are proposing a novel approach based on compression and rarefaction of tissue simultaneously with imaging. The propagating wave is a combination of two pulses. A low frequency pulse is expected to change the local scattering properties of the tissue due to compression/rarefaction while a high frequency pulse is used for imaging. Two transmissions are performed for each scanning line. First, with the imaging pulse that propagates on maximum compression caused by a low frequency wave. Next, the low frequency wave is inverted and the imaging pulse propagates over the maximum rarefaction. After the processing of the subtracted echoes from subsequent transmissions including wavelet transform and band-pass filtering, differential images were reconstructed. The low frequency wave has a visible impact on the scattering properties of the tissue which can be ...
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Papers by Andrzej Nowicki