Perceptual audio processing stethoscope.

Stethoscopes are used to transmit body sounds related to various physiological processes to ears of a physician, providing basic or supportive information for eventual diagnosis. Unfavorably, the dominant frequency components of most of the auscultation signals are localized close to the lower frequency limits of the human auditory system, restricting the achievable selectivity and specificity. The present study introduces an approach that aims at overcoming the existing limitations. A signal processing scheme utilizing knock rejection, dynamic compressor, and pseudo-stereo synthesizer blocks is described, along with hardware implementation and results of the initial subjective evaluation.

Sound differences between electronic and acoustic stethoscopes.

BACKGROUND: The area of application of electronic stethoscopes in medical diagnostics covers the scope of usability of the acoustic stethoscopes, from which they have evolved and which they could potentially replace. However, the principle of operation of these two groups of diagnostic devices is substantially different. Thus, an important question arises, regarding the differences in parameters of the transmitted sound and their potential diagnostic consequences in clinical practice. METHODS: In order to answer this question, heart auscultation signals are recorded using various stethoscopes and divided into short fragments based on the analysis of the synchronized recordings of electrocardiogram signals. Next, a dedicated algorithm is used to extract representative datasets for each case, which are then analyzed for their acoustic parameters. Four different electronic stethoscopes were investigated, together with an acoustic stethoscope as a reference point. RESULTS: The determined acoustic characteristics of the considered stethoscopes differ significantly between each other. CONCLUSIONS: The differences in sound transmitted by various stethoscope models may translate into significant differences in quality of the obtained diagnosis. It is also pointed out, that the terminology and application guidelines regarding the electronic stethoscopes are misleading and should be changed.

Experimental validation of the tuneable diaphragm effect in modern acoustic stethoscopes.

PURPOSE: The force with which the diaphragm chestpiece of a stethoscope is pressed against the body of a patient during an auscultation examination introduces the initial stress and deformation to the diaphragm and the underlying tissues, thus altering the acoustic parameters of the sound transmission path. If the examination is performed by an experienced physician, he will intuitively adjust the amount of the force in order to achieve the optimal sound quality. However, in case of becoming increasingly popular auto-diagnosis and telemedicine auscultation devices with no such feedback mechanisms, the question arises regarding the influence of the possible force mismatch on the parameters of the recorded signal. DESIGN: The present study describes the results of the experimental investigations on the relation between pressure applied to the chestpiece of a stethoscope and parameters of the transmitted bioacoustic signals. The experiments were carried out using various stethoscopes connected to a force measurement system, which allowed to maintain fixed pressure during auscultation examinations. The signals were recorded during examinations of different volunteers, at various auscultation sites. RESULTS: The obtained results reveal strong individual and auscultation-site variability. CONCLUSIONS: It is concluded that the underlying tissue deformation is the primary factor that alters the parameters of the recorded signals.

Acoustic characterization of stethoscopes using auscultation sounds as test signals.

The present study introduces a detailed methodology which can be applied for objective evaluation and comparison of the acoustic parameters of medical stethoscopes using auscultation sounds as test signals. The described approach allows taking into account the acoustic coupling between the body of an auscultated patient and the chest piece of a stethoscope. Information obtained from additional, synchronized electrocardiography measurements is used to extract short, specific fragments of recordings, defined as acoustic events. Analysis of the spectral characteristics of many acoustic events allows us to compare the acoustic properties of various stethoscopes and to estimate the measurement uncertainty. The exemplary results of the comparative evaluation of acoustic properties of bell and diaphragm-type chest pieces of a single stethoscope are presented. The results show that the frequency characteristics of the signals obtained using both examined chest pieces under the conditions of the performed examinations are very similar.

Understanding and optimizing fish counting techniques based on electrical impedance measurements.

Sustainable aquatic resources management requires reliable methods for fish detection in various environmental conditions. Herein, we study fundamental mechanisms underlying the application of electrical impedance measurements in this regard. We present results of experimental studies conducted in laboratory conditions using a low-cost impedance measurement circuit, as well as the corresponding numerical models. We also present evaluation results of a newly developed, real-time detection algorithm based on adaptive thresholding. The numerical model was validated by extracting fish tracks in 3D space from the experimental datasets, and then comparing the calculated versus measured impedance values as functions of fish coordinates in time. Numerical predictions closely resemble the experimental data. The detection sensitivity and specificity values determined for various settings exceeded 90%. Electrode width to spacing ratio is demonstrated to be a crucial parameter influencing the system sensitivity distribution. The introduced approach can constitute a framework for designing electrical impedance-based fish counting systems.

Bioinspired flatfish detection using electrical impedance measurements.

Bottom trawling for flatfish by means of tickler chains has a high ecological impact due to the continuous seabed disturbance, low selectivity and high fuel costs. This issue could be significantly mitigated by using localized startle stimuli, triggered by a detection system that selectively targets flatfishes of landable size. Flatfish, however, constitute a significant challenge for remote detection, due to their low optical and acoustical signatures. Some species of predatory fish feeding on flatfish overcome this issue by using electroreception to localize they prey, even if it is buried in bottom sediments. We take this phenomenon as an inspiration in an attempt to develop a biomimetic remote fish detection technique based on electrical impedance measurements. We constructed a detection system including a set of electrodes and a low-cost analog front-end. The electrodes were mounted on a dedicated frame and dragged above a layer of sand inside a tank with sea water and several common sole (Solea solea). An underwater camera was used to acquire video recordings synchronized with impedance data for reference. We demonstrate that fish presence below the electrodes manifests itself by changes in the measured resistance and reactance values. This phenomenon occurs even if the fish is covered with a layer of sand. The results demonstrate the potential of bioinspired remote flatfish detection, which could be highly useful for monitoring or targeted stimulation.

Self-synchronized reflection-mode acousto-optic imaging system utilizing nanosecond laser pulses.

We present an acousto-optic imaging system operating in reflection-mode and utilizing a pair of compact, triggerable lasers with 532 and 1064 nm wavelength and nanosecond pulse duration. The system maps the fluence rate distribution of light transmitted through optically scattering samples. The imaging is performed using an acousto-optic probe comprising an ultrasound linear array with attached optical fiber on one side and a camera on the other. The described hardware configuration images samples with access restricted to one side only and ensures mobility of the entire setup. The major challenge of the introduced approach is mitigating the effects of laser parameter instabilities and precise synchronization of ultrasound and laser pulses. We solved this issue by developing an electronic feedback circuit and a microcontroller-based synchronization and control system triggering the ultrasound scanner. Schematics and details regarding control algorithms are introduced. The imaging performance of the system is demonstrated on examples of results obtained for solid, acoustically-homogeneous and optically scattering phantoms with and without light absorbing inclusions present. Adjusting the size and location of the region of interest within the camera sensor matrix and the number of laser pulses illuminating every frame allows for significant improvements in terms of the achievable peak signal to noise ratio. We demonstrate that the developed synchronization algorithm and system play a crucial role in ensuring imaging quality and accuracy.

Reflection-mode acousto-optic imaging using a one-dimensional ultrasound array with electronically scanned focus.

SIGNIFICANCE: Practical implementation of acousto-optic imaging (AOI) encounters difficulties that prevent it from rapid adoption in clinical use. In many practical medical applications, the region of interest may be accessed only from one side, and using a water tank for coupling is not feasible. The solution might be to use reflection-mode imaging with an electronically scanned ultrasound (US) focus. Such an approach, however, entails considerable challenges. AIM: The possibilities of detecting and localizing light-absorbing inclusions inside turbid media by combining reflection-mode AOI conducted using a one-dimensional US array with electronic scanning of the US focus are investigated experimentally and signal processing algorithms that could be used for this purpose are introduced. APPROACH: We determine the speckle contrast decrease due to the acousto-optic effect as a function of the US focal point coordinates. Different signal postprocessing techniques are investigated. RESULTS: A significant decrease in the determined speckle contrast difference values is observed due to the presence of light-absorbing inclusions. However, local minima occur in the plots only under specific conditions. Subtracting individual distributions and determining symmetry deviations allow for localizing the inclusions. CONCLUSIONS: Detection and localization of optically distinct regions are possible using the introduced approach. Signal postprocessing is required in a general case.

Technical Note: an algorithm and software for conversion of radiotherapy contour-sequence data to ready-to-print 3D structures.

PURPOSE: Three-dimensional (3D) printing is one of the most promising technologies that can significantly improve the efficiency of various radiotherapy (RT) procedures. In order to 3D print any structure from a DICOM file, it first has to be converted to one of the typical formats recognized by printing software, such as STL files. Due to the specificity of the data from RT planning systems and a lack of standardized methods, the geometry processing might be tricky and complex. However, all the articles presented in the literature so far either describe this step very briefly, or do not mention it at all. METHODS: We present a detailed description of an algorithm and a piece of open-source software, that allow conversion of contour-sequence data included within DICOM files into ready-to-print 3D structures saved as STL files. The algorithm allows automatic handling of the data from RT planning systems and takes into account and corrects for all the typical issues, such as different orientation of curves or artifacts. The implementing software, included as a supplementary material, is distributed as open source under GNU GPL license, which means that it can be freely used, modified, and redistributed by anyone. RESULTS: The algorithm and implementing software were used to convert numerous structures contained within DICOM files created with RT planning systems into ready-to-print 3D structures. The structures were converted with absolute fidelity, without any errors. CONCLUSIONS: The presented tools can be used for research and development of patient-specific accessories for RT. The described algorithm and software can make 3D printing in RT more accessible to medical professionals, contributing to its further development.