The development of acoustic system for noninvasive monitoring of blood perfusion (original) (raw)
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Measurement of blood perfusion using photoacoustic, ultrasound and strain imaging
Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 2007
In many clinical and research applications including cancer diagnosis, tumor response to therapy, reconstructive surgery, monitoring of transplanted tissues and organs, and quantitative evaluation of angiogenesis, sequential and quantitative assessment of microcirculation in tissue is required. In this paper we present an imaging technique capable of spatial and temporal measurements of blood perfusion through microcirculation. To demonstrate the developed imaging technique, studies were conducted using phantoms with modeled small blood vessels of various diameters positioned at different depths. A change in the magnitude of the photoacoustic signal was observed during vessel constriction and subsequent displacement of optically absorbing liquid present in the vessels. The results of the study suggest that photoacoustic, ultrasound and strain imaging could be used to sequentially monitor and qualitatively assess blood perfusion through microcirculation.
Quantitative investigation of acoustic streaming in blood
Acoustic streaming may have practical utility in diagnostic medical ultrasound in distinguishing between stagnant blood and tissue as well as clotted and unclotted blood. This distinction can be difficult with conventional ultrasound but have high value in managing trauma patients with internal hemorrhage. Ultrasound energy applies a force to blood by momentum transfer, resulting in bulk streaming that is a function of the acoustic attenuation, sound speed, acoustic intensity, blood viscosity, and the boundary conditions posed by the geometry around the hematoma. A simple tubular model was studied analytically, by finite element simulation, and experimentally by in vitro measurement. The simulation agreed closely with measurements while the analytic solutions were found to be valid only for beam diameters approximating the diameter of the tubular channel. Experimentally, the acoustic streaming in blood decreased as the blood began to clot and the streaming flow was not detected in clotted blood. In contrast, the echogenicity of the same blood samples did not change appreciably from the unclotted to the clotted state for the stagnant blood studied. Streaming detection appears to offer a potential tool for improving hemorrhage diagnosis.
Ultrasonic Blood Flow Meter with Doppler Velocimetry
2013
A b stra ct-Ultrasonic blood flow meters are a non-invasive method to measure the velocity o f blood. These flow meters are relatively expensive. The goal o f this project was to produce a low-cost ultrasonic blood flow meter that utilizes the Doppler Effect The flow meter constructed costs less than $300 dollars to build, which is less expensive than current flow meters used in the medical field. The flow meter transmits a frequency into the body and receives a Doppler shifted frequency back. This Doppler shifted frequency is proportional to velocity. The constructed flow meter produces an audio signal with this Doppler shifted frequency. The circuit used consisted of a transmitter, receiver, and frequency shifter. The frequency shifter eased the signal processing by shifting the signal up. Signal processing was done on the audio signal to produce velocity profiles of arterial blood flow. MATLAB was used to create spectrograms and low pass filters on the recorded audio signal. Many filters were tested as well as different methods to produce the spectrograms. Spectrogram plots mapped out the velocity profiles. Results showed that the velocity profiles had a roughly parabolic shape and that filters were necessary to reduce high frequency noise. Testing was done on multiple subjects and with different strain on the heart to determine the flow meter's performance under various conditions. Results are promising, it more testing is necessary to determine accuracy and safety. K eyw ords-D o p p ler E ffec t; u ltra so n ic f lo w m eter; spectrogram I. In t r o d u c t i o n
Second harmonic ultrasonic blood perfusion measurement
Ultrasound in Medicine & Biology, 1993
In vitro and in vivo testing of a recently introduced method of evaluating blood perfusion is presented, where the Doppler shift of the second harmonic component of the backscattered echo is measured. Central to this measurement is the administration of a galactose-based contrast agent (Schering AG, Berlin, Germany, SHU-508 or derivative) which has been shown in vitro to exhibit extraordinary nonlinear backscattering properties. Two types of experiments are described: in vitro studies on excised sheep kidneys and in vivo studies on living rabbits. In the animal model, blood perfusion was manipulated by various mechanisms to obtain some indication of the quantitative ability of the measurement. Comparisons between measurements made at the fundamental component of the backscattered echo and at the second harmonic show that use of the second harmonic measurement results in a much improved ratio of blood echo intensity to tissue echo intensity (signal-to-clutter ratio), allowing detection of blood flowing in smaller vessels and opening up the potential for real-time determination of blood volume fluctuations in tissue.
Noninvasive acoustic blood volume measurement system for the POLVAD prosthesis
Bulletin of the Polish Academy of Sciences: Technical Sciences, 2011
Noninvasive acoustic blood volume measurement system for the POLVAD prosthesis The following paper presents researches concerning a noninvasive real-time blood volume measurement system applied in POLVAD prosthesis. The system is based on the acoustic Helmholtz resonator principle. The basis of the measurement method, followed by the preliminary tests of the possibility of incorporating the Helmholtz resonance idea into the POLVAD prosthesis is shown. The paper includes the actual measurement system construction and test results, both static and dynamic obtained at the Foundation for Cardiac Surgery Development in Zabrze, Poland. Conclusions and future plans are presented too.
Jurnal Teknologi
Measurement using the currently available tissue oxygen monitoring systems, such as pulse oximeter, is unreliable in patients with compromised microcirculation. Others offer high diagnostic accuracy, but are complicated and expensive in their operation. This paper is motivated to study the use of photoacoustic (PA) phase change as a predictor of skin tissue oxygen levels. This work used EPOCH 650 ultrasonic flaw detector with a longitudinal transducer and a red laser light of wavelength 633 nm for measurement of PA signals. This pilot study was conducted on a group of four human subjects. The pressure waves were collected from their anterior left arm under three experimental conditions, namely at rest, venous and arterial blood flow occlusions, for extraction of hemoglobin absorption dependent phase information.
Angle Independent Ultrasonic Detection of Blood Flow
IEEE Transactions on Biomedical Engineering, 1987
solenoids) and discovered several physical problems that we will improve upon in future models. Since the springs were individually cut by hand, there were variations in the two intermediate heights from solenoid to solenoid. A possible solution is custom made conical springs with length-dependent spring constants. Friction between the pushrods and the Plexiglas plate created a major physical problem, sometimes altering a solenoid's response to the controlling current. Also the wires routed between the solenoid layers in some cases interfered with the upward motion of the pushrods. An aesthetic problem with the display is that it is quite noisy. When the solenoids move to the fully on position, they make an audible click that is distracting. More details of design, software, and testing of the prototype model are available [ 11]. CONCLUSIONS We were generally encouraged with the results of expenrments with our prototype model. We feel that it satisfied the requirements we set out to achieve. We will use the knowledge gained from these experiments and from observed problems to complete the final design of the haptic display device.
Ultrasonic estimation of tissue perfusion: A stochastic approach
Ultrasound in Medicine & Biology, 1995
Imaging of blood flow perfusion is an area of significant medical interest. Recently, the advantages of using the total integrated Doppler power spectrum as the parameter that is encoded in color has been shown to result in an approximately threefold increase in flow sensitivity, a relative insensitivity to acquisition angle and lack of aliasing. We have taken this mode a step further and demonstrated the potential for quantifying blood flow using correlation-based algorithms applied to the power signal. We show that a( 7) = *(0)eeyr, T > 0, where a(~) is the two-time correlation of the fluctuation in the power signal, and Y is the speciiic flow (reciprocal of mean transit time). Scans of a dog's blood, pumped at a constant rate through gum rubber tubing, were obtained using a Diasonics Spectra lo-MHz linear array transducer at standard range-gated spectral mode (PRF = 1400 Hz, wall filter = 50 Hz, sample gate = 1.5 mm). A fixed Doppler angle of 68" was used. Five different flow rates were tested, and the velocities determined by power decorrelation were compared to the mean velocities calculated from the Doppler shifts by linear regression (R' = 0.987). We believe the results are very encouraging for using power decorrelation in perfusion evaluation.
Non-invasive estimation of blood pressure using ultrasound contrast agents
Physics Procedia, 2010
Local blood pressure measurements provide important information on the state of health of organs in the body and can be used to diagnose diseases in the heart, lungs, and kidneys. This paper presents an experimental setup for investigating the ambient pressure sensitivity of a contrast agent using diagnostic ultrasound. The setup resembles a realistic clinical setup utilizing a single array transducer for transmit and receive. The ambient pressure sensitivity of SonoVue (Bracco, Milano, Italy) was measured twice using two different acoustic driving pressures, which were selected based on a preliminary experiment. To compensate for variations in bubble response and to make the estimates more robust, the relation between the energy of the subharmonic and the fundamental component was chosen as a measure over the subharmonic peak amplitude. The preliminary study revealed the growth stage of the subharmonic component to occur at acoustic driving pressures between 300 and 500 kPa. Based on this, the pressure sensitivity was investigated using a driving pressure of 485 and 500 kPa. At 485 kPa, a linear pressure sensitivity of 0.42 dB/kPa was found having a linear correlation coefficient of 0.94. The second measurement series at 485 kPa showed a sensitivity of 0.41 dB/kPa with a correlation coefficient of 0.89. Based on the measurements at 500 kPa, this acoustic driving pressure was concluded to be too high causing the bubbles to be destroyed. The pressure sensitivity for these two measurement series were 0.42 and 0.25 dB/kPa with linear correlation coefficients of 0.98 and 0.93, respectively.
Design of a wearable ultrasound Doppler sensor to monitor blood flow in the common carotid artery
1999
A novel design for a wearable and non-invasive ultrasound Doppler blood flow measuring device is presented. The device consists of an array of piezoelectric transducers that mount at the neck and generate different ultrasonic beams directed at the common carotid artery. The Doppler frequency shift generated by the moving blood is then processed to reconstruct the centerline velocity of the artery as well as to provide an estimate of the velocity profile and other physiological parameters. The presented design covers key issues relevant to making this technology wearable mainly handling the location uncertainty of the artery and interpreting the measurement without human assistance with the restriction of keeping the technical complexity of the device low for all cases. The array of transducers is designed to enable the coverage of a wide sector in the neck that encompasses the artery. Different beams can be produced by the array depending on the number of transducers that are excited. The centerline velocity of the artery is used as a criterion to decide which transducers are favorably oriented and hence should be operated. Novel algorithms to process the received signal to estimate the velocity profile and the time derivative of pressure are presented. The thesis builds upon theoretical analysis and includes computer simulation and experimental verification of the key ideas.