Single Transducer System Research Articles

Evaluating ECM stiffness and liver cancer radiation response via shear-wave elasticity in 3D culture models

BackgroundThe stiffness of the tumor microenvironment (TME) directly influences cellular behaviors. Radiotherapy (RT) is a common treatment for solid tumors, but the TME can impact its efficacy. In the case of liver cancer, clinical observations have shown that tumors within a cirrhotic, stiffer background respond less to RT, suggesting that the extracellular matrix (ECM) stiffness plays a critical role in the development of radioresistance.MethodsThis study explored the effects of ECM stiffness and the inhibition of lysyl oxidase (LOX) isoenzymes on the radiation response of liver cancer in a millimeter-sized three-dimensional (3D) culture. We constructed a cube-shaped ECM-based millimeter-sized hydrogel containing Huh7 human liver cancer cells. By modulating the collagen concentration, we produced two groups of samples with different ECM stiffnesses to mimic the clinical scenarios of normal and cirrhotic livers. We used a single-transducer system for shear-wave-based elasticity measurement, to derive Young’s modulus of the 3D cell culture to investigate how the ECM stiffness affects radiosensitivity. This is the first demonstration of a workflow for assessing radiation-induced response in a millimeter-sized 3D culture.ResultsIncreased ECM stiffness was associated with a decreased radiation response. Moreover, sonoporation-assisted LOX inhibition with BAPN (β-aminopropionitrile monofumarate) significantly decreased the initial ECM stiffness and increased RT-induced cell death. Inhibition of LOX was particularly effective in reducing ECM stiffness in stiffer matrices. Combining LOX inhibition with RT markedly increased radiation-induced DNA damage in cirrhotic liver cancer cells, enhancing their response to radiation. Furthermore, LOX inhibition can be combined with sonoporation to overcome stiffness-related radioresistance, potentially leading to better treatment outcomes for patients with liver cancer.ConclusionsThe findings underscore the significant influence of ECM stiffness on liver cancer’s response to radiation. Sonoporation-aided LOX inhibition emerges as a promising strategy to mitigate stiffness-related resistance, offering potential improvements in liver cancer treatment outcomes.

SU‐E‐U‐02: The Development of a Practical Ultrasonic System for Cross‐Sectional Imaging of Small Animals

Purpose:To test the feasibility of developing a practical medium frequency ultrasound tomography method for small animal imaging. The ability to produce cross‐sectional or full body images of a live small animal using a low‐cost tabletop ultrasound scanner without any special license would be very beneficial to long term biological studies, where repeated scanning is often required over an extended period of time.Methods:The cross sectional images were produced by compounding multiple B‐scans of a laboratory phantom or an animal acquired at different projection angles. Two imaging systems were used to test the concept. The first system included a programmable 64‐channel phased array controller driving a 128‐channel, 5–10 MHz linear probe to produce 143 B‐Mode projections of the spinning object. The second system designed and manufactured in house, produced 64 or 128 B‐Mode projections with a single unfocused 8 MHz transducer scanning with a 0.116 mm step size.Results:The phased array system provided good penetration through the phantoms/mice (with the exception of the lungs) and allowed to acquire data in a very short time. The cross‐sectional images have enough resolution and dynamic range to detect both high‐ and low‐contrast organs. The single transducer system takes longer to scan, and the data require more sophisticated processing. To date, our images allow seeing details as small as 1–2 mm in the phantoms and in small animals, with the contrast mostly due to highly reflecting bones and air inclusions.Conclusion:The work indicates that very detailed and anatomically correct images can be created by relatively simple and inexpensive means. With more advanced algorithms and improved system design, scan time can be reduced considerably, enabling high‐resolution full 3D imaging. This will allow for quick and easy scans that can help monitor tumor growth and/or regression without contributing any dose to the animal.The authors would like to acknowledge the financial and engineering support from Tessonics.

Handheld photoacoustic probe to detect both melanoma depth and volume at high speed in vivo.

We applied a linear-array-based photoacoustic probe to detect melanin-containing melanoma tumor depth and volume in nude mice in vivo. This system can image melanomas at five frames per second (fps), which is much faster than our previous handheld single transducer system (0.1 fps). We first theoretically show that, in addition to the higher frame rate, almost the entire boundary of the melanoma can be detected by the linear-array-based probe, while only the horizontal boundary could be detected by the previous system. Then we demonstrate the ability of this linear-array-based system in measuring both the depth and volume of melanoma through phantom, ex vivo, and in vivo experiments. The volume detection ability also enables us to accurately calculate the rate of growth of the tumor, which is an important parameter in quantifying the tumor activity. Our results show that this system can be used for clinical melanoma diagnosis and treatment in humans at the bedside. Linear-array-based PA images of melanoma acquired in vivo on day 3 (a) and day 6 (b).

Dynamic footprint analysis by time-of-flight camera

Dynamic pedobarograph measurement is commonly used to evaluate the roll-over process of the foot. Plantar pressure plates, insole sensors or single transducer systems are the most popular devices to analyze dynamic footprint [1]. Notably with the last works of Pataky [2-4], plantar pressure analyses were improved. Nevertheless, the systems available to analyze dynamic footprint are limited to these ‘pressure’ measurement systems with resolution limited to 1 to 4 sensors/cm2, to the authors’ knowledge. The goal of the current study is to propose a new approach, i.e. foot squashing, using a system (dynamic footprint system) with a high resolution.

An optimal stochastic control theory for distributed energy harvesting networks

A new approach, based on H 2 optimal control theory, is presented for the design of feedback controllers for energy harvesting systems for maximal power generation. The theory applies to stochastically excited vibratory systems in broadband stationary response, and allows for harvested power to be explicitly optimized. It is applicable to both single-transducer systems as well as coupled networks of many transducers. The theory accounts for the influence of energy harvesting on the dynamics of the structure to which the transducers are attached. It also accounts for resistive and semiconductor dissipation in the power-electronic network interfacing the transducers with energy storage. Due to its predominance in the literature, a piezoelectric bimorph cantilever beam is used as the context for the theory, and simulation examples are used to illustrate various aspects of the optimal controllers.

Novel Detection System Using Double-Layered Piezoelectric Transducer in Same Polarization Direction for Sub-Harmonic Components Generated from Plastic-Deformed Metal Rod

A novel detection system for sub-harmonic components of ultrasonic pulse waves is constructed. A new double-layered piezoelectric transducer (DLPT), having the same polarization direction for each layer, is introduced to enhance the sensitivity for sub-harmonic components. In the case of DLPT stacked and bonded to one another in the same polarization direction, the resonance frequencies of the DLPT, fr, are f0 in a parallel connection and f0/2 in a series connection. As a result, the receiving sensitivity of the sub-harmonic components is increased by approximately 30 dB and the receiving sensitivity of fundamental components is decreased by approximately 20 dB, compared with those in the parallel connection. As an application of this system, the detection of sub-harmonic components generated from plastic-deformed metal rods is demonstrated. The DLPT system can be used to detect some deformed samples, while sub-harmonic components cannot be detected using a single transducer system.

Frontiers in Intravascular Imaging Technologies

In 1971, Bom et al1 developed one of the first catheter-based real-time imaging techniques for use in the cardiac system. In placing a set of phased-array ultrasound transducers within the cardiac chambers, Bom and colleagues showed that higher frequencies than those used in transthoracic ultrasound imaging could be used to produce high-resolution images of cardiac structures. By the late 1980s, Yock et al2 had successfully miniaturized a single-transducer system to enable transducer placement within coronary arteries. Since then, intravascular ultrasound (IVUS) has become a pivotal catheter-based imaging technology, having provided practical guidance for percutaneous interventions and scientific insights into vascular biology in clinical settings. Technical developments currently being explored consist of further device improvements, a variety of advanced image analyses, and the extension of this ultrasound-based approach to diverse intravascular imaging techniques with other energy sources. ### Ultrasound-Based Approaches IVUS systems produce tomographic images by performing a series of pulse/echo sequences, or vectors, in which an acoustic pulse is emitted and the subsequent reflections from the tissue are detected. Each vector is acquired by directing the ultrasound beam from the catheter in a slightly different direction from the previous vector by mechanical or electrical means. A gray-scale IVUS image is made with all the vectors (commonly 256 vectors), with each vector acquired at a different angle of rotation. Several clinically relevant properties of the ultrasound image, such as the resolution, depth of penetration and attenuation of the acoustic pulse by tissue, are dependent on the geometric and frequency properties of the transducer. A crystal transducer emits a signal that spans a range of frequencies. The higher the center frequency, the better the radial resolution (Figure 1) but the lower the depth of penetration. Conventional IVUS catheters used in the coronary arteries have center frequencies that range from 20 MHz to 40 …

A differential double-coil inductive transducer for measuring electrical conductivity

A differential system of two double-coil inductive transducers for the contactless measurement of the electrical conductivity of conducting materials has been presented. The differential system can be employed in applications that require smaller measurement uncertainty than that provided by the single-transducer system. A mathematical model of the differential system is based on the model of a single double-coil inductive transducer; in this case, a so-called processing function is defined as a ratio of voltages at the measurement coil terminals with and without the test sample. The relative differential voltage of the differential system is derived as a difference of processing functions of two single transducers and depends on a relative difference between conductivities of the test and reference samples. The conductivity of the test sample is obtained either using precalculated graphs or by numerically processing the equation of the differential voltage. In order to verify the obtained theoretical results, experimental investigations have been carried out using a computer-controlled measurement system with the differential system of the transducers. The conductivity measurements have been carried out using samples made of aluminum rods. During the measurements, the temperature of the reference sample was equal to room temperature (20 degrees C), whereas the temperature of the test sample was changed in the range of 0-20 degrees C to obtain the conductivity variation. The obtained experimental results confirmed the accuracy of the theoretical model of the differential transducer.

Time-quantified fetal movement detection with two-transducer data fusion

Objective: Our purpose was to develop an automated ultrasound-based fetal movement detection system to batter define fetal movements. Study design: One hundred one patients had fetal movements recorded over a 20-minute period. Results of movement detection by a single-transducer system (Russell 1) and a two-transducer fusion system (Russell 2) were compared with those of Hewitt-Packard (HP-M-1350-A), maternal perception, and expert ultrasonography review. Results: A total of 86,592 seconds of videotape was scored for fetal movement, Russell 2 had a second-per-second sensitivity of 57.21% compared with Russell 1 at 40.95%, the HP-M-1350-A at 31.44%, and maternal perception at 30.80%. Russell 2 detected 67.57% of discrete movements compared with 57.52%, 41.98%, and 37.92%, respectively, in other systems. Conclusion: Russell 2 represents a significant improvement over existing systems in detection of fetal movement on a second-per-second basis.

Airway Area by Acoustic Reflection: The Two-Microphone Method

This report deals with noninvasive imaging of airway geometry based upon information contained in acoustic reflections measured at the mouth. Here we describe a new theoretical approach that enables development of a new miniaturized apparatus. Unlike the single-transducer systems used currently, this new strategy is based upon a two-transducer system that is a variant of that suggested originally by Shroeder (1967). We have developed, implemented, and tested computational algorithms necessary to reconstruct airway dimensions from acoustic reflection data using this two-transducer strategy.

Echo counting and echo integration with a sector scanning sonar

An investigation is described of the possible application of sector scanning sonar for measuring the spatial density of marine organisms. The two assessment techniques investigated are called echo counting and echo integration. These techniques have been used extensively with single transducer echo sounding equipment for fisheries assessment. One of the main limitations of single transducer assessment systems is that they cannot provide both high resolution and good volume coverage. However, an acoustic assessment system in which a sector scanning sonar is used can provide both. The problems of implementing the two assessment techniques when using a scanning sonar are discussed. The performance of the techniques is evaluated by calculating the normalized rms error in the estimate of spatial density they provide. It is shown that, under certain conditions, the sector scanning assessment will system provide an estimate with a significaantly smaller error than that obtained with a conventional single transducer system.