Array Transducer Research Articles

Large-Array Deep Abdominal Imaging in Fundamental and Harmonic Mode.

Deep abdominal images suffer from poor diffraction-limited lateral resolution. Extending the aperture size can improve resolution. However, phase distortion and clutter can limit the benefits of larger arrays. Previous studies have explored these effects using numerical simulations, multiple transducers, and mechanically swept arrays. In this work, we used an 8.8-cm linear array transducer to investigate the effects of aperture size when imaging through the abdominal wall. We acquired channel data in fundamental and harmonic modes using five aperture sizes. To avoid motion and increase the parameter sampling, we decoded the full-synthetic aperture data and retrospectively synthesized nine apertures (2.9-8.8 cm). We imaged a wire target and a phantom through ex vivo porcine abdominal samples and scanned the livers of 13 healthy subjects. We applied bulk sound speed correction to the wire target data. Although point resolution improved from 2.12 to 0.74 mm at 10.5 cm depth, contrast resolution often degraded with aperture size. In subjects, larger apertures resulted in an average maximum contrast degradation of 5.5 dB at 9-11 cm depth. However, larger apertures often led to visual detection of vascular targets unseen with conventional apertures. An average 3.7-dB contrast improvement over fundamental mode in subjects showed that the known benefits of tissue-harmonic imaging extend to larger arrays.

Assessment of Transarterial Chemoembolization Using Super-resolution Ultrasound Imaging and a Rat Model of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a highly prevalent form of liver cancer diagnosed annually in 600,000 people worldwide. A common treatment is transarterial chemoembolization (TACE), which interrupts the blood supply of oxygen and nutrients to the tumor mass. The need for repeat TACE treatments may be assessed in the weeks after therapy with contrast-enhanced ultrasound (CEUS) imaging. Although the spatial resolution of traditional CEUS has been restricted by the diffraction limit of ultrasound (US), this physical barrier has been overcome by a recent innovation known as super-resolution US (SRUS) imaging. In short, SRUS enhances the visible details of smaller microvascular structures on the 10 to 100 µm scale, which unlocks a host of new clinical opportunities for US. In this study, a rat model of orthotopic HCC is introduced and TACE treatment response (to a doxorubicin-lipiodol emulsion) is assessed using longitudinal SRUS and magnetic resonance imaging (MRI) performed at 0, 7 and 14 d. Animals were euthanized at 14 d for histological analysis of excised tumor tissue and determination of TACE response, that is, control, partial response or complete response. CEUS imaging was performed using a pre-clinical US system (Vevo 3100, FUJIFILM VisualSonics Inc.) equipped with an MX201 linear array transducer. After administration of a microbubble contrast agent (Definity, Lantheus Medical Imaging), a series of CEUS images were collected at each tissue cross-section as the transducer was mechanically stepped at 100 μm increments. SRUS images were formed at each spatial position, and a microvascular density metric was calculated. Microscale computed tomography (microCT, OI/CT, MILabs) was used to confirm TACE procedure success, and tumor size was monitored using a small animal MRI system (BioSpec 3T, Bruker Corp.). Although there were no differences at baseline (p > 0.15), both microvascular density levels and tumor size measures from the complete responder cases at 14 d were considerably lower and smaller, respectively, than those in the partial responder or control group animals. Histological analysis revealed tumor-to-necrosis levels of 8.4%, 51.1% and 100%, for the control, partial responder and complete responder groups, respectively (p < 0.005). SRUS imaging is a promising modality for assessing early changes in microvascular networks in response to tissue perfusion-altering interventions such as TACE treatment of HCC.

Precise Estimation of Intravascular Pressure Gradients.

This study presents a method for noninvasive pressure gradient estimation, which allows the detection of small pressure differences with higher precision compared to invasive catheters. It combines a new method for estimating the temporal acceleration of the flowing blood with the Navier-Stokes equation. The acceleration estimation is based on a double cross-correlation approach, which is hypothesized to minimize the influence of noise. Data are acquired using a 256-element, 6.5-MHz GE L3-12-D linear array transducer connected to a Verasonics research scanner. A synthetic aperture (SA) interleaved sequence with 2 ×12 virtual sources evenly distributed over the aperture and permuted in emission order is used in combination with recursive imaging. This enables a temporal resolution between correlation frames equal to the pulse repetition time at a frame rate of half the pulse repetition frequency. The accuracy of the method is evaluated against a computational fluid dynamic simulation. Here, the estimated total pressure difference complies with the CFD reference pressure difference, which yields an R -square of 0.985 and an RMSE of 3.03 Pa. The precision of the method is tested on experimental data, measured on a carotid phantom of the common carotid artery. The volume profile used during measurement was set to mimic flow in the carotid artery with a peak flow rate of 12.9 mL/s. The experimental setup showed that the measured pressure difference changes from -59.4 to 31 Pa throughout a single pulse cycle. This was estimated with a precision of 5.44% (3.22 Pa) across ten pulse cycles. The method was also compared to invasive catheter measurements in a phantom with a 60% cross-sectional area reduction. The ultrasound method detected a maximum pressure difference of 72.3 Pa with a precision of 3.3% (2.22 Pa). The catheters measured a maximum pressure difference of 105 Pa with a precision of 11.2% (11.4 Pa). This was measured over the same constriction and with a peak flow rate of 12.9 mL/s. The double cross-correlation approach revealed no improvement compared to a normal differential operator. The method's strength, thus, lies primarily in the ultrasound sequence, which allows precise and accurate velocity estimations, at which acceleration and pressure differences can be acquired.

Improved Magneto-Acousto-Electrical Computed Tomography (MAE-CT) With Multi-Angle Plane Wave Excitation.

As a tissue conductivity imaging method, magneto-acousto-electric tomography (MAET) has the advantage of high axial spatial resolution compared with traditional electrical impedance imaging methods. However, it has the problems of difficulty in imaging targets with irregular conductivity distribution and poor lateral spatial resolution. Although the rotation-based MAET method can partly solve the irregular target problem, there is still a poor imaging signal-to-noise ratio (SNR) problem. Our previous study established a framework of an innovative MAET method, which has a very similar imaging theory and reconstruction algorithm to those of computed tomography (CT). Therefore, we name the method magneto-acoustic-electric computed tomography (MAE-CT). This paper proposes an improved implementation of MAE-CT based on multi-angle plane wave excitation. This method combines the electronic steering of the linear array transducer with the mechanical rotation to increase the number of projection angles while keeping the imaging complexity. In this study, we first established a finite element simulation model to verify the method's feasibility. Then phantom experiments were conducted to systematically investigate the performance of the proposed method. Finally, in vitro liver tissue experiment was conducted to further explore the feasibility of the method. The experimental results show that our method improves both the SNR and spatial resolution of the reconstructed image. For the phantom results, this method can detect conductivity of 0.67 S/m in an area with a size of 2 mm. To the best of our knowledge, this is the best result of spatial resolution available for MAET.

Multi-plane Diffractive Acoustic Networks.

Acoustic holograms are able to control pressure fields with high spatial resolution, enabling complex fields to be projected with minimal hardware. This capability has made holograms attractive tools for applications including manipulation, fabrication, cellular assembly, and ultrasound therapy. However, the performance benefits of acoustic holograms have traditionally come at the cost of temporal control. Once a hologram is fabricated, the field it produces is static and cannot be reconfigured. Here, we introduce a technique to project time-dynamic pressure fields by combining an input transducer array with a multi-plane hologram, which is represented computationally as a diffractive acoustic network (DAN). By exciting different input elements in the array, we can project distinct and spatially-complex amplitude fields to an output plane. We numerically show that the multi-plane DAN outperforms a single-plane hologram, while using fewer total pixels. More generally, we show that adding more planes can increase the output quality of the DAN for a fixed number of degrees of freedom (pixels). Finally, we leverage the pixel efficiency of the DAN to introduce a combinatorial projector that can project more output fields than there are transducer inputs. We experimentally demonstrate that a multi-plane DAN could be used to realize such a projector.

A Geometric Model of Ultrasound Backscatter to Describe Microstructural Anisotropy of Tissue.

Methods to assess ultrasound backscatter anisotropy from clinical array transducers have recently been developed. However, they do not provide information about the anisotropy of microstructural features of the specimens. This work develops a simple geometric model, referred to as the secant model, of backscatter coefficient anisotropy. Specifically, we evaluate anisotropy of the frequency dependence of the backscatter coefficient parameterized in terms of effective scatterer size. We assess the model in phantoms with known scattering sources and in a skeletal muscle, a well-known anisotropic tissue. We demonstrate that the secant model can determine the orientation of the anisotropic scatterers, as well as accurately determining effective scatterer sizes, and it may classify isotropic versus anisotropic scatterers. The secant model may find utility in monitoring disease progression as well as characterizing normal tissue architectures.

A probabilistic framework for source localization in anisotropic composite using transfer learning based multi-fidelity physics informed neural network (mfPINN)

The practical application of data-driven frameworks like deep neural network in acoustic emission (AE) source localization is impeded due to the collection of significant clean data from the field. The utility of the such framework is governed by data collected from the site and/or laboratory experiment. The noise, experimental cost and time consuming in the collection of data further worsen the scenario. To address the issue, this work proposes to use a novel multi-fidelity physics-informed neural network (mfPINN). The proposed framework is best suited for the problems like AE source detection, where the governing physics is known in an approximate sense (low-fidelity model), and one has access to only sparse data measured from the experiment (high-fidelity data). This work further extends the governing equation of AE source detection to the probabilistic framework to account for the uncertainty that lies in the sensor measurement. The mfPINN fuses the data-driven and physics-informed deep learning architectures using transfer learning. The results obtained from the data-driven artificial neural network (ANN) and physics-informed neural network (PINN) are also presented to illustrate the requirement of a multi-fidelity framework using transfer learning. In the presence of measurement uncertainties, the proposed method is verified with an experimental procedure that contains the carbon-fiber-reinforced polymer (CFRP) composite panel instrumented with a sparse array of piezoelectric transducers. The results conclude that the proposed technique based on a probabilistic framework can provide a reliable estimation of AE source location with confidence intervals by taking measurement uncertainties into account.

Noninvasive measurement of temperature for simulated tissue based on piezoelectric micromachined ultrasonic transducers

This paper reports a noninvasive measurement of temperature for simulated tissue based on an AlN piezoelectric micromachined ultrasonic transducer array. Polydimethylsiloxane and a built-in heating plate are used to simulate the thermal therapy of human tissue. Based on time-of-flight (ToF) from the simulated tissue surface to the heating plate surface and corresponding temperature data, the piecewise linear fitting method is used to fit the ToF-temperature curve, and its sensitivity is (below 50 °C) and (from 50 °C to 65 °C). The average error of real-time temperature measurements is 0.58 °C for temperatures below 65 °C. The proposed method can provide a good solution for temperature detection during thermal therapy.

Very lean hydrogen vapor cloud explosion testing

AbstractHydrogen is a key energy carrier for modern society. The breaking of the hydrogen bonds within traditional hydrocarbon molecules has been the primary mode of energy utilization since the industrial revolution. An increased focus on “net‐zero” greenhouse gas emissions, specifically carbon dioxide and methane, has resulted in a global push for lower carbon energy vectors, including pure hydrogen. Accurately modeling the dispersion, fire, and explosion hazards associated with new and existing hydrogen production, distribution and transportation networks, and consumption is a key component to the safe expansion of these networks. BakerRisk performed a series of very lean hydrogen‐air vapor cloud explosion (VCE) tests as part of an internal research effort. The goal of these tests was to better understand the VCE hazards associated with very lean hydrogen‐air mixtures (≤14% H2). Flame speeds and blast loads were measured using high‐speed video and an array of dynamic pressure transducers. This paper discusses the test setup and test results, including a comparison with data from prior tests. The measured flame speeds are compared to those predicted using computational fluid dynamics analysis and referenced to deflagration‐to‐detonation criteria. Discussion regarding the application of these test results to facility siting studies is also provided.

OpenMPD: A Low-Level Presentation Engine for Multimodal Particle-Based Displays

Phased arrays of transducers have been quickly evolving in terms of software and hardware with applications in haptics (acoustic vibrations), display (levitation), and audio. Most recently, Multimodal Particle-based Displays (MPDs) have even demonstrated volumetric content that can be seen, heard, and felt simultaneously, without additional instrumentation. However, current software tools only support individual modalities and they do not address the integration and exploitation of the multi-modal potential of MPDs. This is because there is no standardized presentation pipeline tackling the challenges related to presenting such kind of multi-modal content (e.g., multi-modal support, multi-rate synchronization at 10 KHz, visual rendering or synchronization and continuity). This article presents OpenMPD, a low-level presentation engine that deals with these challenges and allows structured exploitation of any type of MPD content (i.e., visual, tactile, audio). We characterize OpenMPD’s performance and illustrate how it can be integrated into higher-level development tools (i.e., Unity game engine). We then illustrate its ability to enable novel presentation capabilities, such as support of multiple MPD contents, dexterous manipulations of fast-moving particles, or novel swept-volume MPD content.

Airborne ultrasound focusing aperture with binary amplitude mask over planar ultrasound emissions

Phased arrays of airborne ultrasound transducers are widely utilized as a key technology to achieve mid-air convergence of intense ultrasound, which is applied to a variety of systems, such as contactless tactile presentation, acoustic levitation and its application, mid-air-flow acceleration, etc. However, it requires considerably precise phase control with temporally severe synchronization between elements, which leads to difficulty in scaling up the entire system beyond the tabletop size as most of the current application systems. Here, we propose a much simpler and easier scaling-up method of airborne ultrasound convergence, where a binary amplitude mask that serves as a Fresnel Zone Plate (FZP) is placed on the planar in-phase ultrasound sources. We experimentally demonstrate that the FZP-based ultrasound focusing achieved a spatial resolution that is comparable to conventional methods, based on the use of phase-controlled transducers. The ultrasound foci created using FZPs are sufficiently intense for most application scenarios that are currently in practical use. We also determine favorable side effects of our method suppressing grating lobes, which is inevitable with the conventional phase-controlling method. The FZPs and planar ultrasound sources are both readily implemented with inexpensive ingredients and components. The result of our study contributes to upsizing dimensions in which a mid-air convergent ultrasound field is successfully generated. Accordingly, unprecedented application scenarios that target the entire room as the workspace will be possible.

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

Abstract 1103: Theoretical basis and formula for tumor-treating fields dose-response curves

Abstract Radiotherapy dose-response curves are linear-quadratic (LQ), chemotherapy’s are generally semi-logarithmic or sigmoidal, and Tumor-Treating Fields’ (TTFields) resemble radiotherapy LQ, while the two modalities are presumed to have fundamentally different mechanisms of action (MoA) [1,2]. Radiotherapy produces single- or double-strand DNA breaks, while TTFields act on polarizable cellular structures. Thus, changing the incident electric field direction improves TTFields efficacy, killing 20% more tumor cells in vitro, with 90⁰ changes in the front-back/left-right (x,y) plane [1]. However, by the same logic, polarizable cell structures that are orthogonal to the (x,y) plane see 0 field strength and thus are unaffected by TTFields. The formula for TTFields effective dose with no direction change, given TTFields’ incident angle on the polarizable cell structure’s axis, is simply Deff = cos θ*Dnom, where Dnom is the electric field strength at the axis. The formulae for TTFields dose-response, given one, two, and three incident directions can be calculated (Mathematica v.12, WRI, Champaign, IL) as n(Dnom|cosθ1|≥k) + n(Dnom|cosθ2|≥k) + n(Dnom|cosθ3|≥k)/N, where n is the counting function, Dnom is the nominal field strength at the axis, θi the 1st, 2nd, or 3rd incident TTFields angle, k is TTFields' efficacy floor in V/cm (see below), and N is the total cell population in vivo, vitro, or silico. The formula assumes: 1) Cells are randomly-oriented in vivo [1]; 2) Polarized cell structures are straight; 3) Electric field strength is Deff not Dnom, 4) Cells are in their radiosensitive state (e.g. mitosis), 5) Reducing TTFields duty cycle/direction has no effect down to 0.25 s ([1], and unpublished data), and 6) TTFields’ minimum efficacious field strength Deff = ~0.75 V/cm for cell structures perfectly aligned with the incident TTFields angle (cf. low dose V/cm data points in MDA-MB-231, F-98, B16F1, and H1299 empirical dose-response curves [1,2]). With feasible TTFields transducer array placements on the head or torso, it is relatively easy to achieve changes of direction in one (x,y) plane, but difficult to achieve an additional change of direction in the z-plane. For a nominal TTFields dose Dnom of 2 V/cm, only a 22⁰ change of direction off the (x,y) plane is necessary to kill the cells with Deff below the efficacy threshold, with Dnom = 1.5 V/cm, a 30⁰ change is needed, and with Dnom = 1 V/cm, a 49⁰ change is needed. In sum, we have derived TTFields’ dose-response formulae from first principles, which differentiates them from those of radiotherapy and chemotherapy, and, toward achieving 100% TTFields efficacy as a monotherapy, given motivation and guidelines for adding an additional TTFields’ change of direction per duty cycle.1.Kirson, E.D., et al., Proc Natl Acad Sci U S A, 2007.2.Moser, J.C., et al.,.Cancer Res, 2022. Citation Format: Kristen Carlson. Theoretical basis and formula for tumor-treating fields dose-response curves [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1103.

Study on Directivity of Underwater Circular Transducer Array

At present, in the detection and identification of underwater noise sources, one of the most commonly used transducer arrays is the circumferential transducer array. The circumferential transducer array is symmetrical in space and has high withstand voltage capability and small sound pressure fluctuation in the horizontal beam. Its directivity is an important index that affects the performance of the array. This paper focuses on the directivity maps of circular arrays with different sizes and numbers of elements. From the graph, it is concluded that the undulation of the directivity graph of the circular array is directly related to the array element spacing. The smaller the array element spacing is, the smaller the undulation is, and vice versa. The directivity formula and law can provide technical guidance for the design of a uniform circular transducer array.

Demonstration of Spiral Wavefront Navigation on an Unmanned Underwater Vehicle

Experiments carried out at NUWC's Seneca Lake facility in the summer of 2020 demonstrate the efficacy of underwater navigation via a single spiral wavefront (SWF) acoustic beacon. An SWF beacon is a transducer array that has the capability of generating a spiral acoustic signal whose phase varies linearly with angular aspect along with a reference signal with constant phase. An unmanned underwater vehicle (UUV) operating in Seneca Lake under various channel conditions receives a regular signal from a fixed position single SWF beacon. The UUV's aspect relative to the beacon and its radial velocity can be determined by comparing the phase of the spiral signal to that of the reference signal. The SWF navigation solutions are compared to the UUVs inertial/GPS navigation. Advances in signal processing for the spiral wavefront navigation in multipath environments are detailed. An example of multipath performance from experimental data is shown.

Full-duplex underwater acoustic communications via self-interference cancellation in space

Traditionally, underwater acoustic communications are half-duplex (HD), i.e., the hydrophones and transducers operate in non-overlapping time-slots/frequency-bands in one direction. To double the spectral efficiency into the full-duplex (FD) mode, which transmit and receive signals simultaneously, a self-interference cancellation (SIC) technique in space is introduced and deployed. Specifically, a novel underwater acoustic system is proposed to perform FD-SIC efficiently via an integrated design combining underwater acoustic vector sensor (AVS) and phased array transducer (PAT) to realize the spatial SIC. The energy focusing function of the beamformer (BF) helps PAT avoid self and mutual spatial interference. The AVS keeps updating the direction of arrival information to let BF adjust the steering angle via an adaptive protocol. The field-programmable gate array (FPGA) Direction of Arrival Estimation (DOA) estimation is done by a 12-element AVS, run-time is 1.22×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> s by MUSIC method, which is promising for real-time applications. In this work, phase-shift keying (PSK) and PSK-based orthogonal frequency-division multiplexing (OFDM) are deployed as the FD transmission modulation methods in the spacial SIC. The proposal is evaluated and verified via both simulations and emulations in real underwater acoustic channels collected in the Gulf of La Spezia, Italy, and it is able to achieve 59 dB SIC while modulating with binary phase-shift keying (BPSK) with carrier wave frequency 80 kHz and AVS steering angle −5°. Moreover, it has at least 37 dB SIC within the steering angle region.

MP23-05 NONINVASIVE ACOUSTIC FORCEPS USING ULTRASOUND TO MANIPULATE OBJECTS IN THE URINARY TRACT

You have accessJournal of UrologyCME1 Apr 2023MP23-05 NONINVASIVE ACOUSTIC FORCEPS USING ULTRASOUND TO MANIPULATE OBJECTS IN THE URINARY TRACT Mohamed Ghanem, Arturo Holmes, Adam Maxwell, Michael Bailey, Mathew Sorensen, and Jonathan Harper Mohamed GhanemMohamed Ghanem More articles by this author , Arturo HolmesArturo Holmes More articles by this author , Adam MaxwellAdam Maxwell More articles by this author , Michael BaileyMichael Bailey More articles by this author , Mathew SorensenMathew Sorensen More articles by this author , and Jonathan HarperJonathan Harper More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003248.05AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Ultrasonic propulsion has been demonstrated in clinical trials to noninvasively reposition renal stones along the direction of the probe. However, extracorporeal manipulation of stones causing ureteral stone obstruction requires controlled movement along a complex path in the urinary tract. Here, we evaluate the safety and utility of a method for controlled manipulation of stone models in vivo in a complex three-dimensional (3D) path using focused ultrasound beams. METHODS: A multi-element ultrasound array transducer with a 12-cm focus was used to produce an acoustic trap around a stone model (3 mm glass sphere) in the bladder of three pigs under anesthesia. The array was coupled to the pig by a water bath and synchronized with a P6-3 ultrasound imaging probe for targeting. A cystoscope was inserted into the bladder to visualize the motion. The sphere was acoustically trapped and steered along three different paths (Figure 1a-c). Deviation of the measured from the intended path was calculated to quantify the accuracy. The total energy exposure to manipulate the stone was low; at 1.5 MHz, the maximum exposure had a maximum peak pressure of 1.4 MPa and a pulse average intensity of 133 W/cm2. The bladder was then evaluated histologically. RESULTS: Spheres were levitated and moved in the three paths in all pigs for a total of 26 manipulations. The spheres were lifted and moved 1) laterally 3 mm and back down, 2) in a horizontal, and 3) in a vertical loop of 3 mm radius. The average discrepancy between the desired path and that observed on ultrasound was 0.24±0.07 mm, and by the cystoscope was 0.17±0.09 mm. The sphere was dragged for 5 cm along the bladder wall by moving the array mechanically (Figure 1d). The skin to stone depth was 2±0.5 cm. Histology showed no signs of injury to the bladder wall. CONCLUSIONS: This work demonstrated the controlled, noninvasive manipulation of stone models in vivo at safe ultrasound power levels. This work potentiates the use of noninvasive ultrasound tweezers to facilitate movement of stones in any direction which could expand the capabilities of ultrasonic propulsion alone. Source of Funding: Work supported by NIDDK P01 DK043881, K25 DK132416 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e307 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Mohamed Ghanem More articles by this author Arturo Holmes More articles by this author Adam Maxwell More articles by this author Michael Bailey More articles by this author Mathew Sorensen More articles by this author Jonathan Harper More articles by this author Expand All Advertisement PDF downloadLoading ...

High-Resolution Ultrasound Characterization of Local Scattering in Cancer Tissue.

Ultrasound (US) has afforded an approach to tissue characterization for more than a decade. The challenge is to reveal hidden patterns in the US data that describe tissue function and pathology that cannot be seen in conventional US images. Our group has developed a high-resolution analysis technique for tissue characterization termed H-scan US, an imaging method used to interpret the relative size of acoustic scatterers. In the present study, the objective was to compare local H-scan US image intensity with registered histologic measurements made directly at the cellular level. Human breast cancer cells (MDA-MB 231, American Type Culture Collection, Manassas, VA, USA) were orthotopically implanted into female mice (N=5). Tumors were allowed to grow for approximately 4 wk before the study started. In vivo imaging of tumor tissue was performed using a US system (Vantage 256, Verasonics Inc., Kirkland, WA, USA) equipped with a broadband capacitive micromachined ultrasonic linear array transducer (Kolo Medical, San Jose, CA, USA). A 15-MHz center frequency was used for plane wave imaging with five angles for spatial compounding. H-scan US image reconstruction involved use of parallel convolution filters to measure the relative strength of backscattered US signals. Color codes were applied to filter outputs to form the final H-scan US image display. For histologic processing, US imaging cross-sections were carefully marked on the tumor surface, and tumors were excised and sliced along the same plane. By use of optical microscopy, whole tumor tissue sections were scanned and digitized after nuclear staining. US images were interpolated to have the same number of pixels as the histology images and then spatially aligned. Each nucleus from the histologic sections was automatically segmented using custom MATLAB software (The MathWorks Inc., Natick, MA, USA). Nuclear size and spacing from the histology images were then compared with local H-scan US image features. Overall, local H-scan US image intensity exhibited a significant correlation with both cancer cell nuclear size (R2 > 0.27, p < 0.001) and the inverse relationship with nuclear spacing (R2 > 0.17, p < 0.001).

Location-Dependent Spatiotemporal Antialiasing in Photoacoustic Computed Tomography.

Photoacoustic computed tomography (PACT) images optical absorption contrast by detecting ultrasonic waves induced by optical energy deposition in materials such as biological tissues. An ultrasonic transducer array or its scanning equivalent is used to detect ultrasonic waves. The spatial distribution of the transducer elements must satisfy the spatial Nyquist criterion; otherwise, spatial aliasing occurs and causes artifacts in reconstructed images. The spatial Nyquist criterion poses different requirements on the transducer elements' distributions for different locations in the image domain, which has not been studied previously. In this research, we elaborate on the location dependency through spatiotemporal analysis and propose a location-dependent spatiotemporal antialiasing method. By applying this method to PACT in full-ring array geometry, we effectively mitigate aliasing artifacts with minimal effects on image resolution in both numerical simulations and in vivo experiments.

434 Ionizing radiation acoustic imaging (iRAI) for volumetric mapping the dose deep in the liver during radiation therapy

OBJECTIVES/GOALS: The goal of this study was to develop a clinically applicable technique to increase the precision of in vivo dose monitoring during radiation therapy by mapping the dose deposition and resolving the temporal dose accumulation while the treatment is being delivered in real time. METHODS/STUDY POPULATION: Ironizing radiation acoustic imaging (iRAI) is a novel imaging concept with the potential to map the delivered radiation dose on anatomic structure in real time during external beam radiation therapy without interrupting the clinical workflow. The iRAI system consisted of a custom-designed two-dimensional (2D) matrix transducer array with integrated preamplifier array, driven by a clinic-ready ultrasound imaging platform. The feasibility of iRAI volumetric imaging in mapping dose delivery and real-time monitoring of temporal dose accumulation in a clinical treatment plan were investigated with a phantom, a rabbit model, and a cancer patient. RESULTS/ANTICIPATED RESULTS: The total dose deposition and temporal dose accumulation in 3D space of a clinical C-shape treatment plan in a targeted region were first imaged and optimized in a phantom. Then, semi-quantitative iRAI measurements were achieved in an in vivo rabbit model. Finally, for the first time, real-time visualization of radiation dose delivered deep in a patient with liver metastases was performed with a clinical linear accelerator. These studies demonstrate the potential of iRAI to monitor and quantify the radiation dose deposition during treatment. DISCUSSION/SIGNIFICANCE: Described here is the pioneering role of an iRAI system in mapping the 3D radiation dose deposition of a complex clinical radiotherapy treatment plan. iRAI offers a cost-effective and practical solution for real-time visualization of 3D radiation dose delivery, potentially leading to personalized radiotherapy with optimal efficacy and safety.