Commercial Ultrasound Probe Research Articles

2D speed of sound mapping using a multilook reflection ultrasound tomography framework

Quantitative ultrasound (QUS) has emerged as a viable tool in diagnosing and staging the onset and progression of various diseases. Within the field of QUS, shear wave elastography (SWE) has emerged as the clinical standard for quantifying and correlating the stiffness of tissue to its underlying pathology. Despite its widespread use, SWE suffers from drawbacks that limit its widespread clinical use; among these are low-frame rates, long settling times, and high sensitivity to operating conditions. Longitudinal speed of sound (SOS) has emerged as a viable alternative to SWE. We propose a framework to obtain 2D sound speed maps using a commercial ultrasound probe. A commercial ultrasound probe is localized in space and used to scan a domain of interest from multiple vantage points; the use of a reflector at the far end of the domain allows us to measure the round trip travel times to and from it. The known locations of the probe and the measured travel times are used to estimate the depth and inclination of the reflector as well as the unknown sound speed map. The use of multiple looks increases the effective aperture of the ultrasound probe and allows for a higher fidelity reconstruction of sound speed maps. We validate the framework using simulated and experimental data and propose a rigorous framework to quantify the uncertainty of the estimated sound speed maps.

Biometric recognition through 3D ultrasound hand geometry

Biometric recognition systems based on ultrasonic images have several advantages over other technologies, including the capability of capturing 3D images and detecting liveness.In this work, a recognition system based on hand geometry achieved through ultrasound images is proposed and experimentally evaluated. 3D images of human hand are acquired by performing parallel mechanical scans with a commercial ultrasound probe. Several 2D images are then extracted at increasing under-skin depths and, from each of them, up to 26 distances among key points of the hand are defined and computed to achieve a 2D template. A 3D template is then obtained by combining in several ways 2D templates of two or more images.A preliminary evaluation of the system is achieved by carrying out verification experiments on a home–made database. Results have shown a good recognition accuracy: the Equal Error Rate was 1.15% when a single 2D image is used and improved to 0.98% by using the 3D template. The possibility to upgrade the proposed system to a multimodal system, by extracting from the same volume other features like palmprint and hand veins, as well as possible improvements are finally discussed.

Miniaturization of External Mechanical Vibration for Shear Wave Elastography Imaging.

Ultrasound shear wave elastography is increasingly used as a non-invasive and quantitative tissue elasticity characterization method. External mechanical vibration (EMV) is an alternative to acoustic radiation force (ARF) for shear wave generation, due to its potential for inducing larger local displacements using lower power. The physical space and mass required for incorporating mechanical vibration sources makes it challenging to integrate EMV into commercial ultrasound systems in a compact and ergonomic manner. In this paper we present the design of a miniature EMV-equipped ultrasound probe that is suitable for clinical tests. Custom vibration motors were designed and tested towards optimizing the "volume-toshear-wave-amplitude" ratio. Then the mechanical design and integration of vibration motors into commercial ultrasound probes is introduced, where the spatial placement and housing of the motors is designed to improve the ergonomics of the device and the performance of the motors.

A proposal to reduce the risk of transmission of human papilloma virus via transvaginal ultrasound

Three steps must be followed to prevent the transmission of infection via a contaminated transvaginal ultrasound probe: cleaning the probe after every use, high-level disinfection, and covering the probe with a single-use barrier during the examination. There may be critical flaws in at least 2 of these steps as they are currently practiced. First, 2 widely used disinfectants, glutaraldehyde and orthophthalaldehyde, have recently been found to be ineffective at neutralizing human papilloma virus type 16 and type 18. Second, commercial ultrasound probe covers have an unacceptable rate of leakage (8-81%) compared to condoms (0.9-2%). We recommend the use of a sonicated hydrogen peroxide disinfectant system rather than aldehyde-type disinfectants. We recommend that the probe be covered with a condom rather than a commercial probe cover during transvaginal ultrasound examination. Combined with probe cleaning, these 2 steps are estimated to result in an 800 million- to 250 billion-fold reduction in human papilloma virus viral load, which should translate to greatly enhanced patient safety.

Self-characterization of commercial ultrasound probes in transmission acoustic inverse scattering: transducer model and volume integral formulation

A self-contained source characterization method for commercial ultrasound probes in transmission acoustic inverse scattering is derived and experimentally tested. The method is based on modified scattered field volume integral equations that are linked to the source-scattering transducer model. The source-scattering parameters are estimated via pair-wise transducer measurements and the nonlinear inversion of an acoustic propagation model that is derived. This combination creates a formal link between the transducer characterization and the inverse scattering algorithm. The method is tested with two commercial ultrasound probes in a transmission geometry including provisions for estimating the probe locations and aligning a robotic rotator. The transducer characterization results show that the nonlinear inversion fit the measured data well. The transducer calibration and inverse scattering algorithm are tested on simple targets. Initial images show that the recovered contrasts are physically consistent with expected values.

Photoacoustic Imaging With a Commercial Ultrasound System and a Custom Probe

Building photoacoustic imaging (PAI) systems by using stand-alone ultrasound (US) units makes it convenient to take advantage of the state-of-the-art ultrasonic technologies. However, the sometimes limited receiving sensitivity and the comparatively narrow bandwidth of commercial US probes may not be sufficient to acquire high quality photoacoustic images. In this work, a high-speed PAI system has been developed using a commercial US unit and a custom built 128-element piezoelectric-polymer array (PPA) probe using a P(VDF-TrFE) film and flexible circuit to define the elements. Since the US unit supports simultaneous signal acquisition from 64 parallel receive channels, PAI data for synthetic image formation from a 64- or 128-element array aperture can be acquired after a single or dual laser firing, respectively. Therefore, two-dimensional (2-D) B-scan imaging can be achieved with a maximum frame rate up to 10 Hz, limited only by the laser repetition rate. The uniquely properties of P(VDF-TrFE) facilitated a wide –6 dB receiving bandwidth of over 120% for the array. A specially designed 128-channel preamplifier board made the connection between the array and the system cable, which not only enabled element electrical impedance matching but also further elevated the signal-to-noise ratio (SNR) to further enhance the detection of weak photoacoustic signals. Through the experiments on phantoms and rabbit ears, the good performance of this PAI system was demonstrated. (E-mail: xdwang@umich.edu)

SU‐FF‐J‐26: Multimodal Sono‐Contrast NIR Spectroscopy System for Breast Cancer Diagnosis

Purpose: To present a multimodal imaging system that combines three modalities, optical spectroscopy, ultrasonography and acoustic radiation force (ARF) for improved diagnosis of breast cancer based on noninvasive interrogation of vasculature. Method and Materials: The scanhead incorporates two 1MHz focused transducers aligned orthogonally to deliver ARF in a 2.4cm region. A commercial ultrasound probe is positioned to image the focal plane. The ultrasound probe and focused transducers have two degrees‐of‐freedom, so that the focal zone can be scanned in tissue depth‐wise and laterally. Three force sensors are mounted on the breast compression plate to ensure consistent, slight compression. A fiber array (6 sources and 12 detectors) connects to the concave bottom plate of the scanhead. Sources are illuminated by two laser diodes (680 and 830nm) through a multi‐channel optical switch. Diffuse reflectance signals are collected by 12 detectors, amplified by avalanche photodiodes, and transmitted through a multi‐channel data acquisition card for analysis. The scanhead is mounted on a 360° ring gantry, which can rotate around the breast and move towards or away from the patient. A software system was implemented in Visual C++ to perform real‐time tasks, including acquisition of optical and force signals, control of optical switch and function generator, and data display. Results: The maximum exposure to laser was controlled within 0.2W⋅cm−2 (ANSI Z136.1). The ARF fields were maintained below FDA diagnostic limits (0.72W⋅cm−2) for manipulating blood flow and oxyhemoglobin concentrations at the time and location of detection, causing measurable differences in the dynamic behavior of tissue blood supply as reported by optical spectroscopy. This technique was demonstrated to be highly diagnostic in a murine tumor model. Conclusions: A multimodal system incorporating ARF, optical spectroscopy and ultrasonography has been developed to characterize breast cancers. Pilot clinical study is being carried out.Acknowledgement: Work supported by NCI Grant CA107860.

SU‐FF‐J‐27: Calibration of the Dual‐Transducer Focused Acoustic Radiation Field for a Multimodal Sono‐Contrast NIR Spectroscopy System

Purpose: To calibrate the dual‐transducer focused acoustic radiation field, register the focus center in the imaging ultrasound system, and establish a monthly calibration protocol for a noninvasive multi‐modal breast cancer scanning system. Method and Materials: The scanhead incorporated two 1MHz focused transducers aligned orthogonally to deliver acoustic radiation force (ARF) in a 2.4cm region. A commercial ultrasound probe, located in the same vertical plane as the focused transducers, was used in the system for image co‐registration. Dielectric fluid was filled into the scanhead as the ultrasound transmission media. The scanhead was merged into a water tank filled with degassed distilled water. A function generator connected with an amplifier was used to drive the focused transducers. The imaging ultrasound probe was connected to a commercial ultrasound system. The focused transducers were excited by 1MHz continuous sine wave with amplitude of 200mv from a function generator, amplified by the amplifier. A hydrophone was aligned vertically below the bottom plate and moved by a 3D motion platform (resolution 0.05mm) in the 3D Cartesian space at a step of 0.1mm. An oscilloscope was connected with the hydrophone for data display and acquisition of the voltage signals for calculating the acoustic intensity. Results: The focal spot that has the maximum peak‐positive voltage signal on the oscilloscope was found at 2.34 cm below the bottom plate, which is the designed intersection of the axes of the two focused transducers. The Spatial Peak Temporal Average Intensity was determined to be 0.4 W⋅cm−2, below the FDA therapeutic ultrasound limits (0.72 W⋅cm−2). The focal spot was then registered in the imaging ultrasound images. Conclusions: This study established the baseline of the dual‐transducer focus acoustic radiation field. A monthly calibration protocol has been developed following the same procedure for the focused acoustic radiation field.Acknowledgement: supported by NCI Grant CA107860.

A method for accurate in silico modeling of ultrasound transducer arrays

This paper presents a new approach to improve the in silico modeling of ultrasound transducer arrays. While current simulation tools accurately predict the theoretical element spatio-temporal pressure response, transducers do not always behave as theorized. In practice, using the probe’s physical dimensions and published specifications in silico, often results in unsatisfactory agreement between simulation and experiment. We describe a general optimization procedure used to maximize the correlation between the observed and simulated spatio-temporal response of a pulsed single element in a commercial ultrasound probe. A linear systems approach is employed to model element angular sensitivity, lens effects, and diffraction phenomena. A numerical deconvolution method is described to characterize the intrinsic electro-mechanical impulse response of the element. Once the response of the element and optimal element characteristics are known, prediction of the pressure response for arbitrary apertures and excitation signals is performed through direct convolution using available tools. We achieve a correlation of 0.846 between the experimental emitted waveform and simulated waveform when using the probe’s physical specifications in silico. A far superior correlation of 0.988 is achieved when using the optimized in silico model. Electronic noise appears to be the main effect preventing the realization of higher correlation coefficients. More accurate in silico modeling will improve the evaluation and design of ultrasound transducers as well as aid in the development of sophisticated beamforming strategies.

Fundamental Study on One-Dimensional-Array Medical Ultrasound Probe with Piezoelectric Polycrystalline Film by Hydrothermal Method: Experimental Fabrication of One-Dimensional-Array Ultrasound Probe

We deposited a lead zirconate titanete (PZT) polycrystalline film on a titanium substrate by the hydrothermal method and fabricated a transducer using the PZT film for use as an ultrasound probe. A 10 MHz miniature one-dimensional-array medical ultrasound probe containing the PZT film was developed. After sputtering titanium on the surface of a hydroxyapatite substrate, the titanium film on the substrate was etched by the photolithography to form a one-dimensional titanium film electrode array. We could thus fabricate a miniature one-dimensional-array ultrasound probe by the hydrothermal method. Transmitted ultrasound pulses from a 10 MHz commercial ultrasound probe were received by the newly fabricated one-dimensional-array ultrasound probe. The fabrication process of the probe and the results of experiments on receiving waveforms were reported in this paper.

Basic study on one-dimensional transducer array using hydrothermally synthesized lead zirconium titanete poly-crystalline film

Recently, high-frequency miniature medical ultrasound probes with high resolution were actively developed. However, it is difficult to fabricate such tiny ultrasound probes using piezoelectric ceramic vibrator with thickness less than 100 μm. We deposited a PZT poly-crystalline film on a titanium substrate using the hydrothermal method and developed transducers using the PZT poly-crystalline film for ultrasound probes. In this study, we applied it to a miniature medical one-dimensional (1-D)-array-type ultrasound probe with resonance frequency of 10 MHz. After sputtering of pure titanium on the surface of a hydroxyapatite substrate, the titanium film was etched using the photolithography method to form a 1-D titanium film electrode array with 75 μm element pitch, 40 μm element width, and 4 mm element length to scan an ultrasound beam electronically by sector scan mode using phased-array technique. Thereby we fabricated a miniature 1-D-array-type ultrasound probe. A transmitted ultrasound pulse from 10 MHz commercial ultrasound probe was received by this fabricated 1-D-array type ultrasound probe with hydrothermally synthesized PZT poly-crystalline film vibrators.