Visibility of Bioresorbable Vascular Scaffold in Intravascular Ultrasound Imaging.

Bioresorbable vascular scaffold (BVS) has recently been spotlighted for its unique characteristics of absorbing into blood vessels and eventually disappearing. Although intravascular ultrasound (IVUS) is the most common guiding tool for stent deployment, the echogenicity of BVS struts has changed as the center of stent lumen and scanning rotation is not concentric, which may cause a critical erroneous measurement in practice. This study investigated the physical conditions for dimming the stent brightness in IVUS images using a finite-difference method (FDM) to numerically solve acoustic wave propagation through nonhomogeneous medium.

Magnetically Actuated Forward-Looking Interventional Ultrasound Imaging: Feasibility Studies.

Objective: Interventional ultrasound imaging is a prerequisite for guiding implants and treatment within the hearts and blood vessels. Due to limitations on the catheter's diameter, interventional ultrasonic transducers have side-looking structures although forward-looking imaging may provide more intuitive and real time guidance in treating diseased sites ahead of catheters. To address the issue, a magnetically actuated forward-looking interventional ultrasound imaging device is implemented for the first time.

CMOS High-Voltage Analog 1-64 Multiplexer/Demultiplexer for Integrated Ultrasound Guided Breast Needle Biopsy.

Ultrasound guided needle biopsy is an important method for collection of breast cancer tissue. In this paper, we report on the design and testing of a high-voltage 1 to 64 Multiplexer/Demultiplexer (MUX/De-MUX) integrated circuit (IC) for ultrasound-guided breast biopsy applications implemented in a high-voltage CMOS process. The IC is intended to be incorporated inside the breast biopsy needle and is designed to fit inside the needle inner diameter of 2.

Development of Dual-Frequency Oblong-Shaped-Focused Transducers for Intravascular Ultrasound Tissue Harmonic Imaging.

Tissue harmonic imaging (THI), an essential mode of commercial ultrasound imaging scanners, can provide images with high spatial and contrast resolutions. For THI, the frequency spectrum of a transducer is generally divided for the transmission of fundamental signal and the reception of its second harmonic. Therefore, it is difficult to use the THI mode for intravascular ultrasound (IVUS) imaging because typical IVUS transducers have a narrow -6-dB fractional bandwidth of about 50%.

Mechanogenetics for the remote and noninvasive control of cancer immunotherapy.

While cell-based immunotherapy, especially chimeric antigen receptor (CAR)-expressing T cells, is becoming a paradigm-shifting therapeutic approach for cancer treatment, there is a lack of general methods to remotely and noninvasively regulate genetics in live mammalian cells and animals for cancer immunotherapy within confined local tissue space. To address this limitation, we have identified a mechanically sensitive Piezo1 ion channel (mechanosensor) that is activatable by ultrasound stimulation and integrated it with engineered genetic circuits (genetic transducer) in live HEK293T cells to convert the ultrasound-activated Piezo1 into transcriptional activities. We have further engineered the Jurkat T-cell line and primary T cells (peripheral blood mononuclear cells) to remotely sense the ultrasound wave and transduce it into transcriptional activation for the CAR expression to recognize and eradicate target tumor cells.

Label-free analysis of the characteristics of a single cell trapped by acoustic tweezers.

Single-cell analysis is essential to understand the physical and functional characteristics of cells. The basic knowledge of these characteristics is important to elucidate the unique features of various cells and causative factors of diseases and determine the most effective treatments for diseases. Recently, acoustic tweezers based on tightly focused ultrasound microbeam have attracted considerable attention owing to their capability to grab and separate a single cell from a heterogeneous cell sample and to measure its physical cell properties.

Calibration of Trapping Force on Cell-Size Objects From Ultrahigh-Frequency Single-Beam Acoustic Tweezer.

In this paper, we report a calibration of acoustic trapping force of single-beam acoustic tweezer (SBAT) at ultrahigh frequency using micropipette aspiration. The acoustic trapping forces ( F) and the trap stiffness on a 5- [Formula: see text] polystyrene microbead for a 110-MHz SBAT were measured against the known force generated from a micropipette. The trap stiffness ( k ), which represents F corresponding to a displacement ( x ) of a microbead from the trap center, was measured and the results showed that a higher duty factor and excitation voltage lead to a stronger trapping force and trap stiffness for a given displacement.

Cell Deformation by Single-beam Acoustic Trapping: A Promising Tool for Measurements of Cell Mechanics.

We demonstrate a noncontact single-beam acoustic trapping method for the quantification of the mechanical properties of a single suspended cell with label-free. Experimentally results show that the single-beam acoustic trapping force results in morphological deformation of a trapped cell. While a cancer cell was trapped in an acoustic beam focus, the morphological changes of the immobilized cell were monitored using bright-field imaging.

Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film.

Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d = 270pC/N and k = 0.51) was employed for SBAT applications and a press-focusing technology was introduced.

Ultrasonic scattering measurements of a live single cell at 86 MHz.

Cell separation and sorting techniques have been employed biomedical applications such as cancer diagnosis and cell gene expression analysis. The capability to accurately measure ultrasonic scattering properties from cells is crucial in making an ultrasonic cell sorter a reality if ultrasound scattering is to be used as the sensing mechanism as well. To assess the performance of sensing and identifying live single cells with high-frequency ultrasound, an 86-MHz lithium niobate press-focused single-element acoustic transducer was used in a high-frequency ultrasound scattering measurement system that was custom designed and developed for minimizing noise and allowing better mobility.

Non-contact acoustic radiation force impulse microscopy via photoacoustic detection for probing breast cancer cell mechanics.

We demonstrate a novel non-contact method: acoustic radiation force impulse microscopy via photoacoustic detection (PA-ARFI), capable of probing cell mechanics. A 30 MHz lithium niobate ultrasound transducer is utilized for both detection of phatoacoustic signals and generation of acoustic radiation force. To track cell membrane displacements by acoustic radiation force, functionalized single-walled carbon nanotubes are attached to cell membrane.

High-frequency dual mode pulsed wave Doppler imaging for monitoring the functional regeneration of adult zebrafish hearts.

Adult zebrafish is a well-known small animal model for studying heart regeneration. Although the regeneration of scars made by resecting the ventricular apex has been visualized with histological methods, there is no adequate imaging tool for tracking the functional recovery of the damaged heart. For this reason, high-frequency Doppler echocardiography using dual mode pulsed wave Doppler, which provides both tissue Doppler (TD) and Doppler flow in a same cardiac cycle, is developed with a 30 MHz high-frequency array ultrasound imaging system.

Multi-particle trapping and manipulation by a high-frequency array transducer.

We report the multiple micro-particle trapping and manipulation by a single-beam acoustic tweezer using a high-frequency array transducer. A single acoustic beam generated by a 30 MHz ultrasonic linear array transducer can entrap and transport multiple micro-particles located at the main lobe and the grating lobes. The distance between trapped particles can be adjusted by changing the transmit arrangement of array-based acoustic tweezers and subsequently the location of grating lobes.

A feasibility study of applications of single beam acoustic tweezers.

Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for and clinical studies.

Non-contact multi-particle annular patterning and manipulation with ultrasound microbeam.

Multiparticle-trapping offers diverse opportunities and applications in biotechnology. It can be applied to creating various functional materials or organizing reactive particles. In this paper, we demonstrate that it is possible to trap and manipulate multi-particles in an annular pattern with a 24 MHz focused ring-type single element ultrasound transducer.

Non-contact high-frequency ultrasound microbeam stimulation for studying mechanotransduction in human umbilical vein endothelial cells.

We describe how contactless high-frequency ultrasound microbeam stimulation (HFUMS) is capable of eliciting cytoplasmic calcium (Ca(2+)) elevation in human umbilical vein endothelial cells. The cellular mechanotransduction process, which includes cell sensing and adaptation to the mechanical micro-environment, has been studied extensively in recent years. A variety of tools for mechanical stimulation have been developed to produce cellular responses.

Cell membrane deformation induced by a fibronectin-coated polystyrene microbead in a 200-MHz acoustic trap.

The measurement of cell mechanics is crucial for a better understanding of cellular responses during the progression of certain diseases and for the identification of the cell's nature. Many techniques using optical tweezers, atomic force microscopy, and micro-pipettes have been developed to probe and manipulate cells in the spatial domain. In particular, we recently proposed a two-dimensional acoustic trapping method as an alternative technique for small particle manipulation.

Investigating contactless high frequency ultrasound microbeam stimulation for determination of invasion potential of breast cancer cells.

In this article, we investigate the application of contactless high frequency ultrasound microbeam stimulation (HFUMS) for determining the invasion potential of breast cancer cells. In breast cancer patients, the finding of tumor metastasis significantly worsens the clinical prognosis. Thus, early determination of the potential of a tumor for invasion and metastasis would significantly impact decisions about aggressiveness of cancer treatment.

A simple method for evaluating the trapping performance of acoustic tweezers.

The purpose of this paper is to present a rapid and simple method to evaluate the trapping performance of high frequency focused ultrasonic transducers for acoustic tweezer applications. The method takes into consideration the friction between the particle to be trapped and the surface that it resides on. As a result it should be more reliable and accurate than the methods proposed previously.

Acoustic trapping with a high frequency linear phased array.

A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

Ultrahigh frequency lensless ultrasonic transducers for acoustic tweezers application.

Similar to optical tweezers, a tightly focused ultrasound microbeam is needed to manipulate microparticles in acoustic tweezers. The development of highly sensitive ultrahigh frequency ultrasonic transducers is crucial for trapping particles or cells with a size of a few microns. As an extra lens would cause excessive attenuation at ultrahigh frequencies, two types of 200-MHz lensless transducer design were developed as an ultrasound microbeam device for acoustic tweezers application.

Focused high frequency needle transducer for ultrasonic imaging and trapping.

A miniature focused needle transducer (<1 mm) was fabricated using the press-focusing technique. The measured pulse-echo waveform showed the transducer had center frequency of 57.5 MHz with 54% bandwidth and 14 dB insertion loss.

Microfluidic droplet sorting with a high frequency ultrasound beam.

This paper presents experimental results demonstrating the feasibility of high frequency ultrasonic sensing and sorting for screening single oleic acid (lipid or oil) droplets under continuous flow in a microfluidic channel. In these experiments, hydrodynamically focused lipid droplets of two different diameters (50 μm and 100 μm) are centered along the middle of the channel, which is filled with deionized (DI) water. A 30 MHz lithium niobate (LiNbO(3)) transducer, placed outside the channel, first transmits short sensing pulses to non-invasively determine the acoustic scattering properties of the individual droplets passing through the beam's focus.

Fluorescence response of human HER2+ cancer- and MCF-12F normal cells to 200MHz ultrasound microbeam stimulation: a preliminary study of membrane permeability variation.

Targeted mechanical cell stimulation has been extensively studied for a better understanding of its effect on cellular mechanotransduction signaling pathways and structures by utilizing a variety of mechanical sources. In this work, an ultrasound-driven single cell stimulation method is thus proposed, and a preliminary study is carried out by comparing the fluorescence intensities representing a change in cell membrane permeability between MDA-MB-435 human HER2+ cancer cells (∼40-50μm in diameter) and MCF-12F normal cells (∼50-60μm) in the presence of ultrasound. A 200MHz single element zinc oxide (ZnO) transducer is employed to generate ultrasound microbeam (UM) whose beamwidth and depth of focus are 9.

Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.

Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2-10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells.