Ultrasound Radiation Research Articles

Local Harmonic Motion Monitoring of Focused Ultrasound Surgery—A Simulation Model

In this paper, a computational model for localized harmonic motion (LHM) imaging-based monitoring of high-intensity focused ultrasound surgery (FUS) is presented. The LHM technique is based on a focused, time-varying ultrasound radiation force excitation, which induces local oscillatory motions at the focal region. These vibrations are tracked, using pulse-echo imaging, and then, used to estimate the mechanical properties of the sonication region. LHM is feasible for FUS monitoring because changes in the material properties during the coagulation process affect the measured displacements. The presented model includes separate models to simulate acoustic sonication fields, sonication-induced temperature elevation and mechanical motion, and pulse-echo imaging of the induced motions. These 3-D simulation models are based on Rayleigh-Sommerfield integral, finite element, and spatial impulse response methods. Simulated-tissue temperature elevation and mechanical motion were compared with previously published in vivo measurements. Finally, the simulation model was used to simulate coagulation and LHM monitoring, as would occur with multiple, neighbouring sonication locations covering a large tumor.

Vascular Functions Examined by MRI and Ultrasound Predict Radiation Response and Distribution of Chemotherapeutic Agents

Vascular Functions Examined by MRI and Ultrasound Predict Radiation Response and Distribution of Chemotherapeutic Agents

Shear Modulus Imaging with Spatially-Modulated Ultrasound Radiation Force

The application of Spatially-Modulated Ultrasound Radiation Force (SMURF) to shear modulus imaging is demonstrated in tissue-mimicking phantoms and porcine liver. Scanning and data acquisition was performed with a Siemens Antares ultrasound scanner and VF7-3 linear array operating at 4.21 MHz. Modulus estimates in uniform phantoms of Zerdine with shear moduli of 5.1 and 12.4 kPa exhibited standard deviations within 6% of the mean value. Zerdine spheres 1 cm in diameter (nominally 2.7, 4.7 and 15 kPa) in a 8 kPa (nominal) background are clearly resolved. Cross sectional images of a soft conical inclusion in a gelatin-based phantom indicate a spatial resolution of approximately 2.5 mm. Images of the shear modulus of an ex-vivo sample of porcine liver tissue show an average value of 3 kPa. A stifflesion induced with 0.5 mL of 10% glutaraldehyde is clearly visible as a region of shear modulus in excess of 10 kPa. A modulus gradient associated with the diffusion of the glutaraldehyde is visible. Two pulse sequences were examined, differing only in the timing of the beams used to generate the shear waves. Details of the beam sequences and subsequent signal processing are presented.

The Possibility of a Simultaneous Transmission οf Ultrasound and Laser Radiation via Flexible Optical Silica Glass Fibre

Glass optical fibres are a promising medium for simultaneous laser-ultrasonic applications. The proposed application system is based on simultaneous transmission of laser radiation and ultrasounds in a flexible silica glass fibre. The optical fibre’s core was made of SiO2 (97%) and GeO2 (3%) and the cladding was 100% SiO2. The material the optical fibre is made of enables simultaneous transmission of laser radiation and ultrasonic wave. Experiments were performed using a Mach–Zehnder optical waveguide interferometer with single-mode optical fibre coupler. This paper presents measurement results for delivering ultrasonic waves to the optical fibre using longitudinal vibrations generated by a sandwich ultrasonic transducer with a velocity transformer. The study presents the relations concerning simultaneous operation of both types of waves and the possibilities of transmission of low frequency, high power ultrasonic wave in optical fibres using a sandwich type transducer.

Study of the Essential Oil Composition of Cumin Seeds by an Amino Ethyl-Functionalized Nanoporous SPME Fiber

An ultrasound assisted SPME method with a new nanoporous SBA-15 fiber functionalized with 3-[bis(2-hydroxyethyl)amino]propyl-triethoxysilane was successfully applied to the study of the essential oil composition of cumin (Cuminum cyminum L.) seeds. The sample was irradiated by ultrasound radiation and its volatile components were collected by the fiber from the sample headspace and directly injected into a GC-MS injection port for analysis. A simplex method was used for optimization of four different parameters affecting the efficiency of the extraction. Under the optimized conditions (i.e. sample weight, 0.6 g; temperature, 70 °C; sonication time, 12 min and extraction time, 28 min), the number of components identified by the proposed method and their amounts were identical to those of a hydrodistillation technique. The extraction efficiency of the SBA-15 fiber was superior to a PDMS commercial fiber. The major components identified were p-menta-1,3-dien-7-al, cuminaldehyde, γ-terpinene and p-cymene, respectively. The proposed method was applied to a comparative study of the essential oil composition of cumin in three different climate conditions of the Lorestan province in Iran. The results indicated that the essential oils in the temperate and tropical locations were 94.0 and 85.6% of the cold region, respectively.

Effect of processing conditions on sonochemical synthesis of nanosized copper aluminate powders

Nanosized copper aluminate (CuAl 2O 4) spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Mono-phasic copper aluminate with a crystallite diameter of 17 nm along the (3 1 1) plane was formed when the products were synthesized using Cu(NO 3) 2·6H 2O and Al(NO 3) 3·9H 2O as starting materials, with urea as a precipitation agent at a concentration of 9 M. The reaction was carried out under ultrasound irradiation at 80 °C for 4 h and a calcination temperature of 900 °C for 6 h. The synthesized copper aluminate particles and the effect of different processing conditions such as the copper source, precipitation agents, sonochemical reaction time, calcination temperature and time were analyzed and characterized by the techniques of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transformation infrared spectroscopy (FT–IR).

Effect of ultrasound irradiation combined with liposome membrane microbubbles on the reorgnization of cytoskeleton in vascular smooth muscle cells

Objective To investigate the effect of ultrasound irradiation combined with liposome membrane microbubbles on the reorgnization of cytoskeleton in vascular smooth muscle cells (VSMCs). Methods Rat thoracic aortic VSMCs were cultured in vitro. VSMCs were exposed to 1 MHz continuous waves ultrasound radiation for 120 s at intensity 0.3 W/cm2in the presence of liposome membrane microbubbles (1 μl/ml) after treated with platelet derived growth factor-BB (PDGF-BB). The reorganizations of microfilaments, microtubules and intermediate filaments were examined by using immunofluorescence and fluorocytochemistry techniques. Results There was a substantial increase in the expression of F-actin and assembly of long bundles of stress fibers in the transversed cell body when treated with PDGF-BB. Neither alterations of β-tubulin nor of vimentin cytoskeletal protein organization were observed in PDGF-BB treated cells as compared to those of the contol group. After ultrasound irradiation combined with liposome membrane microbubbles, the expression of F-actin, β-tubulin and vimentin were reduced along with the simultaneous changes in microfilaments, microtubles and intermediate filaments array. Conclusions Ultrasound irradiation combined with liposome membrane microbubbles can induce significant changes in cytoskeleton structure of VSMCs cultured in vitro. Key words: Ultrasonography; Microbubbles; Aorta,thoracic; Myocytes,smooth muscle; Cytoskeleton

The application of ultrasound radiation to the synthesis of nanocrystalline metal oxide in a non-aqueous solvent

Highly crystalline metal oxide nanoparticles of TiO 2, WO 3, and V 2O 5 were synthesized in just a few minutes by reacting transition metal chloride with benzyl alcohol using ultrasonic irradiation under argon atmosphere in a non-aqueous solvent. The sonochemical process was conducted at a relatively low temperature, 363 K. A unique crystallization process of these nanoparticles has been observed and characterized by powder X-ray diffraction (PXRD), high resolution scanning electron microscopy (HRSEM), and BET. The particles’ size and shape measured from HRSEM reveal “quasi” zero-dimensional, spherical TiO 2 particles in the range of 3–7 nm. The V 2O 5 particles have a “quasi” one-dimensional ellipsoidal morphology, with lengths in the range of 150–200 nm and widths varying between 40 and 60 nm. The WO 3 particles were obtained as “quasi” two-dimensional platelets with square shapes having facets ranging from 30 to 50 nm. The thickness of these platelets was between 2 and 7 nm. The mechanism of the reactions leading to these three metal oxide nanoparticles in a non-aqueous system is substantiated by Nuclear Magnetic Resonance (NMR), and Electron Spin Resonance (ESR).

Vibro-magnetometry: Theoretical aspects and simulations

In this article, we introduce the theory for vibro-magnetometry (VM) with computational simulations for an idealized experimental setup. A method based on acoustic radiation force and magnetic measurement has been proposed for interrogating the mechanical vibrations of a target immersed in fluid medium. In this method, ultrasound radiation is used to exert a low-frequency (in kHz range) force on a rigid magnetized target immersed in a viscoelastic medium. In response, the target vibrates sinusoidally in a pattern determined by viscoelastic properties of the medium. The magnetic field resulting from target vibration is related to both the ultrasonic and low-frequency (kHz range) mechanical characteristics of the medium. We report the relationship between the magnetic field signal and the incident ultrasonic pressure field in terms of the mechanical parameters of the medium. Simulations were conducted to demonstrate a simple approach based on using amplitude-modulated ultrasound to generate a dynamic acoustic radiation force on a magnetic target. The magnetic field generated by vibration of this target is then obtained and used to estimate the radiation-force-induced displacement as a function of time. It was observed that the intensity of the dynamic component of the magnetic field caused by the acoustic excitation is high enough to be registered by a conventional magnetic sensor. When a low stress is applied on a reactive magnetic target embedded in the medium, the subsequent oscillating magnetic field is measured by a dedicated magnetic sensor, yielding the applicable mechanical information of the host medium. The proposed methodology presents a powerful tool for evaluation of acoustic radiation force as well as the mechanical properties of soft materials.

Evaluation of experimental methods for assessing safety for ultrasound radiation force elastography

Standard test tools have been evaluated for the assessment of safety associated with a prototype transducer intended for a novel radiation force elastographic imaging system. In particular, safety has been evaluated by direct measurement of temperature rise, using a standard thermal test object, and detection of inertial cavitation from acoustic emission. These direct measurements have been compared with values of the thermal index and mechanical index, calculated from acoustic measurements in water using standard formulae. It is concluded that measurements using a thermal test object can be an effective alternative to the calculation of thermal index for evaluating thermal hazard. Measurement of the threshold for cavitation was subject to considerable variability, and it is concluded that the mechanical index still remains the preferred standard means for assessing cavitation hazard.

Acousto-magnetometry: A new vibrometery based on acoustic radiation force and magnetic measurement.

This work introduces a new method based on acoustic radiation force and magnetic measurement for interrogating the mechanical properties of fluid and biological tissues. In this method, ultrasound radiation is used to exert a low-frequency (in kHz range) force on a rigid magnetized target immersed in a viscoelastic medium. In response, the target vibrates in a pattern determined by viscoelastic properties of medium. We report the relation between the magnetic field signal and the incident ultrasonic pressure field in terms of the mechanical parameters of the medium. Simulations were conducted to demonstrate a simple approach based on using amplitude-modulated ultrasound to generate a dynamic acoustic radiation force on a magnetic target. The magnetic field generated by vibration of this target is then obtained and used to estimate the radiation-force-induced displacement as a function of time. It was observed that the intensity of the dynamic component of the magnetic field caused by the acoustic excitation is high enough to be registered by a conventional magnetic sensor. This proposed methodology presents a powerful tool for evaluation of acoustic radiation force as well as the mechanical properties of soft material.

ZnO Nanorods Synthesized in Large-Scale via Sonochemical Method and its Sensing Potential towards Methyl Mercaptan

A novel and simple approach has been developed for a large-scale synthesis of ZnO nanorods using ultrasound radiation. Double-pod-like ZnO nanorods were directly grown from the starting precursors of zinc nitrate hydrate [Zn(NO3)26H2O] and hexamethylene tetramine (HMT) in deionized water without any templates or seeds. The obtained double-pod-like product had a diameter ranging from 80 to 150 nm and length ranging from 1 to 5 um. Scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) revealed that these products are of high purity, hexagonal and of single-crystalline structure. The ZnO nanorods synthesized were utilized for gas sensing application. Alumina plate consists of Pt interdigitated electrode was used as sensor substrate. The as-prepared products were transferred to the surface of substrate by screen printing method to fabricate the gas sensor. The sensing properties of the sensor were investigated toward methyl mercaptan (CH3SH). The sensor shows good and fast response towards methyl mercaptan at a fixed operating temperature. The high sensitivity may be ascribed to the high surface area and aspect ration of the double-pod-like nanomaterial.

Optimization of ultrasound radiation force source for shear wave dispersion measurements.

The objective of this study was to analyze and optimize the ultrasound radiation force source for creating shear waves for quantitative elasticity and viscosity measurements. A simulation model based on work by Bercoff et al., [IEEE Trans. Ultrason. Ferroelectr. Freq. Contr. 51(11), 1523–34 (2004)] was utilized to examine the shear wave propagation from a spatiotemporal impulsive force and the simulated radiation force generated from a linear array transducer. Parameters such as aperture size, F-number of the transducer, and medium shear elasticity and viscosity were varied to analyze how the shear wave amplitude and shape changes. The wave attenuation and group and phase velocities were evaluated. The aperture size and the F-number of the transducer affected the spatial distribution of the propagating shear wave significantly. The influence of the coupling term between the bulk and shear waves was analyzed spatially and temporally by evaluating parameters such as shear wave amplitude, wave attenuation, and the group and phase velocities. This simulation model provides insight for making shear wave propagation measurements from the perspective of optimizing the spatial and temporal characteristics of induced shear wave motion from an applied radiation force. [This work was supported in part by Grant EB002167 from NIH.]

Comparison of unconfined compression and spatially modulated ultrasound radiation force estimates of shear modulus.

Spatially modulated ultrasound radiation force (SMURF) [S. McAleavey et al., Ultrason. Imag. 29, 87–104, (2007)] is a novel method for ultrasonic estimation of the low-frequency shear modulus properties of elastic media. In this approach, radiation force with a known lateral magnitude variation is applied impulsively within a region of interest using short (∼30 μs) bursts of ultrasound. The spatial frequency k of the radiation force intensity variation is selectable and determined through beamforming. Application of the radiation force impulse gives rise to a low-frequency (500–2000 Hz) shear wave. The temporal frequency ω of this wave is measured using Doppler ultrasound methods. The modulus is estimated from the relationship G=ρ(ωk)2, where ρ is the material density. To validate this method, the moduli of five samples of Zerdine (CIRS, Incorporated), an ultrasonically tissue-equivalent elastic material, were measured using conventional unconfined cyclic compression and SMURF implemented on a Siemens Antares scanner. The samples were cylindrical with diam 54 mm and height 25 mm. The shear modulus of the samples ranged from 2.5–35 kPa. For all samples, the two methods agreed to within the estimated variation. An intrasample variation of 8% was observed for SMURF in the (assumed uniform) samples. [Work supported by NIH/NIBIB.]

Error in estimates of tissue material properties from shear wave dispersion ultrasound vibrometry

Shear wave velocity measurements are used in elasticity imaging to find the shear elasticity and viscosity of tissue. A technique called shear wave dispersion ultrasound vibrometry (SDUV) has been introduced to use the dispersive nature of shear wave velocity to locally estimate the material properties of tissue. Shear waves are created using a multifrequency ultrasound radiation force, and the propagating shear waves are measured a few millimeters away from the excitation point. The shear wave velocity is measured using a repetitive pulse-echo method and Kalman filtering to find the phase of the harmonic shear wave at 2 different locations. A viscoelastic Voigt model and the shear wave velocity measurements at different frequencies are used to find the shear elasticity (mu(1)) and viscosity (mu(2)) of the tissue. The purpose of this paper is to report the accuracy of the SDUV method over a range of different values of mu(1) and mu(2). A motion detection model of a vibrating scattering medium was used to analyze measurement errors of vibration phase in a scattering medium. To assess the accuracy of the SDUV method, we modeled the effects of phase errors on estimates of shear wave velocity and material properties while varying parameters such as shear stiffness and viscosity, shear wave amplitude, the distance between shear wave measurements (delta r), signal-to-noise ratio (SNR) of the ultrasound pulse-echo method, and the frequency range of the measurements. We performed an experiment in a section of porcine muscle to evaluate variation of the aforementioned parameters on the estimated shear wave velocity and material property measurements and to validate the error prediction model. The model showed that errors in the shear wave velocity and material property estimates were minimized by maximizing shear wave amplitude, pulse-echo SNR, delta r, and the bandwidth used for shear wave measurements. The experimental model showed optimum performance could be obtained for delta r = 3 - 6 mm, SNR =35 dB, with a frequency range of 100 to 600 Hz, and with a shear wave amplitude on the order of a few microns down to 0.5 microm. The model provides a basis to explore different parameters related to implementation of the SDUV method. The experiment confirmed conclusions made by the model, and the results can be used for optimization of SDUV.

Selective excitation of microcantilever array using ultrasound radiation force.

The symmetric and antisymmetric eigenstates of a coupled pair of 500 956 m length microcantilevers were excited using the ultrasound radiation force. The excitation was produced using the difference frequency between the two sidebands of a double sideband suppressed carrier AM (DSB‐SC‐AM) waveform centered on 500 kHz that was emitted by a pair of focused ultrasound transducers. A laser Doppler vibrometer measured the frequency response and deflection shapes of the cantilever pair. When the waveforms sent to the transducer resulted in radiation force from both transducers with the same phase, it excited the 10.00 kHz symmetric state of the cantilever array while suppressing the 10.17 kHz antisymmetric state. Similarly, when the radiation force from the two transducers was 180 degrees out of phase, it selectively excited the antisymmetric state while suppressing the symmetric state. This ability to selectively excite different vibrational eigenstates is a unique capability of this noncontact for modal excitation.

Chirp excitation technique to enhance microbubble displacement induced by ultrasound radiation force

Ultrasound radiation force has been proposed to increase the targeting efficiency in ultrasonic molecular imaging and drug delivery. A chirp excitation technique is proposed to increase the radiation force induced microbubble displacement and might potentially be used for enhancing the targeting efficiency of microbubble clouds. In this study, a modified Rayleigh-Plesset equation is used to estimate the radius-time behavior of insonified microbubbles, and the translation of insonified microbubbles is calculated by using the particle trajectory equation. Simulations demonstrate that the chirp excitation is superior to the sinusoidal one in displacing microbubbles with a wide-size distribution, and that the performance is dependent on the parameters of the chirp signal such as the center frequency and frequency range. For Gaussian size distributed microbubble clouds with mean diameter of 3.5 microm and variance of 1, a 2.25 MHz chirp with frequency range of 1.5 MHz induces about 59.59% more microbubbles over a distance of 10 microm during 200 micros insonification, compared to a 2.25 MHz sinusoidal excitation with equal acoustic pressure.

M6-6 超音波によるマイクロバブル内包型ベシクルの破壊(M6 バイオセンサ・システム)

M6-6 超音波によるマイクロバブル内包型ベシクルの破壊(M6 バイオセンサ・システム)

Validation of SMURF Estimation of Shear Modulus in Hydrogels

A validation study of the Spatially Modulated Ultrasound Radiation Force (SMURF) method for shear modulus estimation is presented. SMURF estimates of uniform gelatin and Zerdine phantoms covering a modulus range of 2 to 18 kPa are compared with results obtained by unconfined mechanical compression and sonoelastography. The results show agreement within the measurement uncertainties over the range indicated for all three methods. Repeatability and variation on the order of 5% of the phantom modulus are found for observations made at a single point within the phantom. Averaging of modulus estimates from several adjacent scan lines further decreases the variation. By using multiple radiation force peaks to induce a shear wave of known wavelength and measure the frequency of the wave, SMURF obtains modulus estimates from tracking data acquired along a single A-line. This is significant, as speckle can bias the measured phase of the shear wave. SMURF is shown to be insensitive to a constant phase error in the shear wave measurement. This results in greatly reduced correlated noise in the modulus estimates, in contrast with methods which track at multiple locations and do not cancel phase errors.

Validation of SMURF Estimation of Shear Modulus in Hydrogels

A validation study of the Spatially Modulated Ultrasound Radiation Force (SMURF) method for shear modulus estimation is presented. SMURF estimates of uniform gelatin and Zerdine™ phantoms covering a modulus range of 2 to 18 kPa are compared with results obtained by unconfined mechanical compression and sonoelastography. The results show agreement within the measurement uncertainties over the range indicated for all three methods. Repeatability and variation on the order of 5% of the phantom modulus are found for observations made at a single point within the phantom. Averaging of modulus estimates from several adjacent scan lines further decreases the variation. By using multiple radiation force peaks to induce a shear wave of known wavelength and measure the frequency of the wave, SMURF obtains modulus estimates from tracking data acquired along a single A-line. This is significant, as speckle can bias the measured phase of the shear wave. SMURF is shown to be insensitive to a constant phase error in the shear wave measurement. This results in greatly reduced correlated noise in the modulus estimates, in contrast with methods which track at multiple locations and do not cancel phase errors.