Armen Sarvazyan

• Ph.D., D,Sc.
• Principal Investigator at Artann Laboratories

Radiation force is a universal phenomenon in any wave motion where the wave energy produces a static or transient force on the propagation medium. The theory of acoustic radiation force (ARF) dates back to the early 19th century. In recent years, there has been an increasing interest in the biomedical applications of ARF. Following a brief history...

This chapter examines how the field of ultrasound elastography has grown over time. It analyses the publication record using PubMed for the field and focuses at different distinctions and trends. The chapter offers a perspective on future investigations that could be pursued for the use of acoustic radiation force (ARF) for ultrasound elastographic...

The results of theoretical and experimental studies are presented for the action of acoustic radiation force (ARF) generated by short (microsecond range) ultrasonic pulses on the liquid-liquid and liquid-gel interfaces, which mimic the boundaries within soft biological tissues. For the boundaries between two liquids, the Laplace equation for the ne...

We have previously hypothesized that the dissipation of mechanical energy of external impact is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In this paper, a mathematical justification of this hypothesis is presented. First, a simple mechanical model, in which the m...

We develop a theory of the elasticity moduli and dissipative properties of a composite material: a phantom simulating muscle tissue anisotropy. The model used in the experiments was made of a waterlike polymer with embedded elastic filaments imitating muscle fiber. In contrast to the earlier developed phenomenological theory of the anisotropic prop...

An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method f...

There are several physical effects responsible for the generation of acoustic radiation force (ARF) in soft tissue. The first effect, which is widely used in elastographic applications of ARF, is the transfer of momentum from ultrasonic wave in an attenuating medium due to absorption and scattering. Two other effects include reflection of sound wav...

Acoustic radiation force (ARF) has been used for many medical applications, the most notable of which is measuring the stiffness of soft tissues. The ARF used in these applications results from the dissipation of acoustic energy due to scattering and absorption of sound and accordingly may be called dissipative ARF. Another source of ARF, which is...

Toward the end of the 20th century, a new technology for measuring and visualizing soft tissue viscoelastic characteristics evolved. This modality is called elastography, or elasticity imaging. Tactile imaging, a form of elastography, translates the sense of touch into a digital image and allows assessment of tissue elasticity and muscle strength....

Acoustic radiation force (ARF) has been used in many medical applications, the most notable of which is measuring the stiffness of soft tissues. The ARF used in these applications results from the dissipation of acoustic energy due to scattering and absorption of sound and, accordingly, may be called dissipative ARF. Another source of ARF, which is...

In the past decade acoustic radiation force (ARF) became a powerful tool in numerous biomedical applications. ARF from a focused ultrasound beam acts as a virtual “finger” for remote probing of internal anatomical structures and obtaining diagnostic information. This presentation deals with generation of shear waves by nonlinear focused beams. Albe...

INTRODUCTION Palpation Imaging (PI) of the breast is based on the principles of tactile imaging, a method for measuring the elasticity lesions using a tactile sensor array. PI provides objective data beyond subjective manual palpation by quantifying the shape and hardness of a lesion as well as creating a permanent digital image. PI is also known a...

In almost any sport, athletes undergoing dehydration often suffer from numerous dehydration related injuries. The purpose of this study was to evaluate the validity of acoustic method to detect changes in the hydration status of athletes after undergoing acute dehydration and a 2-hour rehydration protocol. The acoustic method of assessing body hydr...

One of the major (but the least studied!) functions of skeletal muscle is protecting the skeletal system from external impacts by absorbing and redistributing the energy of mechanical shock in time and space. During muscle contraction, its elasticity modulus is greatly increased, which partly unloads adjacent bones and skeletal joints. Muscle visco...

In this talk, an overview of history and physical basis of biomedical applications of acoustic radiation force with a further look into new developments in this field will be presented. In 1902, Lord Rayleigh published his classical work on the theory of sound, introducing the concept of acoustic radiation pressure. Experimental demonstration of ra...

The paper presents the theory of shear wave propagation in a “soft solid” material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles...

A time-reversal acoustics system includes a transmitter configured to send a high intensity acoustic waveform signal focused on an implantable receiver. The receiver includes a piezoelectric transducer configured to convert received acoustic energy to an electrical signal used to energize an internal electrical circuit. Such circuit may be used to...

A leadless Deep Brain Stimulation system includes an implantable stimulator configured to convert incoming acoustic energy into an electric stimulation signal. The acoustic energy is provided by one or more external transmitters acoustically coupled to a head of the subject. To focus ultrasound energy onto the location of the stimulator, a wireless...

Time reversal acoustics (TRA) is one of the most efficient methods of ultrasound focusing in heterogeneous composite biological media, especially inside reverberating cavities, such as the skull. In this talk, we will overview several recently developed therapeutic applications of TRA focusing of ultrasound including enhanced drug delivery to brain...

Abstract: A method and app. for analyzing a fluid, esp. milk, to obtain its concentrations of N components, N being at least three. The method comprises the steps of bringing a sample of the fluid to a plurality of successive temperatures, measuring a combined total of at least N acoustical and elec. parameters of the sample at each temperature, an...

The last decade has seen a surge in the development of axial transmission QUS (Quantitative UltraSound) technologies for the assessment of long bones using various modes of acoustic waves. The condition of cortical bones and the development of osteoporosis are determined by numerous mechanical, micro-structural, and geometrical or macro-structural...

Acoustic waves exhibit force that pushes objects along the direction of sound propagation. Precise motions require well-focused beams. The technique of time-reversal acoustics (TRA) overcomes beam distortions introduced by propagation along irregular paths to focus sound without knowledge of the medium properties. TRA requires a small receiver to b...

The objective of this study was to evaluate if the Bone UltraSonic Scanner (BUSS) can detect osteoporosis in postmenopausal women. BUSS is an axial transmission multi-frequency ultrasonometer for acquisition of wave propagation profiles along the proximal anterior tibia. We derived 10 diagnostically significant BUSS parameters that were then compar...

Time-reversal acoustics is an effective way of focusing ultrasound deep inside heterogeneous media such as biological tissues. Convection-enhanced delivery is a method of delivering drugs into the brain by infusing them directly into the brain interstitium. These two technologies are combined in a focusing system that uses a "smart needle" to simul...

Time Reversal Acoustic (TRA) system provides effective focusing in inhomogeneous media that can be used in various biomedical applications including high intensity ultrasound treatment, ultrasound-assisted drug delivery, ultrasonic battery charging of implants, etc. In many cases, the TRA focusing is conducted in tissues with time varied properties...

Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term ultrasonography, or its abbreviated version sonography, meant an imaging modality based on the use of ultrasonic compressional bulk waves. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a differe...

Methods and apparatus are disclosed for non-invasive bone evaluation based on a broadband ultrasonic transducer emitting a train of ultrasonic wave packets of multiple carrier frequencies ranging from about 50 kHz to about 2 MHz. Receiving broadband ultrasonic transducer accepts broadband ultrasonic signal propagated through the bone. Computer proc...

A handgrip for a colonoscope shaft is equipped with a novel compact multifunction force and torque sensor allowing for a comprehensive characterization of colonoscope manipulation during a colonoscopy procedure. A two-part hinge design of the handgrip in combination with the multifunction sensor provides for a light weight design in a compact packa...

Purpose: To develop a non-invasive screening method with sufficient sensitivity and specificity to provide evidence of developing osteopenia of prematurity over the first several weeks of life in premature infants. Methods: The proposed method uses ultrasound energy to remotely exert a minute vibrating force on the bone and detects the acoustic r...

In percutaneous procedures there is often a need to focus therapeutic ultrasound to a predefined area without affecting surrounding tissues. Focusing based on Time Reversal Acoustics (TRA) principles constitutes a promising approach for generating high intensity ultrasound field tailored to the shape of the predefined area. Conventional TRA techni...

Various types of acoustic waves: bulk compressional, shear, surface, and numerous modes of guided waves, are used for characterizing structure and composition of biological media. Bulk waves can be used to assess the composition of biological fluids, such as blood, plasma, milk, urine, stomach juice, and biopolymers in solutions and both bulk and s...

Quantification of the mechanical properties of muscle is of significant clinical interest. Local changes in the mechanical properties of muscle are often associated with clinical symptoms. In particular, myofascial trigger points (MTrPs) are a very common, yet poorly understood and overlooked, cause of nonarticular musculoskeletal pain. MTrPs are l...

Colonoscopy is a frequently performed procedure that requires extensive training and a high skill level. Quantification of forces applied to the external portion of the colonoscope insertion tube during the insertion phase of colonoscopy. Observational cohort study of 7 expert and 9 trainee endoscopists for analysis of colonic segment force applica...

Mechanical Imaging (MI) is a branch of Elastography. MI differs from conventional ultrasonic and MR elastography in that it evaluates soft tissue mechanical structure using stress data rather than dynamic or static strain data. MI closely mimics manual palpation because the MI probe with a force sensor array attached to its tip acts as a palpating...

From times immemorial manual palpation served as a source of information on the state of soft tissues and allowed detection of various diseases accompanied by changes in tissue elasticity. During the last two decades, the ancient art of palpation gained new life due to numerous emerging elasticity imaging (EI) methods. Areas of applications of EI i...

From times immemorial manual palpation served as a source of information on the state of soft tissues and allowed detection of various diseases accompanied by changes in tissue elasticity. During the last two decades, the ancient art of palpation gained new life due to numerous emerging elasticity imaging (EI) methods. Areas of applications of EI i...

From times immemorial manual palpation served as a source of information on the state of soft tissues and allowed detection of various diseases accompanied by changes in tissue elasticity. During the last two decades, the ancient art of palpation gained new life due to numerous emerging elasticity imaging (EI) methods. Areas of applications of EI i...

A new medical application of acoustics has recently emerged: assessment of body hydration status by ultrasonic measurement of muscle water content. The need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. Body hypohydration may cause severe health and performance problems, decreasing cognitiv...

The velocity of ultrasonic guided waves in long bones is dependent upon two determinants of bone strength: the cortical thickness and the material properties. In this study, six human proximal tibiae in vitro were examined to test the efficacy of an ultrasonic method based on guided waves. Peripheral quantitative computed tomography (pQCT) was used...

Convection‐enhanced delivery (CED) is used in clinical trials to enhance the distribution of therapeutic molecules directly injected into tissue. Recent time‐reversal acoustics (TRA) experiments [Lewis et al., J. Acous. Soc. Am. 128 2335 (2010)] show potential to improve CED with the use of delivery of acoustic forces within the tissue. TRA was use...

Myofascial trigger points (MTrPs) are a very common, yet poorly understood and overlooked, cause of nonarticular musculoskeletal pain. MTrPs are localized, stiff, hyperirritable tender nodules, palpated in taut bands of skeletal muscle. We are investigating sonoelastography and tactile imaging as complementary objective methods to measure the physi...

We describe a thrombolysis method that combines time‐reversal acoustic (TRA) focusing with an AngioJet thrombectomy catheter to improve the dissolution of thrombus in the treatment of deep venous thrombosis (DVT). Commercially available ultrasound‐assisted DVT systems have been shown to accelerate thrombolysis by up to 40% and reduce the amount of...

There are several applications of ultrasound that require accurate ultrasound focusing to a predefined area without affecting the surrounding medium. We present two methods of generating high intensity ultrasound field accurately tailored to the shape of the predefined area using the time reversal acoustics (TRA) principles. The first method is bas...

We describe a drug delivery method that combines Time-Reversal Acoustics (TRA) with Convection-Enhanced Delivery (CED) to improve the delivery of therapeutics to the interstitium of the brain. The Ultrasound-assisted CED approach (UCED) circumvents the blood-brain barrier by infusing compounds through a cannula that is inserted into the brain while...

We describe a drug delivery method that combines time-reversal acoustics (TRA) with convection-enhanced delivery (CED) to improve the delivery of therapeutics to the interstitium of the brain. The ultrasound-assisted CED approach (UCED) circumvents the blood-brain barrier by infusing compounds through a cannula that is inserted into the brain while...

Thousands of papers on radiation force (RF) and acoustical streaming (AS) have been published since Faraday, Rayleigh, and Langevin. There have been more papers on RF in biomedicine published in the last decade than were written in the entire 20th century. Nevertheless, some nonlinear acoustic phenomena significant for engineering and biomedical ap...

Radiation force is a universal phenomenon in any wave motion, electromagnetic or acoustic. Although acoustic and electromagnetic waves are both characterized by time variation of basic quantities, they are also both capable of exerting a steady force called radiation force. In 1902, Lord Rayleigh published his classic work on the radiation force of...

Changes in the elasticity of the vaginal walls, connective support tissues, and muscles are thought to be significant factors in the development of pelvic organ prolapse, a highly prevalent condition affecting at least 50% of women in the United States during their lifetimes. It creates two predominant concerns specific to the biomechanical propert...

The objective of this study was to evaluate the utility of ultrasound velocity (UV) to detect changes in the hydration status of wrestlers after undergoing acute dehydration and a 2-hour rehydration period. Forty-seven NCAA wrestlers (mean+/-SEM); age 19.1+/-0.2 years, height 1.73+/-0.1 m, body mass (BM) 79.4+/-2.4 kg were tested in euhydrated, deh...

This paper compares the performance of two different systems for dynamic focusing of ultrasonic waves: conventional 2-D phased arrays (PA) and a focusing system based on the principles of time-reversed acoustics (TRA). Focused ultrasound fields obtained in the experiments with the TRA focusing system (TRA FS), which employs a liquid-filled reverber...

We have determined the apparent molar volumes, expansibilities, and adiabatic compressibilities of a homologous series of eight α,ω-aminocarboxylic acids within the temperature range 18-55 °C. We interpret the resulting data in terms of the hydration of the component aliphatic and charged atomic groups. From temperature-dependent studies, we find t...

The ability of a single-channel time reversal acoustic systems to focus and receive ultrasound radiation is considered. The basic element of these systems is a liquid-filled acoustic reverberator. Two types of the reverberators have been experimentally studied; one of them is a thin-wall cylindrical balloon used in ultrasound catheters for treatmen...

The ability to deliver configurable myocardial lesions was noted as a critical factor to the success of atrial fibrillation (AF) treatment. This article considers the implementation of time reversal acoustics (TRA) principles for ultrasound focusing using an AF cardiac catheter developed for pulmonary vein isolation. Experiments conducted with a si...

To perform a colonoscopy, the endoscopist maneuvers the colonoscope through a series of loops by applying force to the insertion tube. Colonoscopy insertion techniques are operator dependent but have never been comprehensively quantified. To determine whether the Colonoscopy Force Monitor (CFM), a device that continually measures force applied to t...

The article is a review of the new dual-frequency method in axial bone quantitative ultrasonometry for assessment of changes in cortical bones in osteoporosis. The method is based on the use of two frequencies for the generation of flexural and longitudinal ultrasonic waves, which opens possibilities for differential diagnostics of changes in vario...

A comparative study of two methods used for dynamic focusing of ultrasound: the conventional phased arrays and a new method based on time reversal of acoustic signals is carried out. A laboratory model of the focusing system based on time reversal is developed and manufactured. One of the principal elements of the system is a reverberator with seve...

Ultrasound focusing based on time reversal acoustics (TRA) principles typically produces short ultrasound pulses having relatively low time‐average intensity, which highly limits the therapeutic applications of these systems. The aim of this study was to explore theoretically and experimentally the possibility of generating long ultrasound signals...

Mechanical Imaging (MI), a.k.a. tactile imaging or stress imaging, is a branch of Elasticity Imaging, a medical diagnostic technique based on the visualization of tissue internal structures in terms of their elasticity modulus. During the last decade, numerous methods and devices have been developed implementing MI technology in various medical app...

The possibility of using acoustic radiation force in standing waves for stirring and mixing small volumes of liquids is theoretically analyzed. The principle of stirring considered in this paper is based on moving the microparticles suspended in a standing acoustic wave by changing the frequency so that one standing wave mode is replaced by the oth...

Acoustic and seismic waves provide a method to localize compliant mines by vibrating the top plate and a thin soil layer above the mine. This vibration is mostly linear, but also includes a small nonlinear deviation. The main goal of this paper is to introduce a method of processing that uses phase-inversion to observe nonlinear effects in a wide f...

The use of ultrasound in resonators for manipulating particles in various biomedical applications is a relatively well studied topic. These studies were mostly concerned with steady-state processes. However, in certain important applications, such as stirring and mixing fluids in microfluidics and biosensors, the time scale of a process plays a cru...

In this paper, an innovative technology based on the use of ultrasonic cylindrical standing waves for continuous monitoring of quality of various liquid food products, such as milk, juices, beer, wine, and drinking water is described. A proprietary unique feature of the developed ultrasonic analyzer is that it employs a combined mode of operation u...

Mechanical imaging yields tissue elasticity map and provides quantitative characterization of a detected pathology. The changes in the surface stress patterns as a function of applied load provide information about the elastic composition and geometry of the underlying tissue structures. The objective of this study is the clinical evaluation of bre...

Most of the medical applications of ultrasound are based on its focusing. The quality of focusing deterr mines the spatial resolution and, as a consequence, the amount of information extracted from ultrasonic visuu alization. In surgery, by focusing the energy of ultraa sound, it is possible to sonicate sites of tissues located deep in the body wit...

The paper presents results of a clinical validation study of Bone UltraSonic Scanner (BUSS), a novel dual-frequency axial transmission ultrasonometer, developed by Artann Laboratories. Assessment of bone conditions is based on evaluating relative changes of the axial profiles of ultrasonic characteristics in long bones and utilizes bulk and guided...

The ability to generate short focused ultrasonic pulses with duration on the order of one period of carrier frequency depends on the bandwidth of the transmitter as the pulse duration is inversely proportional to the bandwidth. Conventional focusing arrays used for focusing ultrasound have limited bandwidth due to the resonant nature of the piezoel...

The time reversal acoustics (TRA) principle has been employed for focusing ultrasonic waves in various biomedical and industrial applications. TRA-based ultrasonic transmitters have numerous advantages over conventional methods of ultrasound focusing such as an ability to effectively focus and steer focal spot with a transmitter comprising even a s...

In this paper, we analyze the physical basis for elasticity imaging of the breast by measuring breast skin stress patterns that result from a force sensor array pressed against the breast tissue. Temporal and spatial changes in the stress pattern allow detection of internal structures with different elastic properties and assessment of geometrical...

Affordability of healthcare is highly limited by its skyrocketing cost. Access to screening and diagnostic medical equipment and medicine in developing countries is inadequate for the majority of the population. There is a tremendous worldwide need to detect breast cancer at its earliest stage. These needs must be balanced by the ability of countri...

This talk presents an overview of physical basis for the action of acoustic radiation force on particles in standing waves in relation to biomedical applications. The effect itself is known since the 19th century (Kundt, 1974) and its biomedical significance was demonstrated in 1971 by Dyson et al. However, despite a long history, extensive studies...

Time reversal focuses seismic waves and excites nonlinear surface vibrations that are large in the presence of a landmine. These soil vibrations provide an accurate localization cue when contrasted with measurements made without a mine. Traditionally nonlinear effects were investigated by measuring the interaction of harmonic waves and nonlinear re...

Acoustic methods of land mine detection are being developed for nonmetal mines where conventional electromagnetic methods fail. One such method, based on time reversal acoustic principles, is the hhase-inversion method; which detects quadratic and even ordered harmonic nonlinearities in the surface vibration above a mine. While this has shown highe...

Time reversal acoustic focusing can be used for local assessment of nonlinear properties of media [Sarvazyan A., Sutin A. , JASA, 115 (5): 2595 (2004)]. Time Reversal focusing provides high acoustic pressure leading to a nonlinear response localized in space and time. Interaction area of two overlapping focused beams acts as a virtual localized sou...

Propagation parameters of ultrasonic guided waves in long bones are sensitive to changes of the cortical thickness, which is one of bone parameters affected by osteoporosis. Meanwhile, the guided waves in bone can be masked by the longitudinal waves in the overlying soft tissues, especially in obese patients. The goal of this study was to explore a...

Time Reversal Acoustic (TRA) focusing system based on an external reverberator can provide good focusing with minimum side lobes even with a few transducers. The focusing ability of such system can be increased using reverberator with rough boundaries or by adding internal random scatterers. The experiments were conducted with a reverberator made o...

Focusing of ultrasonic waves is a fundamental aspect of most of the medical applications of ultrasound. There are three approaches in focusing acoustic energy: geometrical, using concave transducers and acoustic lenses, electronic, using phased arrays, and time-reversal (TR), which allows both spatial and temporal concentration of acoustic energy....

In the recent years numerous Time Reversal Acoustic Focusing Systems (TRA FS) employing various reverberation chambers ("acoustic cavities") accumulating acoustic energy in time were described in the literature. We propose an alternative reverberator composed of a liquid-filled volume comprising a series of spatially distributed membranes with vary...

The concept of Time Reversal Acoustics (TRA) provides an elegant possibility of both temporal and spatial concentrating of acoustic energy in highly inhomogeneous media. We explored the possibility of generating acoustical signals with arbitrary waveforms using the TRA Focusing System (TRA FS). A method has been developed to predict TRA-focused ult...

To evaluate the ability of prostate mechanical imaging (PMI) technology to provide an objective and reproducible image and to assess the prostate nodularity. We evaluated the PMI device developed by Artann Laboratories in a pilot clinical study. For the 168 patients (ages 44 to 94) who presented to an urologist for prostate evaluation, PMI-produced...

We have developed a device entitled the 'Tissue Elastometer' (TE) for evaluating the Young's modulus of soft tissues. Soft tissue specimens are compressed between the object plate of an electronic balance and a linearly actuated indenter with a small rounded tip. The hardware of the device was designed such that a deformation model for semi-infinit...

The article presents a retrospective view on the assessment of long bones condition using topographical patterns of the acoustic properties. The application of ultrasonic point-contact transducers with exponential waveguides on a short acoustic base for detailed measurements in human long bones by the surface transmission was initiated during the 1...

Time reversal acoustics (TRA) provides a way to focus ultrasound in space and time. Standard TRA focusing system produces tone burst signal with a frequency band limited by the bandwidth of the transducer. For certain medical applications, both in therapy and imaging, a wider bandwidth is required. The goal of this study was to explore a possibilit...

Time reversal focusing of acoustic waves has numerous biomedical applications including medical imaging, HIFU treatment, and targeted drug delivery. These various applications pose different requirements. Imaging requires a small spatial focused spot, which can be scanned in 2‐D or 3‐D; therapy requires high deposited energy and controlled‐shape ex...

Acoustic methods of land mine detection are being developed for nonmetal mines where conventional electromagnetic methods fail. Nonlinear acoustic methods have shown higher sensitivity than linear methods. In previous studies, the nonlinear methods, based on interaction of two frequency waves and phase inversion of two pulses, were investigated. We...

Time Reversal Acoustic (TRA) focusing system based on the use of liquid filled resonators with single or few transducers is demonstrated to effectively converge acoustic energy in space and time. Because the wavelength in liquid is typically smaller than in solids, liquid based TRA focusing resonators can have smaller dimensions than solid resonato...

Radiation force is a universal phenomenon in any wave motion, electromagnetic or acoustic. Radiation force is produced by a change in the density of energy of the propagating wave. The concept of radiation pressure follows from Maxwell?s equations (1871), while the idea of electromagnetic wave (light) pressure can be traced back to Johannes Kepler...

The nonlinear vibration response of land mines is an effective detection clue. This response can be measured by application of two frequency acoustic waves producing a vibration spectrum above the mine that is different from its surrounding. As an alternative to this approach, this work investigates time reversal techniques as a method of acoustica...

The use of solid acoustic reverberators for temporal and spatial focusing of acoustic energy based on time reversal acoustic (TRA) principle was described in the literature. We experimentally and theoretically demonstrated that the liquid‐filled TRA reverberators can also efficiently focus acoustic energy and compared the advantages of solid and wa...

An action of radiation force induced by ultrasonic beam in waterlike media such as biological tissues (where the shear modulus is small as compared to the bulk compressibility) is considered. A new, nondissipative mechanism of generation of shear displacement due to a smooth (nonreflecting) medium inhomogeneity is suggested, and the corresponding m...