Alyona Haritonova

Ion and solute transport by prestin in Drosophila and Anopheles

The gut and Malpighian tubules of insects are the primary sites of active solute and water transport for controlling hemolymph and urine composition, pH, and osmolarity. These processes depend on ATPase (pumps), channels and solute carriers (Slc proteins). Maturation of genomic databases enables us to identify the putative molecular players for these processes. Anion transporters of the Slc4 family, AE1 and NDAE1, have been reported as HCO(3)(-) transporters, but are only part of the story. Here we report Dipteran (Drosophila melanogaster (d) and Anopheles gambiae (Ag)) anion exchangers, belonging to the Slc26 family, which are multi-functional anion exchangers. One Drosophila and two Ag homologues of mammalian Slc26a5 (Prestin) and Slc26a6 (aka, PAT1, CFEX) were identified and designated dPrestin, AgPrestinA and AgPrestinB. dPrestin and AgPrestinB show electrogenic anion exchange (Cl(-)/nHCO(3)(-), Cl(-)/SO(4)(2-) and Cl(-)/oxalate(2-)) in an oocyte expression system. Since these transporters are the only Dipteran Slc26 proteins whose transport is similar to mammalian Slc26a6, we submit that Dipteran Prestin are functional and even molecular orthologues of mammalian Slc26a6. OSR1 kinase increases dPrestin ion transport, implying another set of physiological processes controlled by WNK/SPAK signaling in epithelia. All of these mRNAs are highly expressed in the gut and Malpighian tubules. Dipteran Prestin proteins appear suited for central roles in bicarbonate, sulfate and oxalate metabolism including generating the high pH conditions measured in the Dipteran midgut lumen. Finally, we present and discuss Drosophila genetic models that integrate these processes.

In Vivo application and localization of transcranial focused ultrasound using dual-mode ultrasound arrays

Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, and blood-brain barrier opening. A flurry of activity in recent years has generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams has been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. The recent introduction of real-time dual-mode ultrasound array (DMUA) systems offers a new paradigm in transcranial focusing. In this paper, we present first experimental results of ultrasound-guided transcranial FUS (tFUS) application in a rodent brain, both ex vivo and in vivo. DMUA imaging is used for visualization of the treatment region for placement of the focal spot within the brain. This includes the detection and localization of pulsating blood vessels at or near the target point(s). In addition, DMUA imaging is used to monitor and localize the FUS-tissue interactions in real time. In particular, a concave (40 mm radius of curvature), 32-element, 3.5-MHz DMUA prototype was used for imaging and tFUS application in ex vivo and in vivo rat models. The ex vivo experiments were used to evaluate the point spread function of the transcranial DMUA imaging at various points within the brain. In addition, DMUA-based transcranial ultrasound thermography measurements were compared with thermocouple measurements of subtherapeutic tFUS heating in rat brain ex vivo. The ex vivo setting was also used to demonstrate the capability of DMUA to produce localized thermal lesions. The in vivo experiments were designed to demonstrate the ability of the DMUA to apply, monitor, and localize subtherapeutic tFUS patterns that could be beneficial in transient blood-brain barrier opening. The results show that although the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within a sub-millimeter volume. In addition, DMUA transcranial echo data from brain tissue allow for reliable estimation of temperature change.

Robust detection and control of bubble activity during high intensity focused ultrasound ablation

We present results from a real-time ultrasound-guided focused ultrasound platform designed to monitor and control bubble activity. A single element transducer is used in a dual-mode fashion to interleave HIFU therapy with imaging pulses. Use of the same element for both therapy and monitoring creates an inherent alignment between the imaging focus and the therapy focus. Field programmable gate arrays (FPGA) control the signal generation and echo reception enabling real-time data processing to detect and control bubble activity with microsecond latency. Results are presented from in vitro experiments in swine liver and bovine cardiac tissue demonstrating the ability to detect bubble activity and control lesion growth at intensities up to 15 kW/cm2.

Dual-mode ultrasound arrays for image-guided targeting of atheromatous plaques

A feasibility study was undertaken in order to investigate alternative noninvasive treatment options for atherosclerosis. In particular, the aim of this study was to investigate the potential use of Dual-Mode Ultrasound Arrays (DMUAs) for image guided treatment of atheromatous plaques. DMUAs offer a unique treatment paradigm for image-guided surgery allowing for robust image-based identification of tissue targets for localized application of HIFU. In this study we present imaging and therapeutic results form a 3.5 MHz, 64-element fenestrated prototype DMUA for targeting lesions in the femoral artery of familial hypercholesterolemic (FH) swine. Before treatment, diagnostic ultrasound was used to verify the presence of plaque in the femoral artery of the swine. Images obtained with the DMUA and a diagnostic (HST 15-8) transducer housed in the fenestration were analyzed and used for guidance in targeting of the plaque. Discrete therapeutic shots with an estimated focal intensity of 4000-5600 W/cm2 and 500-20...

Multiple-frequency phased array pattern synthesis for HIFU surgery

We present a simulation/experimental study to evaluate and optimize the focusing capabilities of a phased array prototype when excited by multiple-frequency components. A multiple-focus multiple-frequency pattern synthesis algorithm for phased arrays has been developed and tested using linear simulations in Matlab. The algorithm maintains the precise phase relationship between the frequency components at each focal spot to achieve a desirable therapeutic outcome. Preliminary simulations indicate that the focal region can be shaped based on the alignment and phase of multiple-frequency components. The pattern synthesis algorithm is experimentally validated with a 3.5 MHz, 64-element prototype designed for small-animal and superficial therapeutic HIFU applications (Imasonic, Inc) which has a 52% fractional bandwidth, allowing for therapeutic output in the frequency range of 2.7-4.6 MHz. Validation with hydrophone measurements at the focal locations showed that there is in increase in harmonic generation at the focal point with the frequency mixed patterns when compared to a conventional single frequency excitation pattern. This increased non-linearity, will allow for increased thermal absorption at the focal point, thus allowing for larger treatment volumes with the same total power or reduced treatment time per shot when compared to the single frequency case. Ex vivo experiments with fresh porcine liver were conducted to study the effect of multiple-frequency patterns when compared with conventional single frequency patterns during lesion formation. The lesion size was increased for the multiple-frequency patterns when compared the single frequency pattern at normalized power with respect to each other. In conclusion, wideband piezocomposite array transducers, together with multi-channel arbitrary waveform generators are enabling technologies which allow for complex, multiple-focus, multiple-frequency HIFU patterns. These patterns can enhanced the focal gain with proper phase alignment. Furthermore, multiple frequency patterns have been shown to be able to increase the harmonic generation at the focal spot, thus improving local absorption. Our early results with ex vivo porcine liver indicate that multiple frequency excitation can enhance the therapeutic gain at the focal points.

Transcranial focusing and HIFU beam localization with dual-mode ultrasound arrays

Focused ultrasound (FUS) has been proposed for a variety of transcranial applications, including neuromodulation, tumor ablation, blood brain barrier opening. A flurry of activity in recent years have generated encouraging results demonstrating its feasibility in these and other applications. To date, monitoring of FUS beams have been primarily accomplished using MR guidance, where both MR thermography and elastography have been used. With the use of dual-mode ultrasound array (DMUA) systems with real-time imaging capability, it is possible to localize sub-therapeutic and therapeutic transcranial FUS (tFUS) beams using ultrasound. We have designed and implemented a 64-channel DMUA system with real-time GPU-based beamformer capable of supporting single transmit focus (STF) imaging at frame rates in excess of 500 fps. A 3.5-MHz, concave (40-mm roc), 32-element DMUA transducer was used to produce sub therapeutic tFUS while simultaneously imaging a decapitated head of a Copenhagen rat. A 150-μm needle thermocouple was placed at the center of the brain to measure the tFUS induced temperature. DMUA imaging was used to localize the T/C needle and place the tFUS beam near the T/C junction. A number of sub-therapeutic tFUS beams with varying power were then generated while T/C measurements were recorded synchronously with the STF frames. Speckle tracking of echo data from the tFUS beam location within the brain was used to produce transcranial images of temperature change. We have also characterized the distortion to the array psf due to the skull using images of a 50-μm wire at the center of the brain. The results show that, while the DMUA focus is degraded due to the propagation through the skull, it still produces localized heating effects within sub-millimeter volume. In addition, DMUA transcranial echo data from brain tissue allow for reliable estimation of temperature change through speckle tracking.

Close-loop lesion formation control using multiple-focus dual mode ultrasound array

Bubble activity during the high intensity focused ultrasound (HIFU) application could create overexposed lesion in very short period of time due to the increase in acoustic absorption. This process, however, can be utilized to drastically reduce the lesion formation time if the bubble activities can be reliably monitored and controlled. Furthermore, a phased array system could be used to reduce the volume lesion formation time by simultaneously invoking bubble activity at multiple focus locations, and independently adjust the intensity at each location based on the monitoring feedback. We present the results from an ultrasound-guided focused ultrasound platform designed to perform real-time monitoring and control of lesion formation using multiple-focus patterns. A dual-mode ultrasound array (DMUA) is used for both lesion formation and bubble activity monitoring with single transmit focusing (STF) imaging. The beam sequencing is designed to maintain spatial and temporal synchronization between therapy and imaging pulse, this ensures optimum STF imaging performance during the respective therapy application for reliable bubble activity detection. The DMUA is driven by a custom designed 32-channel arbitrary waveform generator and linear power amplifier. Use of arbitrary waveform and linear output allows optimum synthesis of multiple-focus pattern with minimum pre-focal artifacts. The beamformed RF data has been shown to be very sensitive to cavitation activity in response to HIFU in a variety of modes (e.g. boiling cavitation), which is characterized by sudden increase in echogenicity that could occur within milliseconds of the HIFU application. The STF beamforming and the signal processing chain are implemented on a multi-GPU platform and frame rate in excess of 500 fps can be achieved. We present results from a series of experiments in bovine cardiac tissue demonstrating the robustness and increased speed of volumetric lesion formation. Results from our experiments demonstrate the feasibility of producing spatial and temporal modulations of multiple-focus DMUA patterns based on STF imaging feedback with millisecond resolution. This fine temporal and spatial control allows for achieving significant acceleration of volumetric coagulation rates within the target volume without overexposure to the tissue in the prefocal region.

Real-time implementation of a dual-mode ultrasound array system: In vivo results

Background, Motivation and Objective: We have previously presented a method of ultrasound image guidance known as a dual-mode ultrasound array (DMUA). A DMUA uses the same elements for imaging and therapy creating an inherent registration between the two modalities and allowing for precise HIFU targeting. Previous results have demonstrated the abilities of DMUAs on phantoms and in vitro tissues with offline data processing, here we present in vivo results from a fully functional, real-time implementation of a DMUA. Statement of Contribution/Methods: This system utilizes high-performance FPGAs and GPUs to implement a novel ultrasound-guided focused ultrasound (USgFUS) platform. This platform uses 33 frames per second synthetic aperture (SA) imaging to provide guidance for the selection of therapeutic targets. Single transmit focus (STF) imaging is interleaved with therapy at 1000 frame per second to provide real-time feedback on the treatment progress. The array contains a central opening to allow the coaxial alignment of a diagnostic transducer for image fusion between the diagnostic and DMUA imaging modalities. Results: A 3.5 MHz, 32 element DMUA was used for HIFU treatments in swine and rat animal models. The SA imaging allowed for the recognition of tissue structure and the tracking of natural tissue motion. STF imaging during therapy allowed for the detection of HIFU induced echogenic changes. The DMUA images allowed for the targeted placement of HIFU shots with sub-millimeter and millisecond spatial and temporal resolutions, respectively. Histological examinations have confirmed thermal lesion formation within the wall of the vessel. Discussion and Conclusions: Advances in computing power and array technology have enabled the development of a DMUA as a real-time USgFUS platform. These results represent the first in vivo demonstration of a DMUAs imaging and therapeutic capability. The system demonstrates the ability to image anatomical structures and deliver HIFU therapy safely and efficaciously.

Image-based numerical modeling of HIFU-induced lesions

Atherosclerosis is a chronic vascular disease affecting large and medium sized arteries. Several treatment options are already available for treatment of this disease. Targeting atherosclerotic plaques by high intensity focused ultrasound (HIFU) using dual mode ultrasound arrays (DMUA) was recently introduced in literature. We present a finite difference time domain (FDTD) simulation modeling of the wave propagation in heterogeneous medium from the surface of a 3.5 MHz array prototype with 32-elements. After segmentation of the ultrasound image obtained for the treatment region in-vivo, we integrated this anatomical information into our simulation to account for different parameters that may be caused by these multi-region anatomical complexities. The simulation program showed that HIFU was able to induce damage in the prefocal region instead of the target area. The HIFU lesions, as predicted by our simulation, were well correlated with the actual damage detected in histology.

Adaptive lesion formation using dual mode ultrasound array system

We present the results from an ultrasound-guided focused ultrasound platform designed to perform real-time monitoring and control of lesion formation. Real-time signal processing of echogenicity changes during lesion formation allows for identification of signature events indicative of tissue damage. The detection of these events triggers the cessation or the reduction of the exposure (intensity and/or time) to prevent overexposure. A dual mode ultrasound array (DMUA) is used for forming single- and multiple-focus patterns in a variety of tissues. The DMUA approach allows for inherent registration between the therapeutic and imaging coordinate systems providing instantaneous, spatially-accurate feedback on lesion formation dynamics. The beamformed RF data has been shown to have high sensitivity and specificity to tissue changes during lesion formation, including in vivo. In particular, the beamformed echo data from the DMUA is very sensitive to cavitation activity in response to HIFU in a variety of modes...