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Kierski TM, Walmer RW, Tsuruta JK, Yin J, Chérin E, Foster FS, Demore CEM, Newsome IG, Pinton GF, Dayton PA. Acoustic Molecular Imaging Beyond the Diffraction Limit In Vivo. IEEE Open J Ultrason Ferroelectr Freq Control 2022; 2:237-249. [PMID: 38125957 PMCID: PMC10732349 DOI: 10.1109/ojuffc.2022.3212342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Ultrasound molecular imaging (USMI) is a technique used to noninvasively estimate the distribution of molecular markers in vivo by imaging microbubble contrast agents (MCAs) that have been modified to target receptors of interest on the vascular endothelium. USMI is especially relevant for preclinical and clinical cancer research and has been used to predict tumor malignancy and response to treatment. In the last decade, methods that improve the resolution of contrast-enhanced ultrasound by an order of magnitude and allow researchers to noninvasively image individual capillaries have emerged. However, these approaches do not translate directly to molecular imaging. In this work, we demonstrate super-resolution visualization of biomarker expression in vivo using superharmonic ultrasound imaging (SpHI) with dual-frequency transducers, targeted contrast agents, and localization microscopy processing. We validate and optimize the proposed method in vitro using concurrent optical and ultrasound microscopy and a microvessel phantom. With the same technique, we perform a proof-of-concept experiment in vivo in a rat fibrosarcoma model and create maps of biomarker expression co-registered with images of microvasculature. From these images, we measure a resolution of 23 μm, a nearly fivefold improvement in resolution compared to previous diffraction-limited molecular imaging studies.
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Affiliation(s)
- Thomas M Kierski
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
| | - Rachel W Walmer
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
| | - James K Tsuruta
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
| | - Jianhua Yin
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
| | | | - F Stuart Foster
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Christine E M Demore
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Isabel G Newsome
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
| | - Gianmarco F Pinton
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
| | - Paul A Dayton
- Joint Department of Biomedical Engineering, UNC-Chapel Hill and NC State University, Chapel Hill, NC 27599 USA
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Newsome IG, Kierski TM, Pang G, Yin J, Yang J, Cherin E, Foster FS, Carnevale CA, Demore CEM, Dayton PA. Implementation of a Novel 288-Element Dual-Frequency Array for Acoustic Angiography: In Vitro and In Vivo Characterization. IEEE Trans Ultrason Ferroelectr Freq Control 2021; 68:2657-2666. [PMID: 33872146 PMCID: PMC8375591 DOI: 10.1109/tuffc.2021.3074025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Acoustic angiography is a superharmonic contrast-enhanced ultrasound imaging method that produces high-resolution, 3-D maps of the microvasculature. Previous acoustic angiography studies have used twoelement, annular,mechanicallyactuated transducers(called "wobblers") to image microvasculature in preclinical tumor models with high contrast-to-tissue ratio and resolution, but these earlywobbler transducerscould not achieve the depth and sensitivity required for clinical acoustic angiography. In this work, we present a system for performing acoustic angiography with a novel dual-frequency(DF) transducer-a coaxially stacked DF array (DFA). We evaluate the DFA system bothin vitro andin vivo and demonstrate improvements in sensitivity and imaging depth up to 13.1 dB and 10 mm, respectively, compared with previous wobbler probes.
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Yang J, Cherin E, Yin J, Newsome IG, Kierski TM, Pang G, Carnevale CA, Dayton PA, Foster FS, Demore CEM. Characterization of an Array-Based Dual-Frequency Transducer for Superharmonic Contrast Imaging. IEEE Trans Ultrason Ferroelectr Freq Control 2021; 68:2419-2431. [PMID: 33729934 PMCID: PMC8459708 DOI: 10.1109/tuffc.2021.3065952] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Superharmonic imaging with dual-frequency imaging systems uses conventional low-frequency ultrasound transducers on transmit, and high-frequency transducers on receive to detect higher order harmonic signals from microbubble contrast agents, enabling high-contrast imaging while suppressing clutter from background tissues. Current dual-frequency imaging systems for superharmonic imaging have been used for visualizing tumor microvasculature, with single-element transducers for each of the low- and high-frequency components. However, the useful field of view is limited by the fixed focus of single-element transducers, while image frame rates are limited by the mechanical translation of the transducers. In this article, we introduce an array-based dual-frequency transducer, with low-frequency and high-frequency arrays integrated within the probe head, to overcome the limitations of single-channel dual-frequency probes. The purpose of this study is to evaluate the line-by-line high-frequency imaging and superharmonic imaging capabilities of the array-based dual-frequency probe for acoustic angiography applications in vitro and in vivo. We report center frequencies of 1.86 MHz and 20.3 MHz with -6 dB bandwidths of 1.2 MHz (1.2-2.4 MHz) and 14.5 MHz (13.3-27.8 MHz) for the low- and high-frequency arrays, respectively. With the proposed beamforming schemes, excitation pressure was found to range from 336 to 458 kPa at its azimuthal foci. This was sufficient to induce nonlinear scattering from microbubble contrast agents. Specifically, in vitro contrast channel phantom imaging and in vivo xenograft mouse tumor imaging by this probe with superharmonic imaging showed contrast-to-tissue ratio improvements of 17.7 and 16.2 dB, respectively, compared to line-by-line micro-ultrasound B-mode imaging.
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Kierski TM, Dayton PA. Perspectives on high resolution microvascular imaging with contrast ultrasound. Appl Phys Lett 2020; 116:210501. [PMID: 32508345 PMCID: PMC7253217 DOI: 10.1063/5.0012283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 05/13/2023]
Abstract
Recent developments in contrast enhanced ultrasound have demonstrated a potential to visualize small blood vessels in vivo, unlike anything possible with traditional grayscale ultrasound. This Perspective article introduces microvascular imaging strategies and their underlying technology.
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Affiliation(s)
- Thomas M. Kierski
- The Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Campus Box 7575, Chapel Hill, North Carolina 27599, USA
| | - Paul A. Dayton
- The Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Campus Box 7575, Chapel Hill, North Carolina 27599, USA
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Kierski TM, Espindola D, Newsome IG, Cherin E, Yin J, Foster FS, Demore CEM, Pinton GF, Dayton PA. Superharmonic Ultrasound for Motion-Independent Localization Microscopy: Applications to Microvascular Imaging From Low to High Flow Rates. IEEE Trans Ultrason Ferroelectr Freq Control 2020; 67:957-967. [PMID: 31940529 PMCID: PMC7297200 DOI: 10.1109/tuffc.2020.2965767] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Recent advances in high frame rate biomedical ultrasound have led to the development of ultrasound localization microscopy (ULM), a method of imaging microbubble (MB) contrast agents beyond the diffraction limit of conventional coherent imaging techniques. By localizing and tracking the positions of thousands of individual MBs, ultrahigh resolution vascular maps are generated which can be further analyzed to study disease. Isolating bubble echoes from tissue signal is a key requirement for super-resolution imaging which relies on the spatiotemporal separability and localization of the bubble signals. To date, this has been accomplished either during acquisition using contrast imaging sequences or post-beamforming by applying a spatiotemporal filter to the B-mode images. Superharmonic imaging (SHI) is another contrast imaging method that separates bubbles from tissue based on their strongly nonlinear acoustic properties. This approach is highly sensitive, and, unlike spatiotemporal filters, it does not require decorrelation of contrast agent signals. Since this superharmonic method does not rely on bubble velocity, it can detect completely stationary and moving bubbles alike. In this work, we apply SHI to ULM and demonstrate an average improvement in SNR of 10.3-dB in vitro when compared with the standard singular value decomposition filter approach and an increase in SNR at low flow ( [Formula: see text]/frame) from 5 to 16.5 dB. Additionally, we apply this method to imaging a rodent kidney in vivo and measure vessels as small as [Formula: see text] in diameter after motion correction.
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Newsome IG, Kierski TM, Dayton PA. Assessment of the Superharmonic Response of Microbubble Contrast Agents for Acoustic Angiography as a Function of Microbubble Parameters. Ultrasound Med Biol 2019; 45:2515-2524. [PMID: 31174922 PMCID: PMC7202402 DOI: 10.1016/j.ultrasmedbio.2019.04.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 04/25/2019] [Accepted: 04/30/2019] [Indexed: 05/07/2023]
Abstract
Acoustic angiography is a superharmonic contrast-enhanced ultrasound imaging technique that enables 3-D high-resolution microvascular visualization. This technique utilizes a dual-frequency imaging strategy, transmitting at a low frequency and receiving at a higher frequency, to detect high-frequency contrast agent signatures and separate them from tissue background. Prior studies have illustrated differences in microbubble scatter dependent on microbubble size and composition; however, most previously reported data have utilized a relatively narrow frequency bandwidth centered around the excitation frequency. To date, a comprehensive study of isolated microbubble superharmonic responses with a broadband dual-frequency system has not been performed. Here, the superharmonic signal production of 14 contrast agents with various gas cores, shell compositions, and bubble diameters at mechanical indices of 0.2 to 1.2 was evaluated using a transmit 4 MHz, receive 25 MHz configuration. Results indicate that perfluorocarbon cores or lipid shells with 18- or 20-carbon acyl chains produce more superharmonic signal than sulfur hexafluoride cores or lipid shells with 16-carbon acyl chains, respectively. As microbubble diameter increases from 1 to 4 µm, superharmonic generation decreases. In a comparison of two clinical agents, Definity and Optison, and one preclinical agent, Micromarker, Optison produced the least superharmonic signal. Overall, this work suggests that microbubbles around 1 μm in diameter with perfluorocarbon cores and longer-chained lipid shells perform best for superharmonic imaging at 4 MHz. Studies have found that microbubble superharmonic response follows trends different from those described in prior studies using a narrower frequency bandwidth centered around the excitation frequency. Future work will apply these results in vivo to optimize the sensitivity of acoustic angiography.
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Affiliation(s)
- Isabel G Newsome
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, USA
| | - Thomas M Kierski
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, USA
| | - Paul A Dayton
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, USA.
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Fix SM, Koppolu BP, Novell A, Hopkins J, Kierski TM, Zaharoff DA, Dayton PA, Papadopoulou V. Ultrasound-Stimulated Phase-Change Contrast Agents for Transepithelial Delivery of Macromolecules, Toward Gastrointestinal Drug Delivery. Ultrasound Med Biol 2019; 45:1762-1776. [PMID: 31003709 PMCID: PMC6701470 DOI: 10.1016/j.ultrasmedbio.2019.02.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 02/01/2019] [Accepted: 02/06/2019] [Indexed: 05/23/2023]
Abstract
The gastrointestinal (GI) tract presents a notoriously difficult barrier for macromolecular drug delivery, especially for biologics. Herein, we demonstrate that ultrasound-stimulated phase change contrast agents (PCCAs) can transiently disrupt confluent colorectal adenocarcinoma monolayers and improve the transepithelial transport of a macromolecular model drug. With ultrasound treatment in the presence of PCCAs, we achieved a maximum of 44 ± 15% transepithelial delivery of 70-kDa fluorescein isothiocyanate-dextran, compared with negligible delivery through sham control monolayers. Among all tested rarefactional pressures (300-600 kPa), dextran delivery efficiency was consistently greatest at 300 kPa. To explore this unexpected finding, we quantified stable and inertial cavitation energy generated by various ultrasound exposure conditions. In general, lower pressures resulted in more persistent cavitation activity during the 30-s ultrasound exposures, which may explain the enhanced dextran delivery efficiency. Thus, a unique advantage of using low boiling point PCCAs for this application is that the same low-pressure pulses can be used to induce vaporization and provide maximal delivery.
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Affiliation(s)
- Samantha M Fix
- Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Bhanu P Koppolu
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA
| | - Anthony Novell
- IR4M, Université Paris-Saclay, CNRS UMR 8081, 91401 Orsay, France
| | - Jared Hopkins
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA
| | - Thomas M Kierski
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA
| | - David A Zaharoff
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA
| | - Paul A Dayton
- Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA; Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA
| | - Virginie Papadopoulou
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Chapel Hill, NC 27599, USA.
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