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Tsivgoulis G, Safouris A, Alexandrov AV. Ultrasonography. Stroke 2022. [DOI: 10.1016/b978-0-323-69424-7.00046-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Rousou C, Schuurmans CCL, Urtti A, Mastrobattista E, Storm G, Moonen C, Kaarniranta K, Deckers R. Ultrasound and Microbubbles for the Treatment of Ocular Diseases: From Preclinical Research towards Clinical Application. Pharmaceutics 2021; 13:pharmaceutics13111782. [PMID: 34834196 PMCID: PMC8624665 DOI: 10.3390/pharmaceutics13111782] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/08/2021] [Accepted: 10/09/2021] [Indexed: 12/26/2022] Open
Abstract
The unique anatomy of the eye and the presence of various biological barriers make efficacious ocular drug delivery challenging, particularly in the treatment of posterior eye diseases. This review focuses on the combination of ultrasound and microbubbles (USMB) as a minimally invasive method to improve the efficacy and targeting of ocular drug delivery. An extensive overview is given of the in vitro and in vivo studies investigating the mechanical effects of ultrasound-driven microbubbles aiming to: (i) temporarily disrupt the blood–retina barrier in order to enhance the delivery of systemically administered drugs into the eye, (ii) induce intracellular uptake of anticancer drugs and macromolecules and (iii) achieve targeted delivery of genes, for the treatment of ocular malignancies and degenerative diseases. Finally, the safety and tolerability aspects of USMB, essential for the translation of USMB to the clinic, are discussed.
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Affiliation(s)
- Charis Rousou
- Departments of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands; (C.C.L.S.); (E.M.); (G.S.)
- Division of Imaging and Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; (C.M.); (R.D.)
- Correspondence:
| | - Carl C. L. Schuurmans
- Departments of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands; (C.C.L.S.); (E.M.); (G.S.)
- Department of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands
| | - Arto Urtti
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, 70210 Kuopio, Finland;
- Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
- Institute of Chemistry, St. Petersburg State University, Universitetskii Pr. 26, Petrodvorets, 198504 St. Petersburg, Russia
| | - Enrico Mastrobattista
- Departments of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands; (C.C.L.S.); (E.M.); (G.S.)
| | - Gert Storm
- Departments of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Heidelberglaan 8, 3584 CS Utrecht, The Netherlands; (C.C.L.S.); (E.M.); (G.S.)
- Department of Biomaterials Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands
- Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore
| | - Chrit Moonen
- Division of Imaging and Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; (C.M.); (R.D.)
| | - Kai Kaarniranta
- Department of Ophthalmology, Kuopio University Hospital, P.O. Box 100, 70029 Kuopio, Finland;
- Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland
| | - Roel Deckers
- Division of Imaging and Oncology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands; (C.M.); (R.D.)
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Nederhoed JH, Tjaberinga M, Otten RHJ, Evers JM, Musters RJP, Wisselink W, Yeung KK. Therapeutic Use of Microbubbles and Ultrasound in Acute Peripheral Arterial Thrombosis: A Systematic Review. ULTRASOUND IN MEDICINE & BIOLOGY 2021; 47:2821-2838. [PMID: 34272082 DOI: 10.1016/j.ultrasmedbio.2021.06.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 05/15/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
Catheter-directed thrombolysis (CDT) for acute peripheral arterial occlusion is time consuming and carries a risk of major hemorrhage. Contrast-enhanced sonothrombolysis (CEST) might enhance outcomes compared with standard CDT. In the study described here, we systematically reviewed all in vivo studies on contrast-enhanced sonothrombolysis in a setting of arterial thrombosis. A systematic search of the PubMed, Embase, Cochrane Library and Web of Science databases was conducted. Two reviewers independently performed the study selection, quality assessment and data extraction. Primary outcomes were recanalization rate and thrombus weight. Secondary outcome was any possible adverse event. The 35 studies included in this review were conducted in four different (pre)clinical settings: ischemic stroke, myocardial infarction, (peripheral) arterial thrombosis and arteriovenous graft occlusion. Because of the high heterogeneity among the studies, it was not possible to conduct a meta-analysis. In almost all studies, recanalization rates were higher in the group that underwent a form of CEST. One study was terminated early because of a higher incidence of intracranial hemorrhage. Studies on CEST suggest that adding microbubbles and ultrasound to standard intra-arterial CDT is safe and might improve outcomes in acute peripheral arterial thrombosis. Further research is needed before CEST can be implemented in daily practice.
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Affiliation(s)
- Johanna H Nederhoed
- Department of Surgery, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands.
| | - Meike Tjaberinga
- Department of Surgery, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
| | - René H J Otten
- Medical Library Vrije Universiteit, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
| | - Josje M Evers
- Department of Surgery, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
| | - René J P Musters
- Department of Physiology, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
| | - Willem Wisselink
- Department of Surgery, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
| | - Kak K Yeung
- Department of Surgery, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands; Department of Physiology, Amsterdam University Medical Centers (VUmc), Amsterdam, The Netherlands
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Guan L, Wang C, Yan X, Liu L, Li Y, Mu Y. A thrombolytic therapy using diagnostic ultrasound combined with RGDS-targeted microbubbles and urokinase in a rabbit model. Sci Rep 2020; 10:12511. [PMID: 32719362 PMCID: PMC7385658 DOI: 10.1038/s41598-020-69202-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 04/10/2020] [Indexed: 11/22/2022] Open
Abstract
This study aimed to explore thrombolysis therapy based on ultrasound combined with urokinase and Arg–Gly–Asp sequence (RGDS)-targeted microbubbles by evaluating the histological changes in a thrombotic rabbit model. Forty-two New Zealand rabbits featuring platelet-rich thrombi in the femoral artery were randomized to (n = 6/group): ultrasound alone (US); urokinase alone (UK); ultrasound plus non-targeted microbubbles (US + M); ultrasound plus RGDS-targeted microbubbles (US + R); RGDS-targeted microbubbles plus urokinase (R + UK); ultrasound, non-targeted microbubbles and urokinase (US + M + UK); and ultrasound, RGDS-targeted microbubbles and urokinase (US + R + UK) groups. Diagnostic ultrasound was used transcutaneously over the thrombus for 30 min. We evaluated the thrombolytic effect based on ultrasound thrombi detection, blood flow, and histological observations. Among all study groups, complete recanalization was achieved in the US + R + UK group. Hematoxylin and eosin staining showed that the thrombi were completely dissolved. Scanning electron microscopy examination demonstrated that the fiber network structure of the thrombi was damaged. Transmission electron microscopy showed that the thrombus was decomposed into high electron-dense particles. Histology for von Willebrand factor and tissue factor were both negative in the US + R + UK group. This study revealed that a thrombolytic therapy consisting of diagnostic ultrasound together with RGDS-targeted and urokinase coupled microbubbles.
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Affiliation(s)
- Lina Guan
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China
| | - Chunmei Wang
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China
| | - Xue Yan
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China
| | - Liyun Liu
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China
| | - Yanhong Li
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China
| | - Yuming Mu
- Department of Echocardiography, First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, People's Republic of China.
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Borden MA. Intermolecular Forces Model for Lipid Microbubble Shells. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:10042-10051. [PMID: 30543753 DOI: 10.1021/acs.langmuir.8b03641] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Lipid-coated microbubbles are currently used clinically as ultrasound contrast agents for echocardiography and radiology and are being developed for many new diagnostic and therapeutic applications. Accordingly, there is a growing need to engineer specific formulations by employing rational design to guide lipid selection and processing. This approach requires a quantitative relationship between lipid chemistry and interfacial properties of the microbubble shell. Just such a model is proposed here on the basis of lateral Coulomb and van der Waals interactions between lipid head- and tailgroups, using previous coarse graining and force fields developed for molecular dynamics simulations. The model predicts with sufficient accuracy the monolayer permeability, the elasticity as a function of either lipid composition or temperature, and the equilibrium spreading surface tension of the lipid onto an air/water interface. In the future, the intermolecular forces model could be employed to elucidate more complex phenomena and to engineer novel microbubble formulations.
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Affiliation(s)
- Mark Andrew Borden
- Mechanical Engineering , University of Colorado , Boulder , Colorado 80309-0427 , United States
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de Saint Victor M, Carugo D, Barnsley LC, Owen J, Coussios CC, Stride E. Magnetic targeting to enhance microbubble delivery in an occluded microarterial bifurcation. ACTA ACUST UNITED AC 2017; 62:7451-7470. [DOI: 10.1088/1361-6560/aa858f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Gao S, Zhu Q, Dong X, Chen Z, Liu Z, Xie F. Guided longer pulses from a diagnostic ultrasound and intraclot microbubble enhanced catheter-directed thrombolysis in vivo. J Thromb Thrombolysis 2017; 44:48-56. [PMID: 28417266 DOI: 10.1007/s11239-017-1500-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The mechanism of ultrasound thrombolysis (UT) is generally attributed to cavitation. The insufficiency of microbubbles (MB) to serve as cavitation nuclei in the vessel-obstructing thrombi significantly reduces the effectiveness of UT. Taking advantage of the widely performed catheter-directed therapy (CDT), in a thrombo-embolized rabbit IVC model with a simultaneous catheter directed rt-PA thrombolysis procedure, guided moderate mechanical index longer pulses from a modified diagnostic ultrasound transducer, combined with an intraclot infusion of MB, significantly accelerated the thrombolysis process. The higher thrombolysis efficacy score and consistent elevated post-treatment plasma concentration level of D-Dimer, a product of fibrinolysis, both indicated the superiority of CDT + UT over CDT/UT alone. Pathologic examination of the treated occluded IVC segments revealed an almost complete dissolution of the thrombi treated with CDT + UT. There was no evidences of thrombo-embolism or local thrombus formation in the cardiac-pulmonary vessels. Combined with intraclot infusion of MB, guided longer pulse ultrasound from a diagnostic transducer is able to safely and significantly improve a catheter-directed thrombolysis procedure. It thus has the potential to achieve earlier clot removal, administration of a lower dosage of thrombolytic agent and, consequently, a lower incidence of thrombolysis-related side effects.
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Affiliation(s)
- Shunji Gao
- Department of Ultrasound, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, China
| | - Qiong Zhu
- Department of Ultrasound, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, China
| | - Xiaoxiao Dong
- Department of Ultrasound, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, China
| | - Zhong Chen
- Department of Ultrasound, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, China
| | - Zheng Liu
- Department of Ultrasound, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, China.
| | - Feng Xie
- Internal Medicine Cardiology, University of Nebraska Medical Center, Omaha, NE, USA
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Zhu Y, Guan L, Mu Y. Combined Low-Frequency Ultrasound and Urokinase-Containing Microbubbles in Treatment of Femoral Artery Thrombosis in a Rabbit Model. PLoS One 2016; 11:e0168909. [PMID: 28033371 PMCID: PMC5199065 DOI: 10.1371/journal.pone.0168909] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 12/08/2016] [Indexed: 11/19/2022] Open
Abstract
This paper aims to study the thrombolytic effect of low-frequency ultrasound combined with targeted urokinase-containing microbubble contrast agents on treatment of thrombosis in rabbit femoral artery; and to determine the optimal combination of parameters for achieving thrombolysis in this model. A biotinylated-avidin method was used to prepare microbubble contrast agents carrying urokinase and Arg-Gly-Asp-Ser (RGDS) peptides. Following femoral artery thrombosis in New Zealand white rabbits, microbubble contrast agents were injected intravenously, and ultrasonic exposure was applied. A 3 × 2 × 2 factorial table was applied to categorize the experimental animals based on different levels of combination of ultrasonic frequencies (Factor A: 1.6 MHz, 2.2 MHz, 2.8 MHz), doses of urokinase (Factor B: 90,000 IU/Kg, 180,000 IU/Kg) and ultrasound exposure time (Factor C: 30 min, 60 min). A total of 72 experimental animals were randomly divided into 12 groups (n = 6/group). Doppler techniques were used to assess blood flow in the distal end of the thrombotic femoral artery during the 120 minutes thrombolysis experiment. The rate of recanalization following thrombolysis was calculated, and thrombolytic efficacy was evaluated and compared. The thrombolytic recanalization rate for all experimental subjects after thrombolytic therapy was 68.1%. The optimal parameters for thrombolysis were determined to be 1) an ultrasound frequency of 2.2 MHz and 2) a 90,000 IU/kg dose of urokinase. Ultrasound exposure time (30 min vs. 60 min) had no significant effect on the thrombolytic effects. The combination of local low-frequency ultrasound radiation, targeted microbubbles, and thrombolytic urokinase induced thrombolysis of femoral artery thrombosis in a rabbit model. The ultrasonic frequency of 2.2 MHz and urokinase dose of 90,000 IU/kg induced optimal thrombolytic effects, while the application of either 30 min or 60 min of ultrasound exposure had similar effects.
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Affiliation(s)
- Yanping Zhu
- Department of Echocardiography, the First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, P.R. China
| | - Lina Guan
- Department of Echocardiography, the First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, P.R. China
| | - Yuming Mu
- Department of Echocardiography, the First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang, P.R. China
- * E-mail:
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Haršány M, Tsivgoulis G, Alexandrov AV. Ultrasonography. Stroke 2016. [DOI: 10.1016/b978-0-323-29544-4.00046-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Castle J, Feinstein SB. Drug and Gene Delivery using Sonoporation for Cardiovascular Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 880:331-8. [DOI: 10.1007/978-3-319-22536-4_18] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Acconcia C, Leung BYC, Manjunath A, Goertz DE. The Effect of Short Duration Ultrasound Pulses on the Interaction Between Individual Microbubbles and Fibrin Clots. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:2774-2782. [PMID: 26116160 DOI: 10.1016/j.ultrasmedbio.2015.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 02/10/2015] [Accepted: 05/16/2015] [Indexed: 06/04/2023]
Abstract
In previous work, we examined microscale interactions between microbubbles and fibrin clots under exposure to 1 ms ultrasound pulses. This provided direct evidence that microbubbles were capable of deforming clot boundaries and penetrating into clots, while also affecting fluid uptake and inducing fibrin network damage. Here, we investigate the effect of short duration (15 μs) pulses on microscale bubble-clot interactions as function of bubble diameter (3-9 μm) and pressure. Individual microbubbles (n = 45) were placed at the clot boundary with optical tweezers and exposed to 1 MHz ultrasound. High-speed (10 kfps) imaging and 2-photon microscopy were performed during and after exposure, respectively. While broadly similar phenomena were observed as in the 1 ms pulse case (i.e., bubble penetration, network damage and fluid uptake), substantial quantitative differences were present. The pressure threshold for bubble penetration was increased from 0.39 MPa to 0.6 MPa, and those bubbles that did enter clots had reduced penetration depths and were associated with less fibrin network damage and nanobead uptake. This appeared to be due in large part to increased bubble shrinkage relative to the 1 ms pulse case. Stroboscopic imaging was performed on a subset of bubbles (n = 11) and indicated that complex bubble oscillations can occur during this process.
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Affiliation(s)
- Christopher Acconcia
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada.
| | - Ben Y C Leung
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - Anoop Manjunath
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
| | - David E Goertz
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
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Goertz DE. An overview of the influence of therapeutic ultrasound exposures on the vasculature: high intensity ultrasound and microbubble-mediated bioeffects. Int J Hyperthermia 2015; 31:134-44. [PMID: 25716770 DOI: 10.3109/02656736.2015.1009179] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
It is well established that the interaction of ultrasound with soft tissues can induce a wide range of bioeffects. One of the most important and complex of these interactions in the context of therapeutic ultrasound is with the vasculature. Potential vascular effects range from enhancing microvascular permeability to inducing vascular damage and vessel occlusion. While aspects of these effects are broadly understood, the development of improved approaches to exploit these effects and gain a more detailed mechanistic understanding is ongoing and largely anchored in preclinical research. Here a general overview of this established yet rapidly evolving topic is provided, with a particular emphasis on effects arising from high-intensity focused ultrasound and microbubble-mediated exposures.
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Affiliation(s)
- David E Goertz
- Department of Physical Sciences, Sunnybrook Health Sciences Center , Toronto, Ontario , Canada
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Acconcia C, Leung BYC, Manjunath A, Goertz DE. Interactions between individual ultrasound-stimulated microbubbles and fibrin clots. ULTRASOUND IN MEDICINE & BIOLOGY 2014; 40:2134-2150. [PMID: 24882525 DOI: 10.1016/j.ultrasmedbio.2014.03.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 02/23/2014] [Accepted: 03/06/2014] [Indexed: 06/03/2023]
Abstract
The use of ultrasound-stimulated microbubbles (USMBs) to promote thrombolysis is well established, but there remains considerable uncertainty about the mechanisms of this process. Here we examine the microscale interactions between individual USMBs and fibrin clots as a function of bubble size, exposure conditions and clot type. Microbubbles (n = 185) were placed adjacent to clot boundaries ("coarse" or "fine") using optical tweezers and exposed to 1-MHz ultrasound as a function of pressure (0.1-0.39 MPa). High-speed (10 kfps) imaging was employed, and clots were subsequently assessed with 2-photon microscopy. For fine clots, 46% of bubbles "embedded" within 10 μm of the clot boundary at pressures of 0.1 and 0.2 MPa, whereas at 0.39 MPa, 53% of bubbles penetrated and transited into the clots with an incidence inversely related to their diameter. A substantial fraction of penetrating bubbles induced fibrin network damage and promoted the uptake of nanobeads. In coarse clots, penetration occurred more readily and at lower pressures than in fine clots. The results therefore provide direct evidence of therapeutically relevant effects of USMBs and indicate their dependence on size, exposure conditions and clot properties.
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Affiliation(s)
- Christopher Acconcia
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Sunnybrook Research Institute, Toronto, Ontario, Canada.
| | - Ben Y C Leung
- Sunnybrook Research Institute, Toronto, Ontario, Canada
| | | | - David E Goertz
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Sunnybrook Research Institute, Toronto, Ontario, Canada
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de Saint Victor M, Crake C, Coussios CC, Stride E. Properties, characteristics and applications of microbubbles for sonothrombolysis. Expert Opin Drug Deliv 2014; 11:187-209. [DOI: 10.1517/17425247.2014.868434] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Kutty S, Wu J, Hammel JM, Xie F, Gao S, Drvol LK, Lof J, Radio SJ, Therrien SL, Danford DA, Porter TR. Microbubble mediated thrombus dissolution with diagnostic ultrasound for the treatment of chronic venous thrombi. PLoS One 2012; 7:e51453. [PMID: 23251539 PMCID: PMC3520800 DOI: 10.1371/journal.pone.0051453] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 11/01/2012] [Indexed: 11/19/2022] Open
Abstract
Background Central venous catheter (CVC) thrombi result in significant morbidity in children, and currently available treatments are associated with significant risk. We sought to investigate the therapeutic efficacy of microbubble (MB) enhanced sonothrombolysis for aged CVC associated thrombi in vivo. Methods and Results A model of chronic indwelling CVC in the low superior vena cava with thrombus in situ was established after feasibility and safety testing in 7 pigs; and subsequently applied for repeated, sonothrombolytic treatments in 9 pigs (total 24 treatments). Baseline intracardiac echocardiography (ICE, 10.5F, Siemens), fluoroscopy and saline flushing confirmed the absence of any pre-existing CVC thrombus. A thrombus was then allowed to form and age over 24 hours. The created thrombus was localized and measured by ICE, and transthoracic image guided high mechanical index (MI) two-dimensional US treatments (1.1–1.7 MI; iE33, Philips) applied intermittently whenever intravenously infused MBs (3% MRX-801; NuVox) were visualized near the thrombus (n = 10; Group A). Control pigs (n = 10; Group B) received US without MB. All treatments were randomized. Post-treatment thrombus area by ICE planimetry was compared with pre-treatment measurements. Thrombus area measurements before and after treatment were 0.22 and 0.10 cm2 respectively in Group A; compared to 0.24 and 0.21 cm2 in Group B (p = 0.0003). Effectiveness of longer duration US and MB thrombolytic treatments were studied (n = 4), which suggested that near complete thrombus dissolution is possible. No pulmonary emboli, alterations in oxygen saturation, or hemodynamics occurred with either treatment. Conclusions Guided high MI diagnostic US+systemic MB facilitates reduction of aged CVC associated thrombi in vivo. MB enhanced sonothrombolytic therapy may be a non-invasive safe alternative to thrombolytic agents in treating thrombotic CVC occlusions.
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Affiliation(s)
- Shelby Kutty
- Joint Division of Pediatric Cardiology, University of Nebraska College of Medicine/Creighton University, Children’s Hospital and Medical Center, Omaha, Nebraska, United States of America
| | - Juefei Wu
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - James M. Hammel
- Division of Cardiovascular Surgery, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Feng Xie
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Shunji Gao
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Lucas K. Drvol
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - John Lof
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Stanley J. Radio
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Stacey L. Therrien
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - David A. Danford
- Joint Division of Pediatric Cardiology, University of Nebraska College of Medicine/Creighton University, Children’s Hospital and Medical Center, Omaha, Nebraska, United States of America
| | - Thomas R. Porter
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- * E-mail:
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Influences of microbubble diameter and ultrasonic parameters on in vitro sonothrombolysis efficacy. J Vasc Interv Radiol 2012; 23:1677-1684.e1. [PMID: 23106936 DOI: 10.1016/j.jvir.2012.08.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 08/07/2012] [Accepted: 08/13/2012] [Indexed: 12/20/2022] Open
Abstract
PURPOSE To quantify the effects of microbubble (MB) size, elasticity, and pulsed ultrasonic parameters on in vitro sonothrombolysis (ultrasound [US]-mediated thrombolysis) efficacy. MATERIALS AND METHODS Monodispersive MBs with diameters of 1 μm or 3 μm were exposed to pulsed US (1 MHz or 3 MHz) to lyse rabbit blood clots. Sonothrombolysis efficacy (clot mass loss) was measured as functions of MB size and concentration, ultrasonic frequency and intensity, pulse duration (PD), pulse repeat frequency (PRF), and duty factor. RESULTS Sonothrombolysis at 1 MHz was more effective using 3-μm MBs and at 3 MHz using 1-μm MBs. Sonothrombolysis was more effective at 1 MHz when≥75% of MBs remained intact, especially for 3-μm MBs; improving sonothrombolysis by increasing PRF from 100 Hz to 400 Hz at 3 MHz was associated with increasing 3-μm MB survival. However, 60% of 1-μm MBs were destroyed during maximal sonothrombolysis at 3 MHz, indicating that considerable MB collapse may be required for sonothrombolysis under these conditions. CONCLUSIONS The ability to control MB size and elasticity permits using a wide range of US parameters (eg, frequency, intensity) to produce desired levels of sonothrombolysis. Comparable, maximal sonothrombolysis efficacy was achieved at 20-fold lower intensity with 3-μm MBs (0.1W/cm(2)) than with 1-μm MBs (2.0W/cm(2)), a potential safety issue for in vivo sonothrombolysis. US parameters that maximized MB survival yielded maximal sonothrombolysis efficacy except with 1-μm MBs at 3MHz where most MBs were destroyed.
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Abstract
OBJECTIVES To characterize the ability of high-intensity focused ultrasound to achieve thrombolysis in vitro and investigate the feasibility of this approach as a means of restoring blood flow in thrombus-occluded arteries in vivo. MATERIALS AND METHODS All experiments were approved by the Institutional Animal Care Committee. Thrombolysis was performed with a 1.51-MHz focused ultrasound transducer with pulse lengths of 0.1 to 10 milliseconds and acoustic powers up to 300 W. In vitro experiments were performed with blood clots formed from rabbit arterial blood and situated in 2-mm diameter tubing. Both single location and flow bypass recanalization experiments were conducted. In vitro clot erosion was assessed with 30-MHz ultrasound, with debris size measured with filters and a Coulter counter. In vivo clots were initiated in the femoral arteries of rabbits (n = 26). Cavitation signals from bubbles formed during exposure were monitored. In vivo flow restoration was assessed with 23-MHz Doppler ultrasound. RESULTS At a single location, in vitro clot erosion volumes increased with exposure power and pulse length, with debris size reducing with increasing pulse length. Flow bypass experiments achieved 99.2% clot erosion with 1.1% of debris above 0.5 mm in size. In vivo, 10 milliseconds pulses were associated with bleeding, but at 1 millisecond, it was feasible to achieve partial flow restoration in 6 of the 10 clots with only 1 of the 10 showing evidence of bleeding. In all cases, thrombolysis occurred only in the presence of cavitation. CONCLUSION High-intensity focused ultrasound thrombolysis is feasible as a means of restoring partial blood flow in thrombus-occluded arteries in the absence of thrombolytic agents. The potential for bleeding with this approach requires further investigation.
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Meairs S, Alonso A, Hennerici MG. Progress in Sonothrombolysis for the Treatment of Stroke. Stroke 2012; 43:1706-10. [DOI: 10.1161/strokeaha.111.636332] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Stephen Meairs
- From the Department of Neurology, Universitätsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
| | - Angelika Alonso
- From the Department of Neurology, Universitätsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
| | - Michael G. Hennerici
- From the Department of Neurology, Universitätsmedizin Mannheim, University of Heidelberg, Mannheim, Germany
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Wright CC, Hynynen K, Goertz DE. Pulsed focused ultrasound-induced displacements in confined in vitro blood clots. IEEE Trans Biomed Eng 2011; 59:842-51. [PMID: 22194235 DOI: 10.1109/tbme.2011.2180904] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ultrasound has been shown to potentiate the effects of tissue plasminogen activator to improve clot lysis in a range of in vitro and in vivo studies as well as in clinical trials. One possible mechanism of action is acoustic radiation force-induced clot displacements. In this study, we investigate the temporal and spatial dynamics of clot displacements and strain initiated by focused ultrasound pulses. Displacements were produced by a 1.51 MHz f-number 1 transducer over a range of acoustic powers (1-85 W) in clots constrained within an agar vessel phantom channel. Displacements were tracked during and after a 5.45 ms therapy pulse using a 20 MHz high-frequency ultrasound imaging probe. Peak thrombus displacements were found to be linear as a function of acoustic power up to 60 W before leveling off near 128 μm for the highest transmit powers. The time to peak displacement and recovery time of blood clots was largely independent of acoustic powers with measured values near 2 ms. A linear relationship between peak axial strain and transmit power was observed, reaching a peak value of 11% at 35 W. The peak strain occurred ~0.75 mm from the focal zone for all powers investigated in both lateral and axial directions. These results indicate that substantial displacements can be induced by focused ultrasound in confined blood clots, and that the spatial and temporal displacement patterns are complex and highly dependent on exposure conditions, which has implications for future work investigating their link to clot lysis and for developing approaches to exploit these effects.
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Affiliation(s)
- Cameron C Wright
- Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
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Amaral-Silva A, Piñeiro S, Molina CA. Sonothrombolysis for the treatment of acute stroke: current concepts and future directions. Expert Rev Neurother 2011; 11:265-73. [PMID: 21306213 DOI: 10.1586/ern.11.3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Achieving rapid reperfusion transcranial color-coded duplex is the critical issue in acute stroke treatment. Ultrasound (US) generates negative pressure waves that are associated with an increase in either intrinsic or intravenous tissue plasminogen activator (tPA)-induced fibrinolytic activity. Higher rates of tPA-induced arterial recanalization, associated with a trend towards better functional outcome, have been safely achieved by using high-frequency US. By contrast, the use of low-frequency US and transcranial color-coded duplex has been linked to significant hemorrhagic complications. US-accelerated thrombolysis has been safely enhanced by lowering the amount of energy needed for acoustic cavitation with the administration of microbubbles. Other applications of US are being studied, including its intra-arterial use. Operator-independent devices, which will spread the use of these US techniques further, are also being developed. This article reviews the present status of sonothrombolysis in acute stroke treatment, highlighting both experimental and clinical studies addressing this issue, and discusses its future regarding both efficacy and safety.
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Affiliation(s)
- Alexandre Amaral-Silva
- Cerebrovascular Unit, Hospital de São José, Centro Hospitalar de Lisboa Central, Lisbon, Portugal
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21
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Culp WC, Flores R, Brown AT, Lowery JD, Roberson PK, Hennings LJ, Woods SD, Hatton JH, Culp BC, Skinner RD, Borrelli MJ. Successful microbubble sonothrombolysis without tissue-type plasminogen activator in a rabbit model of acute ischemic stroke. Stroke 2011; 42:2280-5. [PMID: 21700942 DOI: 10.1161/strokeaha.110.607150] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Microbubbles (MB) combined with ultrasound (US) have been shown to lyse clots without tissue-type plasminogen activator (tPA) both in vitro and in vivo. We evaluated sonothrombolysis with 3 types of MB using a rabbit embolic stroke model. METHODS New Zealand White rabbits (n=74) received internal carotid angiographic embolization of single 3-day-old cylindrical clots (0.6 × 4.0 mm). Groups included: (1) control (n=11) embolized without treatment; (2) tPA (n=20); (3) tPA+US (n=10); (4) perflutren lipid MB+US (n=16); (5) albumin 3 μm MB+US (n=8); and (6) tagged albumin 3 μm MB+US (n=9). Treatment began 1 hour postembolization. Ultrasound was pulsed-wave (1 MHz; 0.8 W/cm²) for 1 hour; rabbits with tPA received intravenous tPA (0.9 mg/kg) over 1 hour. Lipid MB dose was intravenous (0.16 mg/kg) over 30 minutes. Dosage of 3 μm MB was 5 × 10⁹ MB intravenously alone or tagged with eptifibatide and fibrin antibody over 30 minutes. Rabbits were euthanized at 24 hours. Infarct volume was determined using vital stains on brain sections. Hemorrhage was evaluated on hematoxylin and eosin sections. RESULTS Infarct volume percent was lower for rabbits treated with lipid MB+US (1.0%± 0.6%; P=0.013), 3 μm MB+US (0.7% ± 0.9%; P=0.018), and tagged 3 μm MB+US (0.8% ± 0.8%; P=0.019) compared with controls (3.5%± 0.8%). The 3 MB types collectively had lower infarct volumes (P=0.0043) than controls. Infarct volume averaged 2.2% ± 0.6% and 1.7%± 0.8% for rabbits treated with tPA alone and tPA+US, respectively (P=nonsignificant). CONCLUSIONS Sonothrombolysis without tPA using these MB is effective in decreasing infarct volumes. Study of human application and further MB technique development are justified.
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Affiliation(s)
- William C Culp
- Department of Radiology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
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Meairs S, Hennerici M, Mohr J. Ultrasonography. Stroke 2011. [DOI: 10.1016/b978-1-4160-5478-8.10044-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Abstract
Ultrasound is a very effective modality for drug delivery and gene therapy because energy that is non-invasively transmitted through the skin can be focused deeply into the human body in a specific location and employed to release drugs at that site. Ultrasound cavitation, enhanced by injected microbubbles, perturbs cell membrane structures to cause sonoporation and increases the permeability to bioactive materials. Cavitation events also increase the rate of drug transport in general by augmenting the slow diffusion process with convective transport processes. Drugs and genes can be incorporated into microbubbles, which in turn can target a specific disease site using ligands such as the antibody. Drugs can be released ultrasonically from microbubbles that are sufficiently robust to circulate in the blood and retain their cargo of drugs until they enter an insonated volume of tissue. Local drug delivery ensures sufficient drug concentration at the diseased region while limiting toxicity for healthy tissues. Ultrasound-mediated gene delivery has been applied to heart, blood vessel, lung, kidney, muscle, brain, and tumour with enhanced gene transfection efficiency, which depends on the ultrasonic parameters such as acoustic pressure, pulse length, duty cycle, repetition rate, and exposure duration, as well as microbubble properties such as size, gas species, shell material, interfacial tension, and surface rigidity. Microbubble-augmented sonothrombolysis can be enhanced further by using targeting microbubbles.
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Affiliation(s)
- H-D Liang
- School of Engineering, Cardiff University, Cardiff, UK.
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Chen SC, Ruan JL, Cheng PW, Chuang YH, Li PC. In vitro evaluation of ultrasound-assisted thrombolysis using a targeted ultrasound contrast agent. ULTRASONIC IMAGING 2009; 31:235-246. [PMID: 20458876 DOI: 10.1177/016173460903100402] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A thrombus-targeted ultrasound contrast agent bound with tirofiban - a glycoprotein (GP) IIb/IIIa antagonist that can specifically bind to activated platelets in the thrombus - was designed to enhance both the image contrast and thrombolysis effect. In this study, we used 76 canine thrombi for investigation. The targeting ability to thrombi was confirmed by microphotography and high-frequency ultrasound (40 MHz) imaging. The effect of the targeted microbubbles on thrombolysis enhancement was investigated using an in vitro flow system: targeted and nontargeted microbubbles flowed through the clot for 30 seconds with a washing step; the microbubbles remained on the clot that were then cavitated by ultrasound (frequency = 1 MHz, MI = 1.2). The extent of thrombolysis was evaluated by weight reduction and histology analysis. The targeted microbubbles reduced the weight of thrombi by a factor of 1.7 times that of the nontargeted microbubbles. (clot weight reduction: 23.1 +/- 5.3% versus 13.6 +/- 4.9%, p < 0.01 between targeted and nontargeted group), and the signal enhancement was 3.34 +/- 0.30 dB (mean +/- SD, p < 0.01 compared to control). We conclude that targeted microbubbles are applicable not only for molecular imaging of thrombi but also for improving the effectiveness of ultrasound-assisted thrombolysis.
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Affiliation(s)
- Szu-Chia Chen
- Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan
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25
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Porter TR. The utilization of ultrasound and microbubbles for therapy in acute coronary syndromes. Cardiovasc Res 2009; 83:636-42. [PMID: 19541670 DOI: 10.1093/cvr/cvp206] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultrasound has become a useful high resolution imaging modality for examining the cardiac microcirculation. With the use of microbubbles as an ultrasound contrast agent, ultrasound can be utilized to image the microcirculation and detect capillary flow abnormalities in acute ischaemia. A wide range of ultrasound frequencies (including those used for diagnostic transthoracic imaging) have also been utilized therapeutically to augment the effectiveness of fibrinolytic therapy in ST-segment elevation myocardial infarction (STEMI). Ultrasound and microbubbles are now being explored as methods of improving both microcirculatory and epicardial flow in acute STEMI. This article will review the mechanisms by which ultrasound and microbubbles assist in thrombus detection and dissolution. In addition, the pre-clinical studies utilizing transthoracic ultrasound as a therapeutic entity in acute STEMI will be reviewed. Clinical studies, completed and ongoing, will also be presented.
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Affiliation(s)
- Thomas R Porter
- University of Nebraska Medical Center, 982265 Nebraska Medical Center, Omaha, NE 68198-2265, USA.
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26
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Barreto AD, Sharma VK, Lao AY, Schellinger PD, Amarenco P, Sierzenski P, Alexandrov AV, Molina CA. Safety and dose-escalation study design of Transcranial Ultrasound in Clinical SONolysis for acute ischemic stroke: the TUCSON Trial. Int J Stroke 2009; 4:42-8. [PMID: 19236498 DOI: 10.1111/j.1747-4949.2009.00252.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rationale Transcranial Doppler (TCD) monitoring during intravenous tissue plasminogen activator (i.v.-tPA) infusion increases recanalization rates in acute ischemic stroke. Addition of perflutren-lipid microspheres MRX-801 (microS) may further enhance the process of recanalization. This article describes the design of the Transcranial Ultrasound in Clinical SONolysis (TUCSON) trial. Aims and Design TUCSON is a phase I-II, randomized, placebo-controlled, open-label, safety, dose-escalation clinical trial of microS+TCD ultrasound (sonolysis). Patients with acute ischemic stroke and arterial intracranial occlusions are enrolled within 3 h of symptom onset. All patients receive standard i.v.-tPA and will be randomized to 90 min of continuous 2-MHz TCD+microS or 90 min of saline+brief TCD vessel assessments. The safety profile of four escalating dose tiers will be assessed. Arterial occlusions and recanalization are defined with the Thrombolysis in Brain Ischemia flow grades. Study Outcomes Safety is determined by the rates of symptomatic intracerebral hemorrhage within 36 h. Neurological deficits and outcomes are measured with the National Institute of Health Stroke Scale and modified Rankin Scale (mRS). The signal-of-efficacy is determined by rates of recanalization, dramatic or early clinical recovery within 2 h, clinical recovery at 24-36 h and independent outcome (mRS 0-2) at 90 days.
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Affiliation(s)
- Andrew D Barreto
- Department of Neurology, University of Texas-Houston Stroke Team, Houston, TX, USA
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27
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Xie F, Lof J, Matsunaga T, Zutshi R, Porter TR. Diagnostic ultrasound combined with glycoprotein IIb/IIIa-targeted microbubbles improves microvascular recovery after acute coronary thrombotic occlusions. Circulation 2009; 119:1378-85. [PMID: 19255341 DOI: 10.1161/circulationaha.108.825067] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The high mechanical index (MI) impulses from a diagnostic ultrasound transducer may be a method of recanalizing acutely thrombosed vessels if the impulses are applied only when microbubbles are channeling through the thrombus. METHODS AND RESULTS In 45 pigs with acute left anterior descending thrombotic occlusions, a low-MI pulse sequence scheme (contrast pulse sequencing) was used to image the myocardium and guide the delivery of high-MI (1.9 MI) impulses during infusion of either intravenous platelet-targeted microbubbles or nontargeted microbubbles. A third group received no diagnostic ultrasound and microbubbles. All groups received half-dose recombinant prourokinase, heparin, and aspirin. Contrast pulse sequencing examined replenishment of contrast within the central portion of the risk area and guided the application of high-MI impulses. Angiographic recanalization rates, resolution of ST-segment elevation on ECG, and wall thickening were analyzed. Pigs receiving platelet-targeted microbubbles had more rapid replenishment of the central portion of the risk area (80% versus 40% for nontargeted microbubbles; P=0.03) and higher epicardial recanalization rates (53% versus 7% for prourokinase alone; P=0.01). Replenishment of contrast within the risk area (whether with platelet-targeted microbubbles or nontargeted microbubbles) was associated with both higher recanalization rates and even higher rates of ST-segment resolution (82% versus 21% for prourokinase alone; P=0.006). ST-segment resolution occurred in 6 pigs (40%) treated with microbubbles who did not have epicardial recanalization, of which 5 had recovery of wall thickening. CONCLUSIONS Intravenous platelet-targeted microbubbles combined with brief high-MI diagnostic ultrasound impulses guided by contrast pulse sequencing improve both epicardial recanalization rates and microvascular recovery.
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Affiliation(s)
- Feng Xie
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, Omaha, NE 68198-2265, USA.
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Shaw GJ, Meunier JM, Lindsell CJ, Holland CK. Tissue plasminogen activator concentration dependence of 120 kHz ultrasound-enhanced thrombolysis. ULTRASOUND IN MEDICINE & BIOLOGY 2008; 34:1783-92. [PMID: 18468773 PMCID: PMC2614894 DOI: 10.1016/j.ultrasmedbio.2008.03.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 03/03/2008] [Accepted: 03/12/2008] [Indexed: 05/11/2023]
Abstract
It has been known for some time that the application of ultrasound can enhance the efficacy of thrombolytic medications such as recombinant tissue plasminogen activator (rt-PA). Potential clinical applications of this ultrasound-enhanced thrombolysis (UET) include the treatment of myocardial infarction, acute ischemic stroke, deep venous thrombosis and other thrombotic disorders. It may be possible to reduce the dose of rt-PA while maintaining lytic efficacy; however there is little data on the rt-PA concentration dependence of UET. In this work, the rt-PA concentration dependence of clot lysis resulting from 120 kHz UET exposure was measured in an in vitro human clot model. Clots were exposed to rt-PA for 30 min, with (UET treated) or without 120 kHz ultrasound (rt-PA treated) at 37 degrees C, and the clot width measured as a function of time. The rt-PA concentration ranged from 0-10 microg/mL. The initial lytic rate for the UET-treated group was greater than that of the rt-PA group at almost all rt-PA concentrations, and exhibited a maximum over concentration values of 1-3 microg/mL.
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Affiliation(s)
- George J Shaw
- Department of Emergency Medicine, University of Cincinnati College ofMedicine, Cincinnati, OH 45267-0769, USA.
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Tsivgoulis G, Culp WC, Alexandrov AV. Ultrasound enhanced thrombolysis in acute arterial ischemia. ULTRASONICS 2008; 48:303-11. [PMID: 18511094 DOI: 10.1016/j.ultras.2007.11.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 08/21/2007] [Accepted: 11/13/2007] [Indexed: 05/08/2023]
Abstract
In vitro and animal studies have shown that thrombolysis with intravenous tissue plasminogen activator (tPA) can be enhanced with ultrasound. Ultrasound delivers mechanical pressure waves to the clot, thus exposing more thrombus surface to circulating drug. Moreover, intravenous gaseous microspheres with ultrasound have been shown to be a potential alternative to fibrinolytic agents to recanalize discrete peripheral thrombotic arterial occlusions or acute arteriovenous graft thromboses. Small phase I-II randomized and non-randomized clinical trials have shown promising results concerning the potential applications of ultrasound-enhanced thrombolysis in the setting of acute cerebral ischemia. CLOTBUST was an international four-center phase II trial, which demonstrated that, in patients with acute ischemic stroke, transcranial Doppler (TCD) monitoring augments tPA-induced arterial recanalization (sustained complete recanalization rates: 38% vs. 13%) with a non-significant trend toward an increased rate of clinical recovery from stroke, as compared with placebo. The rates of symptomatic intracerebral hemorrhage (sICH) were similar in the active and placebo group (4.8% vs. 4.8%). Smaller single-center clinical trials using transcranial color-coded sonography (TCCD) reported recanalization rates ranging from 27% to 64% and sICH rates of 0-18%. A separate clinical trial evaluating the safety and efficacy of therapeutic low-frequency ultrasound was discontinued because of a concerning sICH rate of 36% in the active group. To further enhance the ability of tPA to break up thrombi, current ongoing clinical trials include phase II studies of a single beam 2 MHz TCD with perflutren-lipid microspheres. Moreover, potential enhancement of intra-arterial tPA delivery is being clinically tested with 1.7-2.1 MHz pulsed wave ultrasound (EKOS catheter) in ongoing phase II-III clinical trials. Intravenous platelet-targeted microbubbles with low-frequency ultrasound are currently investigated as a rapid noninvasive technique to identify thrombosed intracranial and peripheral vessels. Multi-national dose escalation studies of microspheres and the development of an operator independent ultrasound device are underway.
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Affiliation(s)
- Georgios Tsivgoulis
- Comprehensive Stroke Center, Department of Neurology, University of Alabama at Birmingham, Suite 226, RWUHM, 1719 6th Avenue South, Birmingham, AL 35294, USA
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Dalecki D. WFUMB Safety Symposium on Echo-Contrast Agents: bioeffects of ultrasound contrast agents in vivo. ULTRASOUND IN MEDICINE & BIOLOGY 2007; 33:205-13. [PMID: 17239521 DOI: 10.1016/j.ultrasmedbio.2006.07.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- Diane Dalecki
- Department of Biomedical Engineering, Rochester Center for Biomedical Ultrasound, University of Rochester, Rochester, NY 14627, USA.
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Tsutsui JM, Xie F, Johanning J, Lof J, Cory B, He A, Thomas L, Matsunaga T, Unger E, Porter TR. Treatment of deeply located acute intravascular thrombi with therapeutic ultrasound guided by diagnostic ultrasound and intravenous microbubbles. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2006; 25:1161-8. [PMID: 16929017 DOI: 10.7863/jum.2006.25.9.1161] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
OBJECTIVE We sought to determine the added value of simultaneous imaging of intravenously infused microbubbles that are being used to dissolve an intravascular thrombus with therapeutic ultrasound (TUS). METHODS In a chronic canine arteriovenous graft occluded by a thrombus, TUS (1 MHz) was applied through a 6-cm-thick tissue-mimicking phantom (measured mean +/- SD peak negative pressure through the phantom, 958 +/- 104 kPa) during an intravenous infusion of either saline (n = 6 occlusions) or lipid-encapsulated microbubbles (ImaRx Therapeutics, Inc, Tucson, AZ). Therapeutic ultrasound was intermittently applied during the microbubble infusion either at set time intervals (n = 6 occlusions) or when simultaneous diagnostic ultrasound (DUS) indicated a sustained presence of microbubbles (n = 12 occlusions). Success was defined as return of rapid flow within the graft (grade 3 flow). RESULTS Diagnostic ultrasound showed microbubbles moving through small channels within the thrombus before angiographic evidence of flow in the graft. This guided the timing of TUS application better than using set time intervals. Angiographic clearance of the thrombus and restoration of grade 3 flow at 45 minutes of treatment were seen in 33% of deeply located thrombosed grafts treated with TUS at set time intervals and 92% of grafts treated with TUS guided by DUS (P < .001 compared with set time intervals). CONCLUSIONS The use of TUS with intravenous microbubbles has a high success rate in recanalizing deeply located thrombosed arteriovenous grafts when performed with DUS guidance.
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Affiliation(s)
- Jeane M Tsutsui
- Department of Internal Medicine, Section of Cardiology, University of Nebraska Medical Center, 981165 Nebraska Medical Center, Omaha, 68198-1165 USA
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Topcuoglu MA, Saka E, Onal MZ. Hyperoxia potentiated sonothrombolysis as a method of acute ischemic stroke therapy. Med Hypotheses 2006; 66:59-65. [PMID: 16144745 DOI: 10.1016/j.mehy.2005.07.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Accepted: 07/05/2005] [Indexed: 11/21/2022]
Abstract
The main goal in the treatment of acute ischemic stroke is prompt arterial recanalization. Thrombolysis with recombinant tissue plasminogen activator (rtPA) is efficient in humans, but shows significant problems including slow and incomplete recanalization and frequent bleeding complications. Limited therapeutic window (the first three hours after onset) is the major limitation resulting in reach too few patients. Therefore, adjunctive therapies extending the reperfusion time window, increasing efficacy and reducing side effects of rtPA are needed. Ultrasound augmentation of rtPA-mediated thrombolysis is suggested to overcome some of these problems, but low-frequency ultrasound (less than 1 MHz) is not safe and high frequency ultrasound (2 MHz) is not much effective. We suggest that normobaric hyperoxia (NBO) may increase the efficacy of ultrasound and rtPA combination in addition to its own efficacy in acute ischemic stroke. Briefly, NBO increases arterial partial oxygen pressure (pO(2)) significantly up to 6-fold. Increase of pO(2) results in an increase of dissolved oxygen in the blood according to Henry's law. Enhanced dissolved oxygen increases gas nuclei formation around and inside of the clot, and decreases the Blake threshold. Under ultrasound field, these small gas nuclei form nano bubbles which fuel inertial cavitation as substrates, and therefore increase the clot fragmentation and lysis. This hypothesis has not been tested so far. The combination of rtPA, therapeutic ultrasound and NBO may be more efficacious than rtPA alone or its combination with ultrasound as acute stroke treatment modality, because each has different and probably additive mechanism of action.
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Affiliation(s)
- Mehmet Akif Topcuoglu
- Akdeniz University, Faculty of Medicine, Department of Neurology and Neurosonology Laboratory, 07054 Antalya, Turkey.
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Abstract
Transcranial Doppler (TCD) is an evolving neurovascular ultrasound technique that has an established diagnostic and potential therapeutic role in acute stroke management. Angiographically validated criteria for circle-of-Willis occlusion and thrombolysis in brain ischemia classification of residual flow have set the stage for the further development of this technique. TCD has shown its clinical value in thrombolysis monitoring and early emboli detection. The therapeutic effect requires confirmation and may be enhanced further by nanobubble technologies.
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Affiliation(s)
- Andrew M Demchuk
- Department of Clinical Neurosciences, University of Calgary, AB, Canada.
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Xie F, Tsutsui JM, Lof J, Unger EC, Johanning J, Culp WC, Matsunaga T, Porter TR. Effectiveness of lipid microbubbles and ultrasound in declotting thrombosis. ULTRASOUND IN MEDICINE & BIOLOGY 2005; 31:979-85. [PMID: 15972204 DOI: 10.1016/j.ultrasmedbio.2005.03.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2004] [Revised: 03/12/2005] [Accepted: 03/17/2005] [Indexed: 05/03/2023]
Abstract
The objectives of this study were to determine the effectiveness of lipid-encapsulated microbubbles and ultrasound (US) in recanalizing arteriovenous graft thrombi and the effect that tissue attenuation has on the success rate. A total of 55 thrombotic occlusions were created in four canines. The thrombosed grafts were randomly treated with two different 1-MHz US intensities, low (0.4 to 0.6 W/cm(2)) and high (10 W/cm(2)). Intragraft microbubbles were compared with intragraft saline and with the same dose of microbubbles given IV. IV microbubbles were also given both in the presence and absence of a tissue-mimicking phantom. High-intensity US (10 W/cm(2)) with intragraft microbubbles produced significantly higher patency and flow scores than did US with saline (p < 0.01). US with IV microbubbles had higher success rates in recanalizing thrombosed grafts than did US alone at all intensities. Attenuation reduced the rate at which successful recanalization occurred at both low and high intensities. US and microbubbles are capable of recanalizing acute arteriovenous graft thromboses. Higher intensities may be needed in the presence of tissue attenuation.
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Affiliation(s)
- Feng Xie
- Internal Medicine/Cardiology Department, University of Nebraska Medical Center, Omaha, NE 68196-1165, USA
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Bekeredjian R, Grayburn PA, Shohet RV. Use of ultrasound contrast agents for gene or drug delivery in cardiovascular medicine. J Am Coll Cardiol 2005; 45:329-35. [PMID: 15680708 DOI: 10.1016/j.jacc.2004.08.067] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Revised: 08/16/2004] [Accepted: 08/17/2004] [Indexed: 11/19/2022]
Abstract
The clinical utility of ultrasound contrast agents has been established in diagnostic echocardiography. Recently, the use of such agents has been promoted for transport and delivery of various bioactive substances, thus providing a technique for non-invasive gene therapy and organ-specific drug delivery. In this review, we give a critical update of published studies using ultrasound contrast agents for therapeutic use. We discuss the potential applications and limitations of this technique and suggest future applications in cardiovascular medicine.
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Affiliation(s)
- Raffi Bekeredjian
- Department of Internal Medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Yang X, Roy RA, Holt RG. Bubble dynamics and size distributions during focused ultrasound insonation. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2004; 116:3423-31. [PMID: 15658693 DOI: 10.1121/1.1823251] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The deposition of ultrasonic energy in tissue can cause tissue damage due to local heating. For pressures above a critical threshold, cavitation will occur, inducing a much larger thermal energy deposition in a local region. The present work develops a nonlinear bubble dynamics model to numerically investigate bubble oscillations and bubble-enhanced heating during focused ultrasound (HIFU) insonation. The model is applied to calculate two threshold-dependent phenomena occurring for nonlinearly oscillating bubbles: Shape instability and growth by rectified diffusion. These instabilities in turn are shown to place physical boundaries on the time-dependent bubble size distribution, and thus the thermal energy deposition.
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Affiliation(s)
- Xinmai Yang
- National Center for Physical Acoustics, University of Mississippi, 1 Coliseum Drive, University, Mississippi 38677, USA.
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Tsutsui JM, Grayburn PA, Xie F, Porter TR. Drug and gene delivery and enhancement of thrombolysis using ultrasound and microbubbles. Cardiol Clin 2004; 22:299-312, vii. [PMID: 15158941 DOI: 10.1016/j.ccl.2004.02.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This article reviews some important characteristics of microbubbles that give them therapeutic properties. It discusses the use of microbubbles and ultrasound for targeted delivery of adenovirus and nonviral vectors to myocytes and endothelial cells and for the dissolution of thrombus or potentiation of fibrinolytic agents for acutely thrombosed vessels. Potential applications, such as induction of angiogenesis, inhibition of neointimal hyperplasia, and in the setting of acute myocardial infarction and ischemic stroke,are discussed briefly.
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Affiliation(s)
- Jeane Mike Tsutsui
- Section of Cardiology, Department of Internal Medicine, University of Nebraska Medical Center, 600 South 42nd Street, Omaha, NE 68198, USA
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Culp WC, Porter TR, Lowery J, Xie F, Roberson PK, Marky L. Intracranial Clot Lysis With Intravenous Microbubbles and Transcranial Ultrasound in Swine. Stroke 2004; 35:2407-11. [PMID: 15322299 DOI: 10.1161/01.str.0000140890.86779.79] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background and Purpose—
Destruction of microbubbles by transcutaneous low-frequency ultrasound (LFUS) has been used to lyse adjacent clot and recanalize acutely thrombosed vessels. LFUS with intraarterial microbubbles has been shown to lyse cerebral clot rapidly in pigs without thrombolytic drugs. We hypothesized that intravenous platelet-targeted microbubbles with LFUS may be a rapid noninvasive technique to recanalize thrombosed intracerebral vessels.
Methods—
After angiography, 0.5 cc of autogenous thrombus was injected into 1 ascending pharyngeal artery of a pig, occluding it and the rete mirabile. These vessels connect the carotid to the internal carotid and are the main cerebral blood supply. Saline control or intravenous decafluorobutane-sonicated dextrose albumin microbubbles tagged with a subtherapeutic quantity of glycoprotein 2b/3a receptor inhibitor eptifibatide (75 U/kg plus 12 cc of microbubbles administered over 21 minutes), or eptifibatide control, was given with transcutaneous temporal LFUS (1 MHz at 2.0 W/cm
2
) for 24 minutes. Angiography followed with scoring of declotting and flow. The same protocol was repeated on the contralateral side with the other test fluid so each animal received a saline control and either tagged microbubble or eptifibatide alone.
Results—
Fifteen pigs completed the protocol with a mean clot age of 4.6 hours. Using tagged microbubbles, 6 of 8 achieved success compared with 0 of 7 receiving eptifibatide alone (
P
=0.007) and 1 of 15 receiving saline alone (
P
=0.02).
Conclusions—
Intravenous platelet-targeted microbubbles combined with transcranial LFUS can rapidly open acute intracranial thrombotic occlusions. Further development for ischemic stroke therapy is justified.
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Affiliation(s)
- William C Culp
- Department of Radiology, University of Arkansas for Medical Sciences, 4301 W Markham St, Slot 556, Little Rock, AR 72205-7199, USA.
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Abstract
Ultrasound is used widely in medicine as both a diagnostic and therapeutic tool. Through both thermal and nonthermal mechanisms, ultrasound can produce a variety of biological effects in tissues in vitro and in vivo. This chapter provides an overview of the fundamentals of key nonthermal mechanisms for the interaction of ultrasound with biological tissues. Several categories of mechanical bioeffects of ultrasound are then reviewed to provide insight on the range of ultrasound bioeffects in vivo, the relevance of these effects to diagnostic imaging, and the potential application of mechanical bioeffects to the design of new therapeutic applications of ultrasound in medicine.
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Affiliation(s)
- Diane Dalecki
- Department of Biomedical Engineering and the Rochester Center for Biomedical Ultrasound, University of Rochester, Rochester, New York 14627, USA.
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Unger EC, Porter T, Culp W, Labell R, Matsunaga T, Zutshi R. Therapeutic applications of lipid-coated microbubbles. Adv Drug Deliv Rev 2004; 56:1291-314. [PMID: 15109770 DOI: 10.1016/j.addr.2003.12.006] [Citation(s) in RCA: 377] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Accepted: 12/20/2003] [Indexed: 11/15/2022]
Abstract
Lipid-coated microbubbles represent a new class of agents with both diagnostic and therapeutic applications. Microbubbles have low density. Stabilization of microbubbles by lipid coatings creates low-density particles with unusual properties for diagnostic imaging and drug delivery. Perfluorocarbon (PFC) gases entrapped within lipid coatings make microbubbles that are sufficiently stable for circulation in the vasculature as blood pool agents. Microbubbles can be cavitated with ultrasound energy for site-specific local delivery of bioactive materials and for treatment of vascular thrombosis. The blood-brain barrier (BBB) can be reversibly opened without damaging the neurons using ultrasound applied across the intact skull to cavitate microbubbles within the cerebral microvasculature for delivery of both low and high molecular weight therapeutic compounds to the brain. The first lipid-coated PFC microbubble product is currently marketed for diagnostic ultrasound imaging. Clinical trials are currently in process for treatment of vascular thrombosis with ultrasound and lipid-coated PFC microbubbles (SonoLysis Therapy). Targeted microbubbles and acoustically active PFC nanoemulsions with specific ligands can be developed for detecting disease at the molecular level and targeted drug and gene delivery. Bioactive compounds can be incorporated into these carriers for site-specific delivery. Our aim is to cover the therapeutic applications of lipid-coated microbubbles and PFC emulsions in this review.
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Culp WC, Erdem E, Roberson PK, Husain MM. Microbubble potentiated ultrasound as a method of stroke therapy in a pig model: preliminary findings. J Vasc Interv Radiol 2004; 14:1433-6. [PMID: 14605109 DOI: 10.1097/01.rvi.0000096767.47047.fa] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
Abstract
PURPOSE Low-frequency ultrasound (LFUS) with intraarterial or intravenous microbubbles can recanalize thrombosed dialysis grafts and arteries. A similar method for declotting intracranial arteries in an animal model has been developed. MATERIALS AND METHODS Swine underwent selective cerebral angiography, and 1 mL of 2-6 hour old clot was placed in one ascending pharyngeal artery and rete mirabile. This occluded the primary brain blood supply from the rete mirabile in the base of the skull. Human albumin octafluoropropane microbubbles were injected through the same catheter in 0.5-1.0-mL doses for a total of 4.5 mL in 21 minutes. Transcutaneous pulsed-wave 1-MHz ultrasound was administered through a temporal approach using 2.2 W/cm(2). Repeated angiography was performed through 24 minutes. Saline controls underwent an identical process on the opposite side. Declotting was graded on a scale of 0-4, and flow used the 0-3 thrombolysis in myocardial infarction (TIMI) scale. Success was defined as declotting of grade >/= 3 (>70% clearing) with flow of >/= 2. RESULTS Seven pigs received 14 declotting sequences. Average clot age was 217 minutes. Average declotting score was 3.1, and flow was 2.1 for microbubbles and 1.4 and 0.1 for saline controls, P =.016 in each. Success occurred with microbubbles in six of seven attempts and in controls in zero of seven attempts, P =.031. CONCLUSIONS LFUS with microbubble augmentation rapidly lyses intracranial clot and restores flow at ultrasound ranges similar to those required in humans. Further development of this possible acute stroke therapy is justified.
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Affiliation(s)
- William C Culp
- Department of Radiology, University of Arkansas for Medical Sciences, Slot 556, 4301 W. Markham St., Little Rock, Arkansas 72205-7199, USA.
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Culp WC, Porter TR, McCowan TC, Roberson PK, James CA, Matchett WJ, Moursi M. Microbubble-augmented ultrasound declotting of thrombosed arteriovenous dialysis grafts in dogs. J Vasc Interv Radiol 2003; 14:343-7. [PMID: 12631639 DOI: 10.1097/01.rvi.0000058409.01661.b4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Transcutaneous low-frequency ultrasound (LFUS) can effectively lyse clots in the presence of microbubbles. This study was designed to test the commercially available human albumin microspheres injectable suspension octafluoropropane formulation, Optison, to establish efficacy and assess US parameters of intensity and wave modes in a canine model of a thrombosed arteriovenous (dialysis) graft. MATERIALS AND METHODS Arteriovenous grafts in five dogs were cannulated, temporarily ligated, and thrombosed. Different declotting techniques were randomized to treat nine groups. Control groups involved direct saline (4.5 mL) clot injection in 0.5-1.0-mL increments. One group underwent peripheral intravenous microbubble injection (13.5 mL). Six groups underwent direct incremental clot injection of 4.5 mL of microspheres with LFUS for 30 minutes in 3-5-minute increments with use of various intensity settings in continuous-wave and pulsed-wave (PW) modes. At each increment, angiography was used to grade flow, declotting, and overall success. RESULTS One hundred four procedures showed success in all 24 high-intensity PW modes (1.2-2.0 W/cm(2)); only one of 20 control experiments was successful (P <.0001). Medium-intensity modes yielded intermediate success rates. Lowest-intensity direct-injection groups and intravenous and control groups ranked lower. Results at 30 minutes were better than at 15 minutes (P <.0001). CONCLUSIONS LFUS with direct injection of microbubbles is effective in lysing moderate-sized clots and recanalizing thrombosed arteriovenous grafts. It best succeeds at the higher range of intensity settings tested in PW mode. Further development is justified.
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Affiliation(s)
- William C Culp
- Department of Radiology, University of Arkansas for Medical Sciences, 4301 West Markham, Slot 556, Little Rock, Arkansas 72205-7199, USA.
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