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Kalayeh K, Fowlkes JB, Yeras S, Chen A, Daignault-Newton S, Schultz WW, Sack BS. A Comparative Study of Commercially Available Ultrasound Contrast Agents for Sub-harmonic-Aided Pressure Estimation (SHAPE) in a Bladder Phantom. ULTRASOUND IN MEDICINE & BIOLOGY 2024; 50:1494-1505. [PMID: 39054243 DOI: 10.1016/j.ultrasmedbio.2024.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 05/14/2024] [Accepted: 05/19/2024] [Indexed: 07/27/2024]
Abstract
OBJECTIVE The goal of this study was to evaluate the performance of different commercial ultrasound contrast microbubbles (MBs) when measuring bladder phantom pressure with sub-harmonic-aided pressure estimation (SHAPE) methodology. We hypothesized that SHAPE performance is dependent on MB formulation. This study aimed to advance the SHAPE application for bladder pressure measurements in humans. METHODS Using a previously designed and built bladder phantom, we tested four different commercial agents: Definity, Lumason, Sonazoid and Optison. A standard clinical cystometrogram (CMG) system was used to infuse a MB-saline mixture into the bladder phantom to measure pressure. Ultrasound imaging was performed using the GE Healthcare LOGIQ E10 scanner. RESULTS All agents showed a predicted inverse linear relationship between change in pressure and SHAPE signal. However, they differ from each other in terms of stability, linear correlation, sensitivity to pressure and error. Generally, Definity and Lumason showed the highest performance during the SHAPE-based bladder phantom pressure assessments. CONCLUSION Our results show that the SHAPE signal decreases as bladder phantom pressures increases, regardless of the agent or CMG phase, suggesting the possibility of using SHAPE for measuring bladder pressure without a catheter. However, the efficacy of SHAPE in measuring pressure varies by MB formulation. These observations support using Lumason and Definity in a human subject feasibility study as we advance toward a catheter-free solution for measuring voiding bladder pressure via SHAPE.
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Affiliation(s)
- Kourosh Kalayeh
- Department of Urology, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Sophia Yeras
- College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, MI, USA
| | - Amy Chen
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, USA
| | | | - William W Schultz
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Bryan S Sack
- Department of Urology, University of Michigan, Ann Arbor, MI, USA.
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Azami RH, Forsberg F, Eisenbrey JR, Sarkar K. Ambient Pressure Sensitivity of the Subharmonic Response of Coated Microbubbles: Effects of Acoustic Excitation Parameters. ULTRASOUND IN MEDICINE & BIOLOGY 2023; 49:1550-1560. [PMID: 37100673 PMCID: PMC10306329 DOI: 10.1016/j.ultrasmedbio.2023.02.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 01/20/2023] [Accepted: 02/27/2023] [Indexed: 05/17/2023]
Abstract
OBJECTIVE The sensitivity of the acoustic response of microbubbles, specifically a strong correlation between their subharmonic response and the ambient pressure, has motivated development of a non-invasive subharmonic-aided pressure estimation (SHAPE) method. However, this correlation has previously been found to vary depending on the microbubble type, the acoustic excitation and the hydrostatic pressure range. In this study, the ambient pressure sensitivity of microbubble response was investigated. METHODS The fundamental, subharmonic, second harmonic and ultraharmonic responses from an in-house lipid-coated microbubble were measured for excitations with peak negative pressures (PNPs) of 50-700 kPa and frequencies of 2, 3 and 4 MHz in the ambient overpressure range 0-25 kPa (0-187 mmHg) in an in vitro setup. RESULTS The subharmonic response typically has three stages-occurrence, growth and saturation-with increasing excitation PNP. We find distinct decreasing and increasing variations of the subharmonic signal with overpressure that are closely related to the threshold of subharmonic generation in a lipid-shelled microbubble. Above the excitation threshold, that is, in the growth-saturation phase, subharmonic signals decreased linearly with slopes as high as -0.56 dB/kPa with ambient pressure increase; below the threshold excitation (at atmospheric pressure), increasing overpressure triggers subharmonic generation, indicating a lowering of subharmonic threshold, and therefore leads to an increase in subharmonic with overpressure, the maximum enhancement being ∼11 dB for 15 kPa overpressure at 2 MHz and 100 kPa PNP. CONCLUSION This study indicates the possible development of novel and improved SHAPE methodologies.
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Affiliation(s)
- Roozbeh H Azami
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC, USA
| | - Flemming Forsberg
- Department of Radiology, Thomas Jefferson University, Philadelphia, PA, USA
| | - John R Eisenbrey
- Department of Radiology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC, USA.
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Kalayeh K, Fowlkes JB, Chen A, Yeras S, Fabiilli ML, Claflin J, Daignault-Newton S, Schultz WW, Sack BS. Pressure Measurement in a Bladder Phantom Using Contrast-Enhanced Ultrasonography-A Path to a Catheter-Free Voiding Cystometrogram. Invest Radiol 2023; 58:181-189. [PMID: 36070543 DOI: 10.1097/rli.0000000000000919] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES The long-term goal of this study is to investigate the efficacy of a novel, ultrasound-based technique called subharmonic-aided pressure estimation (SHAPE) to measure bladder pressure as a part of a cystometrogram (CMG) in a urodynamic test (ie, pressure-flow study). SHAPE is based on the principle that subharmonic emissions from ultrasound contrast microbubbles (MBs) decrease linearly with an increase in ambient pressure. We hypothesize that, using the SHAPE technique, we can measure voiding bladder pressure catheter-free. This is of importance because the CMG catheter, due to its space-occupying property and non-physiological effects, can undermine the reliability of the test during voiding and cause misdiagnosis. In this study, we tested this hypothesis and optimized the protocol in a controlled benchtop environment. MATERIALS AND METHODS A bladder phantom was designed and built, capable of simulating clinically relevant bladder pressures. Laboratory-made lipid-shelled MBs (similar in composition to the commercial agent, DEFINITY) was diluted in 0.9% normal saline and infused into the bladder phantom using the CMG infusion system. A typical simulated CMG consists of 1 filling and 4 post-filling events. During CMG events, the bladder phantom is pressurized multiple times at different clinically relevant levels (small, medium, and large) to simulate bladder pressures. Simultaneous with pressurization, MB subharmonic signal was acquired. For each event, the change in MB subharmonic amplitude was correlated linearly with the change in bladder phantom pressure, and the SHAPE conversion factor (slope of the linear fit) was determined. In doing so, a specific signal processing technique (based on a small temporal window) was used to account for time-decay of MB subharmonic signal during a simulated CMG. RESULTS A strong inverse linear relationship was found to exist between SHAPE and bladder phantom pressures for each of the CMG filling and post-filling events ( r2> 0.9, root mean square error < 0.3 dB, standard error <0.01 dB, and P < 0.001). SHAPE showed a transient behavior in measuring bladder phantom pressure. The SHAPE conversion factor (in dB/cm H 2 O) varied between filling and post-filling events, as well as by post-filling time. The magnitude of the SHAPE conversion factor tended to increase immediately after filling and then decreases with time. CONCLUSIONS Microbubble subharmonic emission is an excellent indicator of bladder phantom pressure variation. The strong correlation between SHAPE signal and bladder phantom pressure is indicative of the applicability of this method in measuring bladder pressure during a CMG. Our results suggest that different SHAPE conversion factors may be needed for different events during a CMG (ie, at different time points of a CMG). These findings will help us better protocolize this method for introduction into human subjects and allow us to take the next step toward developing a catheter-free voiding CMG using SHAPE.
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Affiliation(s)
| | | | - Amy Chen
- Department of Biomedical Engineering
| | | | | | | | | | - William W Schultz
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI
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Qiao X, Wen Y, Yu J, Bouakaz A, Zong Y, Wan M. Noninvasive Pressure Estimation Based on the Subharmonic Response of SonoVue: Application to Intracranial Blood Pressure Assessment. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:957-966. [PMID: 34941508 DOI: 10.1109/tuffc.2021.3138100] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Intracranial blood pressure can directly reflect the status of blood vessels in real time. However, it can only be estimated invasively using a microcatheter during craniotomy. Subharmonic-aided pressure estimation (SHAPE) is a promising technique for estimating cardiac pressures but mainly uses Sonazoid, whereas SHAPE using SonoVue is still in the early stages of development. The aim of this study was to optimize transcranial SHAPE using SonoVue by investigating the relationship between subharmonic signals and middle cerebral artery pressure (MCAP) (20-160 mmHg) in vitro. We examined the effect of acoustic output levels (peak negative pressures (PNPs) of 238, 346, and 454 kPa), time in suspension (time from reconstituting the suspension to extracting it: 0-30 min), and exposure to gas-equilibrated saline (3 min, 1 h, or original gas completely replaced by air) on the subharmonic-pressure relationship. A mean subharmonic amplitude over a 0.4 MHz bandwidth was extracted using a 5 MHz 12-cycle pulse. A PNP of 346 kPa elicited the best subharmonic sensitivity for assessing hydrostatic pressures up to 0.24 dB/mmHg, possibly because compression-only behavior no longer occurs at this pressure. Moreover, the expansion force is not large enough to offset the effects of hydrostatic pressure. A linear monotonic relationship between the subharmonic amplitude and hydrostatic pressure was only observed for just prepared SonoVue. Excessive exposure to gas-equilibrated saline also affected the subharmonic-pressure relationship. Therefore, just prepared SonoVue should be used, and the duration of the pressure estimation process should be strictly controlled.
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Sojahrood AJ, Haghi H, Karshafian R, Kolios MC. Nonlinear dynamics and bifurcation structure of ultrasonically excited lipid coated microbubbles. ULTRASONICS SONOCHEMISTRY 2021; 72:105405. [PMID: 33360533 PMCID: PMC7803687 DOI: 10.1016/j.ultsonch.2020.105405] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 11/08/2020] [Accepted: 11/09/2020] [Indexed: 05/04/2023]
Abstract
In many applications, microbubbles (MBs) are encapsulated by a lipid coating to increase their stability. However, the complex behavior of the lipid coating including buckling and rupture sophisticates the dynamics of the MBs and as a result the dynamics of the lipid coated MBs (LCMBs) are not well understood. Here, we investigate the nonlinear behavior of the LCMBs by analyzing their bifurcation structure as a function of acoustic pressure. We show that, the LC can enhance the generation of period 2 (P2), P3, higher order subharmonics (SH), superharmonics and chaos at very low excitation pressures (e.g. 1 kPa). For LCMBs sonicated by their SH resonance frequency and in line with experimental observations with increasing pressure, P2 oscillations exhibit three stages: generation at low acoustic pressures, disappearance and re-generation. Within non-destructive oscillation regimes and by pressure amplitude increase, LCMBs can also exhibit two saddle node (SN) bifurcations resulting in possible abrupt enhancement of the scattered pressure. The first SN resembles the pressure dependent resonance phenomenon in uncoated MBs and the second SN resembles the pressure dependent SH resonance. Depending on the initial surface tension of the LCMBs, the nonlinear behavior may also be suppressed for a wide range of excitation pressures.
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Affiliation(s)
- A J Sojahrood
- Department of Physics, Ryerson University, Toronto, Canada; Institute for Biomedical Engineering, Science and Technology (IBEST) a partnership between Ryerson University and St. Michael's Hospital, Toronto, Ontario, Canada.
| | - H Haghi
- Department of Physics, Ryerson University, Toronto, Canada; Institute for Biomedical Engineering, Science and Technology (IBEST) a partnership between Ryerson University and St. Michael's Hospital, Toronto, Ontario, Canada
| | - R Karshafian
- Department of Physics, Ryerson University, Toronto, Canada; Institute for Biomedical Engineering, Science and Technology (IBEST) a partnership between Ryerson University and St. Michael's Hospital, Toronto, Ontario, Canada
| | - M C Kolios
- Department of Physics, Ryerson University, Toronto, Canada; Institute for Biomedical Engineering, Science and Technology (IBEST) a partnership between Ryerson University and St. Michael's Hospital, Toronto, Ontario, Canada
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A new safety index based on intrapulse monitoring of ultra-harmonic cavitation during ultrasound-induced blood-brain barrier opening procedures. Sci Rep 2020; 10:10088. [PMID: 32572103 PMCID: PMC7308405 DOI: 10.1038/s41598-020-66994-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Accepted: 05/29/2020] [Indexed: 11/25/2022] Open
Abstract
Ultrasound-induced blood-brain barrier (BBB) opening using microbubbles is a promising technique for local delivery of therapeutic molecules into the brain. The real-time control of the ultrasound dose delivered through the skull is necessary as the range of pressure for efficient and safe BBB opening is very narrow. Passive cavitation detection (PCD) is a method proposed to monitor the microbubble activity during ultrasound exposure. However, there is still no consensus on a reliable safety indicator able to predict potential damage in the brain. Current approaches for the control of the beam intensity based on PCD employ a full-pulse analysis and may suffer from a lack of sensitivity and poor reaction time. To overcome these limitations, we propose an intra-pulse analysis to monitor the evolution of the frequency content during ultrasound bursts. We hypothesized that the destabilization of microbubbles exposed to a critical level of ultrasound would result in the instantaneous generation of subharmonic and ultra-harmonic components. This specific signature was exploited to define a new sensitive indicator of the safety of the ultrasound protocol. The approach was validated in vivo in rats and non-human primates using a retrospective analysis. Our results demonstrate that intra-pulse monitoring was able to exhibit a sudden appearance of ultra-harmonics during the ultrasound excitation pulse. The repeated detection of such a signature within the excitation pulse was highly correlated with the occurrence of side effects such as hemorrhage and edema. Keeping the acoustic pressure at levels where no such sign of microbubble destabilization occurred resulted in safe BBB openings, as shown by MR images and gross pathology. This new indicator should be more sensitive than conventional full-pulse analysis and can be used to distinguish between potentially harmful and safe ultrasound conditions in the brain with very short reaction time.
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Visscher M, Lajoinie G, Blazejewski E, Veldhuis G, Versluis M. Laser-activated microparticles for multimodal imaging: ultrasound and photoacoustics. Phys Med Biol 2019; 64:034001. [PMID: 30523821 DOI: 10.1088/1361-6560/aaf4a2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The increasing personalization of medical treatment demands refined imaging and increased monitoring capabilities, as well as an improved efficacy through targeted drug delivery. Such a transition in health care can be facilitated by the use of multimodal contrast agents. In this paper, we present a novel type of multimodal contrast agents, that enhances contrast both in ultrasound and in photoacoustic imaging, while at the same time being capable of triggered drug delivery. Upon pulsed laser irradiation, polymeric microparticles-containing a dye and an oil core-can create a cavitation bubble that subsequently emits a strong acoustic wave. We investigated different formulations of these particles, by changing the oil content, dye concentration and probing conditions using a combination of pulsed laser excitation and an ultrasound chirp. We demonstrated that capsules with a core containing a low boiling point oil give the highest photoacoustic and acoustic response. The laser activation threshold for this system is high in the visible range, but within the near infrared medical limits. The same system also produces a stable bubble. US scattering by these stable bubbles results in medically relevant frequencies, making the particles of interest for biomedical and pre-clinical imaging. Finally, the system has potential to carry a functional drug-load, and a route to these applications is discussed.
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Affiliation(s)
- Mirjam Visscher
- Physics of Fluids Group, Technical Medical (TechMed) Centre and MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. Department of Biomedical Engineering, Thorax Center, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands
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Shekhar H, Smith NJ, Raymond JL, Holland CK. Effect of Temperature on the Size Distribution, Shell Properties, and Stability of Definity ®. ULTRASOUND IN MEDICINE & BIOLOGY 2018; 44:434-446. [PMID: 29174045 PMCID: PMC5759968 DOI: 10.1016/j.ultrasmedbio.2017.09.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 09/28/2017] [Accepted: 09/29/2017] [Indexed: 05/08/2023]
Abstract
Physical characterization of an ultrasound contrast agent (UCA) aids in its safe and effective use in diagnostic and therapeutic applications. The goal of this study was to investigate the impact of temperature on the size distribution, shell properties, and stability of Definity®, a U.S. Food and Drug Administration-approved UCA used for left ventricular opacification. A Coulter counter was modified to enable particle size measurements at physiologic temperatures. The broadband acoustic attenuation spectrum and size distribution of Definity® were measured at room temperature (25 °C) and physiologic temperature (37 °C) and were used to estimate the viscoelastic shell properties of the agent at both temperatures. Attenuation and size distribution was measured over time to assess the effect of temperature on the temporal stability of Definity®. The attenuation coefficient of Definity® at 37 °C was as much as 5 dB higher than the attenuation coefficient measured at 25 °C. However, the size distributions of Definity® at 25 °C and 37 °C were similar. The estimated shell stiffness and viscosity decreased from 1.76 ± 0.18 N/m and 0.21 × 10-6 ± 0.07 × 10-6 kg/s at 25 °C to 1.01 ± 0.07 N/m and 0.04 × 10-6 ± 0.04 × 10-6 kg/s at 37 °C, respectively. Size-dependent differences in dissolution rates were observed within the UCA population at both 25 °C and 37 °C. Additionally, cooling the diluted UCA suspension from 37 °C to 25 °C accelerated the dissolution rate. These results indicate that although temperature affects the shell properties of Definity® and can influence the stability of Definity®, the size distribution of this agent is not affected by a temperature increase from 25 °C to 37 °C.
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Affiliation(s)
- Himanshu Shekhar
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA.
| | - Nathaniel J Smith
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Jason L Raymond
- Department of Engineering Science, University of Oxford, Oxford, UK
| | - Christy K Holland
- Division of Cardiovascular Health and Disease, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio, USA
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Kanbar E, Fouan D, Sennoga CA, Doinikov AA, Bouakaz A. Impact of Filling Gas on Subharmonic Emissions of Phospholipid Ultrasound Contrast Agents. ULTRASOUND IN MEDICINE & BIOLOGY 2017; 43:1004-1015. [PMID: 28214036 DOI: 10.1016/j.ultrasmedbio.2016.12.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 12/16/2016] [Accepted: 12/20/2016] [Indexed: 06/06/2023]
Abstract
Subharmonic signals backscattered from gas-filled lipid-shelled microbubbles have generated significant research interest because they can improve the detection and sensitivity of contrast-enhanced ultrasound imaging. However, the emission of subharmonic signals is strongly characterized by a temporal dependence, the origins of which have not been sufficiently elucidated. The features that influence subharmonic emissions need to be identified not only to better develop next-generation microbubble contrast agents, but also to develop more efficient subharmonic imaging (SHI) modes and therapeutic strategies. We examined the effect of microbubble filling gas on subharmonic emissions. Phospholipid shelled-microbubbles with different gaseous compositions such as sulfur hexafluoride (SF6), octafluoropropane (C3F8) or decafluorobutane (C4F10), nitrogen (N2)/C4F10 or air were insonated using a driving frequency of 10 MHz and peak negative pressure of 450 kPa, and their acoustic responses were tracked by monitoring both second harmonic and subharmonic emissions. Microbubbles were first acoustically characterized with their original gas and then re-characterized after substitution of the original gas with air, SF6 or C4F10. A measureable change in intensity of the subharmonic emissions with a 20- to 40-min delayed onset and increasing subharmonic emissions of the order 12-18 dB was recorded for microbubbles filled with C4F10. Substitution of C4F10 with air eliminated the earlier observed delay in subharmonic emissions. Significantly, substitution of SF6 for C4F10 successfully triggered a delay in the subharmonic emissions of the resultant agents, whereas substitution of C4F10 for SF6 eliminated the earlier observed suppression of subharmonic emissions, clearly suggesting that the type of filling gas contained in the microbubble agent influences subharmonic emissions in a time-dependent manner. Because our agents were dispersed in air-stabilized phosphate-buffered saline, these results suggest that the diffusivity of the gas from the agent to the surrounding medium is correlated with the time-dependent evolution of subharmonic emissions.
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Affiliation(s)
- Emma Kanbar
- Imagerie et Cerveau, Inserm UMR U930, Université François Rabelais, Tours, France
| | - Damien Fouan
- Imagerie et Cerveau, Inserm UMR U930, Université François Rabelais, Tours, France
| | - Charles A Sennoga
- Imagerie et Cerveau, Inserm UMR U930, Université François Rabelais, Tours, France
| | - Alexander A Doinikov
- Imagerie et Cerveau, Inserm UMR U930, Université François Rabelais, Tours, France
| | - Ayache Bouakaz
- Imagerie et Cerveau, Inserm UMR U930, Université François Rabelais, Tours, France.
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Ultrasound Microbubbles Enhance the Neuroprotective Effect of Mouse Nerve Growth Factor on Intraocular Hypertension-Induced Neuroretina Damage in Rabbits. J Ophthalmol 2016; 2016:4235923. [PMID: 27994883 PMCID: PMC5138486 DOI: 10.1155/2016/4235923] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/30/2016] [Accepted: 10/10/2016] [Indexed: 12/29/2022] Open
Abstract
Ultrasound microbubble combined optic protection drugs have obvious protective effect on optic nerve damage. This way of targeting drug delivery is becoming more simple, not through the whole body metabolism, avoiding drug via blood circulation when facing the decomposition and the environment in the interference and destruction process of drugs, to maximize the guarantee to reach target organs of drug concentration and to reache the maximum therapeutic effect. The technique of ultrasound microbubbles is safe, controllable, nonimmunogenic, and repeatable. It provides us with a novel idea in the administration of neuroprotective drugs.
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Shekhar H, Huntzicker S, Awuor I, Doyley MM. Chirp-Coded Ultraharmonic Imaging with a Modified Clinical Intravascular Ultrasound System. ULTRASONIC IMAGING 2016; 38:403-419. [PMID: 26634777 DOI: 10.1177/0161734615618639] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Imaging plaque microvasculature with contrast-enhanced intravascular ultrasound (IVUS) could help clinicians evaluate atherosclerosis and guide therapeutic interventions. In this study, we evaluated the performance of chirp-coded ultraharmonic imaging using a modified IVUS system (iLab™, Boston Scientific/Scimed) equipped with clinically available peripheral and coronary imaging catheters. Flow phantoms perfused with a phospholipid-encapsulated contrast agent were visualized using ultraharmonic imaging at 12 MHz and 30 MHz transmit frequencies. Flow channels with diameters as small as 0.8 mm and 0.5 mm were visualized using the peripheral and coronary imaging catheters. Radio-frequency signals were acquired at standard IVUS rotation speed, which resulted in a frame rate of 30 frames/s. Contrast-to-tissue ratios up to 17.9 ± 1.11 dB and 10.7 ± 2.85 dB were attained by chirp-coded ultraharmonic imaging at 12 MHz and 30 MHz transmit frequencies, respectively. These results demonstrate the feasibility of performing ultraharmonic imaging at standard frame rates with clinically available IVUS catheters using chirp-coded excitation.
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Affiliation(s)
- Himanshu Shekhar
- Department of Electrical and Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, USA
| | - Steven Huntzicker
- Department of Electrical and Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, USA
| | - Ivy Awuor
- Department of Electrical and Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, USA
| | - Marvin M Doyley
- Department of Electrical and Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, USA
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Huntzicker S, Shekhar H, Doyley MM. Contrast-Enhanced Quantitative Intravascular Elastography: The Impact of Microvasculature on Model-Based Elastography. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:1167-81. [PMID: 26924697 PMCID: PMC4811726 DOI: 10.1016/j.ultrasmedbio.2015.12.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 12/18/2015] [Accepted: 12/22/2015] [Indexed: 05/03/2023]
Abstract
Model-based intravascular ultrasound elastography visualizes the stress distribution within vascular tissue-information that clinicians could use to predict the propensity of atherosclerotic plaque rupture. However, there are concerns that clusters of microvessels may reduce the accuracy of the estimated stress distribution. Consequently, we have developed a contrast-enhanced intravascular ultrasound system to investigate how plaque microvasculature affects the performance of model-based elastography. In simulations, diameters of 200, 400 and 800 μm were used, where the latter diameter represented a cluster of microvessels. In phantoms, we used a microvessel with a diameter of 750 μm. Peak stress errors of 3% and 38% were incurred in the fibrous cap when stress recovery was performed with and without a priori information about microvessel geometry. The results indicate that incorporating geometric information about plaque microvasculature obtained with contrast-enhanced ultrasound imaging improves the accuracy of estimates of the stress distribution within the fibrous cap precisely.
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Affiliation(s)
- Steven Huntzicker
- Department of Electrical & Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, New York, USA
| | - Himanshu Shekhar
- Department of Electrical & Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, New York, USA
| | - Marvin M Doyley
- Department of Electrical & Computer Engineering, Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, New York, USA.
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Kumar KN, Sarkar K. Interfacial Rheological Properties of Contrast Microbubble Targestar P as a Function of Ambient Pressure. ULTRASOUND IN MEDICINE & BIOLOGY 2016; 42:1010-1017. [PMID: 26777069 DOI: 10.1016/j.ultrasmedbio.2015.11.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 11/04/2015] [Accepted: 11/18/2015] [Indexed: 06/05/2023]
Abstract
In this Technical Note, we determine the interfacial rheological parameters of the encapsulation of the contrast agent Targestar P using ultrasound attenuation. The characteristic parameters are obtained according to two interfacial rheological models. The properties-surface dilatational elasticity (0.09 ± 0.01 N/m) and surface dilatational viscosity (8 ± 0.1E-9 N·s/m)-are found to be of similar magnitude for both models. Contrast microbubbles experience different ambient pressure in different organs. We also measure these parameters as functions of ambient pressure using attenuation measured at different overpressures (0, 100 and 200 mm Hg). For each value of ambient hydrostatic pressure, we determine the rheological properties, accounting for changes in the size distribution caused by the pressure change. We discuss different models of size distribution change under overpressure: pure adiabatic compression or gas exchange with surrounding medium. The dilatational surface elasticity and viscosity are found to increase with increasing ambient pressure.
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Affiliation(s)
- Krishna N Kumar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA.
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