SEARCH · PubMed Health

Results for “Microbubbles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources

PubMed2003

The dynamic bubble trap reduces microbubbles in extracorporeal circulation and high intensity transient signals in the middle cerebral artery: a case report.

Microemboli during extracorporeal circulation (ECC) might be a reason for postoperative neuropsychological dysfunction. This case report shows that reduction of microbubbles in the arterial line, as well as high intensity transient signals (HITS) in the middle cerebral artery (MCA), could be accomplished by use of a dynamic bubble trap (DBT) during routine coronary artery bypass graft (CABG) surgery in a 63-year-old male. The DBT was placed after the arterial filter, an ultrasound Doppler device was used for detection of microemboli before and after the DBT. HITS were measured by a transcranial ultrasound Doppler in both MCAs. For first 32 min of ECC, the DBTwas excluded; 54 916 microbubbles and 507 HITS were counted. In the next 30 min, blood flow was directed through the DBT. This led to a significant reduction of microbubbles from 55 888 to 18 237; accordingly, only 120 HITS were registered. A DBT, integrated in ECC for routine CABG, effectively reduces air bubbles, thus protecting the cerebrovascular system from microembolization, as demonstrated by lower HITS counts.

Cerebrovascular Circulation↗

PubMed1986

Microbubbles as a contrast agent for neurosonography and ultrasound-guided catheter manipulation: in vitro studies.

Tissue-equivalent ultrasound phantoms, including models of the ventricular system and cyst phantoms, may be useful for developing expertise in both biopsy procedures and shunt catheter placement that use ultrasound guidance. These phantoms have been constructed (1) to assess the ability to position biopsy needles and manipulate shunt catheters with conventional angiographic guidewires and (2) to evaluate the usefulness of microbubbles as an ultrasound contrast agent. Optimal catheter and needle position and catheter patency are demonstrated with microbubbles generated by hand injection of small volumes of saline, a safe ultrasound contrast agent that, to our knowledge, has not been previously exploited in neurosonography. Microbubbles can define biopsy needle location without direct imaging of the biopsy needle; they can also define the extent of communication or separation of fluid-filled or loculated spaces.

Air↗

PubMed1997

Inflammatory pancreatic masses: differentiation from ductal carcinomas with contrast-enhanced sonography using carbon dioxide microbubbles.

OBJECTIVE: The aim of this study was to evaluate the clinical efficacy of contrast-enhanced sonography using carbon dioxide microbubbles to differentiate inflammatory pancreatic masses from ductal carcinomas of the pancreas. SUBJECTS AND METHODS: Fifty-five patients, including 35 patients with ductal carcinomas and 20 with inflammatory pancreatic masses, underwent contrast-enhanced sonography, CT, and digital subtraction angiography (DSA). Carbon dioxide microbubbles were prepared by mixing 10 ml of carbon dioxide and the same amount of 25% soybean oil vigorously. Carbon dioxide microbubbles were injected through an angiographic catheter that was placed in the celiac axis. Vascularity of the tumors as determined by those three techniques was interpreted by three physicians who had no knowledge of the pathologic results. RESULTS: Contrast-enhanced sonography was best at revealing tumor vascularity among the three techniques. On contrast-enhanced sonography, 19 (95%) of the 20 inflammatory pancreatic masses were isovascular and 32 (91%) of the 35 ductal carcinomas were hypovascular. In contrast, the isovascularity of inflammatory masses was five (25%) on CT, and two (10%) on DSA, respectively. The sensitivity and accuracy rate of differentiating both diseases on contrast-enhanced sonography were 98% and 95%, respectively; on CT, they were both 73%; and on DSA they were both 67%. From our results, an isovascular mass is probably an inflammatory mass, whereas a hypovascular mass is most likely a ductal carcinoma on contrast-enhanced sonography. CONCLUSION: Contrast-enhanced sonography can help differentiate an inflammatory pancreatic mass from a ductal carcinoma.

Adenocarcinoma↗

PubMed2002

[Assessment of myocardial ischemia and infarction by intravenous myocardial contrast echocardiography with perfluorocarbon microbubbles]

OBJECTIVE: To assess the value of myocardial contrast echocardiography (MCE) with intermittent second harmonic technique and perfluorocarbon microbubbles in identifying myocardial ischemia and infarction. METHODS: Open-chest dogs were performed by intravenous MCE with perfluorocarbon microbubbles after 3 h of left anterior descending coronary artery (LAD) occlusion. The parameters of time-intensity curve were measured and compared between the normal and ischemic myocardial area at short-axis view of left ventricule midpapillary muscle level. The infarct size assessed by MCE was compared with the gross pathologic specimen stained with triphenyltetrazolium chloride (TTC). RESULTS: The peak intensity (PI), T1/2, and area under curve (AUC) in the ischemic area were significantly different versus the normal area 13.5+/-1.9 compared with 22.5+/-2.4; 16.6+/-0.9 compared with 9.7+/-0.5; 231.6+/-14.9 compared with 405.6+/-12.3 P<0.02). The percents of the no flow area determined by MCE had correlation with those by TTC stain(r=0.89, P=0.01). CONCLUSION: Intermittent second harmonic MCE using intravenous injection of perfluorocarbon microbubbles could assess myocardial perfusion, diagnose ischemia, and define myocardial infarct size.

Journal Article↗

PubMed2002

Observation on the integrity of the blood-brain barrier after microbubble destruction by diagnostic transcranial color-coded sonography.

OBJECTIVE: To investigate alteration of the blood-brain barrier from ultrasonic contrast agent destruction by diagnostic transcranial color-coded sonography using gadolinium-enhanced magnetic resonance imaging. METHODS: Healthy male volunteers received 10 mL (400 mg/dL) of Levovist (SH U 508A; Schering AG, Berlin, Germany; n = 6) or 3 mL of Optison (FS069; Mallinckrodt Inc, St Louis, MO; n = 4) followed by 0.3 mmol/kg magnetic resonance imaging contrast agent (Magnevist; Schering) intravenously. Then transcranial color-coded sonography was performed with a conventional color duplex sonographic system, which insonated the brain in a slightly angulated axial plane with temporal average intensity of less than 700 mW/cm2 or acoustic pressure amplitude of less than 2.69 MPa, attenuated by the temporal bone. Before, immediately after, and 2 hours after insonation, T1-weighted axial magnetic resonance imaging was performed. All magnetic resonance images were individually assessed, and T1 signal intensities were measured in 2 regions of interest in both hemispheres at the 3 time points. RESULTS: No focal contrast enhancement or damage to the brain and no significant difference between T1 signal intensities in the right and left brain regions could be detected during early or late phases when either ultrasonic contrast agent was used. CONCLUSIONS: This bioeffects study gives further evidence of the safety of ultrasonic destruction of Levovist and Optison microbubbles by diagnostic transcranial color-coded sonography. However, more subtle local effects may have been missed by gadolinium-enhanced magnetic resonance imaging. Studies on diagnostic contrast-enhanced transcranial color-coded sonography as well as microbubble-based drug delivery strategies should consider ultrasonic contrast agent microbubble characteristics and concentration as well as ultrasound transmission power levels.

Adult↗

PubMed1992

Time to detection of circulating microbubbles as a risk factor for symptoms of altitude decompression sickness.

This study investigated the association between time at onset of circulating microbubbles (CMB) and symptoms of altitude decompression sickness (DCS), using Cox proportional hazard regression models. The study population consisted of 125 individuals who participated in direct ascent, simulated extravehicular activities profiles. Using individual CMB status as a time-dependent variable, we found that the hazard for symptoms increased significantly (at the end of 180 min at altitude) in the presence of CMB (Hazard Ratio = 29.59; 95% confidence interval [95% CI] = 7.66-114.27), compared to no CMB. Further examination was conducted on the subgroup of individuals who developed microbubbles during the test (n = 49), by using Cox regression. Individuals with late onset of CMB (> 60 min at altitude) showed a significantly reduced risk of symptoms (hazard ratio = 0.92; 95% CI = 0.89-0.95), compared to those with early onset (< or = 60 min), while controlling for other risk factors. We conclude that time to detection of circulating microbubbles is an independent determinant of symptoms of DCS.

Adult↗

PubMed1989

M-mode ultrasonic detection of microbubbles following saturation diving: a case report and proposal for a new grading system.

An M-mode ultrasound system was used to obtain a reliable method for the evaluation of microbubbles caused by decompression. When the probe is focused in the outflow tract of the right ventricle it is easy to recognize a linear configuration of the echoes caused by the microbubbles. A quantitative study of microbubbles can be done by counting the number of linear echoes per second. Application of this method is reported following saturation diving decompression. We think the reported method is worthy of further use.

Decompression↗

PubMed1986

A method for production of N2 microbubbles in platelet-rich plasma in an aggregometer-like apparatus, and effect on the platelet density in vitro.

The mechanisms involved in the interactions between microgasbubbles and platelets are not clear. The platelet aggregatory response to agonist-induced, receptor-mediated stimuli has been studied extensively. As a direct in vitro approach to elucidate the interaction between gas bubbles and platelets, N2 microbubbles were used as a platelet agonist in an experimental apparatus similar to an ordinary aggregometer. N2 microbubbles of varying number and size were produced in platelet-rich plasma (PRP) and incubated at 37 degrees C. The gas-liquid interface of the gas bubbles consists of plasma proteins and lipids. In stirred PRP a considerable decrease occurred in the platelet density, which could not be attributed to formation of citrate complexes with calcium and/or the corresponding reduction in the concentration of free calcium. Gas bubbles with a diameter in the range of 40-120 micron caused the greatest reduction in the platelet density. The platelet movements in PRP and the curvature of the N2 microbubble surface seemed more important for the interaction than the total gas bubble surface available for contact.

Analysis of Variance↗

PubMed1996

[Detection of microbubbles formed in the blood/CO2 interphase during decompression in barometric conditions similar to laparoscopy].

HYPOTHESIS AND OBJECTIVES: Intraperitoneal insufflation (IPI) with CO2 during laparoscopic surgery establishes a pressure gradient that determines the passage of gas from the peritoneal cavity to the blood and surrounding tissues. The transport and clearance of CO2 are assured by proper sweeping when regional blood flow is adequate in volume and distribution. But if IPI hyperpressure surpasses regional venous capillary pressure (10 to 15 mmHg) and there is no cardio-circulatory adaptation to the phenomenon, CO2 clearance may be compromised. Under these conditions, the expected post-insufflation increase in PetCO2 will not take place. Bearing in mind the physical characteristics of CO2, retention of this gas in the intraperitoneal cavity produces blood and tissue saturation under a higher-than-atmospheric pressure, after a certain period of time in contact. Rapid intraperitoneal decompression after laparoscopic surgery carries with it the risk of microbubble formation due to release of CO2 that had been dissolved under hyperbaric conditions. MATERIAL AND METHODS: To test this hypothesis, the barometric conditions of laparoscopy were reproduced inside an observation capsule containing blood and CO2. RESULTS: Magnification revealed that after decompression bubbles formed in the blood/CO2 interphase. The images were recorded on magnetic videotape. Thirty minutes after decompression, the bubbles could still be seen, even after the interphase was swept with a current of air. DISCUSSION: Rapid intraperitoneal decompression after laparoscopy can generate the formation of microbubbles which, if not eliminated, will give rise to local ischemic manifestations. This same decompression, correcting the local circulatory alterations and activating the CO2 transport that had been compromised, could introduce gas bubbles into the blood stream such as are responsible for delayed gaseous microembolism. The simultaneous observation of changes in PetCO2 (stability or post-insufflation decreases) and hemodynamic parameters during laparoscopy, would allow evolving anomalies to be detected early and therapeutic action to be taken to prevent the formation of microbubbles.

Carbon Dioxide↗

PubMed1998

[Usefulness of enhanced US by CO2 microbubbles for segmental-subsegmental TAE for hepatocellular carcinoma].

Enhanced US by intraarterial infusion of CO2 microbubbles is useful for segmental to subsegmental TAE of hepatocellular carcinoma for several reasons. First, we can obtain better recognition of the tumor stain of hepatocellular carcinoma which is even faint on DSA. Secondly, we can recognize the co-relation between tumor stain and its related segment or subsegment well. Therefore, subsegmental or segmental TAE can be performed easily and precisely using enhanced US by CO2 microbubbles. We noted the bigger advantage of enhanced US by CO2 microbubbles especially in the repeated treated cases of TAE for hepatocellular carcinoma.

Carbon Dioxide↗

PubMed2003

A microbubble agent improves the therapeutic efficiency of high intensity focused ultrasound: a rabbit kidney study.

Eighty kidneys (40 left and 40 right kidneys) of New Zealand rabbits were ablated using high intensity focused ultrasound (HIFU), (14,300 W/cm(2), 1.0 MHz). Kidneys were randomly divided into two groups. HIFU was performed in the manner of linear scan in both groups. Prior to HIFU, normal saline solution and isovolumetric microbubble agent were administrated intravenously in groups I and II, respectively. HIFU was finished in all left kidneys and in 26/40 right ones. The therapeutic efficiency was reflected using necrosis rate (cubic centimeters per second), which was the tissue volume of coagulative necrosis per 1 s HIFU exposure. In both groups, predetermined volumes were damaged without harming overlying tissues. Necrosis rates were increased in group II both in left (0.0089+/-0.0107 vs. 0.0493+/-0.0777, P=0.0323) and in right (0.0039+/-0.0055 vs. 0.0162+/-0.0168, P=0.0248) kidneys. Pathological examinations confirmed that there were no intact tissue focuses within exposed regions in either group. These findings suggested that the microbubble agent improved the therapeutic efficiency of HIFU. Hemorrhage and hyperemia were also detected on the margin of the ablated tissues (both in cortex and medulla) in both groups.

Animals↗

PubMed2005

Use of a microbubble agent to increase the effects of high intensity focused ultrasound on liver tissue.

In order to find out whether high intensity focused ultrasound (HIFU) might be useful against hepatocellular carcinoma, we analyzed the effect of a microbubble agent (Levovist) on the temperature rise and tissue necrosis induced by HIFU. Rabbits were given 7 ml Levovist (300 mg/ml) or saline intravenously. Up to six areas per rabbit liver were exposed to HIFU for 60 s (2.18 MHz, I(SPTA)=400 W/cm(2)). The volume of the tissue coagulated by HIFU was measured 10 min after the start of HIFU. HIFU-induced lesions were larger in the animals given Levovist: (mm(3), Levovist versus saline) 371+/-104 versus 166+/-71 (P<0.001). Temperatures in the animals given Levovist were also higher 60 s after the start of exposure: ( degrees C, Levovist versus saline) 20.3+/-3.5 versus 13.2+/-3.8 (P<0.001). The amount of damage differed greatly, but the pathological changes caused by HIFU with Levovist were the same as those caused by HIFU with saline. Hemorrhagic areas and implosion cysts were seen, and many cells had been disrupted or destroyed. Microbubble agents developed for diagnostic uses could also be used in anticancer therapy.

Animals↗

PubMed2005

Detection of focal renal perfusion defects in rabbits after sulphur hexafluoride-filled microbubble injection at low transmission power ultrasound insonation.

The aim of this study was to assess the feasibility of contrast-enhanced ultrasound (US) at low transmission power insonation for diagnosis of focal renal perfusion defects (RPDs) in rabbits. In seven adult New Zealand White rabbits focal RPDs were induced by polyvinyl alcohol embolizing particles (150-250 microm in diameter) injected into the abdominal aorta. Three other rabbits that were not subjected to embolization were considered as controls. Both kidneys were insonated at baseline and after injection of sulphur hexafluoride-filled microbubbles at low transmission power (mechanical index 0.09-0.12). One sonologist assessed on-site RPD dimensions and conspicuity (visual score 0-4). Digital cine-clips were also reviewed off-site by two other independent readers, blinded, who assigned a confidence level (grades 1-5) for the RPD diagnosis. At on-site analysis RPDs appeared as focal areas of absent or diminished enhancement with a median visual conspicuity score=4. At off-site analysis RPDs >6 mm in diameter were identified at contrast-enhanced US, and the confidence in RPD diagnosis improved significantly (P<0.05) after microbubble injection (area under receiver operating characteristic curve 0.615 vs 0.972 by reader 1; 0.720 vs 0.953 by reader 2). Contrast-enhanced US at low transmission power insonation effectively identified RPDs with diameters >6 mm in rabbits.

Animals↗

PubMed2004

Microbubble contrast agents for echocardiography: rationale, composition, ultrasound interactions, and safety.

Imaging the small blood vessels within the myocardium, which contains only a small fraction of the total coronary blood volume, is a significant challenge for ultrasound imaging. Recent advances in microbubble design and ultrasound technology have improved our ability to image the microcirculation. It is essential to understand the fundamentals of microbubble behavior in an ultrasound field and how it impacts technology and safety.

Coronary Vessels↗

PubMed2004

Drug and gene delivery and enhancement of thrombolysis using ultrasound and microbubbles.

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.

Cardiovascular Agents↗

PubMed2004

Treatment of acute myocardial infarction by hepatocyte growth factor gene transfer: the first demonstration of myocardial transfer of a "functional" gene using ultrasonic microbubble destruction.

OBJECTIVES: We examined whether ultrasonic microbubble destruction (US/MB) enables therapeutic myocardial gene transfer of hepatocyte growth factor (HGF) for acute myocardial infarction (MI). BACKGROUND: Hepatocyte growth factor gene transfer provides cardioprotective effects in MI, which requires direct intramyocardial injection or special vectors. Although US/MB was used in myocardial gene transfer, its feasibility in transfer of a therapeutic gene with non-viral vector remains unknown. METHODS: In a rat model of acute MI, naked plasmid (pVaxl) encoding human HGF (1,500 microg) was infused into the left ventricular (LV) chamber during US/MB (HGF-US/MB) or insonation only (HGF-US) or alone (HGF-alone), while control MI rats received empty pVaxl during US/MB (pVaxl-US/MB). For US/MB, transthoracic intermittent insonation with a diagnostic transducer (1.3 MHz) was performed for 2 min at a peak negative pressure of -2,160 kPa during intravenous 20% Optison. RESULTS: Baseline risk area was comparable among the groups. Immunohistology seven days after treatment revealed significant myocardial expression of HGF protein only in HGF-US/MB. At three weeks, LV weight in HGF-US/MB (0.89 +/- 0.03 g) was significantly lower than those in HGF-alone (1.09 +/- 0.08 g), HGF-US (1.04 +/- 0.07 g), and pVaxl-US/MB (1.04 +/- 0.05 g). Moreover, scar size was significantly smaller (16 +/- 6% vs. 39 +/- 5%, 41 +/- 6%, and 40 +/- 4% of total myocardial circumferential length, respectively), while capillary density (49 +/- 8 vs. 34 +/- 5, 37 +/- 6, and 36 +/- 4 capillaries/high-power field, respectively) and arterial density (37 +/- 7 vs. 15 +/- 9, 18 +/- 4, and 14 +/- 11 arterioles/high-power field, respectively) in the risk area were higher in HGF-US/MB than the other groups. CONCLUSIONS: Ultrasound-mediated microbubble destruction may enable myocardial HGF gene transfer with systemic administration of naked plasmid, which enhances angiogenesis, limits infarction size, and prevents LV remodeling after MI.

Animals↗

PubMed2005

Ultrasound radiation force enables targeted deposition of model drug carriers loaded on microbubbles.

A novel drug delivery vehicle that specifically targets using ultrasound radiation force (USRF) and biotin-avidin interactions is presented. Model vehicles consist of avidinated fluorescent nanobeads bound directly to the biotinylated lipid shells of preformed microbubbles. USRF was used to deflect the vehicle from the center of flow to a tube surface in order to facilitate receptor-ligand mediated adhesion. At wall shear stress levels commensurate with venous and arterial flow, USRF was used to direct the vehicles to a biotinylated tube surface. Subsequent high-pressure pulses fragmented the carrier, and molecular interactions induced deposition of the nanobeads on the wall. Targeting of nanobeads to the tube was molecularly specific and dependent on, in order of importance, vehicle concentration, wall shear stress, nanobead size, and insonation time. The observation that portions of the microbubble lipid monolayer shell remain attached to adherent nanobeads is important for future consideration of drug transport mechanisms. This versatile method of delivery is shown to enable targeted deposition of nanoparticles in shear flow and could be modified to carry therapeutic agents for controlled release in targeted delivery applications.

Avidin↗

PubMed2006

Investigating the nonlinear microbubble response to chirp encoded, multipulse sequences.

A modified Rayleigh-Plesset model was used to investigate the nonlinear acoustic response of ultrasound contrast microbubbles to multipulse phase and amplitude modulated, chirp encoded sequences. Trade-offs between the signal-to-noise ratio (SNR) and axial resolution were quantified for differing chirp time-bandwidth products and methods for minimising the artifacts formed in the postprocessing stages were developed. It was found that the chirp length can be increased and bandwidth reduced to improve SNR, though resolution is sacrificed. Results from the simulated chirp, pulse inverted, amplitude modulated (chirp PIAM) sequences were also compared with equivalent short pulse PIAM sequences and it was found that the chirp sequences preserve their extra energy after scattering, which translates to an improved SNR after processing. Compression artifacts were reduced by using chirps with a centre frequency and bandwidth tuned to the frequency response of the microbubble and reversing the frequency sweep of one chirp in the sequence.

Artifacts↗