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PubMed2005

Comparison of low-mechanical index pulse sequence schemes for detecting myocardial perfusion abnormalities during vasodilator stress echocardiography.

Myocardial contrast echocardiography has the potential to accurately detect functionally significant coronary artery disease during pharmacologic stress testing. Different low-mechanical index modalities, including triggering replenishment imaging (TRI) and real-time imaging (RTI), are currently used to identify myocardial perfusion defects. We compared the ability of TRI with that of RTI for detecting and localizing perfusion abnormalities. Thirty-six patients (62 +/- 14 years old, 15 men) underwent single-photon emission computed tomography (SPECT) with technetium-99m sestamibi and myocardial contrast echocardiography at baseline and after infusion of 0.56 mg/kg of dipyridamole. Sixteen of these patients also underwent quantitative angiography. Contrast-enhanced images were obtained in 4-, 3-, and 2-chamber views after intravenous bolus injections of lipid-encapsulated microbubbles (0.1 ml of Definity). A myocardial perfusion defect was defined by myocardial contrast echocardiography as a delay of >2 seconds in contrast replenishment after high-mechanical index flash impulse. The myocardial segments were divided into 3 major coronary territories. There was agreement in detecting perfusion defects between SPECT and TRI in 26 patients (72%, kappa = 0.46) and between SPECT and RTI in 27 patients (75%, kappa = 0.50). Agreements between myocardial contrast echocardiography and SPECT for localizing coronary territories with perfusion defects were 81% for TRI (kappa = 0.43) and 85% for RTI (kappa = 0.61). Accuracy of RTI for detecting >50% diameter stenoses by quantitative angiography was 79%, that of TRI was 71%, and that of SPECT was 65%. These data indicate that the different low-mechanical index imaging schemes are equivalent to radionuclide SPECT in accurately detecting diseased coronary artery territories during vasodilator stress.

Coronary Angiography↗

PubMed2004

Impact of fluoride and other aquatic parameters on radon concentration in natural waters.

Radon (222Rn) accumulation in water in relation to stable elements was studied for the purpose of determining factors influencing the transfer of 222Rn to and from water. In 72 groundwater samples, 222Rn and about 70 analytical parameters were analysed using radiometric and ICP-MS techniques. Using multivariate statistics (partial least squares), it was observed that 222Rn has a positive correlation with fluoride and uranium. The correlation with fluoride was further investigated by a laboratory time-scale experiment to measure the emanation of 222Rn from water as a function of fluoride, pH and carbonate. The transfer of 222Rn from water was measured by continuous monitoring in air in a closed loop set-up. It was observed that fluoride in water adhere or trap 222Rn preferably in acidic water (pH 3). It is suspected that natural physical processes (such as diffusion and microbubble phenomenon) are less effective to transport 222Rn in the presence of fluoride.

Air↗

PubMed2006

Anorectal ultrasound for neoplastic and inflammatory lesions.

Accurate staging of rectal and anal carcinoma is crucial for planning surgery and indicating adjuvant therapy. Although, computed tomography and magnetic resonance imaging are very sensitive in detecting metastatic disease, the local staging of rectal cancer with these techniques has been disappointing. Endorectal ultrasound (ERUS) and anal endosonography (AE) remain the most accurate methods for staging rectal and anal cancer. Anal endosonography is also of value in evaluating perianal sepsis: it can assist the surgeon in planning the surgical strategy by delineating the anatomy of fistula tracts, and can aid in puncturing abscesses in the operating room. Continued research and development has made the instrumentation for ERUS and AE more accurate and user-friendly. New techniques that have contributed significantly to the evolution of ERUS include three-dimensional ERUS, high-frequency miniprobes, transrectal ultrasound-guided biopsy techniques and hydrogen peroxide-enhanced endosonography. Further improvements can be expected from contrast enhancement with microbubbles and colour Doppler imaging. In this new millennium, new developments in ERUS and anal endosonography, such as tri-dimensional ERUS and anal endosonography and radial electronic probing, widen the role of ERUS in the staging of rectal and anal carcinoma, as well as for perianal inflammatory conditions.

Endosonography↗

PubMed2005

Simultaneous integrin alphavbeta3 and glycoprotein IIb/IIIa inhibition causes reduction in infarct size in a model of acute coronary thrombosis and primary angioplasty.

OBJECTIVE: We tested the hypothesis that simultaneous inhibition of the endothelial integrin alpha(v)beta(3) and the platelet glycoprotein IIb/IIIa receptor will substantially reduce infarct size in a model of acute coronary thrombosis and primary angioplasty. METHODS: Dogs were subjected to thrombus formation in the left anterior descending coronary artery followed by primary angioplasty. Prior to angioplasty, they were randomized into 3 treatment groups. Group 1 (n=7) received saline; Group 2 (n=9) received MK-383 that inhibits only IIb/IIIa; and Group 3 (n=9) received CP-4715, that inhibits both IIb/IIIa and alpha(v)beta(3). RESULTS: There was a 59% reduction in infarct size in dogs receiving CP-4715 compared to controls (p=0.002) and a 37% reduction compared to the dogs receiving MK-383 (p=0.04). Myocardium microthrombi were seen to be reduced similarly with both drugs on post-mortem (99m)Tc-DMP444 autoradiography that reflects in vivo IIb/IIIa receptor activity. In vivo imaging using echistatin-conjugated and leukocyte-targeted microbubbles revealed significant alpha(v)beta(3) inhibition and reduction in active leukocyte recruitment only in Group 3 dogs. Myocardial blood flow and regional function after reperfusion were also significantly better in this group. CONCLUSION: Simultaneous inhibition of IIb/IIIa and alpha(v)beta(3) causes a marked reduction in infarct size in a model of acute coronary thrombosis and primary PTCA that is associated with reduced myocardial microthrombi and inflammation, as well as improved myocardial blood flow and regional function. These results may have important implications in the treatment of acute coronary syndromes.

Acute Disease↗

PubMed2006

Targeting the heart with gene therapy-optimized gene delivery methods.

With evolving knowledge in molecular and cellular cardiology, cardiac gene therapy has already been investigated in clinical studies. Different vector systems for cardiac gene therapy have been developed in recent years. While non-viral vectors, such as plasmid DNA, allow remarkable organ specificity, they are often limited by low transfection efficiency and transient gene expression. In contrast, adenoviral or adeno-associated virus-based vectors transfer the transgene more efficiently, but organ specificity may be reduced and immunogenic properties can limit their applicability. Using advanced transcriptional and transductional targeting strategies, viral vectors have been improved in the last few years. Recently, more efficient serotypes of adeno-associated viruses have been identified that show increased transduction rates, thus reducing the necessity for high virus titers. Combination with specific application techniques, such as intramyocardial injection, catheter-based perfusion, ultrasound targeted microbubble destruction, or retroinfusion may further enhance vector efficiency. This review article will give a broad overview of different gene delivery strategies that have been applied in experimental and clinical studies targeting the heart.

Animals↗

PubMedDate not supplied

Advanced dynamic flow imaging with contrast-enhanced ultrasonography for the evaluation of tumor vascularity in liver tumors.

To examine the usefulness of advanced dynamic flow imaging in diagnosing hepatic tumor and in assessing therapeutic effects in patients with hepatocellular carcinoma (HCC) and metastatic hepatic tumor, we performed contrast-enhanced ultrasonography (US) with Levovist, a microbubble contrast agent. Twenty-two patients of 35 HCC nodules infected with hepatitis C virus (HCV) and six patients with metastatic liver nodules were studied. They were diagnosed as having HCC or metastasis with helical dynamic computed tomography (CT) and/or celiac angiography. Tumor vascularities in the early arterial and postvascular phases were assessed by real-time scanning of advanced dynamic flow imaging and intermittent interval-delay scanning of contrast pulse subtraction imaging with a wide-band power Doppler technology. All patients showed hypervascular enhancement of HCC on contrast-enhanced US and/or dynamic CT. The advanced dynamic flow could be obtained as vascular and perfusion images of hepatic tumors. Tumor vascularities, including tumor vessels and parenchymal flow, were able to demonstrate in 27 of 29 nodules including 17 patients with 27 HCC nodules and 2 patients with 2 metastatic nodules before radiofrequency ablation (RFA) treatment by the advanced dynamic flow on contrast-enhanced harmonic US. Two nodules gave insufficient dynamic flow which were located approximately 12 cm in depth from the body surface. The advanced dynamic flow, which was done 7-10 days after RFA, indicated disappearance of the tumor vessels in 27 of visible 27 nodules. The study on early phase of helical dynamic CT revealed the same results as noted in early vascular phase of dynamic flow US. No major complication of RFA procedure was noted. The results indicated that contrast-enhanced advanced dynamic flow imaging on US clearly depicted intratumoral vascularity in real time and thus it is useful to diagnose and assess therapeutic efficacy in patients with HCC and metastatic liver tumor.

Aged↗

PubMed2005

Targeted contrast agents for magnetic resonance imaging and ultrasound.

The development of contrast agents that can be localized to a particular tissue or cellular epitope will potentially allow the noninvasive visualization and characterization of a variety of disease states. Recent advances have been made in the field of molecular imaging with magnetic resonance imaging and ultrasound and varied approaches have been devised to overcome the high background tissue signal. The types of agents and applications developed include gadolinium-conjugated targeting molecules for imaging of fibrin, superparamagnetic iron oxide particles for stem-cell tracking, multimodal perfluorocarbon nanoparticles for visualization of angiogenesis, liposomes for targeting atheroma components, and microbubbles for imaging transplant rejection.

Animals↗

PubMed2007

Contrast echocardiography.

Myocardial contrast echocardiography (MCE) is a noninvasive imaging technique that relies on the ultrasound detection of microbubble contrast agents. These agents are confined to the intravascular space thereby producing signal enhancement from the blood pool. This review encompasses many of the key concepts regarding the clinical application of MCE. The first section focuses on the composition, safety, and biokinetics of ultrasound contrast agents. Then we discuss new ultrasound imaging methodology that has been developed to enhance detection of contrast agent and to assess perfusion at the tissue level. Next, the clinical applications of contrast ultrasound are reviewed. These include enhancement of the cardiac chambers for better assessment of cardiac function and masses, myocardial perfusion imaging for the detection of coronary artery disease, and the assessment of myocardial viability and microvascular reflow. Finally, we discuss some of the future applications for MCE, which include molecular imaging of disease and drug/gene delivery. The overall aim of the review is to update the clinician on state-of-the-art MCE and how it can be applied in patients with cardiovascular disease.

Animals↗

PubMed2005

Visualization of coronary arteries using intravenous contrast agent and real-time 3-dimensional echocardiography in a patient with hypertrophic cardiomyopathy.

Real-time 3-dimensional echocardiography is a recently developed imaging technique that provides unique information on spatial geometry in real time. We described an asymptomatic patient with hypertrophic obstructive cardiomyopathy for whom 3-dimensional echocardiography was performed after intravenous injection of perfluorocarbon-filled microbubbles. It resulted in enhancement of the left ventricular endocardial border delineation and myocardial perfusion in the hypertrophic septum. A clear visualization of the entire course of the left anterior descending coronary artery and its septal perforator branches was obtained. This case illustrates the potential of real-time 3-dimensional echocardiography to improve the anatomic evaluation of coronary arteries, especially when combined with contrast agents.

Adult↗

PubMed2005

Interrupted infusion of echocardiographic contrast as a basis for accurate measurement of myocardial perfusion: ex vivo validation and analysis procedures.

BACKGROUND: Echocardiographic quantification of myocardial perfusion is based on analysis of contrast replenishment after destructive high-energy ultrasound impulses (flash-echo). This technique is limited by nonuniform microbubble destruction and the dependency on exponential fitting of a small number of noisy time points. We hypothesized that brief interruptions of contrast infusion (ICI) would result in uniform contrast clearance followed by slow replenishment and, thus, would allow analysis from multiple data points without exponential fitting. METHODS: Electrocardiographic-triggered images were acquired in 14 isolated rabbit hearts (Langendorff) at 3 levels of coronary flow (baseline, 50%, and 15%) during contrast infusion (Definity) with flash-echo and with a 20-second infusion interruption. Myocardial videointensity was measured over time from flash-echo sequences, from which characteristic constant beta was calculated using an exponential fit. Peak contrast inflow rate was calculated from ICI data using analysis of local time derivatives. Computer simulations were used to investigate the effects of noise on the accuracy of peak contrast inflow rate and beta calculations. RESULTS: ICI resulted in uniform contrast clearance and baseline replenishment times of 15 to 25 cardiac cycles. Calculated peak contrast inflow rate followed the changes in coronary flow in all hearts at both levels of reduced flow (P < .05) and had a low intermeasurement variability of 7 +/- 6%. With flash-echo, contrast clearance was less uniform and baseline replenishment times were only 4 to 6 cardiac cycles. beta Decreased significantly only at 15% flow, and had intermeasurement variability of 42 +/- 33%. Computer simulations showed that measurement errors in both perfusion indices increased with noise, but beta had larger errors at higher rates of contrast inflow. CONCLUSION: ICI provides the basis for accurate and reproducible quantification of myocardial perfusion using fast and robust numeric analysis, and may constitute an alternative to the currently used techniques.

Animals↗

PubMed2006

Effects of ultrasound contrast agents on Doppler tissue velocity estimation.

The combination of Doppler tissue imaging and myocardial contrast echocardiography has the potential to provide information about motion and perfusion of the myocardium in a single examination. The purpose of this study was to establish how the presence of ultrasound contrast agent (UCA) affects measurements of Doppler tissue velocities in vivo and in vitro. We performed echocardiography in 12 patients with ischemic heart disease before and immediately after a slow intravenous infusion of the UCA Optison, using color Doppler tissue imaging to examine the effect of contrast agents in vivo. The myocardial peak systolic velocities and their integrals were analyzed in digitally stored cineloops before and after contrast administration. To distinguish between methodologic and physiologic factors affecting the measurement of tissue velocity in vitro, experiments with a rotating disk and a flow cone phantom were also carried out for the 3 contrast agents: Optison, Sonovue, and Sonazoid. In vivo results show that the values for peak systolic velocity increased by about 10% during contrast infusion, from mean 5.2 +/- 1.8 to 5.7 +/- 2.3 cm/s (P = .02, 95% confidence interval 2%-16%). The increase in myocardial peak systolic velocities was verified in experimental models in which the UCA increased the estimated mean velocity in the order of 5% to 20% for the motion interval of 5 to 7 cm/s, corresponding to the myocardial velocities studied in vivo. The response was similar for all 3 contrast agents and was not affected by moderate variations in concentration of the agent. We have shown that the presence UCA will affect Doppler tissue measurements in vivo and in vitro. The observed bias is presumed to be an effect of harmonic signal contribution from rupturing contrast agent microbubbles and does not indicate biologic or physiologic effects.

Aged↗

PubMed2004

Guidance and monitoring of radiofrequency liver tumor ablation with contrast-enhanced ultrasound.

Radiofrequency (RF) treatments of non-resectable hepatic tumors are generally guided with real-time sonography, which, however, cannot differentiate necrotic changes from viable tumor. To achieve complete treatment of hepatic tumors, accurate imaging techniques are needed for close treatment follow-up. Usually contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) are used; however, they can be performed only at the end of treatment sessions. In this field, contrast-enhanced ultrasound (CEUS) has shown to improve the sensitivity of plain ultrasonography. Recently, further developments of contrast-enhanced US technique have significantly increased its clinical utility. Continuous mode, low MI scans performed with harmonic imaging and contrast specific software appears as a very useful technique for the visualization of both macro- and microcirculation with depiction of tumor vascularisation. In our hospital, we have been employing contrast-enhanced sonography with sulphur hexaflouride microbubbles (SonoVue, Bracco, Italy) before, during and immediately at the end of RF ablation procedures to monitor and assess the therapeutic result prior to closing the treatment session. The results obtained in a group of 109 patients with hepatocellular carcinoma (HCC) in liver cirrhosis (192 lesions) and in 53 patients with liver metastases (97 lesions) undergoing a single session of percutaneous RF tumor ablation, showed that the sensitivity of CEUS for the detection of residual tumor was almost equivalent to that of contrast-enhanced helical CT. More importantly, since the introduction of intraoperative CEUS the rate of partially unablated tumors has dropped from 16.1 to 5.9%. Cost-effectiveness and reduction of patients' discomfort related to the need of re-treatment are the two most outstanding advantages of CEUS in this field.

Carcinoma, Hepatocellular↗

PubMed2005

Therapeutic response assessment of percutaneous radiofrequency ablation for hepatocellular carcinoma: utility of contrast-enhanced agent detection imaging.

PURPOSE: To assess the utility of contrast-enhanced agent detection imaging (ADI) in the assessment of the therapeutic response to percutaneous radiofrequency (RF) ablation in patients with hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Ninety patients with a total of 97 nodular HCCs (mean, 2.1+/-1.3 cm; range, 1.0-5.0 cm) treated with percutaneous RF ablation under the ultrasound guidance were evaluated with contrast-enhanced ADI after receiving an intravenous bolus injection of a microbubble contrast agent (SH U 508A). We obtained serial contrast-enhanced ADI images during the time period from 15 to 90 s after the initiation of the bolus contrast injection. All of the patients underwent a follow-up four-phase helical CT at 1 month after RF ablation, which was then repeated at 2-4 month intervals during a period of at least 12 months. The results of the contrast-enhanced ADI were compared with those of the follow-up CT in terms of the presence or absence of residual unablated tumor and local tumor progression in the treated lesions. RESULTS: On contrast-enhanced ADI, technical success was obtained in 94 (97%) of the 97 HCCs, while residual unablated tumors were found in three HCCs (3%). Two of the three tumors that were suspicious (was not proven) for incomplete ablation were subjected to additional RF ablation. The remaining one enhancing lesion that was suspicious of a residual tumor on contrast-enhanced ADI was revealed to be reactive hyperemia at the 1-month follow-up CT. Therefore; the diagnostic concordance between the contrast-enhanced ADI and 1-month follow-up CT was 99%. Of the 94 ablated HCCs without residual tumors on both the contrast-enhanced ADI and 1-month follow-up CT after the initial RF ablation, five (5%) had CT findings of local tumor progression at a subsequent follow-up CT. CONCLUSION: Despite its limitations in predicting local tumor progression in the treated tumors, contrast-enhanced ADI is potentially useful for evaluating the early therapeutic effect of percutaneous RF ablation for HCCs.

Adult↗

PubMed2004

Second harmonic transthoracic echocardiography: the new reference screening method for the detection of patent foramen ovale.

AIM: Transesophageal echocardiography (TEE) is still considered as the reference method for the non-invasive detection of right-to-left shunts. Echocardiographic laboratories are spending most of their time performing TEE studies to exclude a thromboembolic cardiac disease. In a considerable proportion of these patients the question can be simplified to exclude a PFO. Replacing these TEE studies by TTE would result in a considerable gain in time and money. We evaluated the value of transthoracic echocardiography with second harmonic imaging (TTE) (SH) and peripheral intravenous agitated saline solutions in the detection of patent foramen ovale (PFO) in a large cohort of patients. METHODS: In 256 consecutive patients, TEE and TTE (SH) with the consecutive administration of three intravenous contrast injections of agitated saline injections before the release phase of the Valsalva manoeuvre were performed. Semi-quantification and timing of contrast passage were assessed during both imaging modalities. A shunt was present if at least one imaging modality showed microbubbles appearing in the left atrium. PFO was defined when these bubbles appeared early and arteriovenous pulmonary malformations were suspected if bubbles appeared late after the opacification of the right atrium. Shunts were considered important when >20 bubbles were present in one frame in the left atrium or left ventricle. RESULTS: From the 256 patients, 60 presented a passage of contrast from the right to the left atrium in at least one imaging modality. PFO was detected by TEE in 53 patients and by TTE in 55 patients (sensitivity: 90.5% and specificity: 96.5% if TEE is accepted as the golden standard) (p>0.05). Considering only the important shunts TEE detected 39 important shunts and TTE 46 important shunts (sensitivity: 89.7% and specificity: 94.6%) (p>0.05). AV pulmonary malformations were detected by TEE in 7 patients and by TTE in 10 patients (sensitivity: 85.7% and specificity: 98.3%) (p>0.05). CONCLUSIONS: In this large cohort of patients TTE (SH) is as accurate as TEE for the detection of PFO and late right-to-left shunts. If the only purpose of TEE is the detection of PFO such as in young cryptogenic stroke patients and in divers, TEE can be replaced by TTE (SH).

Chi-Square Distribution↗

PubMed2004

Assessment of the physiologic significance of coronary disease with dipyridamole real-time myocardial contrast echocardiography. Comparison with technetium-99m sestamibi single-photon emission computed tomography and quantitative coronary angiography.

OBJECTIVES: The purposes of this study were to test whether quantitative real-time myocardial contrast echocardiography (RT-MCE) can detect coronary disease during pharmacologic stress and to compare this approach with single-photon emission computed tomography (SPECT). BACKGROUND: Assessing myocardial perfusion during stress is important for the diagnosis and risk stratification of patients with coronary disease. METHOD: Thirty-five patients referred for coronary angiography underwent RT-MCE and technetium-99m methoxyisobutylisonitrile (MIBI) SPECT at baseline and after 0.84 mg/kg dipyridamole. The modalities of RT-MCE and SPECT were analyzed both qualitatively and quantitatively. For this purpose, myocardial flow reserve was calculated from microbubble replenishment curves, and regional MIBI uptake was measured on circumferential profiles. Segments and vascular territories were categorized into five groups with increasing stenosis severity by quantitative coronary angiography. RESULTS: With dipyridamole, beta and A x beta increased in all but the highest stenosis severity group. The increase in beta and A x beta was significantly lower in territories supplied by stenotic arteries than in those supplied by arteries with <50% stenosis. Graded decreases in beta and A x beta reserves were noted with increasing stenosis severity. Using the cutoff value of 2.00 for beta reserve, quantitative RT-MCE correctly identified 97% of the territories supplied by significant stenoses and 82% of those supplied by normal arteries. In contrast, quantitative SPECT correctly identified only 71% of the territories supplied by significant stenoses and 81% of those supplied by normal arteries. CONCLUSIONS: This study shows that RT-MCE, with dipyridamole, can define the presence and severity of coronary disease in a manner that compares favorably with quantitative SPECT.

Adult↗

PubMed2004

Accuracy of dipyridamole myocardial contrast echocardiography for the detection of residual stenosis of the infarct-related artery and multivessel disease early after acute myocardial infarction.

OBJECTIVES: We aimed to evaluate the ability of vasodilator myocardial contrast echocardiography (MCE) to detect significant infarct-related artery (IRA) stenosis and multivessel disease (MVD) after thrombolysis. BACKGROUND: The detection of residual IRA stenosis subtending significant viable myocardium and the identification of MVD may help to triage patients who may benefit from mechanical revascularization after acute myocardial infarction (AMI) and thrombolysis. METHODS: Patients with AMI underwent low-power MCE at rest and after dipyridamole stress during SonoVue infusion seven to 10 days after thrombolysis. RESULTS: Of the 73 patients, 61 demonstrated significant myocardial viability, of whom 57 (93%) showed significant IRA stenosis. Sensitivities to detect >50% IRA stenosis and MVD were 88% and 72%, respectively. The accuracy of detecting significant coronary stenosis in the anterior (left anterior descending coronary artery) versus inferoposterior (right coronary artery/left circumflex artery) circulation was similar for both IRA (85% vs. 91%) and remote territories (91% vs. 81%). Quantitative peak contrast intensity (p = 0.02), microbubble velocity (p = 0.0001), and myocardial blood flow (p < 0.0001) were significantly lower in patients with significant coronary stenosis during dipyridamole compared with rest. Only beta reserve discriminated various grades of coronary stenosis. CONCLUSIONS: Use of MCE accurately predicted significant IRA stenosis and MVD after thrombolysis. This information is valuable for identifying patients who may benefit from mechanical revascularization.

Aged↗

PubMed2006

Clinical application of transcranial Doppler monitoring for embolic signals.

A major advantage of transcranial ultrasound is its suitability for continuous monitoring. Microembolic signals (MES) are brief, high-intensity transients that occur when particulate microemboli or gaseous microbubbles pass through the ultrasound beam. These MES have been detected in several clinical scenarios, but rarely in age-matched controls. The detection of MES provides important pathophysiological information in a variety of disorders, but their clinical importance and possible therapeutic implications are still under debate. The present article summarizes the significance of MES in different clinical settings and outlines some of the problems to be resolved so that transcranial ultrasound can be applied in clinical practice.

Animals↗

PubMed2005

A respiration-metabolism chamber system and a GC-MS method developed for studying exhalation of perfluorobutane in rats after intravenous injection of the ultrasound contrast agent Sonazoid.

Sonazoid is a new contrast agent for ultrasound imaging comprising an aqueous suspension of lipid-stabilised perfluorobutane (PFB) gas microbubbles. A respiration-metabolism chamber system was developed to collect exhaled air following intravenous administration of Sonazoid to rats. Analysis of PFB in the exhaled rat air was performed using a modified version of an earlier published method for blood samples, i.e. an automatic headspace gas chromatographic mass spectrometric (GC-MS) method using electron impact ionisation. The calibration standards were PFB diluted in air (2.5-1800 pg/ml). Perfluoropentane (PFP) was used as an internal standard and the MS detector was set to single ion monitoring of the base fragment ions of PFB (m/z 69 and 119) and PFP (m/z 69). The calibration curve, made by plotting the peak area ratios of PFB (m/z 69) to PFP (m/z 69) against the theoretical concentration of PFB, was fitted to a linear equation with weighting 1/y2 and found to be reproducible. The lower limit of quantification (LLOQ) was 2.5 pg PFB/ml. The between-day variation of the method was below 2.6% relative standard deviation (R.S.D.) and the within-day variation of the method was below 6.4% R.S.D. The accuracy of the method was evaluated and showed a relative error less than 5.2%. PFB was found to be stable for 14 days when stored in Tedlar sample bags at room temperature. An even lower detection limit may be obtained by using the more time-consuming process of solid-phase micro extraction; thus, by concentrating PFB on carboxen-PDMS fibres an LLOQ of 0.5 pg PFB/ml was obtained. When five rats were given an i.v. bolus injection of Sonazoid at a dose of 8 microl microbubbles/kg a mean recovery of 96% (range, 81-110%) was found during 24 h; more than 50% was exhaled during the first 30 min after injection.

Animals↗