Correlation between myocardial perfusion abnormalities detected with intermittent imaging using intravenous perfluorocarbon microbubbles and radioisotope imaging during high-dose dipyridamole stress echo

BACKGROUND: The clinical accuracy of myocardial contrast echocardiography (MCE) using intermittent harmonic imaging and intravenous perfluorocarbon containing microbubbles during dipyridamole stress has not been evaluated in a multicenter setting. HYPOTHESIS: The accuracy of dipyridamole stress contrast echo in the detection of coronary artery disease (CAD) using myocardial perfusion images is high in comparison with technetium-99 (99Tc) sestamibi single-photon emission computed tomography (MIBI SPECT) and increases the accuracy of wall motion data. METHODS: In 68 consecutive nonselected patients (46 men; mean age 66 years) from three different institutions in two countries. dipyridamole stress echo and SPECT with 99mTc MIBI were compared. Continuous intravenous (IV) infusion of perfluorocarbon exposed sonicated dextrose albumin (PESDA) (2-5 cc/min) was administered for baseline myocardial perfusion using triggered harmonic end systolic frames. Real-time digitized images were used for wall motion analysis. Dipyridamole was then injected in two steps: (1) 0.56 mg/kg for 3 min, (2) 0.28 mg/kg for 1 min, if the first step was negative for an inducible wall motion abnormality. After dipyridamole injection, myocardial contrast enhancement and wall motion were analyzed again by the same methodology. RESULTS: There were 35 patients with perfusion defects by SPECT. Wall motion was abnormal in 22, while MCE was abnormal in 32. Wall motion and MCE each had one false positive. The proportion of correctly assigned patients was significantly better with MCE than with wall motion (p = 0.03; chi square test). CONCLUSIONS: Myocardial contrast echocardiography, using intermittent harmonic imaging and intravenous perfluorocarbon containing microbubbles, is a very effective method for detecting coronary artery disease during dipyridamole stress echo.     

Detection of angiographically significant coronary artery disease with accelerated intermittent imaging after intravenous administration of ultrasound contrast material

BACKGROUND: Accelerated intermittent harmonic imaging (AII) is used to detect myocardial perfusion abnormalities after intravenous injection of ultrasound contrast medium. A low mechanical index and frame rates of 10 to 20 Hz are used to allow simultaneous wall motion analysis. The purpose of this study was to determine whether the myocardial contrast enhancement achieved with AII can be used to detect angiographically significant coronary artery disease during stress echocardiography. METHODS: We gave intravenous perfluorocarbon containing microbubbles to 45 patients (total of 270 regions) during dobutamine (n = 27) or exercise (n = 18) stress testing with AII. Quantitative angiography was performed on all patients after the stress echocardiograms were interpreted. RESULTS: Quantitative angiography showed >50% diameter stenosis of at least 1 vessel in 32 patients (total of 118 regions). There were visually evident contrast defects in 100 (85%) of these regions, and wall motion was abnormal in 64 (54%). Overall, there was agreement between regional perfusion and quantitative angiographic findings in 217 of the 270 regions (kappa = 0.61; 80% agreement). Agreement with findings at quantitative angiography was good for both dobutamine stress (kappa = 0.66; 83% agreement) and exercise (kappa = 0.53; 77% agreement). The greatest incremental benefit of AII versus wall motion was gained during dobutamine stress. The contrast studies depicted 90% of the regions supplied by a vessel with >50% stenosis, whereas wall motion depicted only 32% (P =.001). CONCLUSIONS: The results of this study indicated that accelerated intermittent perfusion imaging during stress echocardiography can improve the sensitivity of the study in detecting angiographically significant coronary artery disease, especially during dobutamine stress.     

Real-time assessment of myocardial perfusion and wall motion during bicycle and treadmill exercise echocardiography: comparison with single photon emission computed tomography.

OBJECTIVES: We sought to determine the feasibility and accuracy of real-time imaging of myocardial contrast echocardiography (MCE) in detecting myocardial perfusion defects during exercise echocardiography compared with radionuclide tomography. BACKGROUND: Ultrasound imaging at a low mechanical index and frame rate (10 to 20 Hz) after intravenous injections of perfluorocarbon containing microbubbles has the potential to evaluate myocardial perfusion and wall motion (WVM) simultaneously and in real time. METHODS: One hundred consecutive patients with intermediate-to-high probability of coronary artery disease underwent treadmill (n = 50) or supine bicycle (n = 50) exercise echocardiography. Segmental perfusion with MCE and WM w ere assessed in real time before and at peak exercise using low mechanical index (0.3) and frame rates of 10 to 20 Hz after 0.3 ml bolus injections of intravenous Optison (Mallinckrodt Inc., San Diego, California). All patients had a dual isotope (rest thallium-201, stress sestamibi) study performed during the same exercise session, and 44 patients had subsequent quantitative coronary angiography. RESULTS: In the 100 patients, agreement between MCE and single photon emission computed tomography (SPECT) was 76%, while it was 88% between MCE and WM assessment. Compared with quantitative angiography, sensitivity of MCE, SPECT and WM was comparable (75%), with a specificity ranging from 81% to 100%. The combination of MCE and WM had the best balance between sensitivity and specificity (86% and 88%,respectively) with the highest accuracy (86%). CONCLUSIONS: The real-time assessment of myocardial perfusion during exercise stress echocardiography can be achieved with imaging at low mechanical index and frame rates. The combination of WM and MCE correlates well with SPECT and is a promising important addition to conventional stress echocardiography.     

Effect of a Residual Stenosis by Quantitative Angiography on the Myocardial Contrast Defect Observed Following Coronary Reperfusion Using Intermittent Harmonic Ultrasound Imaging and Intravenous Perfluorocarbon Ultrasound Contrast

Intermittent harmonic imaging following intravenously injected perfluorocarbon-containing microbubbles can detect myocardial perfusion abnormalities caused by ischemia. It is unknown whether this technique can differentiate viable, ischemic myocardium from infarcted myocardium immediately following coronary reperfusion. The objective of this paper was to determine whether intermittent harmonic imaging with intravenous microbubbles could define myocardial perfusion abnormalities following reperfusion. In 26 dogs, a prolonged total coronary occlusion (mean occlusion time 2.1 ± 0.4 hours) was followed by coronary reperfusion. Wall thickening (WT) and peak myocardial video intensity (PMVI) within and outside the risk area (PMVI ratio) were measured following intravenous perfluorocarbon microbubbles under resting conditions and during a 5 μ/kg per minute dobutamine [low dose dobutamine (LDD)] infusion in the presence and absence of a ≥ 50% diameter stenosis in the reperfused vessel. Infarct size was determined postmortem. The resting contrast defect in all dogs correlated closely (r = 0.93) with infarct size when no residual stenosis was present but correlated more closely with risk area (r = 0.88) when a ± 50% diameter residual stenosis was present. In dogs with infarction involving > 50% of the risk area, the PMVI ratio was lower under resting conditions (0.51 ± 0.27) than in dogs with no or partial infarction when no residual stenosis was present. However, in dogs with no or partial infarction, the PMVI ratio fell significantly when a ≥ 50% diameter stenosis was present, both under resting conditions and during LDD. We conclude that the myocardial contrast defect observed with intermittent harmonic imaging and intravenous ultrasound contrast is affected by both the infarct size and the presence of a significant residual stenosis.     

Contrast echocardiography for myocardial perfusion imaging using intravenous agents: progress and promises.

AIMS: This article is a convenient overview to assist the interested echocardiographist towards acquiring his own experience in the field of myocardial perfusion imaging using intravenous contrast agents. This goal is now pursued in many centres, since contrast echo holds the advantages of cardiac ultrasound (non-invasiveness, high spatial and temporal resolution, wide availability, use of non-ionizing radiation), and because a variety of transpulmonary agents-together with a spectrum of imaging modalities-are becoming available. METHODS AND RESULTS: Many technical considerations need to be addressed for optimal myocardial perfusion imaging: characteristics of the contrast medium (air-filled or perfluorocarbon filled and/or encapsulated agents), modality of administration (bolus injection or continuous infusion) and interaction between microbubbles and ultrasound (dependency on power output). Moreover, intermittent harmonic imaging, intermittent harmonic power Doppler, pulse inversion and amplitude modulation imaging have all been developed to enhance microbubble detection over myocardial tissue. These new acquisition modalities also yield specific artifacts impacting on myocardial perfusion assessment. Finally, acute myocardial infarction and chronic ischaemic heart disease (at baseline and during stress) are the most studied clinical models for perfusion imaging with contrast echo, and are reviewed in this article. CONCLUSION: Perfusion imaging with intravenous contrast agents has never been as close to widespread clinical use as it is today, but many methodological issues remain unsettled before the wish of the contrast echocardiographist comes true: that is, a cheap, user-friendly and widely available technology that would disclose new information in echocardiography.     

Clinical experience in the detection of coronary artery disease with myocardial contrast echocardiography

Myocardial contrast enhancement following intravenous infusions or injections of perfluorocarbon-containing microbubbles has now been observed consistently in humans. Currently, the major challenge facing us is interpreting accurately what we see. The myocardial contrast patterns we observe have, thus far, been shown to detect myocardial perfusion abnormalities during dipyridamole, adenosine, and dobutamine stress echocardiography. They also have been shown to detect zones of no reflow following coronary revascularization in patients with acute myocardial infarction. These preliminary data will require validation in larger multicenter clinical studies.     

Imaging of Myocardial Perfusion with SonoVue™ in Patients with a Prior Myocardial Infarction

Myocardial contrast echocardiography (MCE) is an evolving noninvasive imaging technique that can be used to assess regional myocardial perfusion. MCE relies upon the detection of nonlinear ultrasound signal from gas-filled microbubbles during their microvascular transit, resulting in tissue opacification. Provided that the relation between myocardial microbubble concentration and video intensity (VI) is within the linear range, VI measured from any myocardial region reflects the relative tissue concentration of microbubbles, which is influenced by three factors: (1) microbubble concentration in blood; (2) the myocardial blood volume fraction; and (3) microbubble destruction that occurs within the ultrasound beam. In this article, we discuss how these three factors may influence myocardial perfusion information provided by MCE and highlight the importance of image processing. In order to illustrate these concepts, we examine data obtained during perfusion imaging in patients with prior myocardial infarction using intermittent harmonic imaging at various ultrasound pulsing intervals (PIs) during bolus and continuous venous infusions of a second-generation microbubble agent (SonoVue™). Our results suggest that evaluation of resting perfusion is most accurate when both myocardial blood volume and blood velocity are assessed. This information is provided only with continuous infusions of microbubbles during imaging protocols that vary the ultrasound PI.     

Newly developed technology for intravenous contrast echocardiography

Until now we have not been able to employ a contrast enhancer for ultrasonic echocardiography at the everyday clinical level because the agent itself, composed of microbubbles, was too easily dispersed or even destroyed by several factors. However, contrast echocardiography has made a great leap forward with major developments on two fronts; the application of some new intravenous contrast enhancers, and newly developed machine technology permitting second harmonic imaging, intermittent or triggered imaging, pulse inversion harmonic imaging, and so on. New contrast enhancing agents are proving durability enough to permit greatly enhanced imaging for more than several minutes after injection. Recent new echocontrast specific imaging allows real-time visualizing of myocardial perfusion and assessment of myocardial function.     

Clinical Experience with SonoVue in Myocardial Perfusion Imaging

Ultrasound-enhancing agents have the potential to evaluate myocardial perfusion, adding a new dimension to echocardiography. This article summarizes the clinical studies involving SonoVue, a new intravenous ultrasound contrast agent, in assessing myocardial perfusion. Safe and well tolerated, SonoVue coupled with echocardiography has the capability to identify perfusion abnormalities, as confirmed by scintigraphic imaging. While the optimal modalities for ultrasound perfusion assessment are not yet determined, numerous technical advances have been introduced: continuous infusion or slow intravenous administration of the agent, harmonic intermittent imaging, pulse inversion, background subtraction, color coding, and others. SonoVue is a promising new agent in the booming field of myocardial contrast echocardiography.     

Real-time perfusion imaging with low mechanical index pulse inversion Doppler imaging.

OBJECTIVES: We sought to determine how successful pulse inversion Doppler (PID) imaging would be in detecting myocardial perfusion defects during dobutamine stress echocardiography. BACKGROUND: By transmitting multiple pulses of alternating polarity (PID) at a low mechanical index, myocardial contrast enhancement from intravenously injected microbubbles can be detected using real-time frame rates. Pulse inversion Doppler imaging was performed in 117 patients during dobutamine stress echocardiography by using an intravenous bolus of a perfluorocarbon-filled, albumin-(Optison: n = 98) or liposome- (Definity: n = 19) encapsulated microbubble and a mechanical index of <0.3. The visual identification of myocardial contrast defects and wall motion abnormalities was determined by blinded review. Forty of the patients had quantitative angiography (QA) performed to correlate territorial contrast defects with stenosis diameter >50%. RESULTS: There was a virtual absence of signal from the myocardium before contrast injections in all patients. Bright myocardial opacification at peak stress was observed in at least one coronary artery territory at frame rates up to 25 Hz in 114 of the 117 patients during dobutamine stress echocardiography. Regional myocardial contrast defects at peak stress were observed in all 30 patients with >50% stenosis in at least one vessel (13 with single-vessel and 17 with multivessel disease). Contrast defects were observed in 17 territories subtended by >50% diameter stenosis that had normal wall motion at peak stress. Overall agreement between QA and myocardial contrast enhancement on a territorial basis was 83%, as compared with 72% for wall motion. CONCLUSIONS: Pulse inversion Doppler imaging allows the detection of myocardial perfusion abnormalities in real-time during stress echocardiography and will further add to the quality and sensitivity of this test.     

Assessment of regional myocardial hypoperfusion with myocardial contrast echocardiography using intravenous bolus application in patients with acute chest pain: a double case report.

Myocardial contrast echocardiography using power Doppler harmonic imaging is able to document myocardial hypoperfusion. Two case reports demonstrate the potential of intravenous bolus application of microbubbles in patients with acute chest pain due to myocardial ischaemia to detect regional low flow conditions. The case reports will focus on the necessity to present Doppler intensity kinetics by Doppler intensity vs time plots or coloured M-modes to present the data more objectively. In addition, the hypoperfusion detected with myocardial contrast echocardiography via bolus injection of microbubbles can only be proven by changes of regional perfusion between repetitive myocardial contrast echocardiography measurements or by additional perfusion analysis, e.g. by scintiscanning.     

Detection of Myocardial Perfusion in Multiple Echocardiographic Windows With One Intravenous Injection of Microbubbles Using Transient Response Second Harmonic Imaging

Objectives. The purpose of this study was to prove that transient response harmonic imaging could detect normal and abnormal myocardial perfusion in multiple echocardiographic windows with one intravenous injection of microbubbles in humans.Background. Myocardial ultrasound contrast can be produced from intravenous perfluorocarbon-exposed sonicated dextrose albumin, and ultrasound can be significantly improved by briefly suspending the interval between frame rates. Whether this contrast can noninvasively quantify myocardial perfusion in humans is unknown.Methods. In 28 patients, harmonic transient response imaging was used to image the heart in multiple different imaging planes after one intravenous injection of ultrasound contrast agent. Twenty-five of these 28 patients had a repeat injection during dipyridamole stress. In the primary view, the ultrasound transmission rate was one frame per cardiac cycle; in secondary and tertiary views, the transmission rate was once every multiple cardiac cycles. Regional myocardial contrast was visually assessed and quantified off-line. Quantitative rest thallium and dipyridamole stress sestamibi imaging was also performed.Results. Perfusion abnormalities were evident in the secondary and tertiary views only with one frame every multiple cardiac cycles. Regional peak myocardial videointensity (PMVI) correlated closely with regional tracer uptake in individual patients both at rest (r = 0.84) and during stress (r = 0.88). A PMVI ratio (abnormal region divided by the region with highest nuclear uptake) <0.6 in any view had a 92% sensitivity and a 84% specificity in identifying a regional nuclear perfusion abnormality.Conclusions. Transient response imaging produces myocardial contrast in multiple views with one intravenous injection of contrast agent and can accurately identify regional myocardial perfusion abnormalities.(J Am Coll Cardiol 1997;29:791–9)     

Myocardial Perfusion Abnormalities by Intravenous Administration of the Contrast Agent NC100100 in an Experimental Model of Coronary Artery Thrombosis and Reperfusion

The aim of this study was to evaluate a second-generation echo contrast agent (NC100100) for the study of myocardial perfusion. In eight anesthetized open-chest dogs, this agent was injected intravenously under baseline conditions, during acute coronary thrombosis, and after reperfusion, using both fundamental (FI) and harmonic (HI) imaging, both continuous and intermittent imaging, and both ultrasound (US) and integrated backscatter (IBS) imaging. Contrast injections did not modify the hemodynamic parameters. With all imaging modalities, myocardial contrast enhancement (MCE) was higher with intermittent than with continuous imaging (134 vs 82 gray level/pixel using FI, P = 0.02; 62 vs 32 acoustic units using US HI, P = 0.02; and 52 vs 12 dB using IBS, P = 0.05). MCE equally increased using either US or IBS imaging. The accuracy of MCE in detecting perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis was very good (sensitivity and specificity = 93% and 95% and 89% and 93%, respectively). The extent of myocardial perfusion defects by echo contrast showed a closer correlation with microspheres using HI (r = 0.82) than FI (r = 0.53). Thus, the intravenous administration of NC100100 during intermittent HI allows myocardial perfusion abnormalities to be accurately detected during acute myocardial infarction.     

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 collateral development during chronic ischemia: serial assessment using harmonic myocardial contrast echocardiography

OBJECTIVES: We sought to characterize collateral development in an experimental model of chronic myocardial ischemia by using myocardial contrast echocardiography (MCE). BACKGROUND: Coronary collaterals maintain myocyte viability during myocardial ischemia. The natural history and determinants of collateral development are difficult to study serially in vivo. METHODS: The left anterior descending coronary artery (LAD) in nine dogs was encircled (day 0) with a hydraulic occluder and ameroid constrictor to enable reversible and gradual total LAD occlusion, respectively. Myocardial contrast echocardiography was performed using intravenous injection of perfluorocarbon gas-containing microbubbles during two-dimensional harmonic echocardiographic imaging. Myocardial contrast echocardiography images and radiolabeled microsphere flow measurements were obtained during transient LAD occlusion on day 0. Over the ensuing six weeks, MCE imaging was performed during LAD occlusion at 10-day intervals. RESULTS: Myocardial contrast echocardiography risk area size (expressed as a percent of the left ventricular short axis slice) decreased over the course of six weeks (32%+/-3% on day 0, 21% +/-3% at day 10, 5+/-3% at day 20, 1%+/-1% at day 30 and 1%+/-1% at day 42, p< or =0.001 vs. day 0). Radiolabeled microsphere-derived LAD flow, normalized to left circumflex flow, correspondingly increased between day 0 and day 42 (0.14+/-0.02 to 0.90+/-0.07, p<0.02). CONCLUSIONS: Collateral development occurs relatively early and rapidly in this chronic canine model. Myocardial contrast echocardiography using harmonic imaging and intravenous injection of microbubbles can uniquely track the spatial and temporal course of collateral growth, and may be a powerful tool for noninvasively mapping the efficacy of therapeutic angiogenic strategies in vivo.     

Comparison of dobutamine stress echocardiography with and without real-time perfusion imaging for detection of coronary artery disease

In a pilot study of 27 patients, those who presented with chest pain underwent 2 dobutamine stress echocardiographic studies, 1 with high mechanical index harmonic imaging to analyze wall motion without contrast and 1 with real-time low mechanical index perfusion imaging with intravenous Optison to assess myocardial perfusion and wall motion. All patients then underwent quantitative coronary angiography. Two independent reviewers demonstrated an improvement in sensitivity when analyzing myocardial perfusion. In the 21 patients who had significant coronary stenoses, 14 had abnormal myocardial perfusion detected at peak stress and 7 had abnormal wall motion detected by standard dobutamine stress echocardiography. There was decreased specificity with perfusion imaging by 1 reviewer. The addition of real-time perfusion imaging after intravenous contrast during dobutamine stress echocardiography has the potential to improve detection of coronary artery disease.     

Myocardial perfusion by contrast echocardiography: diagnosis of coronary artery disease using contrast-enhanced stress echocardiography and assessment of coronary anatomy and flow reserve

The advent of intravenous contrast agents, and newer ultrasound technology to enhance their detection, promises to improve and augment our conventional stress echocardiographic practice by improving diagnostic accuracy and providing novel information regarding myocardial perfusion and functional assessment of the coronary vasculature. The combination of intravenous contrast and harmonic stress echocardiography is a powerful tool for improved wall motion analysis through enhanced image quality, routinely permitting the evaluation of patients with suboptimal images. In this era of cost containment, we await studies in large populations addressing resource utilization and cost-effectiveness to determine if, indeed, all patients presenting with stress echocardiography should receive contrast. Myocardial perfusion can be observed using the technique, but the complex interactions of microbubbles and ultrasound in patients must be understood more fully before its implementation becomes routine practice. Non-invasive imaging of coronary arteries using contrast-enhanced transthoracic harmonic echo/Doppler promises to expand the field of diagnostic and experimental echocardiography, bringing new insight into the pathophysiology of ischemic and non-ischemic heart disease. The continued development of newer contrast agents and refinement of ultrasound imaging equipment ensures that the applications of contrast echocardiography in the assessment of CAD will continue to increase.     

A method of detecting and quantifying severity of myocardial perfusion defects with intravenous ultrasound contrast and breath holding during stress echocardiography

Although breath holding is commonly used to improve and maintain image quality during stress echocardiography, its effects on the qualitative and quantitative analysis of myocardial contrast enhancement (MCE) following intravenously injected microbubbles is unknown. The purpose of this study was to determine how breath holding affects MCE following either an intravenous bolus or continuous infusion of perfluorocarbon containing microbubbles. In 48 patients, intravenous Optison was given at peak dobutamine stress to assess myocardial perfusion. The degree of myocardial opacification was assessed immediately following a breath hold in inspiration (BH(ini)), at the end of a breath hold (BH(term)), and following expiration and a subsequent second breath hold (BH(reinsp)). Pulmonary venous time velocity integrals were recorded during these different phases as well. Eleven patients had quantitative coronary angiography. Mean duration of the breath hold was 7 +/- 1 seconds. Pulmonary venous return fell by 29% +/- 18% at BH(term) (P < 0.001). There was complete disappearance of MCE at BH(term) in 27 of 35 bolus injection patients at peak stress, and no return of MCE following flash destruction during breath holding in 11 of 13 patients receiving continuous infusions. BH(reinsp) resulted in a boluslike return of contrast, with a transient, bright MCE in 44 of 48 patients, and a time intensity plot that resembled a gamma variate function. Perfusion defects were visualized in 25 patients during BH(ini) and 28 patients during BH(reinsp). Coronary artery territory agreement between perfusion assessed during BH(ini) and BH(reinsp) and quantitative coronary angiography was 76% and 81%, respectively.     

Contrast echocardiography

The intravenous application of an ultrasound contrast agent induces enhanced display of blood in all its pathways. Within cardiology, this principle is mainly utilized for signal enhancement of color Doppler and spectral Doppler in order to improve quantification of congenital and acquired valvular lesions and also for improved endocardial delineation during stress tests and in the evaluation of LV function. The new domaine of myocardial perfusion imaging by contrast echocardiography, however, needed profound technical developments before realization of the clinical potential could even be conceived. These are based on the complex reactions of microbubbbles in the acoustic field in order to allow the sensitive and bubble specific display of intramyocardial contrast effects. The presently available acquisition techniques, second harmonic imaging and harmonic power Doppler, demonstrate significant improvements if compared to traditional fundamental 2-d echocardiography; however, they are still subjected to important limitations. There are many anatomical, physiological, and technical reasons for insufficient display of intramyocardial microbubbles, the most important one being attenuation. It is hoped that the most recently developed imaging modality, pulse inversion technique, allows the necessary diagnostic accuracy and reproducibility in myocardial perfusion imaging.     

Evaluation of myocardial, hepatic, and renal perfusion in a variety of clinical conditions using an intravenous ultrasound contrast agent (Optison) and second harmonic imaging

OBJECTIVE: To assess the potential of intravenous Optison, a second generation ultrasound contrast agent, and various ultrasound imaging modes to determine myocardial, kidney, and liver perfusion in normal subjects and patients with left ventricular dysfunction or chronic pulmonary disease together with renal or hepatic dysfunction. METHODS: Five normal subjects and 20 patients underwent grey scale echocardiographic imaging of myocardium, kidney, and liver during 505 intravenous injections of Optison. Images were assessed qualitatively by two independent observers and quantitatively using video densitometry to determine the peak contrast enhancement effect. RESULTS: Qualitative analysis showed that intermittent harmonic imaging was superior to either conventional fundamental or continuous harmonic imaging for all organs. Quantitative analysis showed that the peak change in echocardiographic intensity v baseline during continuous harmonic imaging was 11 units for myocardium (p < 0.03), 7 units for kidney (NS), and 14 units for liver (p < 0.05). During intermittent harmonic imaging the peak change was significantly greater, being 33 units for myocardium (p < 0.0001), 24 units for kidney (p < 0.0002), and 16 units for liver (p < 0.001). CONCLUSIONS: Organ tissue perfusion can be demonstrated following intravenous injection of Optison, particularly when used in combination with intermittent harmonic imaging techniques. This contrast agent is effective in a variety of clinical conditions.