Quantification of images obtained during myocardial contrast echocardiography

Myocardial blood volume reserve by intravenous contrast echocardiography predicts improvement in left ventricular function in patients with nonischemic dilated cardiomyopathy

BACKGROUND

Impaired myocardial perfusion has been shown in nonischemic dilated cardiomyopathy (DCM). Intravenous myocardial contrast echocardiography (MCE) has been introduced to examine myocardial blood volume (MBV) noninvasively. This study was designed to evaluate if MBV reserve assessed by intravenous MCE with adenosine triphosphate (ATP) can predict efficacy of optimal medical therapy in patients with DCM.

METHODS AND RESULTS

Fifteen DCM patients and 8 control subjects underwent conventional echocardiography and intravenous MCE. We obtained the change in peak contrast integrated backscatter intensity (∆PI) by ATP on the left ventricular (LV) anteroseptal myocardium. After 3 months of optimal medical therapy in DCM patients, we reperformed conventional echocardiography. A good responder to therapy was defined as a decrease in LVDd >5 mm to final LVDd <55 mm and increase in LVEF >20 % to final LVEF >45 %. In DCM patients, ∆PI was lower compared to controls (p < 0.001). Good responders to therapy (n = 6) had higher ∆PI than poor responders (n = 9) (p < 0.05).

CONCLUSIONS

The present study demonstrates that the response to the medical therapy in DCM is predicted by the assessment of dilator reserve in MBV. Intravenous MCE with ATP may provide useful information to evaluate MBV reserve.

Phasic changes in arterial blood volume is influenced by collateral blood flow: implications for the quantification of coronary stenosis at rest

BACKGROUND

The systolic to diastolic arteriolar blood volume (aBV) ratio derived using myocardial contrast echocardiography (MCE) can identify the presence of coronary stenosis at rest. There are some patients with moderate to severe coronary stenosis who nonetheless exhibit a normal systolic to disatolic aBV ratio.

AIM

To test the hypothesis that collateral blood flow influences the systolic to diastolic aBV ratio. MCE-defined phasic changes in aBV were recorded at baseline and up to 2 degrees of non-critical stenosis in 12 dogs. Measurements were made from MCE-defined collateralised and non-collateralised portions of the left anterior descending arterial bed.

RESULTS

Increases in both systolic and diastolic aBV were noted in the non-collateralised region with increasing degrees of stenosis. Although these increases in the absolute values did not reach statistical significance, the systolic to diastolic aBV signal ratio in the non-collateralised bed increased significantly between stages (analysis of variance, p = 0.003). In comparison, in the collateralised bed neither the absolute systolic nor diastolic aBV signals changed with increasing degrees of stenosis. Consequently, the aBV signal ratio between systole and diastole also did not change in this bed.

CONCLUSION

Phasic changes in aBV are influenced by the degree of collateral blood flow. Thus, if the region of interest is not placed in the centre of the vascular bed, the degree of stenosis may be underestimated by the systolic to diastolic aBV ratio. On the other hand, as extensive collateralisation may indicate excellent prognosis, this ratio may provide prognostic information independent of the coronary anatomy.

The powerful microbubble: from bench to bedside, from intravascular indicator to therapeutic delivery system, and beyond

This review discusses the development, current applications, and therapeutic potential of ultrasound contrast agents. Microbubbles containing gases act as true, intravascular indicators, permitting a noninvasive, quantitative analysis of the spatial and temporal heterogeneity of blood flow and volumes within the microvasculature. These shelled microbubbles are near-perfect reflectors of acoustic ultrasound energy and, when injected intravenously into the bloodstream, reflect ultrasound waves within the capillaries without disrupting the local environment. Accordingly, microbubble ultrasound contrast agents are clinically useful in enhancing ultrasound images and improving the accuracy of diagnoses. More recently, ultrasound contrast agents have been used to directly visualize the vasa vasorum and neovascularization of atherosclerotic carotid artery plaques, thus suggesting a new paradigm for diagnosis and treatment of atherosclerosis. Future applications of these microscopic agents include the deliver of site-specific therapy to targeted organs in the body. Medical therapies may use these microbubbles as carriers for newer therapeutic options.

Evaluation of myocardial perfusion with grey-scale ultra-harmonic and multiple-frame triggering. The need for quantification

BACKGROUND AND OBJECTIVE

Contrast echocardiography has been recently introduced as a new technique for evaluating myocardial perfusion in a qualitative basis. The objective of this study was to test whether a visual subjective evaluation of myocardial perfusion by myocardial contrast echocardiography adequately matches the data obtained with an off-line quantification of myocardial perfusion.

METHODS

Sixty-one myocardial segments were evaluated by myocardial contrast echocardiography with Ultra-harmonic and Multiframe Triggering in 11 patients 3-7 days after an anterior myocardial infarction, using SH-U 563A (Levovistâ, Schering AG, Berlin, Germany) as contrast agent. Myocardial perfusion was classified as grade 1 (absent), 2 (patchy or incomplete) and 3 (complete) in each segment. The quantitative analysis was performed off-line by a different investigator blinded to the qualitative evaluation, using a commercially available software. The quantitative data on grey-scale obtained were compared between grade 1, 2 and 3 segments.

RESULTS

Of the 61 segments, 45 (73.8%) were classified as grade 3, whereas the remaining 16 (26.2%) were considered to be abnormally perfused (grade 2: n=12, 19.6%; grade 1: n=4, 6.6%). Segments with grade 1 perfusion had a significantly higher grey-scale value (123.6 +/- 41.3 vs. 70.1 +/- 34.3, p=0.004). However, there were no significant differences between segments with perfusion grade 2 and 3 (76.8 +/- 33.2 vs. 68.3 +/- 34.8, p=0.452).

CONCLUSION

Qualitative assessment of myocardial perfusion by Ultra-harmonic and Multiframe Triggering is of limited value, since only myocardial segments with absent perfusion may be reliably identified. This findings support the need of quantification in the evaluation of myocardial perfusion by contrast echocardiography.

Dobutamine versus dipyridamole for inducing reversible perfusion defects in chronic multivessel coronary artery stenosis

OBJECTIVES

We hypothesized that, although the effects of dipyridamole and dobutamine on myocardial blood volume (MBV) and mean microbubble velocity (VEL) are different, the magnitude of perfusion deficit during both forms of stress is the same because both drugs unmask abnormal myocardial blood flow (MBF) reserve.

BACKGROUND

Both dipyridamole and dobutamine are used clinically as pharmacologic stress agents to induce reversible perfusion defects in patients with chronic coronary artery disease (CAD), but the basis for doing so for dobutamine is not clear.

METHODS

Eleven chronically instrumented closed-chest dogs with multivessel coronary stenosis were studied. Hemodynamics, radiolabeled microsphere-derived MBF, and myocardial contrast echocardiography (MCE)-derived myocardial perfusion were measured at rest, after dipyridamole infusion (0.56 mg x kg(-1)), and at peak dobutamine dose (either 30 or 40 microg x kg(-1) x min(-1)). Abnormal beds were defined as those demonstrating an MBF reserve <3 with dipyridamole.

RESULTS

In the presence of either drug, MBV increased more in the normal bed than in the abnormal bed, but the increase was higher in both beds with dobutamine than with dipyridamole. The slope of the relationship between MBF reserve and MBV reserve was greater during dobutamine than dipyridamole (p < 0.05). The converse was true for VEL reserve (p < 0.05). Consequently, the relationship between the ratios of either variable, or the product of the two, between the abnormal bed and normal bed was similar for both drugs.

CONCLUSIONS

Although the effects of dipyridamole and dobutamine on MBV and VEL are different, both are equally effective in detecting physiologically relevant coronary stenoses on MCE. Both can therefore be used interchangeably with myocardial perfusion imaging for the detection of CAD.

Rapid quantitative assessment of myocardial perfusion: spectral analysis of myocardial contrast echocardiographic images

We described a novel rapid spectral analysis technique performed on raw digital in-phase quadrature (IQ) data that quantitatively differentiated perfused from nonperfused myocardium based on the simultaneous comparison of local fundamental and harmonic frequency band intensity levels. In open-chest pigs after ligation of the left anterior descending coronary artery (LAD) and continuous venous contrast infusion, the fundamental-to-harmonic intensity ratio (FHIR) for samples placed within the left ventricular (LV) cavity (10.8 +/- 1.7 dB) and perfused myocardium (13.7 +/- 1.6 dB) were significantly (P <.001) lower than for nonperfused myocardium (27.1 +/- 2.9 dB). In attenuated images, the FHIR for the LV cavity and perfused myocardium were also significantly (P <.05) lower than for the nonperfused myocardium (21.4 +/- 3.0 dB, 34.4 +/- 3.2 dB, and 40.2 +/- 4.4 dB, respectively). Spectral properties of contrast microbubbles, as characterized by the FHIR, allow for rapid quantitative assessment of myocardial perfusion from data contained in a single-image frame, without requiring background image subtraction and image averaging.

Detection and quantification of coronary stenosis severity with myocardial contrast echocardiography

The development of microbubble contrast agents and new imaging modalities now allows the assessment of myocardial perfusion during echocardiography. These microbubbles are excellent tracers of red blood cell kinetics. Apart from providing a spatial assessment of myocardial perfusion, myocardial contrast echocardiography (MCE) can also be used to quantify the 2 specific components of myocardial blood flow-flow velocity and myocardial blood volume. The method to quantify myocardial blood flow velocity is based on rapid destruction of microbubbles by ultrasound, and subsequent assessment of the rate of replenishment of microbubbles into the myocardial microcirculation within the ultrasound beam elevation. Assessment of steady state myocardial video intensity (VI) provides a measure of myocardial or capillary blood volume. Perfusion defects that develop distal to a stenosis during hyperemia are therefore due to capillary derecruitment. We have shown that the degree of derecruitment (and therefore the severity of a perfusion defect) is proportional to stenosis severity. Because the capillary bed also provides the greatest resistance to hyperemic flow, decreases in capillary blood volume distal to a stenosis during hyperemia result in increases in microvascular resistance, which is the mechanism underlying the progressive decrease in flow reserve in the presence of a stenosis. Consequently, both the severity of a perfusion defect and quantification of abnormal myocardial blood flow reserve on MCE can be used to determine stenosis severity. As imaging methods with MCE continue to be refined, the optimal imaging algorithms for clinical practice still need to be determined. MCE, however, holds promise as a noninvasive, instantaneous, on-line method for the detection and quantification of coronary artery disease.

Assessment of myocardial perfusion by myocardial contrast echocardiography using harmonic power and the transvenous contrast agent SHU 563A in acute coronary occlusion and after reperfusion

BACKGROUND

Harmonic power Doppler imaging is a novel technique for the assessment of myocardial perfusion by contrast echocardiography. In this study, we examined whether myocardial contrast echocardiography using harmonic power Doppler and the new transvenous contrast agent SHU 563A can identify myocardial perfusion defects during coronary occlusion and reperfusion.

METHODS

To assess the potential of this technique, we occluded either the left anterior descending coronary artery or the circumflex coronary artery for 2 to 3 h followed by 1 h reperfusion in 10 dogs in an open chest model. After transvenous administration of SHU 563A, an air-filled, polymeric contrast agent, myocardial contrast echocardiography was performed in short and long axis views with triggered harmonic power Doppler imaging after coronary occlusion and reperfusion. Post-mortem triphenyl tetrazolium chloride staining was performed to verify infarction. Harmonic power Doppler and anatomic data were analyzed by independent observers.

RESULTS

During coronary occlusion, harmonic power Doppler showed perfusion defects in all 10 dogs. The defect size in the short axis view at papillary muscle level ranged 4-51% (14+/-13%) and 3-43% (16+/-10%) in the long axis view (% total LV slice area). After reperfusion (1 h) and infusion of dipyridamole (0.56 mg/kg), power Doppler demonstrated perfusion defects in seven dogs: 0-20% (9+/-8%) (short axis view) and 0-48% (13+/-14%) (long axis view). Five dogs showed anatomic infarction. The anatomic infarct area was 0-18% (6+/-8%) (slices corresponding to the echocardiographic short axis images). Perfusion defect size by harmonic power Doppler correlated well with residual infarct size (r=0.82, P<0.01).

CONCLUSIONS

Myocardial contrast echocardiography using harmonic power Doppler and the new contrast agent SHU 563A accurately displays perfusion defects during acute coronary occlusion and after reperfusion. The site and size of residual myocardial infarction is reliably identified on line, in color. This approach has excellent potential for clinical application.

Noninvasive ultrasound imaging of inflammation using microbubbles targeted to activated leukocytes

BACKGROUND

Lipid microbubbles used for perfusion imaging with ultrasound are retained within inflamed tissue because of complement-mediated attachment to leukocytes within venules. We hypothesized that incorporation of phosphatidylserine (PS) into the microbubble shell may enhance these interactions by amplifying complement activation and thereby allow ultrasound imaging of inflammation.

METHODS AND RESULTS

In 6 mice, intravital microscopy of tissue necrosis factor-alpha-treated cremaster muscle was performed to assess the microvascular behavior of fluorescein-labeled lipid microbubbles with and without PS in the shell. Ten minutes after intravenous injection, microbubble attachment to leukocytes within inflamed venules was greater for PS-containing than for standard lipid microbubbles (20+/-4 versus 10+/-3 per 20 optical fields, P<0.05). The ultrasound signal from retained microbubbles was assessed in the kidneys of 6 mice undergoing renal ischemia-reperfusion injury and in 6 control kidneys. The signal from retained microbubbles in control kidneys was low (<2.5 video intensity units) for both agents. After ischemia-reperfusion, the signal from retained microbubbles was 2-fold higher for PS-containing than for standard lipid microbubbles (18+/-6 versus 8+/-2 video intensity units, P<0.05). An excellent relation was found between the ultrasound signal from retained microbubbles and the degree of renal inflammation, assessed by tissue myeloperoxidase activity.

CONCLUSIONS

-We conclude that noninvasive assessment of inflammation is possible by ultrasound imaging of microbubbles targeted to activated leukocytes by the presence of PS in the lipid shell.

Noninvasive imaging of inflammation by ultrasound detection of phagocytosed microbubbles

BACKGROUND

We have previously shown that microbubbles adhere to leukocytes in regions of inflammation. We hypothesized that these microbubbles are phagocytosed by neutrophils and monocytes and remain acoustically active, permitting their detection in inflamed tissue.

METHODS AND RESULTS

In vitro studies were performed in which activated leukocytes were incubated with albumin or lipid microbubbles and observed under microscopy. Microbubbles attached to the surface of activated neutrophils and monocytes, were phagocytosed, and remained intact for up to 30 minutes. The rate of destruction of the phagocytosed microbubbles on exposure to ultrasound was less (P</=0.05) than that of free microbubbles at all acoustic pressures applied. Intravital microscopy and simultaneous ultrasound imaging of the cremaster muscle was performed in 6 mice to determine whether phagocytosed microbubbles could be detected in vivo. Fifteen minutes after intravenous injection of fluorescein-labeled microbubbles, when the blood-pool concentration was negligible, the number of phagocytosed/attached microbubbles within venules was 7-fold greater in tumor necrosis factor-alpha (TNF-alpha)-treated animals than in control animals (P<0.01). This increase in retained microbubbles resulted in a 5- to 6-fold-greater (P<0.01) degree of ultrasound contrast enhancement than in controls.

CONCLUSIONS

After attaching to activated neutrophils and monocytes, microbubbles are phagocytosed intact. Despite viscoelastic damping, phagocytosed microbubbles remain responsive to ultrasound and can be detected by ultrasound in vivo after clearance of freely circulating microbubbles from the blood pool. Thus, contrast ultrasound has potential for imaging sites of inflammation.

Influence of the ultrasound contrast agent Levovist on human nailfold capillary microcirculation

Little is known about the behavior of ultrasound contrast microbubbles in human capillaries. The evaluation of circulatory effects of echo contrast media may bring valuable information for the interpretation of echo contrast phenomena in the human myocardium. In 12 healthy volunteers (aged 31 +/- 6.7 years; five women), nailfold capillaries were examined by means of TV microscopy. The authors investigated acral microcirculation at rest and after local cold application with and without saccharide-based microbubbles (10 mL Levovist 300 mg/mL IV). The mean blood flow velocity at rest was 1.18 +/- 0.18 mm/s (mean value +/-1 SD) and 1.11 +/- 0.11 mm/s (mean value +/- 1 SD) after the injection of Levovist (ns). One minute after local cold exposure a decrease of the blood flow velocity by 61% before and by 75% after intravenous Levovist was found. In both groups the cold-induced decrease of blood flow velocity was statistically significant (p<0.01), whereas there was no significant difference in flow reaction between the two groups. No wall adhesion of blood cells or extravasation of contrast into the surrounding tissue was detected. After intravenous injection of a regular dose of saccharide-based microbubbles Levovist, no change of blood cell flow velocity and no wall adhesion or extravasation could be found at rest and after cold application in human nailfold capillaries. Since microcirculatory flow characteristics in the finger nailfold capillaries are not influenced by Levovist, it might be assumed also that myocardial blood flow behavior remains unchanged, so that this contrast agent may be used as a flow tracer for cardiac investigation.

Assessment of transmural distribution of myocardial perfusion with contrast echocardiography

BACKGROUND

We hypothesized that by using our newly defined method of destroying microbubbles and measuring their rate of tissue replenishment, we could assess the transmural distribution of myocardial perfusion.

METHODS AND RESULTS

We studied 12 dogs before and after creation of left anterior descending coronary artery stenoses both at rest and during hyperemia (n=62 stages). Microbubbles were administered as a constant infusion, and myocardial contrast echocardiography (MCE) was performed with the use of different pulsing intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-ebetat), where A reflects microvascular cross-sectional area (or myocardial blood volume), and beta reflects mean myocardial microbubble velocity. The product A . beta represents myocardial blood flow (MBF). Average values for these parameters were derived from the endocardial and epicardial regions of interest placed over the left anterior descending coronary artery bed. Radiolabeled microsphere-derived MBF was also measured from the same regions. There was poor correlation between radiolabeled microsphere-derived MBF and A-endocardial/epicardial ratios (EER) (r=0.46). The correlation with beta-EER was better (r=0. 69, P<0.01). The best correlation with radiolabeled microsphere-derived MBF-EER was noted with A . beta-EER (r=0.88, P<0. 01).

CONCLUSIONS

The transmural distribution of myocardial perfusion can be accurately assessed with MCE with the use of our newly described method of tissue replenishment of microbubbles after their ultrasound-induced destruction. In the model studied, an uncoupling of the transmural distribution of MBF and myocardial blood volume was observed during reversal of the MBF-EER.

Basis for detection of stenosis using venous administration of microbubbles during myocardial contrast echocardiography: bolus or continuous infusion?

OBJECTIVES

This study sought to determine the basis of detection of stenosis by myocardial contrast echocardiography using venous administration of microbubbles and to define the relative merits of bolus injection versus continuous infusion.

BACKGROUND

The degree of video intensity (VI) disparity in myocardial beds supplied by stenosed and normal coronary arteries can be used to quantify stenosis severity after venous administration of microbubbles. However, the comparative merits of administering microbubbles as a bolus injection or continuous infusion has not been studied.

METHODS

Coronary stenoses of varying severity were created in either the left anterior descending or the left circumflex coronary artery in 18 dogs. Imagent US (AF0150) was given as a bolus injection in 10 dogs (Group I) and as both a bolus injection and a continuous infusion in 8 dogs (Group II). For bolus injections, peak VI was derived from time-intensity plots. During continuous infusion, microbubble velocity and microvascular cross-sectional area were derived from pulsing interval versus VI plots. Myocardial blood flow (MBF) was determined using radiolabeled microspheres.

RESULTS

During hyperemia, VI ratios from the stenosed versus normal beds correlated with radiolabeled microsphere-derived MBF ratios from those beds for both bolus injections (r = 0.81) and continuous infusion (r = 0.79). The basis for detection of stenosis common to both techniques was the decrease in myocardial blood volume distal to the stenosis during hyperemia. The advantage of continuous infusion over bolus injection was the abolition of posterior wall attenuation and the ability to quantify MBF.

CONCLUSIONS

Both bolus injection and continuous infusion provide quantitative assessment of relative stenosis severity. Compared with bolus injection, continuous infusion also allows quantification of MBF and data acquisition without attenuation of any myocardial bed.

Contrast echocardiography: review and future directions

Recent developments and advances in contrast echocardiography have been made to improve the diagnosis and evaluation of cardiac structures and function. By coupling new developments in acoustic instrumentation with new contrast agents, information that was previously difficult or impossible to gather by standard 2-dimensional echocardiography can now be obtained. Numerous studies have been published confirming the advantages of using contrast during echocardiographic studies, particularly with stress testing and myocardial perfusion. This review aims to summarize (1) the various contrast agents that are available or being developed; (2) factors that have been found to affect the strength of enhanced signals; (3) the new developments in instrumentation that improve the ability of scanners to differentiate echo contrast from cardiac tissue; and (4) the documented and possible future uses of contrast echocardiography.

Quantification of myocardial blood flow with ultrasound-induced destruction of microbubbles administered as a constant venous infusion

BACKGROUND

Ultrasound can cause microbubble destruction. If microbubbles are administered as a continuous infusion, then their destruction within the myocardium and measurement of their myocardial reappearance rate at steady state will provide a measure of mean myocardial microbubble velocity. Conversely, measurement of their myocardial concentration at steady state will provide an assessment of microvascular cross-sectional area. Myocardial blood flow (MBF) can then be calculated from the product of the two.

METHODS AND RESULTS

Ex vivo and in vitro experiments were performed in which either flow was held constant and pulsing interval (interval between microbubble destruction and replenishment) was altered, or vice versa. In vivo experiments were performed in 21 dogs. In group 1 dogs (n=7), MBF was mechanically altered in a model in which coronary blood volume was constant. In group 2 dogs (n=5), MBF was altered by direct coronary infusions of vasodilators. In group 3 dogs (n=9), non-flow-limiting coronary stenoses were created, and MBF was measured before and after the venous administration of a coronary vasodilator. In all experiments, microbubbles were delivered as a constant infusion, and myocardial contrast echocardiography was performed using different pulsing intervals. The myocardial video intensity versus pulsing interval plots were fitted to an exponential function: y=A(1-e[-betat]), where A is the plateau video intensity reflecting the microvascular cross-sectional area, and beta reflects the rate of rise of video intensity and, hence, microbubble velocity. Excellent correlations were found between flow and beta, as well as flow and the product of A and beta.

CONCLUSIONS

MBF can be quantified with myocardial contrast echocardiography during a venous infusion of microbubbles. This novel approach has potential for measuring tissue perfusion in any organ accessible to ultrasound.

Myocardial contrast echocardiography in acute myocardial infarction using aortic root injections of microbubbles in conjunction with harmonic imaging: potential application in the cardiac catheterization laboratory

OBJECTIVES

The aim of this study was to evaluate myocardial contrast echocardiography using aortic root injections with harmonic imaging in experimental acute myocardial infarction to determine the potential of this approach in the cardiac catheterization laboratory.

BACKGROUND

It would be desirable to have an adjunctive procedure that could evaluate myocardial perfusion at the time of cardiac catheterization in patients with acute myocardial infarction. A single injection of contrast medium in the aortic root would provide complete information on myocardial perfusion in a cross section of the heart. High quality images would provide on-line assessment of myocardial perfusion without recourse to image processing. These data could be very valuable for determining patient management.

METHODS

Perfusion defects on myocardial contrast echocardiography were measured during coronary occlusion and reflow, using fundamental and harmonic imaging in both continuous and intermittent modes in nine open chest dogs. These defects were compared with risk area on technetium-99m autoradiography and infarct size on tissue staining.

RESULTS

Whereas harmonic imaging increased myocardial video intensity by more than twofold (p < 0.001) compared with fundamental imaging after aortic root injection of contrast medium, intermittent imaging was not superior to continuous imaging. The improved signal to noise ratio of harmonic imaging allowed on-line definition of risk area (r = 0.98) and infarct size (r = 0.93) without recourse to off-line processing. Similar results could be obtained with fundamental imaging only after off-line processing.

CONCLUSIONS

Aortic root injection of contrast medium coupled with harmonic imaging can be used to provide accurate on-line assessment of risk area and infarct size during acute myocardial infarction. These results have important implications for the catheterization laboratory.

Integrated backscatter and digital acquisition during myocardial contrast echocardiography: is there an advantage over conventional echocardiography for intracoronary injections?

This study was designed to answer the question of whether, despite their theoretic superiority, integrated backscatter imaging (IBS) and digital data acquisition (DA) offer any advantage over conventional echocardiography (CE) during quantitative myocardial contrast echocardiography. In vitro experiments were performed (1) to determine the microbubble concentration versus videointensity relationships for CE and IBS and (2) to define the relationship between flow through and microbubble transit rates for CE and IBS. These data were stored on videotape. In vivo experiments were performed whereby microbubbles were injected into the left anterior descending artery at different flow rates in 14 dogs and IBS and CE data were stored both in digital format and on videotape. Although the level of compression did not affect the microbubble concentration versus videointensity plots during IBS compared with CE, in practical terms the mean transit rate, peak intensity, and area under the curve were not affected by the level of compression for both forms of imaging as long as the postprocessing used for CE imaging was linear and the microbubble dose was small. In addition, although DA resulted in higher peak intensity and area under the curve compared with storage on videotape because of its broader dynamic range, the correlation between these measurements was excellent with both forms of image storage. We conclude that, although differences exist between CE and IBS and between Da and analog acquisition, these differences do not significantly affect the derivation of parameters from time-intensity plots during myocardial contrast echocardiography when contrast material is injected into a coronary artery.