Yasushi Kashiwagi

Flash effect of contrast microbubbles by ultrasound exposure

BackgroundMicrobubbles used in contrast echo examination are destroyed by exposure to ultrasound but develop a new ultrasound wave on destruction; the so-called flash effect. Factors influencing the magnitude of the new wave have yet to be elucidated. Here we investigate the method of assessing this effect and attempt to clarify the relevant differences between contrast agents.MethodsThree contrast agents were used: Albunex, Optison (FS 069), and Levovist. We used fundamental mode (3.75 MHz) and harmonic mode (2.5 to 5.0 MHz) ultrasound produced by a prototype echocardiograph (Toshiba) and measured the video intensity (VI) (256 gray scale) of each contrast agent contained in a thin rubber sack while changing acoustic power from a minimum level to high levels of +10.5 dB +16.5 dB, and +22.5 dB.ResultsVI was not changed by low acoustic power; however, it increased rapidly for a short time and then decreased rapidly when exposed to high acoustic power. The increase in VI varied with acoustic power: 30 to 60 at +10.5 dB and 70 to 115 at +22.5 dB. The increase in VI was larger in harmonic mode than in fundamental mode. The degree of decrease in VI after the flash effect correlated with the extent of increase in VI produced by the flash effect.ConclusionsThe flash effect occurred with each of the contrast agents, and its magnitude varied with acoustic power and contrast agent.

Setting up ultrasonic equipment for myocardial contrast echocardiography with venous injection of optison (FS-69): An experimental study

BackgroundAlthough Optison (FS-69) is commercially available in the United States, the optimal setup of ultrasonic equipment for myocardial contrast echocardiography has yet to be elucidated. Here we examine the optimal setting for adequate opacification of the myocardium.MethodOptison (0.1 ml) was administered intravenously during recording of the short axis view of the left ventricle using the Toshiba prototype echocardiographic system in 11 open-chest beagledogs. Myocardial opacification was evaluated by calculating the baseline-subtracted peak video intensity (256 gray scale) at four regions of the left ventricular wall: the anterior, lateral, posterior, and septal walls. We examined the fundamental (3.75 MHz) and second harmonic (2.5/5.0 MHz) imaging during both continuous and intermittent (one pulse per cardiac cycle) mode. Acoustic power (AP) decreased in steps of 1.5 dB from maximal mechanical index (1.4). We also examined the effect of the distance between and the heart by placing an ultrasonic spacer with a width of 1 cm or 3 cm.ResultsMyocardial opacification was hardly, recognized by the continuous mode; however, the intermittent mode provided sufficient opacification in either the fundamental or harmonic mode. Excessive acoustic power did not improve myocardial opacification. The influence of high acoustic power was significant in the field near the transducer.ConclusionThe left ventricular myocardium is clearly opacified by venous administration, of Optison when the mechanical settings of the ultrasonic equipment are appropriate.

Optimum trigger timing for intermittent mode in intravenous myocardial contrast echocardiography

BackgroundAlthough the intermittent mode is necessary for myocardial opacification in intravenous myocardial contrast echocardiography (MCE), the effect of EGG trigger timing, on good myocardial opacification without production of artifacts, is not clear.MethodMCE was performed on six closed-chest dogs by injecting FS 69 (0.1 ml) intravenously using an Acuson Sequoia 512 ultrasound system with intermittent harmonic imaging (1.75/3.5 MHz) in the short-axis view. Myocardial opacification and acoustic shadow were evaluated from a video tape recording triggered at every end-systole or end-diastole phase. Peak video intensity of four quadrant regions and extent of the acoustic shadow expressed as the incident angle viewed from the center of the left ventricular cavity were measured.ResultsThe angle of acoustic shadow was significantly larger in the image triggered at end-diastole than in the image triggered at end-systole. However, trigger timing did not affect myocardial opacification in either region.ConclusionTrigger timing should be set at end-systole to minimize acoustic shadowing.

Nicorandil preserves collateral circulation even at low systemic pressure in comparison with nitroglycerin: real-time myocardial contrast echocardiographic study

lar damage in patrents with AMI. We investigated MCE with harmonic power Doppler (HPD), CFR and CF by using transthoracic echocardiography (TTE) in predicting func- tional recovery. Methods: We performed MCE (SONOSSSOO, Philips) by using 1:4 inter- mittent HPD with Levovist at rest and during ATP in 30 patients two weeks after anterior AMI. Peak videointenstty was measured within the risk and control regions. The peak intensity ratios of the risk area to the control area (PIR) at rest and during hyperemia were calculated. We measured CFR of the left anterior descending artery (LAD) two weeks after AMI. CF of LAD by TTE was also obtained within 24 hours after successfully recanalization

Three-dimensional reconstruction of coronary arteriole plexus image by contrast echocardiography using high frequency transducer

OBJECTIVE This study was established to examine the efficacy of a high-frequency liner probe for visualizing fine anatomy of coronary microcirculation. METHODS The vessel size and its velocity-time integral at the anterior wall in dogs by real-time contrast echocardiography with high-frequency liner probe and pulse Doppler methods, and the coronary flow volume, were measured before and after adenosine triphosphate injection. A 3-dimensional (3D) image was reconstructed by the built-in 3D system using intermittent flash echocardiographic images. RESULTS The increments of flow volume calculated from vessel sizes and velocity-time integral were well correlated with those of coronary flow volume. Using intermittent flash echocardiographic images, fine dots and lines of contrast echocardiographic-expected arterioles were evident, and easily and quickly reconstructed as coronary plexus by 3D system. CONCLUSION A high-frequency liner probe provides the fine-vessel images to evaluate those morphologic changes; a 3D reconstruction image could provide new information about coronary arterioles.

Real-time myocardial contrast echocardiography reveals microvessel recruitment soon after coronary occlusion

Background and Aim: Collateral flow at the micro-vessel level is important to salvage the myocardium after acute coronary obstruction, although larger collateral vessels are observed by coronary angiography. The aim of this study was to elucidate the presence of micro-collateral channel by real-time myocardial contrast echocardiography (MCE). Methods: Short axis view of the left ventricle was recorded using real -time imaging by Sequoia 512 during infusion of 0.1 ml/min of Optison( in 17 open-chest dogs. All bubbles were destroyed by one-second exposur e of high acoustic power just after LCx occlusion. The territory of LCx was divided into 3 areas (1 Core and 2 Border zones), and the systolic wall thickening (s-WT) and contrast echo video intensity (VI) were evaluated in each zone just before and 20 seconds after LCx occlusion. It was defined that the collateral channels were good when the mean VI of core and border zones were over 20/256 gray level despite complete occlusion of LCx. The flow volume of left anterior descending coronary artery (LAD) was measured by an ultrasonic flowmeter. Results: It was determined that 7 cases had good collateral channels and other 10 cases had not. The area of risk was gradually but definitely opacified in Good group. Total VI of 3zones was significantly higher in Good group than those in Poor group (69.8+40.3 vs 12.3+6.4, p<0.001). Even in Good group, the VI of core zone was significantly lower than that of border zone (11.3+11.2 vs. 35.3+17.4, p<0.001). Mean s-WT of 3 zones was significantly higher in Good group than those in Poor group (18.8+8.6 vs. 5.5+3.3, p<0.001). S-WT correlated well with VI in all zones of all cases (r=0.916, p<0.001). The LAD flow volume increased 26.2+13.6% during LCx occlusion in Good group, while 10.5+5.3 % in Poor group. Conclusion: It is revealed that real-time MCE demonstrates the recruitment of a fine and thin collateral channel appearing soon after coronary occlusion. This finding has not been elucidated so far by other modalities. Real-time MCE can elucidate the mechanism of myocardial salvage after acute coronary obstruction in both clinical and experimental aspect.