Juri Okazaki

Myocardial blood flow parameters derived from contrast replenishment using harmonic power doppler imaging are underestimated by ultrasound signal attenuation

The effect of ultrasound signal attenuation on myocardial blood flow parameters derived from contrast replenishment was evaluated using harmonic gray-scale (HGS) and harmonic power Doppler (HPD) imaging. In vitro experiments were performed in a flow model, whereas in vivo experiments were performed in 5 open-chest dogs. In each study, intermittent HGS and HPD images were acquired at various pulsing intervals during contrast infusion. A silicone pad was interposed between the transducer and target region to simulate attenuation conditions. Baseline-subtracted HGS and HPD signal intensities were measured with and without silicone pad, and myocardial blood flow parameters A and beta were calculated using contrast replenishment. Attenuation with HGS images could be offset by baseline subtraction, as baseline images provided the reference for attenuation. However, attenuation with HPD images could not be compensated for, as baseline signal intensity was theoretically 0. In HGS mode, silicone attenuation produced no significant decreases in A and beta. In HPD mode, however, A and beta were significantly decreased by silicone attenuation (A, P <.001; beta, P <.05). Compared with nonattenuated regions, myocardial blood flow parameters in attenuated regions are underestimated when HPD imaging is used. Baseline-subtracted HGS imaging may be useful to compensate for thoracic wall attenuation.

Significance of acoustic field for the myocardial opacification by intravenous contrast echocardiography

Purpose: Myocardial opacification is not always homogeneous even in a normal heart. The aim of this study is to clarify why myocardial opacification is faint at the lateral side of the field or at the part far from the focus point.Methods: In canine study, videointensity of the opacification at septal and lateral walls of the short axis view was examined by using both electric and mechanical transducers. In in vitro study, acoustic pressure at several points away from the beam direction was measured using a hydrophone in a water tank. In particular, the effect of position of focus point was evaluated with an electronic transducer.Results: In canine experiment, myocardial opacification of the lateral wall was faint with the electronic transducer, however the mechanical one obtained homogeneous opacification. In vitro, using the electronic type the acoustic pressure was low as the beam shifted, laterally, whereas it was almost uniform in the mechanical type. With the electronic type, moreover, the beam width at the near field was not sharp when the focus point was far, resulting in execessive acoustic pressure.Conclusion: To obtain homogeneous opacifiction, a homogeneous acoustic field is indispensable.

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