Enhanced methods for visualizing myocardial perfusion with peripheral venous injection of Levovist (R): Application of triggered harmonic imaging andtriggered harmonic power Doppler imaging techniques

Objectives: The purpose of this study was to determine whether triggered ha rmonic imaging (THI) or triggered harmonic power Doppler imaging (THPDI) co uld obtain the myocardial contrast enhancement using peripheral venous inje ction of a first generation echocardiographic contrast agent, Levovist(R). Methods: In a phantom model, we examined the influence of an acoustic power , harmonic filters, transmitted frequencies and focus positions of transduc er on Levovist(R). Then fundamental, harmonic or harmonic power Doppler ima ging were performed with ECG-triggered imaging in eight closed-chest dogs u sing bolus injection of Levovist(R)>. Results: In a phantom model, the high est transmission power (Mechanical index 1.6), a medium harmonic filter and a focus position (6 cm) resulted in the best enhanced contrast in both THI and THPDI. Furthermore, higher pulse repetition frequency (5500 Hz) of har monic power Doppler made clearer enhancement. In animal models, we could no t observe the apparent myocardial contrast using triggered fundamental imag ing, and the intensity of each region of interest (ROI) of myocardium had n ot changed significantly. However, homogeneous myocardial contrast could be obtained using THI, which was conditioned on the highest transmission powe r, a medium harmonic filter same as the phantom model, at a lower transmitt ed frequency (1.8 MHz) and a focus position, which were located in the midd le portion of the left ventricle. The peak intensity of each ROI increased significantly in a gray level. Furthermore, THPDI caused emphasized myocard ial contrast visually. Conclusions: These results indicate that THI and THP DI produce obvious MCE using peripheral venous injection of Levovist(R).