Newer imaging techniques in contrast echocardiography

Newer imaging techniques in contrast echocardiography are rapidly evolving concurrent with the development of newer contrast agents able to produce left ventricular cavity and myocardial opacification after an intravenous injection. Harmonic imaging and noncontinuous ultrasound transmission are such developments in the application of ultrasound technology. Harmonic imaging is a new approach to the detection of echocardiographic contrast agents which exploits the nonlinear response of microbubbles when exposed to ultrasound energy. Microbubbles resonating in an acoustic field generate sub and supra harmonic emissions which occur at multiples of the insonifying frequency. Since tissues that do not contain contrast agent do not produce such a response, the identification of contrast in perfused structures is enhanced by detection of higher harmonic signals. Blood pool cavities, vascularized tissue and coronary vessels have been clearly defined during harmonic imaging of contrast agents. Early observations in patients have demonstrated the potential of harmonic imaging alone, or in combination with transient suspension of ultrasound, to achieve enhanced noninvasive assessment of ventricular function and myocardial perfusion.