Quantification of myocardial perfusion using contrast echocardiography: methodological basis of image postprocessing

Intravenous contrast agents have provided the opportunity to clinically assess myocardial perfusion using ultrasound. In perfusion echocardiography, obtaining maximal diagnostic information requires the use of digital image postprocessing techniques, since subjective visual interpretation can be frequently inaccurate. Prior research using other intravascular tracers such as radioactive microspheres provides the theoretical basis for perfusion analysis that can be readily implemented to contrast echocardiography. Aspects of digital videodensitometric quantification, fitting to gamma-variable mathematical wash-in/wash-out functions and parameter analysis have been well validated for other tracers and have demonstrated excellent applicability in contrast echo. Currently available scanner technologies provide with a number of image-acquisition modalities, from standard continuous to intermittent-triggered images that require specific postprocessing algorithms. The present paper reviews the basis of temporal and spatial contrast postprocessing. The issues of image registration, background subtraction, videointensity measurement and mathematical function fitting are also discussed. This theoretical background should be helpful to understand the general aspects of currently available and future systems of perfusion densitometric systems.