Intravascular ultrasound: catheter-based Doppler and two-dimensional imaging.

Intracoronary Doppler and two-dimensional imaging devices have been developed to aid in the search for more precise information about vessel pathology and local vessel hemodynamics. Measurement of coronary flow reserve using Doppler catheters has been well-validated experimentally and is being used clinically in certain groups of patients. Current designs using Fast-Fourier Transform of the signal and real-time video spectral display allows for instantaneous modification in positioning of the catheter within the artery to minimize artifacts. Studies are underway to assess whether measurement of coronary flow reserve and estimations of absolute flow add practical information to the quantitative assessment of vascular disease. Contrast angiography has been the "gold standard" for in vivo study of vascular disease. The recent development of two-dimensional imaging catheters has potentially opened up a new frontier of clinical assessment of vessel pathology. Imaging catheters can be used in a diagnostic role as a means of guiding therapeutic interventions. Direct analysis of the radiofrequency output of the catheter may allow for more precise characterization of plaque composition.