Acquisition and processing of the radio-frequency signal in echocardiography: a new global approach

Recently there has been an increasing interest in the use of the "raw" radio-frequency (RF) signal generated in echocardiography for use in tissue-characterization to distinguish between normal and pathological myocardium, for automatic delineation of the endocardial border without being limited by the weak contrast of the traditional video images, and for use in contrast echography, where it could offer the possibility to visualize perfusion using intravenous contrast injections. One of the main problems in this kind of research is the acquisition of the signal having a high frequency and large bandwidth. We have developed a new global method for the acquisition of this RF signal. To digitize the data, a video sequencer is used. In this way it becomes possible to sample all available data generated by the echographic equipment during at least 1 s. This means that all data of the complete sector scan during a complete heart-cycle can be digitized without using any data reduction technique or triggering on the electrocardiogram. The advantage of this approach is that all characteristics of the signal can be studied, without being limited by data reduction techniques used during acquisition. This method enables us to calculate parameters such as "integrated backscatter," or to investigate the signal more extensively, e.g., by using spectrum analysis. We can compare different regions of the myocardium and examine them during the heart-cycle, all within the same beat. We have also written a software package for the processing of the large amount of data resulting from the acquisition.