Discussion

Abstract

The results of Doppler sonography have been compared with those of other methods to elucidate the biological significance of the Doppler parameters. There proved to be basic problems associated with such an undertaking. There is no direct way to control the precision of a measurement. Neither the “true” cerebral blood flow nor the “true” blood flow velocities can be determined with any method. The examinations are usually not performed simultaneously, since each of the techniques requires a different amount of time. Changes in the “true” parameters can occur between measure-ments, which can seriously affect the results.