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Transcranial Doppler ultrasound is capable of detecting microembolic material, both gaseous and solid, within the intracranial cerebral arteries. To avoid discrediting this promising and exciting new technique, experts in this field met in January 1997 in Frankfurt, Germany, to discuss the limitations and problems of embolus detection and to determine guidelines for its proper use in clinical practice, as well as in scientific investigations. In particular, the authors suggest that studies report the following parameters:(1) ultrasound device,(2) transducer type and size,(3) insonated artery,(4) insonation depth,(5) algorithms for signal intensity measurement,(6) scale settings,(7) detection threshold,(8) axial extension of sample volume,(9) fast Fourier transform (FFT) size (number of points used),(10) FFT length (time),(11) FFT overlap,(12) transmitted ultrasound frequency,(13) high-pass filter settings, and (14) recording time. There was agreement that no current system of automatic embolus detection has the required sensitivity and specificity for clinical use.