Abstract
The embolic signals detected by transcranial Doppler ultrasonography (TCD) are characterized as high-intensity transient signals (HITS) . Two types of TCD devices, conventional and embolus-oriented, are currently used. HITS demonstrated by an embolus-oriented TCD device correspond almost specifically to embolic signals. However, the characteristics of HITS in conventional TCD and their specificity to embolic signals remain to be studied. In this study, 10 ischemic patients were examined using a conventional TCD device. Six of these patients showed HITS. In all cases, these were partly unidirectional and partly bidirectional with a unilateral tendency, and the HITS were accompanied by chirping sounds. Since the chirping sounds had the typical characteristics of embolus origin which we had revealed experimentally, the HITS were interpreted to originate from moving emboli. We conclude that HITS with chirping sounds can be regarded as embolic signals in conventional TCD, irrespective of whether they are unidirectional or bidirectional with a unilateral tendency.
