Guidelines for Detection of Micro-embolic Signals (HITS/MES) 2003

A proposal has been made to introduce a new Japanese guideline for detection of micro-embolic signals using trans-cranial Doppler (TCD). This guideline is in accordance with the Consensus on Micro-Embolus Detection by TCD proposed by the International Consensus Group on Micro-Embolus Detection in 1998. Micro-embolic signals are called HITS or MES. HITS include artifacts in place of MES. Recommended settings are: (1) use of a 2-MHz probe; (2) sample volume within 10 mm; (3) power set as low as reasonably possible; and (4) use of a headband to affix the TCD probe. The characteristics of HITS/MES are: (5) an intensity at least 3 dB higher than the background that reflects the blood stream; (6) a recording time of more than 30 minutes but not more than one hour to maintain the normal brain temperature; and (7) signals without associated sounds or a low emboli-blood ratio (EBR) excluding HITS. Other recommendations include: (8) recording HITS as digital data, using digital audio tape or CD-R; (9) having data double-checked by an expert who is not familiar with the clinical profile of the examinee; and (10) checking all data manually. The results are better than those obtained from an automatically detected HITS/MES system that is not yet at the completion stage.