THE NARROW-BAND HYPOTHESIS - AN INTERESTING APPROACH FOR HIGH-INTENSITY TRANSIENT SIGNALS (HITS) DETECTION

We propose a new approach to detect microemboli automatically using th e narrow band hypothesis, An initial database of 560 peripheral arteri al Doppler high-intensity transient signals (HITS) was created to stud y microemboli and to define the normal Limits to be used in our method , When a HITS occurs, our approach consists of modelling the Doppler s ignal using amplitude and frequency wave modulation, A threshold was d efined experimentally using this database and then applied to 38 recor dings from 12 patients, Using another database, sis expert Doppler use rs reported 140, 176, 155, 161, 161 and 146 HITS, corresponding to a t otal of 197 different observed HITS, When an event was detected by 6, 5, 4, 3, 2 and 1 of the observers, the sensitivity of the automatic de tection was 94.8%, 75.9%, 55.6%, 42.9%, 30% and 0%, respectively, The sensitivity of our automatic detection thus is highly associated with the likelihood (defined as the ratio of observers in agreement to the total number of observers) of an event: r = 0.99 for p < 0.0001, Altho ugh future research would result in improvement of the specificity, th e narrow band hypothesis appears to be a promising technique for the d etection of HITS. (C) 1998 World Federation for Ultrasound in Medicine & Biology.