Intraoperative EEG monitoring: (II). Similarity analysis using density-modulated t array

A method of showing the similarity, in other words, defining the difference between a pair of EEG patterns has been developed. By using the student t test on the power spectra at the appropriate frequency intervals, the t values obtained can be used as an indicator of the difference between the spectral patterns with respect to the frequency intervals. This so-called t-profile can be computed on real time basis and the result superimposed in different colors using the apparatus described previously to produce a 3-dimensional picture. We call this picture a density-modulated t array or DTA. Along with CSA and DSA (compressed/density-modulated spectral arrays), it proved to be a very powerful tool in intraoperative EEG monitoring.