A New Approach for Early Diagnosis of Delayed Cerebral Ischemia After Subarachnoid Hemorrhage

A new approach for detection of the time of onset of delayed cerebral ischemia after subarachnoid hemorrhage is proposed. The algorithm is based on the analysis of such ischemia indexes as decrease of the relative alpha variability and the alpha/delta ratio. To find relative alpha variability and the alpha/delta ratio the algorithm uses a wide Hamming window for spectrum finding, as well as the ratio of the maximum spectral power density in the frequency bands of alpha/delta rhythms. The proposed algorithms showed high sensitivity and moderate specificity values exceeding the results of previous research. The advantage of this algorithm is that the calculation of ischemia indexes from the maxima of the signal spectrum considers the personal localization of alpha and delta rhythms in the frequency domain and does not require additional averaging because of initially wide window of finding the spectrum. The results of the study can be used in the development of the algorithm for automatic detection in the real time of the onset of delayed cerebral ischemia after subarachnoid hemorrhage. Further study is aimed at clarifying the specificity and verification of sensitivity and specificity indicators by increasing the sample of patients.