Performance Estimation of an Implantable Epileptic Seizure Detector with a Low-power On-chip Oscillator

Abstract: Implantable closed-loop epilepsy controllers require ideally both accurate epileptic seizure detection andlow power consumption. On-chip oscillators can be used in implantable devices because they consume less powerthan other oscillators such as crystal oscillators. In this study, we investigated the tolerable error range of a lowerpower on-chip oscillator without losing the accuracy of seizure detection. We used 24 ictal and 14 interictal intrac-ranial electroencephalographic segments recorded from epilepsy surgery patients. The performance variations withrespect to oscillator frequency errors were estimated in terms of specificity, modified sensitivity, and detection timingdifference of seizure onset using Generic Osorio Frei Algorithm. The frequency errors of on-chip oscillators wereset at ± 10% as the worst case. Our results showed that an oscillator error of ± 10% affected both specificity andmodified sensitivity by less than 3%. In addition, seizure onsets were detected with errors earlier or later than with-out errors and the average detection timing difference varied within less than 0.5 s range. The results suggest thaton-chip oscillators could be useful for low-power implantable devices without error compensation circuitry requiringsignificant additional power. These findings could help the design of closed-loop systems with a seizure detector andautomated stimulators for intractable epilepsy patients.Key words: implantable biomedical devices, low power, on-chip oscillators, performance evaluation, seizure detector