Calibration and measurement uncertainty analysis of a medical drill with integrated temperature sensors to minimise patient risk during minimally invasive drilling at the lateral skull base

The main risk to the patient's health during minimally invasive drilling is thermal injury to nerve or bone tissue due to increased heat input. A drill with integrated temperature sensor was developed to determine the temperature of the drill base in parallel with the process. However, this measured temperature has an unknown correlation with the actual drill base temperature, as uncertainties influence the measurement. To be able to use the temperature as a reliable basis for decision-making during minimally invasive drilling, systematic deviations of the measured temperature from the real temperature must be known. Random deviations and systematic deviations that cannot be corrected must be summarised in a measurement uncertainty analysis. To determine the calibration curve, a measurement setup is designed to be able to compensate for systematic errors in the temperature measurement with the drill. The results of the uncertainty analysis show that the uncertainty increases with increasing temperature. The uncertainty is conservatively estimated with u(T) = 1 K. The CEM43 is used to assess thermal damage to the tissue, but its quality depends to a large extent on the underlying data quality. In an analysis of the influence of the measurement uncertainty on the CEM43 using uncertainty propagation and Monte Carlo methods, it was found that even small uncertainties in the temperature measurement lead to considerable deviations in the CEM43. The intraoperative use of CEM43 as a parameter for thermal tissue damage is therefore not possible.