Detection of rabbit intracranial hemorrhage based on permittivity

Abstract

Intracranial hemorrhage (ICH), with extremely high morbidity and mortality, can only be detected by computed tomography (CT) and magnetic resonance imaging (MRI), which do not meet the requirements for bedside continuous monitoring and pre-hospital first aid. The magnetic induction method is a potential means of non-contact, non-invasive and continuous measurement of ICH. However, the current magnetic induction method measures the conductivity of the measured object. Because the conductivity of blood is only half that of cerebrospinal fluid (CSF) and the compensatory mechanism of CSF during hemorrhage, the sensitivity of measuring changes in intracranial conductivity to reflect the amount of bleeding is low. Since the permittivity of blood is far larger than that of other brain tissues, here a new method was used to determine the amounts of bleeding by measuring the head permittivity. The perturbed magnetic field produced by the measured head relative to the excitation magnetic field (ΔB/B) was measured using an excitation coil and a receiving coil. The real part of ΔB/B, which includes permittivity information, was used to reflect the amount of bleeding. First, three solutions of alcohol, distilled water and blood (60 ml each) were detected. Then the rabbit heads were measured during the intracerebral blood injection. The injection amount was 2 ml at the rate of 2 ml/12 min. The real part data were extracted and evaluated. The physical experiments showed the real parts ranked as blood > distilled water > alcohol, which was consistent with the ranking of known permittivity among the three solutions. The animal experiments indicated the real part data of each animal changed little without blood injection, but slowly declined with increasing amount of injection. The real parts changed in the same trends among the ten animals. Analysis suggested the changing amounts of the real part data without injection were significantly smaller than those during the injection (P < 0.05). The physical experiments confirm the real part of ΔB/B can differentiate the three solutions of alcohol, distilled water and blood. The animal experiment results also reveal the feasibility of using this method for intracranial hemorrhage measurement.