A Basic Research On The Fast Detection Method Of The Intracranial Injury

The intracranial injury seriously threatens the lives of the patients and early detection and treatment are of paramount importance to the prognosis. But unfortunately, there are few monitoring devices which can detect the intracranial injury early and non-invasively.Earlier researches have indicated that the impedance of the pathologic tissues could be changed when the intracranial injury happens, so it is impossible to make use of this change to detect the injury. The researches of the impedance on this subject are mainly focus on the EIT, MIT and some methods of 1D.A 1D impedance method of detecting the intracranial injury using the voltage differences of the symmetrical electrodes is discussed in this paper. The safe current is injected to the head along the sagittal axis, and the voltages are detected by the electrodes around the head. The differences of voltages are very small to the common people while the differences are evident to the patient who has the intracranial injury such as the cerebral hemorrhage, cerebral ischemia and cerebral edema. So it is possible to diagnose the pathological changes of the brain.According to the theory above, the two researches of the software simulation and the experimental verification are mainly done as followed.1. The simulation research of the voltage differences of the symmetrical electrodes based on AnsoftThe brain model with and without scalp and skull are build up using the software of Ansoft. The voltage differences of the symmetrical electrodes are also measured on the polar driving pattern. The model without scalp and skull which is used to simulate the brain is a cylinder with the diameter of 20cm, height of 2cm, and conductance of 0.24s/m. The model with scalp and skull is a coaxial cylinder with the diameter of 18cm, 19cm, 20cm and the height of 2cm. The conductance of each layer is 0.24s/m, 0.014s/m, 0.24s/m respectively, which is used to simulate the brain, skull and scalp. A cubical disturbance made of agar is used to simulate the cerebral hemorrhage. The stimulated electrodes have their diameter of 1cm and thickness of 1mm. The results of the two cases show that the differences of voltages are negligible without the agar while they are not negligible when the agar exists.2. The experimental research based on physical modelThe two researches are mainly completed:A: The research of the preparation and the conductance determination of the agarThe agar is made of the pure water, agar powder and Nacl. The mass of the pure water and agar powder are fixed, and the mass of Nacl is changeable. The agar solution are heated in the microwave oven while an alcohol burner is used the in the early heating method, so the solution can be heated homogeneously and quickly. The agar is homogeneous and stable, and can be preserved for a long time at room temperature.The conductance of the agar is measured with the four-electrode method using the Solartron 1255B and 1294 impedance interface. The agar solution fill in the four-electrode impedance measure assembly, and the impedance is measured repetitively between the frequency 10k and 100k after cooled under 20℃. The analysis shows that the conductance of the agar and the mass of Nacl is approximately linearity and the conductance of the agar change with the time and frequency indistinctively.B: The feasibility research on the detecting method based on the voltage differences of the symmetrical electrodesThe EIT monitoring system which is developed all by the FMMU EIT group is used in the experiments. The three experiments are the same agar on the same plan but different positions, the same agar on the different plans but same position, and different agars on the same plan and the same position. The results show that this method can catch the existence and the change of the disturbance, and the differences of the voltage are connected with the size and the position of the disturbance. The simulated result and the experimental result have a similar trend, and prove that the detecting method has its feasibility.This paper supports the way of detecting the intracranial injury using the 1D impedance method on the basic research.