Animal Experimental Study Of Closed Craniocerebral Hemorrhage Based On Multi-channel Microwave Detection Technology

Research background and Objective:With the continuous application of high-tech technology in the military field,compared with the traditional war,explosion injury and impact injury gradually replace the traditional shrapnel injury and become the primary factor of battlefield craniocerebral injury.With the continuous improvement and upgrading of bulletproof helmet,although it effectively prevents open craniocerebral injury,the risk of closed craniocerebral injury increases greatly.The characteristics of this kind of closed craniocerebral injury are that the skull of the wounded is not fractured,the dura is still intact,but there is traumatic hemorrhage in the brain,that is,closed craniocerebral hemorrhage.Due to the complexity and particularity of battlefield environment,mainstream clinical detection methods of CCH,such as computed tomography(CT),magnetic resonance imaging(MRI),intracranial pressure(ICP)monitoring and near infrared spectrum instrument(NIRS),are not suitable for fire line rescue.At present,the wartime fire line health workers mainly use Glasgow Coma Scale(GCS)combined with vital signs to make empirical diagnosis of CCH,but its observation and detection content is complex and subjective.The multichannel detection system of craniocerebral hemorrhage based on microwave is portable,low-cost,non-invasive and non-contact.In the process of wartime rescue,it is expected to quickly detect whether there is CCH in the wounded,so as to guide the follow-up treatment process,maintain the combat capability of wartime troops to the greatest extent and reasonably allocate wartime medical resources.The main work of this paper:Part Ⅰ: Based on the basic theory of electromagnetic field and microwave detection technology,using the multi-channel microwave detection experimental system developed by the research group,in order to theoretically demonstrate the feasibility of microwave technology detection of CCH,the following main research work has been carried out:(1)Through systematic analysis of the equivalent circuit model of the Maxwell equations and the biological tissue(the Debye model),different biological tissues may be calculated relative dielectric constant and the conductivity at each frequency in theory;(2)By constructing a four-layer sphere model of cranial conductivity,it is analyzed that in the early stage of CCH,with the increase of intracranial hemorrhage,the overall cranial conductivity(dielectric constant)shows a downward trend;(3)Discussed the experimental configuration multichannel microwave detection system,introduced the signal generation processing module,a signal acquisition module and a multiplex switch three main components of the respective configurations and functions.The maximum output power of the system is 10 dbm,which is far less than the minimum safety standard of "GB 8702-88 Electromagnetic Radiation Protection Regulations".Part Ⅱ : physical simulation experiment research.Sodium chloride solutions with solubility of 11.934(7)(8)lg /,17.082(7)(8)lg /,8.132(7)(8)lg / and 5.353(7)(8)lg / were used to simulate the electrical properties of blood,cerebrospinal fluid,brain gray matter and white matter.The microwave-based multichannel craniocerebral hemorrhage detection system designed in this paper was used to measure the different volumes(0～10)of four biological tissue simulation solutions,and obtained by analyzing the measured S21 phase value: When the system is at frequencies of 2.2GHz and 2.85 GHz,for each unit increase in the simulated solution volume,the S21 phase change value is the largest,that is,the sensitivity is better.Define these two points as the characteristic frequency points of the system;Taking the volume of the simulated solution as the independent variable,and the S21 phase value at the characteristic frequency point as the dependent variable,perform a univariate linear regression analysis to analyze the sensitivity of each of the 16 channels to volume changes.The p are all less than 0.05,and the regression model has statistical significance;The Friedman M test results showed that the difference of the S21 phase values of the four different conductivity simulation fluids was statistically significant(p<0.05),indicating that the detection system can distinguish different volumes of the simulation fluids with different conductivity.Part Ⅲ: Animal experiment research of the craniocerebral hemorrhage detection system based on microwave.Analyze and compare the commonly used animal craniocerebral injury models,combine the characteristics of the rabbit craniocerebral CCH model required in this experiment,and use the BIM-II horizontal bio-impacter independently developed by the Army Characteristic Medical Center to perform CCH animals Model preparation.By observing the anatomy of the brains of 20 rabbits after impacting under different impact methods,impact locations and impact parameters of the impact machine,a stable rabbit brain injury model required for this experiment was constructed.The injury model used BIM-Type II horizontal bio-impacter impacts the top of the rabbit’s cranium.The impact pressure is0.9Mpa,the impact distance is 2.5cm,and the head diameter is 2cm.Under this injury model,a craniocerebral impact experiment was performed on 10 rabbits of similar body weight,combined with the conclusions of the previous physical simulation experiment,through the pre-impact(time t-1),t0 after the impact,and t20 after the impact.The "analysis of variance for random block design" of the phase measurement values of 10 rabbits at the characteristic frequency point of 2.2GHz at three times,we can see: The variances of the 16 channels are the same,and the p-values of the main-effects test at all times are less than 0.05;the LSD test at the three times,all the p-values are less than 0.05.According to the sensitivity of each of the16 channels of the system to blood at 2.2GHz in the physical experiment,the corresponding weight value is assigned.Through the analysis of the S21 phase value after the weighted summation of the 16 channels over time,it can be known: The S21 phase value gradually decreases with time,and this change is consistent with the first part of the theoretical analysis.The S21 phase value 20 times after the impact and the S21 phase value before the impact are paired t-tests,and the p values are all less than 0.05.Animal experiments show that it is feasible to use the microwave system to detect CCH.Conclusion:(1)Through physical simulation experiments of different concentrations of sodium chloride solution,it is verified that the microwave-based multi-channel craniocerebral hemorrhage detection system designed in this paper can analyze the S21 phase measurement value to achieve different volumes and different tissues with the same conductivity.Distinguish between the conductivity tissues,and at the same time determine the characteristic frequency of the detection system,and analyze the sensitivity of each of the 16 channels to the simulated blood under the characteristic frequency;(2)The BIM-Ⅱ horizontal bio-impact machine independently developed by the Army Special Medical Center was used to impact the top of the rabbit’s cranium.With an impact pressure of 0.9Mpa,an impact distance of 2.5cm and a collision head diameter of 2cm,a stable Rabbit CCH model(the skull is not fractured and the dura mater remains intact);(3)Through the analysis of the rabbit brain impact experiment,it is verified that the multi-channel brain hemorrhage detection system based on Microwave designed in this paper has the detection ability and certain monitoring ability for the rabbit brain hemorrhage after impact when the skull remains intact without fracture.