The Numerical Simulation Research Of Noninvasive Intracranial Pressure Monitoring System Based On Propagation Characteristics Of Ultrasonic

Cerebral lesions often accompanies with increased intracranial pressure, so it ishigh clinical significant to realize intracranial pressure monitoring. Most of the existingtechnologies about intracranial pressure monitoring are invasive, and the widely usednoninvasive ones also have many disadvantages. The intracranial pressure monitoringby ultrasonic has appeared in recent years, because of its cheap, noninvasive andequipments’ simple, people pay more attention to it now. Most of the existing researchesare about the scattering and reflection of ultrasonic signal, electrical signals. In order torealize noninvasive real-time monitoring of intracranial pressure, we must knowultrasonic propagation characteristics within the brain very clearly. The main works ofthis paper are as follows:(1) It introduces the research status at home and abroad about intracranial pressuremonitoring, and discusses the advantages and disadvantages of intracranial pressuremonitoring technologies existing now. At the same time, this paper introduces thechanges of ultrasonic propagation characteristic parameters can reflect the biologicaltissue lesions.(2) Using the acoustic elasticity theory, we can deduce the acoustic equation ofmotion about the relationship between wave velocity and hydrostatic pressure, we canalso get the equivalent stiffness matrix for finite element analysis and calculation.There is phase difference of the excitation signal and response signal when theultrasonic signal gets through the medium, and the between the equation about therelationship phase difference and the wave velocity is deduced in this paper.(3) Choose a material agar gel to make it into solid block, and use it to do theexperiment about the ultrasonic wave through the compressed of brain tissue. The resultshows that ultrasonic wave velocity decreases when the pressure on the solid blockincreases. Establish linear elastic finite element model about agar block, and do thenumerical simulation of the ultrasonic propagation characteristics in the model by usingABAQUS software, the difference between calculated results and experimental value isvery small. Considering that the actual brain tissue is sticky, to establish another finiteelement model of brain tissue which constitutive relation is viscoelastic, the numericalsimulation result also shows the relationship that the ultrasonic wave velocity willdecrease when the pressure increase. (4) Reference to anatomical of the human brain and the biological mechanism ofthe increased intracranial pressure, this paper establishes a simplified model of cerebralwhich only consists of skull, brain tissue and cerebrospinal fluid which are theorganizational structure closely associated with increasing pressure. Ignore thedeformation of the skull and assume that the total volume of cranial cavity will notchange, intracranial pressure change makes the proportion of cerebrospinal fluid andbrain tissue volume change. Finally to do the numerical simulation and analysis of theultrasonic propagation characteristics in different models established with differentproportion of cerebrospinal fluid and brain tissue. The result shows the relationshipbetween the ultrasonic propagation characteristics and the proportion of cerebrospinalfluid brain tissue volume in cranial cavity, and shows that the relationship between thephase difference and the intracranial pressure. All the above provide a theoreticalguidance for clinical applications of noninvasive intracranial pressure monitoring byultrasonic.