Simulation On The Parameters Of Transcranial Focused Ultrasound Neuromodulation System

Transcranial focused ultrasound（t FUS）is an ultrasound modulation method for brain diseases,which has become a hot topic in non-invasive neuromodulation research because of its higher spatial accuracy and depth of modulation compared to transcranial magnetic stimulation and electrical stimulation methods.It is difficult to determine the focus and intensity of ultrasound within the skull due to the altered path and intensity that occurs as ultrasound penetrates the skull.Numerical simulation methods can fill this gap by helping to determine ultrasound transducer locations,optimize ultrasound modulation parameters,etc.Medial temporal lobe epilepsy with hippocampal sclerosis is the most common syndrome,and bilateral hippocampal sclerosis is difficult to remove in treatment.This paper investigates focused ultrasound transducer positioning and focused sound field intensity in the context of transcranial neuromodulation in temporal lobe epilepsy,and analyses issues such as the thermal effects of ultrasound sequences.The main research components of this thesis include.（1）A 3D brain model was constructed based on k-Wave simulation software to build a focused ultrasound transducer,and the focusing effect of the transducer with different parameters was simulated.Based on the tissue attenuation effect and other factors,a simulation scheme was designed for the action of transcranial focused ultrasound in the hippocampal region of the temporal lobe.（2）A cranial model of the human brain was constructed using binary processed CT image data,and a transducer localization scheme was designed.The focused sound field of the extracranial location focal array was simulated on the Quadro RTX 4000 GPU computing platform.Based on the sound pressure intensity analysis,the central location point of the transducer was determined,and the target area of the temporal hippocampus was simulated.（3）A systematic study was conducted on the positioning of the transducer of transcranial focused ultrasound,the effect of different accuracy models on the position and intensity of the ultrasound focus,and the analysis of the thermal analysis of its ultrasound sequence.The results of the study show that the ultrasound transducer and its focal position can be accurately determined with a simulation accuracy model close to the sub-millimeter CT data.（4）Based on the acoustic field simulation of the skull model,the thermal effect analysis of the focused ultrasound sequence was carried out to analyze the temperature changes in the modulation area and the safety effects on biological tissues to prevent brain tissue damage caused by excessive internal tissue temperature.The safety at set modulation parameters was verified,providing an estimate of temperature variation for low-intensity focused ultrasound applications.The study in this paper determines the vector angles of the ultrasound path in each direction based on the acoustic pressure simulation results,showing that the incidence angle of the ultrasound changes while the thickness of the cranial layer is affected due to the model accuracy.Safe and reliable modulation parameters were later obtained by thermal effect analysis of the ultrasound sequence.It provides a reliable basis for further experiments and offers some new approaches and mentalities for the use of transcranial focused ultrasound in the study of brain function-related diseases.