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Laser-Generated Focused Ultrasound for Brain Stimulation Using Carbon Nanotube Composite Transducer

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Abstract
Focused Ultrasound (FUS) can non-invasively and precisely intervene in key circuits that control common and challenging brain disorders. Neurons can be activated or inhibited by adjusting the parameters of FUS. However precise targeting at the microscopic level requires a spatial accuracy of several millimeters. Therefore, the development of high precision neurostimulation is essential to stimulate specific brain regions effectively. Laser-generated focused ultrasound (LGFUS) has shown potential for precision therapeutic ultrasound applications due to its ability to generate high-pressure, broadband shock waves with a narrow focal spot. However, there has been little research on neurostimulation using shock waves with pulse durations of sub microseconds. Our study thoroughly explores the potential of neurostimulation by LGFUS using carbon nanotube (CNT) composite transducers and presents LGFUS as an excellent precision tool for brain stimulation. In this study, we explore the structural properties of CNT composite transducers as LGFUS tools to achieve high-precision neuromodulation. To comprehensively investigate the LGFUS properties, CNT composite transducers with different diameters and support structures were fabricated. The peak positive and negative sound pressure generated by the CNT composite transducer are 32 to 52 MPa and -9 to -24 MPa for 2 to 8 cm diameters, respectively. Our experiments confirmed a correlation between increasing transducer diameter and increasing peak pressure in LGFUS. We investigated responses to rat brain stimulation with LGFUS generated from the explored CNT composite transducers. Electroencephalographic (EEG) signals recorded from rat brains before and after LGFUS stimulation show distinct differences in time and frequency domains. After stimulation, the EEG signal has increased, indicating increased neural activity and distinct changes in the 1-30 Hz band. These changes in the EEG signal highlight the ability to accurately stimulate the brain with LGFUS generated by CNT composite transducers. Finally, as a preliminary experiment to confirm the possibility of human brain stimulation, the possibility of LGFUS penetration into the human cadaver skull was investigated. The peak positive sound pressures before and after skull penetration were 14.6 MPa and 1.1 MPa, respectively, and the central frequency was changed from 1 MHz and 464 kHz, respectively. These results of LGFUS have important implications for future neurostimulation research and transcranial applications, suggesting potential use for high-precision brain stimulation.
Author(s)
이주호
Issued Date
2024
Awarded Date
2024-02
Type
Dissertation
URI
https://dcoll.jejunu.ac.kr/common/orgView/000000011616
Alternative Author(s)
Lee Joo ho
Affiliation
제주대학교 대학원
Department
대학원 지구해양융합학부
Advisor
팽동국
Table Of Contents
CONTENTS 3
LIST OF FIGURES 7
LIST OF TABLES 14
ABSTRACT 15
CHAPTER Ⅰ INTRODUCTION 17
1.1 Background of Therapeutical Ultrasound 17
1.2 Neuromodulation Of Therapeutic Ultrasound 25
1.3 Characteristics of LGFUS 28
1.4 Motivation 30
1.5 Specific Aims 32
1.6 Thesis Outline 34
CHAPTER Ⅱ LASER GENERATED FOCUSED ULTRASOUND AND TRANSDUCER STRUCTURE 35
2.1 Background. 35
2.2 Principles of LGFUS. 38
2.3 Materials and Method 43
2.3.1 Fabrication of CNT composite transducer 43
2.3.2 Difference structure of LGFUS transducer 45
2.3.3 LGFUS Acquisition 47
2.4 Results 49
2.4.1 Structure Changing of CNT Composite Transducer 49
2.4.2 Acoustic Pressure According to Diameter Changing 51
2.4.3 Relationship between Laser Energy and Acoustic Pressure 54
2.5 Discussion 60
2.6 Conclusion 64
CHAPTER Ⅲ APPLICATION OF LASER GENERATED FOCUSED ULTRASOUND 65
3.1 Application of Rat using LGFUS 65
3.2 Method and Experimental Set up 67
3.2.1 Animal Preparation 67
3.2.2 EEG Signal Acquisition and Analysis 67
3.2.3 Experimental set up 69
3.2.4 LGFUS Acquisition 71
3.3 Results 73
3.3.1 EEG Channel Selection 73
3.3.2 EEG Real Time Monitoring during LGFUS Brain Stimulation 76
3.3.3 EEG Signal Before and After LGFUS Brain Stimulation 80
3.4 Discussion 88
3.5 Conclusion 94
CHAPTER Ⅳ PRELIMINARY EXPERIMENT TO EXPLORE THE CHARACTERISTICS OF LGFUS THROUGH HUMAN SKULL CADAVER 95
4.1 Introduction 95
4.2 Material and Experimental set up 98
4.2.1 Skull Acquisition 98
4.2.2 Morphological Information and Experimental Set up 98
4.3 Results 101
4.3.1 Characterization of LGFUS with and without Skull Cadaver 101
4.3.2 Comparison of HIFU and LGFUS with and without Skull Cadaver Penetration 104
4.4 Discussion 107
4.5 Conclusion 110
CHAPTER Ⅴ CONCLUSION AND FUTURE STUDIES 111
5.1 Conclusion 111
5.2 Future Studies 113
REFERENCE 115
Degree
Doctor
Publisher
제주대학교 대학원
Citation
이주호. (2024). Laser-Generated Focused Ultrasound for Brain Stimulation Using Carbon Nanotube Composite Transducer.
Appears in Collections:
Faculty of Earth and Marine Convergence > Earth and Marine Science
Faculty of Earth and Marine Convergence > Ocean System
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  • Embargo2024-02-12
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