Biomedical applications of closed-loop accumulation of single scattering microscopy
CLASS현미경의 생물 의학 응용
- 주제(키워드) CLASS microscopy , Biomedical application
- 발행기관 고려대학교 대학원
- 지도교수 최원식
- 발행년도 2021
- 학위수여년월 2021. 2
- 학위구분 박사
- 학과 대학원 물리학과
- 원문페이지 117 p
- UCI I804:11009-000000235421
- DOI 10.23186/korea.000000235421.11009.0001159
- 본문언어 영어
- 제출원본 000046072197
초록/요약
About 80% of human cancer cells grow at a depth of a millimeter or more from the surface of organs. Cell nuclei are enlarged at the initial stage, but it is difficult to identify them with existing medical imaging techniques because their size is only a few microns. Therefore, the growth of tumor cells can only be identified at a later stage after they grow big enough to emerge from the surface as a polyp. To accelerate the early diagnosis of the disease, it is necessary to develop high-resolution optical microscopy that can observe subcelluar structures individual cells deep within biological tissues. This requires the addressing of the fundamental problem of image distortion by the multiple light scattering and aberrations induced by the complex scattering tissues. Previously, we developed an optical microscopy based on the collective accumulation of single scattering (CASS) for effectively reducing multiple scattering noise. It has been shown that it can be used to image objects located deep within scattering tissues. Taking this study further, we analyzed the trends in the spatial frequency spectrum of single- and multiple-scattered waves in CASS microscopy. Single scattering signal to multiple scattering noise ratio was theoretically derived depending on the object spatial frequency, and experiments were conducted to support this theory. This study led us to quantitatively predict the achievable spatial resolution given the depth of a target object. Essentially, it provides a theoretical framework for understanding high-resolution optical imaging in the presence of multiple-scattered light. On the basis of the CASS microscopy, a method termed closed-loop accumulation of single scattering (CLASS) was developed that can eliminate the tissue-induced aberrations in the presence of strong multiple scattering noise. In this CLASS microscopy, the aberration of single-scattered waves caused by living tissues was found through the closed-loop optimization between the illumination and detection pathways. By computationally correcting the identified aberrations, we achieved a spatial resolution of 600 nm up to the imaging depth of seven scattering mean free paths. I conducted imaging of a rabbit’s cornea infected by the Aspergillus fumigatus, a type of fungi, and successfully visualized individual fungal filaments embedded within opaque fungal infection. Since the initial development of CLASS microscopy, I have been seeking for its biological applications. In particular, I have designed and conducted imaging of retina cells in mice and human subjects in conditions where scattering noise and eye aberrations are pronounced. Currently, the performance of the system was validated for a model eye mimicking the human eye and conventional optical coherence tomography system was combined to guide the CLASS system. We plan to apply the developed system in interrogating human retina cells in the near future.
more목차
Chapter 1. Introduction 1
1.1 Multiple light scattering 1
1.1.1 Detrimental effects of scattering 1
1.1.2 Temporal or coherence gating 1
1.1.3 Using waves that are scattered multiple times at small deflection 2
1.1.4 Exploits multiple-scattered waves in full 2
1.2 Aberration 3
1.2.1 Detrimental effects of aberrations 3
1.2.2 Adaptive optics based on wavefront sensing. 5
1.2.3 Sensor-less adaptive optics 7
1.3 Bibliography 8
Chapter 2. Optical transfer function in the presence of a scattering medium 13
2.1 Introduction 13
2.2 Angular compounding and CASS imaging 16
2.3 Description of single- and multiple-scattered waves 18
2.4 Optical transfer function of incoherent imaging 21
2.5 Optical transfer function of CASS microscopy 25
2.6 Comparison between incoherent imaging and CASS microscopy 28
2.7 Experimental results 31
2.8 Conclusion 35
2.9 Bibliography 36
Chapter 3. Closed-loop accumulation of single scattering microscopy 42
3.1 Introduction 42
3.2 The effects of sample-induced aberrations 45
3.3 Theoretical framework for dealing with aberrations 50
3.4 Experimental setup 57
3.5 Data acquisition and image reconstruction 59
3.6 Experimental demonstration of CLASS microscopy with phantom samples 65
3.7 Demonstration of CLASS microscopy for biological specimens 67
3.7.1 Rat villi 67
3.7.2 Ex vivo fungal keratitis rabbit cornea infected by A. fumigatus 69
3.8 Conclusion 72
3.9 Bibliography 74
Chapter 4. CLASS microscopy for retina imaging 77
4.1 Introduction 77
4.2 Imaging trials using animal eyes 77
4.2.1 System combining confocal microscopy and CLASS microscopy 77
4.2.2 Mouse sample preparation 80
4.2.3 Mouse retina imaging using the confocal system 81
4.3 Imaging trials using model eyes 84
4.3.1 Combined system of OCT and CLASS microscopy 84
4.3.2 Model-eye observation using OCT system 86
4.3.1 Model-eye observation using CLASS system 89
4.4 Human retina observation using OCT system 95
4.5 Future plan 97
4.6 Conclusion 98
4.7 Bibliography 99
Chapter 5. Summary 102
