Theses and Dissertations at Montana State University (MSU)
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Item Widefield micro-camera integrated into the objective lens of a reflectance confocal microscope for concurrent image registration(Montana State University - Bozeman, College of Engineering, 2023) Aist, Joseph Nicholas; Chairperson, Graduate Committee: David L. DickensheetsWith millions of new skin disease cases reported annually, non-invasive imaging methods have been developed to diagnose skin disease accurately. Reflectance confocal microscopes (RCM) have led these new technologies with high sensitivity and specificity. However, current methods use multiple devices: a digital camera, a dermoscope, and an RCM, which are not co-registered. Therefore, locating small, microscopic RCM fields-of-view (0.5x0.5 mm) at specific suspicion sites within the larger dermoscopic field-of-view (10x10 mm) is extremely difficult. This 'blind' RCM imaging results in lower and more variable diagnostic accuracy, particularly sensitivity, where positive and negative predictive values can drop by up to 30%. Our team has designed a new objective lens with an integrated micro-camera to deliver a concurrent widefield image of the skin surface surrounding the location of microscopic RCM imaging. The widefield image can be used directly to provide context for RCM or can be registered to a previously stored high-resolution clinical image to show where RCM imaging is occurring. In this thesis, the micro-camera is characterized and tested in laboratory and clinical settings. In addition, this thesis investigates a co- and cross-polarized micro-camera and LED system. It compares them to the non-polarized system to explore whether the cross-polarized version enhances feature contrast and enables better dermoscopic imaging. Non-polarized, co-polarized, and cross-polarized mock-up probes of the objective lens with a micro-camera were designed and built for testing. Images of resolution targets, color charts, and skin were taken to obtain modulation transfer function (MTF) measurements, color analysis data, and representative skin images. The results showed improvement in the MTF for the cross- polarized probe when compared to the co- and non-polarized probes. It was also found that the polarization of the imaging system did not significantly affect the color quality of the images. When tested by scientists at Memorial Sloan Kettering Cancer Center, sub-surface features not seen with the co- and non-polarized probes were observed with the cross-polarized probe. The cross-polarized probe suppressed the surface reflections, allowing for sub-surface information to be captured.Item MEMS 3-dimensional scanner with SU-8 flexures for a handheld confocal microscope(Montana State University - Bozeman, College of Engineering, 2018) Liu, Tianbo; Chairperson, Graduate Committee: David DickensheetsThe conventional method for diagnosing skin cancer is to perform a biopsy followed by pathology. However not only are biopsies invasive and likely to leave permanent scarring, they also sample the body sparsely. Fortunately, a non-invasive method of imaging called confocal laser scanning microscopy has shown great potential to replacing invasive biopsies. Confocal microscopy can use light to achieve high-resolution imaging of cells that lie underneath the surface of the skin. However, the large size of current confocal microscopes limits their application to all but the most accessible sites. In this dissertation, I address the miniaturization of confocal microscopy through the development of a new microelectromechanical systems scan mirror that can scan a focused beam in three dimensions. The scanner has a 4 mm aperture, and has the capability to replace all of the bulky beam scanners and focus mechanisms that contribute to the large size of current confocal microscopes. The fabrication of the scanner explores the use of the polymer SU-8 for its mechanical structures. The gimbal mirror has demonstrated scan angles in excess of plus or minus 3° mechanical for lateral scanning, and its deformable surface provided controllable deflection up to 10 microns for focus control. This newly developed scanner was integrated into a confocal system to test its imaging capabilities. The device demonstrated high-resolution scanning with simultaneous focus adjustment suitable for the next generation of miniaturized confocal laser scanning microscopes.Item Development of an active/adaptive laser scanning microscope(Montana State University - Bozeman, College of Engineering, 2018) Archer-Zhang, Christian Chunzi; Chairperson, Graduate Committee: David L. DickensheetsLaser scanning techniques such as confocal microscopy and two-photon excitation fluorescence microscopy (TPM) are powerful tools for imaging biological samples with high resolution, offering three-dimensional (3D) visualization of the behavior of cells in their natural environment. Traditionally, the 3D images are acquired from 2D image stacks with focusing depth controlled through mechanical movement of the specimen relative to the objective lens. The slow mechanical movement (~<20Hz) does not allow the spot of light to be scanned axially sufficiently fast to monitor cell:cell and cell:environment interactions in real time over hundreds of microns in all three dimensions. A fast focus control mirror supports agile scan patterns such as vertical or oblique planes or even arbitrary surfaces, minimizing the time and photo damage required to monitor features of interest within the 3D volume. Because aberrations cause image quality to decrease as the focal point of the beam penetrates deeper into the sample, adaptive optics can enhance resolution and contrast at depth for confocal microscopy and TPM. Combining a fast focus control mirror with a fast aberration correcting mirror leads to a flexible platform called the active/adaptive laser scanning microscope, capable of aberration-corrected beam scanning throughout a 3D volume of tissue. This opens up the possibility of fully corrected, variable-depth imaging along oblique sections or more complex user-defined surfaces within a single image frame.Item A Confocal Microscope and Raman Spectroscopy Probe for Mars exploration(Montana State University - Bozeman, College of Engineering, 2002) Crowder, Dawn MichelleItem Mems 3-D scan mirror for an endoscopic confocal microscope(Montana State University - Bozeman, College of Engineering, 2005) Shao, Yuhe; Chairperson, Graduate Committee: David L. Dickensheets.Optical MEMS is at a very exciting stage and has become an enabling technology for a variety of applications in telecommunications and high-resolution display and imaging. Among many novel MEMS devices, MEMS scanners and deformable membrane mirrors are especially useful for scanned-beam imaging systems. MEMS scanners are usually used for laser beam scanning. Deformable mirrors provide an approach to modify the optical wavefront adaptively. In optical microsystems, packaging is often a critical part of the system design. Combining functionalities at a single device can reduce complexity of the system. Biaxial beam scanning and focus control are combined together in the MEMS 3-D scan mirror. The mirror surface is made of a goldcoated silicon nitride deformable membrane and works as a positive lens of variable focal length. The membrane sits on a torsional plate that can scan about two orthogonal axes. This architecture is able to move the focus of a laser beam throughout a threedimensional space with a single optical surface. The overall size of the 3-D mirror is 1.5 mm with a usable optical aperture of 0.7 mm. Both the inner and outer scanning axes achieved more than 5o zero-to-peak mechanical scan angles; the deformable membrane achieved a maximum center displacement of more than 3.7 æm, corresponding to an adjustable focal length from infinity to approximately 8 mm. For a confocal laser scanning microscope with illumination wavelength at 500 nm, they provide Nx = Ny = 488 resolvable spots for lateral resolution, and Nz = 32 depth-of-focus distances for depth resolution. To drive the 3-D mirror, the inner axis is operated near resonance (~ 650 Hz); and the outer axis quasi-statically. Operating the outer axis at 2 Hz provides a line resolution of 325 lines/frame at a refresh rate of 2 frames/second. The performance of the 3-D mirror is well matched to the intended application of endoscopic confocal microscopy, and similar devices could prove useful in a variety of optical microsystems needing beam scanning and focus control. This dissertation describes the design, fabrication, characterization, imaging experiment and target applications of the MEMS 3- D scan mirror.Item Heterodyne detection fiber confocal microscope for in vivo skin imaging(Montana State University - Bozeman, College of Engineering, 2011) Xue, Xiaohu; Chairperson, Graduate Committee: David L. DickensheetsConfocal microscopy has been demonstrated to be a very effective tool for imaging in-vivo samples. The confocal imaging geometry provides a dramatic optical advantage for microscopy by discriminating against out-of-focus background with minimal loss of image-forming signal. Because of these advantages, the confocal laser scanning microscope (CLSM) can image a thin layer clearly from a thick sample without biopsy. However, current usage of CLSM is limited by the signal-to-noise ratio using conventional optical detection. In order to achieve deeper penetration into the skin in a clinical setting, a technique called heterodyne detection is incorporated into the CLSM system. This thesis describes the optical, mechanical and electrical design of the system, evaluates system noise and imaging performance, and provides initial skin images collected by the heterodyne system, comparing the results with direct detection. The heterodyne detection system is proved to have deeper penetration than the direct detection system, but the image quality is degraded.Item A combined confocal imaging and raman spectroscopy microscope for in vivo skin cancer diagnosis(Montana State University - Bozeman, College of Engineering, 2008) Arrasmith, Christopher Lyman; Chairperson, Graduate Committee: David L. DickensheetsConfocal microscopy has provided a useful tool for imaging biopsied tissue samples. The cross sectioning ability inherent in confocal microscopes provides a method for viewing of cellular structure at different layers of a histology sample, allowing for optical cross sectioning and viewing structures below the surface of the sample. As a cancer diagnosis technique, confocal microscopy has been shown to provide valuable information showing differences in cell morphology of malignant and benign regions. Raman spectroscopy has also been shown to be a useful tool for cancer diagnosis in skin tissues due to its ability to distinguish different types of chemical bonds. While both of these methods may be used for cancer detection, current devices are limited to ex vivo samples. The goal of this project was to design and build a hand held microscope which could be used for in vivo confocal imaging and Raman spectroscopy of suspected malignant lesions in skin. This thesis describes the optical, mechanical and electrical design and fabrication of the microscope, as well as performance testing and initial in vivo skin data collected with the microscope. It is our hope that this instrument will be used to gather important in vivo skin cancer data and spur future developments in small diagnosis tools that can be used in a clinical setting.