Optical Coherence Tomography and Its Non-medical Applications

Optical coherence tomography (OCT) is a promising non-invasive non-contact 3D imaging technique that can be used to evaluate and inspect material surfaces, multilayer polymer films, fiber coils, and coatings. OCT can be used for the examination of cultural heritage objects and 3D imaging of microstructures. With subsurface 3D fingerprint imaging capability, OCT could be a valuable tool for enhancing security in biometric applications. OCT can also be used for the evaluation of fastener flushness for improving aerodynamic performance of high-speed aircraft. More and more OCT non-medical applications are emerging. In this book, we present some recent advancements in OCT technology and non-medical applications

A Multidisciplinary Analysis of Frequency Domain Metal Detectors for Humanitarian Demining

This thesis details an analysis of metal detectors (low frequency electromagnetic induction devices) with emphasis on Frequency Domain (FD) systems and the operational conditions of interest to humanitarian demining. After an initial look at humanitarian demining and a review of their basic principles we turn our attention to electromagnetic induction modelling and to analytical solutions to some basic FD direct (forward) problems. The second half of the thesis focuses then on the analysis of an extensive amount of experimental data. The possibility of target classification is first discussed on a qualitative basis, then quantitatively. Finally, we discuss shape and size determination via near field imaging

Computational Imaging Approach to Recovery of Target Coordinates Using Orbital Sensor Data

This dissertation addresses the components necessary for simulation of an image-based recovery of the position of a target using orbital image sensors. Each component is considered in detail, focusing on the effect that design choices and system parameters have on the accuracy of the position estimate. Changes in sensor resolution, varying amounts of blur, differences in image noise level, selection of algorithms used for each component, and lag introduced by excessive processing time all contribute to the accuracy of the result regarding recovery of target coordinates using orbital sensor data. Using physical targets and sensors in this scenario would be cost-prohibitive in the exploratory setting posed, therefore a simulated target path is generated using Bezier curves which approximate representative paths followed by the targets of interest. Orbital trajectories for the sensors are designed on an elliptical model representative of the motion of physical orbital sensors. Images from each sensor are simulated based on the position and orientation of the sensor, the position of the target, and the imaging parameters selected for the experiment (resolution, noise level, blur level, etc.). Post-processing of the simulated imagery seeks to reduce noise and blur and increase resolution. The only information available for calculating the target position by a fully implemented system are the sensor position and orientation vectors and the images from each sensor. From these data we develop a reliable method of recovering the target position and analyze the impact on near-realtime processing. We also discuss the influence of adjustments to system components on overall capabilities and address the potential system size, weight, and power requirements from realistic implementation approaches

医用超音波における散乱体分布の高解像かつ高感度な画像化に関する研究

Ultrasound imaging as an effective method is widely used in medical diagnosis andNDT (non-destructive testing). In particular, ultrasound imaging plays an important role in medical diagnosis due to its safety, noninvasive, inexpensiveness and real-time compared with other medical imaging techniques. However, in general the ultrasound imaging has more speckles and is low definition than the MRI (magnetic resonance imaging) and X-ray CT (computerized tomography). Therefore, it is important to improve the ultrasound imaging quality. In this study, there are three newproposals. The first is the development of a high sensitivity transducer that utilizes piezoelectric charge directly for FET (field effect transistor) channel control. The second is a proposal of a method for estimating the distribution of small scatterers in living tissue using the empirical Bayes method. The third is a super-resolution imagingmethod of scatterers with strong reflection such as organ boundaries and blood vessel walls. The specific description of each chapter is as follows: Chapter 1: The fundamental characteristics and the main applications of ultrasound are discussed, then the advantages and drawbacks of medical ultrasound are high-lighted. Based on the drawbacks, motivations and objectives of this study are stated. Chapter 2: To overcome disadvantages of medical ultrasound, we advanced our studyin two directions: designing new transducer improves the acquisition modality itself, onthe other hand new signal processing improve the acquired echo data. Therefore, the conventional techniques related to the two directions are reviewed. Chapter 3: For high performance piezoelectric, a structure that enables direct coupling of a PZT (lead zirconate titanate) element to the gate of a MOSFET (metal-oxide semiconductor field-effect transistor) to provide a device called the PZT-FET that acts as an ultrasound receiver was proposed. The experimental analysis of the PZT-FET, in terms of its reception sensitivity, dynamic range and -6 dB reception bandwidth have been investigated. The proposed PZT-FET receiver offers high sensitivity, wide dynamic range performance when compared to the typical ultrasound transducer. Chapter 4: In medical ultrasound imaging, speckle patterns caused by reflection interference from small scatterers in living tissue are often suppressed by various methodologies. However, accurate imaging of small scatterers is important in diagnosis; therefore, we investigated influence of speckle pattern on ultrasound imaging by the empirical Bayesian learning. Since small scatterers are spatially correlated and thereby constitute a microstructure, we assume that scatterers are distributed according to the AR (auto regressive) model with unknown parameters. Under this assumption, the AR parameters are estimated by maximizing the marginal likelihood function, and the scatterers distribution is estimated as a MAP (maximum a posteriori) estimator. The performance of our method is evaluated by simulations and experiments. Through the results, we confirmed that the band limited echo has sufficient information of the AR parameters and the power spectrum of the echoes from the scatterers is properly extrapolated. Chapter 5: The medical ultrasound imaging of strong reflectance scatterers based on the MUSIC algorithm is the main subject of Chapter 5. Previously, we have proposed a super-resolution ultrasound imaging based on multiple TRs (transmissions/receptions) with different carrier frequencies called SCM (super resolution FM-chirp correlation method). In order to reduce the number of required TRs for the SCM, the method has been extended to the SA (synthetic aperture) version called SA-SCM. However, since super-resolution processing is performed for each line data obtained by the RBF (reception beam forming) in the SA-SCM, image discontinuities tend to occur in the lateral direction. Therefore, a new method called SCM-weighted SA is proposed, in this version the SCM is performed on each transducer element, and then the SCM result is used as the weight for RBF. The SCM-weighted SA can generate multiple B-mode images each of which corresponds to each carrier frequency, and the appropriate low frequency images among them have no grating lobes. For a further improvement, instead of simple averaging, the SCM applied to the result of the SCM-weighted SA for all frequencies again, which is called SCM-weighted SA-SCM. We evaluated the effectiveness of all the methods by simulations and experiments. From the results, it can be confirmed that the extension of the SCM framework can help ultrasound imaging reduce grating lobes, perform super-resolution and better SNR(signal-to-noise ratio). Chapter 6: A discussion of the overall content of the thesis as well as suggestions for further development together with the remaining problems are summarized.首都大学東京, 2019-03-25, 博士（工学）首都大学東

Microscopic characterization of functionalized paper as a platform for 3D cell cultures

To achieve an understanding and complete description of the functional properties of three dimensional (3D) cell culture systems, a large set of parameters is required, which clearly contrasts this cell cultivation approach from traditional two dimensional (2D), planar cultivation techniques . As an alternative to describe the characteristics of a 3D cell culture system by its physicochemical properties (e. g. stiffness, porosit y, level of crosslinking), the behavior of the cultivated cells can be used as a read-out parameter to characterize the 3D cultivation system . In this work, the cellular parameters membrane dynamics, actin fiber morphology and migration were used to investigate the differences between classic, planar and a collagen based three dimensional cell culture system Membrane dynamics – assessed by FRAP measurements of CAAX -mCherry – as well as actin formation – visualized by in vitro staining with LifeAct -tagRFP – showed distinct differences when investigated in planar or three dimensional systems. FRAP experiments with CAAX - mCherry showed, that even though the overall membrane composition does not appear to be different, mobility of the membrane is significantl y higher in three dimensional cell culture systems than in two dimensional . A view at the actin cytoskeleton revealed the already established difference: stress fibers and cortical actin are more pronounced in planar cell culture systems compared to cells c ultivated in three dimensional systems. Interestingly, cells originall y seeded in collagen hydrogels which migrated towards the glass surface show features in actin cytoskeleton formation resembling both culture conditions: both, actin stress fibers within the cell body as well as cortical actin are visible in those parts of the cells directly contacting the glass surface . The observed migration towards the glass surface gave rise to the investigation of this behavior. Migration in response to mechanical si gnals is termed durotaxis . Cells cultivated in collagen hydrogels or collagen hydrogels supported by cellulose sheets over a period of time were microscopicall y investigated to determine the distribution of cells . Cell distribution in unsupported collagen hydrogels was clearly in favor of hydrogel regions in close proximity to the glass surface. By applying supporting material in form of cellulose sheets, the cell culture was freely floating in the culture medium, resulting in an even distribution throughout the entire thickness of the cell culture system . As 3D cell culture systems make it more challenging to perform high quality imaging due to the inherent scattering and loss of intensity with increasing optical penetration, a post imaging processing tool set was evaluated and benchmarked in order to counteract these image corrupting effects and improve the image quality. This in turn also improves the compatibility of cellulose sheets with the commonly used tool set in life sciences: fluorescence microscopy. Special emphasis was put on the identification of a serviceable and performance -linked deconvolution setup . A GPU based CUDA Deconvolution plugin showed the best time performance but ultimately failed to produce the same quality level of image restoration as the three tested CPU based deconvolution applications. Among these three, the commercial HyugensPro software showed the best results in terms of increasing the contrast . The Iterative Deconvolution 3D plugin comes close to producing comparable results to the HuygensPro software, however, the time consumption for this application is up to 10 times larger. Finally, the plugin Deconvolution Lab showed reasonably satisfying results in terms of image restoration quality, while performing deconvolution slightly faster than HuygensPro. Finally, cellulose sheets are used for the cultivation of cells in 3D as an example of for paper as a versatile platform for the development of functional devices . Therefore a method is required that delivers spatially resolved, quantitative, sensitive, and, most importantly, also dynamic measurements . Optical microscopy has long been recognized as a method to characterize the heterogeneous and complex structure of paper. With fluorescence detection, the functionality has even been extended to provide chemical selectivity, e . g. to determine the distribution of secondary modifications like coatings and fillers throughout a sheet of paper. Here it is shown that quantitative widefield and confocal fluorescence microscopy are versatile methods to meet this set of demands. Confocal microscopy was used to achieve a detailed view of the interface between a hyd rophobic and rhodamine labeled polymer and a FITC labeled dextran solution. Furthermore, confocal microscopy revealed that the spatial propagation of the FITC labeled dextran solution occurs along the surface of the cellulose fibers, instead of the inter -fibers space. Widefield fluorescent microscopy was subsequently used for dynamic investigations of this spatial propagation