Dispersive Fourier Transformation for Versatile Microwave Photonics Applications

Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well

Towards Picogram Detection of Superparamagnetic Iron-Oxide Particles Using a Gradiometric Receive Coil

Superparamagnetic iron-oxide nanoparticles can be used in a variety of medical applications like vascular or targeted imaging. Magnetic particle imaging (MPI) is a promising tomographic imaging technique that allows visualizing the 3D nanoparticle distribution concentration in a non-invasive manner. The two main strengths of MPI are high temporal resolution and high sensitivity. While the first has been proven in the assessment of dynamic processes like cardiac imaging, it is unknown how far the detection limit of MPI can be lowered. Within this work, we will present a highly sensitive gradiometric receive-coil unit combined with a noise-matching network tailored for the measurement of mice. The setup is capable of detecting 5 ng of iron in vitro at 2.14 sec acquisition time. In terms of iron concentration we are able to detect 156 {\mu}g/L marking the lowest value that has been reported for an MPI scanner so far. In vivo MPI mouse images of a 512 ng bolus at 21.5 ms acquisition time allow for capturing the flow of an intravenously injected tracer through the heart of a mouse. Since it has been rather difficult to compare detection limits across MPI publications we propose guidelines improving the comparability of future MPI studies.Comment: 15 Pages, 7 Figures, V2: Changed the initials of Author Kannan M Krishnan, added two citations, corrected typo

Implementation of medical imaging with telemedicine for the early detection and diagnoses of breast cancer to women in remote areas

Nowadays, the cancer topic has become a global concern. Furthermore, breast cancer persists to be the top leading cause of death to women population and the second cause of cancer death after the lung cancer globally. Various technologies and techniques have been searched, developed and studied over the years to detect the disease at the early stage; the early diagnosis saves many lives in both developed and developing countries. The detection of cancer through a screening process before its symptoms emerge increases the survival rate dramatically (Li, Meaney and Paulsen). Moreover, sufficient knowledge of the disease, qualified staff, accurate, appropriate treatment and diagnosis contribute to the successful cure of the disease; however, the cancer treatment is not affordable by many and sometimes not available to the very needy, and more precisely in developing countries. In this research, we aimed to explore the early detection of breast cancer using the new image compression algorithm: DYNAMAC, a compression tool that finds its basis in nonlinear dynamical systems theory; we implemented this algorithm through the D-transform, a digital sequence used to compress the digital media (Wang and Huang) & (Antoine, Murenzi and Vandergheynst). The goal is to use this method to analyze the average profile of diseased and healthy breast images obtained from a digital mammography to detect diseased tissues. After the detection of cancerous tumors, we worked to establish a remote care to women victims of breast cancer using the Telecommunication infrastructure through primarily Teleradiology and the Next Generation Internet (NGI) technology. Over the methods and techniques previously used in the area of medical imaging techniques, DYNAMAC algorithm is the most easily implemented along with its features that include cost saving in addition to best meeting the requirements of the breast imaging technology

Hyperspectral terahertz microscopy via nonlinear ghost-imaging

Ghost-imaging, based on single-pixel detection and multiple pattern illumination, is a crucial investigation tool in difficult-to-access wavelength regions. In the terahertz domain, where high-resolution imagers are mostly unavailable, Ghost-imaging is an optimal approach to embed the temporal dimension, creating a ‘hyperspectral’ imager. In this framework high-resolution is mostly out-of-reach. Hence, it is particularly critical to developing practical approaches for microscopy. Here we experimentally demonstrate Time-Resolved Nonlinear Ghost-Imaging, a technique based on near-field, optical-to-terahertz nonlinear conversion and detection of illumination patterns. We show how space-time coupling affects near-field time-domain imaging and we develop a complete methodology that overcomes fundamental systematic reconstruction issues. Our theoretical-experimental platform enables high-fidelity subwavelength imaging and carries relaxed constrains on the nonlinear generation crystal thickness. Our work establishes a rigorous framework to reconstruct hyperspectral images of complex samples inaccessible through standard fixed-time methods

System Characterization of a Human-Sized 3D Real-Time Magnetic Particle Imaging Scanner for Cerebral Applications

Since the initial patent in 2001, the Magnetic Particle Imaging (MPI) community has been striving to develop an MPI scanner suitable for human applications. Numerous contributions from different research fields, regarding tracer development, reconstruction methods, hardware engineering, and sequence design have been employed in pursuit of this objective. In this work, we introduce and thoroughly characterize an improved head-sized MPI scanner with an emphasis on human safety. The scanner is operated by open-source software that enables scanning, monitoring, analysis, and reconstruction, designed to be handled by end users. Our primary focus is to present all technical components of the scanner, with the ultimate objective to investigate brain perfusion imaging in phantom experiments. We have successfully achieved full 3D single- and multi-contrast imaging capabilities at a frame rate of 4 Hz with sufficient sensitivity and resolution for brain applications. To assess system characterization, we devised sensitivity, resolution, perfusion, and multi-contrast experiments, as well as field measurements and sequence analysis. The acquired images were captured using a clinically approved tracer and suitable magnetic field strengths, while adhering to the established human peripheral nerve stimulation thresholds. This advanced scanner holds potential as a tomographic imager for diagnosing conditions such as ischemic stroke or intracranial hemorrhage in environments lacking electromagnetic shielding. Furthermore, due to its low power consumption it may have the potential to facilitate long-term monitoring within intensive care units for various applications.Comment: 22 pages, 9 figure

Scanless optical coherence tomography for high-speed 3d biomedical microscopy

Optical coherence tomography (OCT) is a high-resolution cross-sectional imaging modality that has found applications in a wide range of biomedical fields, such as ophthalmology diagnosis, interventional cardiology, surgical guidance, and oncology. OCT can be used to image dynamic scenes, in quantitative blood flow sensing and visualization, dynamic optical coherence elastography, and large-scale neural recording. However, the spatiotemporal resolution of OCT for dynamic imaging is limited by the approach it takes to scan the three-dimensional (3-D) space. In a typical OCT system, the incident light is focused to a point at the sample. The OCT system uses mechanical scanners (galvanometers or MEMS scanners) steer the probing beam to scan the transverse plane and acquires an A-scan at each transverse coordinate. For volumetric imaging, the OCT system scans individual voxels in a 3D Cartesian coordinate sequentially, resulting a limited imaging speed. In addition to limited spatiotemporal resolution, the use of mechanical scanners results in bulky sample arm and complex system configuration. This dissertation seeks to overcome limitations of conventional raster scanning approach for OCT data acquisition, by investigating novel methods to address OCT voxels in 3D space. Scanless OCT imaging is achieved through the use of spatial light modulator that precisely manipulates light wave to generate output with desired amplitude and phase. It is anticipated that the scanless OCT imaging technologies developed in this dissertation will introduce a significant paradigm shift in OCT scanning of 3D space and allow the observation of transient phenomena (neural activities, blood flow dynamics, etc.) with unprecedented spatiotemporal resolution. This research focuses on technology development and validation. Two approaches for scanless OCT imaging are investigated. One approach is optically computed optical coherence tomography (OC-OCT), and the other approach is Line field Fourier domain OCT (LF-FDOCT) based on spatial light modulator. OC-OCT takes a highly innovative optical computation strategy to extract signal from a specific depth directly without signal processing in a computer. The optical computation module in OC-OCT performs Fourier transform optically before data acquisition, by calculating the inner product between a Fourier basis function projected by the spatial light modulator and the Fourier domain interferometric signal. OC-OCT allows phase resolved volumetric OCT imaging without mechanical scanning, and has the capability to image an arbitrary 2D plane in a snapshot manner. LF-FDOCT illuminates the sample with a line field generated by a spatial light modulator. Interferometric signals from different transverse coordinates along the line field are dispersed by a grating and detected in parallel by the rows of a 2D camera. Cross-sectional image (Bscan) is obtained by performing Fourier transform along the rows of the camera. By scanning the line field electronically at the SLM, volumetric OCT imaging can be performed without mechanical scanning. In this dissertation, the principles of OC-OCT and LF-FDOCT technology are described. The imaging capability of OC-OCT and LF-FDOCT systems are quantitatively evaluated and demonstrated in 2D and 3D imaging experiments on a variety of samples