X-ray phase-contrast imaging has seen rapid development in recent decades due to its superior performance in imaging low-absorption objects, compared to traditional attenuation x-ray imaging. Having higher demand on coherence, x-ray phase-contrast imaging is performed mostly at synchrotrons. With the development of different imaging techniques, and the development of laboratory sources and x-ray optics, x-ray phase-contrast imaging can now be implemented on laboratory systems, which is promising and practical for broader range of applications. The subject of this thesis is the implementation, development and comparison of different laboratory phase-contrast methods using a liquid-metal-jet source. The three x-ray phase-contrast imaging methods included in this thesis are the propagation-, grating-, and speckle-based techniques. The grating-based method has been implemented on a laboratory system with a liquid-metal-jet source, which yields several times higher brightness than a standard solid-anode microfocus source. This allows shorter exposure time or a higher signal-to-noise ratio. The performance of the grating-based method has been experimentally and numerically compared with the propagation-based method, and the dose required to observe an object as a function of the object’s diameter has been investigated with simulations. The result indicates a lower dose requirement for the propagation-based method in this system but a potential advantage for the grating-based method to detect relatively large samples using a monochromatic beam. The speckle-based method, both the speckle-tracking and speckle-scanning techniques, has been implemented on a laboratory system for the first time, showing its adaptability to radiation of low temporal coherence. Tomography has been performed and shows the potential applications of this method on quantitative analysis on both absorption and phase information of materials. As a basis for further optimization and comparisons to other methods, the noise properties of the differential phase contrast of the speckle-based method have been studied and an analytical expression for the noise variance introduced, showing a similarity to the grating-based method. / Faskontrastavbildning med röntgenstrålning är en teknik som har utvecklats kraftigt de senaste årtiondena, eftersom den fungerar bättre än traditionella, absorptionsbaserade röntgenundersökningar för objekt med låg absorption. Den har dock höga krav på koherens, vilket gjort att den huvudsakligen används vid stora synkrotron-anläggningar. Tack vare utveckligen av nya avbildningstekniker, laboratoriekällor och röntgenoptik kan numera faskontrast användas även med laboratoriesystem, vilket är lovande då tekniken kan användas vid ett större antal olika tillämpningsområden Denna avhandling syftar till att tillämpa, utveckla och jämföra olika faskontrastmetoder i laboratoriemiljö, med en metallstråleröntgenkälla. De tre faskontrastmetoderna som behandlas i denna avhandling är propogation, gitter och speckelbaserad faskontrast. Den gitterbaserade metoden har implementerats i ett laboratoriesystem med en metallstrålekälla som ger flera gånger högre radians än en vanlig, fast mikrofokuskälla. Den högre radians en möjliggör kortare exponeringstider eller högre signal-brusförhållande. Den gitterbaserade tekniken har jämförts experimentellt och numeriskt med den propageringsbaserade metoden. Den strålningsdos som krävs för observera ett objekt, som funktion av dess diameter, har jämförts för de båda teknikerna, den här gången via simuleringar. Resultaten visar på en lägre strålningsdos för den propagationsbaserade tekniken i detta fall, men även att det finns en potentiell fördel för den gitterbaserade tekniken för något större objekt med monokromatisk röntgenstrålning. Speckelbaserade tekniker, nämare bestämt den som bygger på att spåra speckel och den som bygger på att scanna diffusorn, har för första gången implementerats i laboratoriemiljö. Därmed har visats att de fungerar även för strålning med låg tidskoherens. Tekniken har även använts för tomografi och visar möjliga tillämpningar inom kvantitativ analys av material. För att förenkla framtida optimeringar och jämförelser av tekniken med andra metoder, har brusegenskaperna för den speckelbaserade metoden studerats och visat sig likna den gitterbaserade metoden. / <p>QC 20160921</p>

Analyzer crystal based imaging techniques such as diffraction enhanced imaging (DEI) and multiple imaging radiography (MIR) utilize the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes. These X-ray techniques extend the capability of conventional radiography, which derives image contrast from absorption, by providing a large change in intensity for a small angle change introduced by the X-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultra small angle X-ray scattering (USAXS) contrast thus improving visualization and extending the utility of X-ray imaging. To improve on the current DEI technique this body of work describes the design of an X-ray prism (XRP) included in the imaging system which allows the analyzer crystal to be aligned anywhere on the rocking curve without moving the analyzer from the Bragg angle. By using the XRP to set the rocking curve alignment rather than moving the analyzer crystal physically the needed angle sensitivity is changed from ìradians for direct mechanical movement of the analyzer crystal to milliradian control for movement the XRP angle. In addition to using an XRP for the traditional DEI acquisition method of two scans on opposite sides of the rocking curve preliminary tests will be presented showing the potential of using an XRP to scan quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single fast measurement thus removing the occurrence of motion artifacts for each point or line used during a scan. The XRP design is also intended to be compatible with combined imaging systems where more than one technique is used to investigate a sample. Candidates for complimentary techniques are investigated and measurements from a combined X-ray imaging system are presented.

Analyzer crystal based imaging techniques such as diffraction enhanced imaging (DEI) and multiple imaging radiography (MIR) utilize the Bragg peak of perfect crystal diffraction to convert angular changes into intensity changes. These X-ray techniques extend the capability of conventional radiography, which derives image contrast from absorption, by providing a large change in intensity for a small angle change introduced by the X-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultra small angle X-ray scattering (USAXS) contrast thus improving visualization and extending the utility of X-ray imaging. To improve on the current DEI technique this body of work describes the design of an X-ray prism (XRP) included in the imaging system which allows the analyzer crystal to be aligned anywhere on the rocking curve without moving the analyzer from the Bragg angle. By using the XRP to set the rocking curve alignment rather than moving the analyzer crystal physically the needed angle sensitivity is changed from ìradians for direct mechanical movement of the analyzer crystal to milliradian control for movement the XRP angle. In addition to using an XRP for the traditional DEI acquisition method of two scans on opposite sides of the rocking curve preliminary tests will be presented showing the potential of using an XRP to scan quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single fast measurement thus removing the occurrence of motion artifacts for each point or line used during a scan. The XRP design is also intended to be compatible with combined imaging systems where more than one technique is used to investigate a sample. Candidates for complimentary techniques are investigated and measurements from a combined X-ray imaging system are presented.

This Ph.D. work is dedicated to advancements in burst-mode laser technology and their applications in MHz-rate high-speed gas-phase environments. A comprehensive computational model for simulating experimental burst-mode systems is discussed. Direct comparison of the modeled results to the output of a constructed nanosecond (ns) burst-mode laser shows agreement within a factor of 2 for output energy, the temporal domain skews positively in an appropriate manner, and the spectral domain correctly remains unchanged. The modeled output of a femtosecond (fs) burst-mode laser displays near perfect agreement with its hardware, generating only a 1.7% deviation for output energy, an 11% deviation in spectral bandwidth, and a temporal profile that correctly remains unchanged. The experimental ns to fs burst-mode lasers systems used to compare with the aforementioned model are described in detail and demonstrated for use in measurements of temperature, species, and velocity at high repetition rates. In the ns regime, a compact-footprint (0.18 m2 ) flashlamp-pumped, burst-mode Nd:YAGbased master-oscillator power-amplifier (MOPA) laser is developed with a fundamental 1064 nm output of over 14 J per burst. This portable laser system uses a directly modulated diode laser seed source to generate 10 ms duration arbitrary sequences of 500 kHz doublet or MHz singlet pulses for flow-field velocity or species measurements, respectively. In the fs regime, a flashlamp-pumped burst-mode laser system with high peak power and a broad spectral bandwidth of >10 nm is constructed without the use of nonlinear compression techniques. A mode-locked, 1064.6 nm fundamental-wavelength broadband master oscillator, a fiber amplifier/pulse stretcher, and four Nd:glass power amplifiers are used to generate a sequence of high-repetition-rate, transform-limited 234 fs pulses over a 1 ms burst duration at a 0.1 Hz burst repetition rate. The generated peak powers are 1.24 GW at 100 kHz and 500 MW at 1 MHz with M2∼1.5. An adaptation of the fs burst-mode laser is used for femtosecond laser electronic excitation tagging (FLEET) of nitrogen for tracking the velocity field in high-speed flows at kilohertz– megahertz (kHz–MHz) repetition rates without the use of added tracers. The fs burst-mode laser is used to produce 500 pulses per burst with pulses having a temporal separation as short as 1 µs, an energy of 120 µJ, and a duration of 274 fs. This enables 2 orders of magnitude higher measurement bandwidth over conventional kHz-rate FLEET velocimetry. 15 The fs burst-mode system was further improved to include a picosecond (ps) leg for hybrid fs/ps rotational coherent anti-Stokes Raman scattering (RCARS) at MHz rates. Using a common fs oscillator, the system simultaneously generates time synchronized 1061 nm, 274 fs and 1064 nm, 15.5 ps pulses with peak powers of 350 MW and 2.5 MW, respectively. The system is demonstrated for two-beam fs/ps RCARS in N2 at 1 MHz with a signal-to-noise ratio of 176 at room temperature. This repetition rate is an order of magnitude higher than previous CARS using burst-mode ps laser systems and two to three orders of magnitude faster than previous continuously pulsed fs or fs/ps laser systems. As a continuation of the above advances in fs regime, a regenerative fs burst-mode laser is discussed in detail with motivations, design layouts, and cavity physics laid out. Preliminary construction of the system with a ns seed source is underway to assess the detailed system design and evaluate the potential for optical damage due to Kerr lensing or other nonlinear effects. This system and other potential follow-on research topics are discussed.

No description available.

Background and Rationale: Reproductive dysfunction affects more than 15% of Canadian women; however, the underlying causes remain largely unknown. Ultrasonography is the most commonly used research and diagnostic tool for imaging the ovaries and uterus. However, current ultrasonographic techniques allow the detection of ovarian structures (eg. follicles, corpora lutea) at diameters of only ≥2 mm. The increased effectiveness of synchrotron technology for imaging ovaries in comparison to conventional imaging methods is currently unknown. Overall Objective: The overall objective of this research was to determine the effectiveness of synchrotron techniques for imaging ovaries. We hypothesized that synchrotron techniques would provide greater contrast for visualizing structural details of follicles, corpora lutea (CL), and cumulus oocyte complexes (COC), compared to conventional ultrasonography. Materials and Methods: Three studies were conducted to evaluate phase-contrast based synchrotron imaging methods. The first study involved Diffraction Enhanced Imaging (DEI) of bovine ovaries (n=6). The second study involved Propagation-Based Computed Tomography (PB-CT) imaging of bovine (n=4) and human ovaries (n=4). A third, preliminary study was conducted to explore the use of Talbot Grating Interferometry (TGI-CT) imaging of bovine (n=1) and human ovaries (n=1). Fresh and formalin-fixed bovine and human ovaries were imaged without or with contrast injection into the ovarian artery. Following synchrotron imaging, all ovarian samples were evaluated using diagnostic ultrasonography and histology. Images obtained using synchrotron techniques, ultrasonography and histology were qualitative and quantitatively compared. Results: DEI allowed the identification of 71% of follicles ≥2 mm and 67% of CL detected using ultrasonography. Mean follicle diameter was similar between DEI (9.6 ± 2.4 mm), ultrasonography (9.0 ± 2.6 mm), and histology (6.9 ± 1.9 mm) for fresh ovaries without contrast (P = 0.70). Likewise, no difference in CL diameter was detected between DEI (11.64 ± 1.67 mm), ultrasonography (9.34 ± 0.35 mm), and histology (9.6 ± 0.4 mm), (P = 0.34). Antral Follicle Count (AFC; ≥2mm) was similar between ultrasonography (6.5 ± 0.7 mm, fresh with no contrast; 6.5 ± 2.5 mm, preserved with no contrast) and DEI ( 4.5 ± 0.5 mm, fresh with no contrast; 6.5 ± 0.50 mm, preserved with no contrast) (P > 0.05). However, the contrast resolution for differentiating follicles and CL was inferior with DEI compared to ultrasonography. Small antral follicles <2mm, cell layers comprising the follicle wall and COC were not detected using either DEI or ultrasonography. PB-CT imaging enabled the visualization of 100% of follicles ≥2 mm and 100% of CL that were detected with ultrasonography. CL containing a central cystic cavity were identified using PB-CT; however, CL without a central cystic cavity were not well-visualized. Mean follicle and luteal diameters did not differ among PB-CT, ultrasonography and histology (P>0.05). PB-CT was superior to ultrasonography for detecting small antral follicles <2 mm in bovine ovaries (P = 0.04), and the granulosa and theca cell layers of the follicle wall in bovine and human ovaries (P < 0.0001). However, TGI-CT images exhibited greater contrast resolution for visualizing small and large antral follicles, CL, and the cell layers of the follicle wall compared to both PB-CT and ultrasonography. High contrast structures resembling COC were detected with both PB-CT and TGI-CT, but not with ultrasonography. Only TGI-CT permitted the visualization of the oocyte within the COC in fresh and preserved ovaries. Conclusions: DEI was inferior to ultrasonography for detecting ovarian follicles and CL. PB-CT was superior to ultrasonography for visualizing follicles <2 mm, COC, and the cell layers of the follicle wall. However, PB-CT was as effective as ultrasonography for detecting and measuring follicles ≥2 mm and cystic CL. Preliminary findings suggest that TGI-CT provides the greatest contrast for imaging both ovarian macro- and microanatomy compared to PB-CT, DEI, and ultrasonography.

In dentistry optical coherence tomography (OCT) technology has shown some promise as a method to distinguish between enamel, dentin, and restorative materials of tooth specimens. Ultrasound (US) technology has been reported with applications in dentistry to image deep tissues which offers a means to further characterize various soft tissue anomalies. While it is believed that both US and OCT technologies have real-time imaging potential for dentistry, their ability to visualize multiple types of simulated defects within root canal systems has yet to be tested. This study was setup to help determine the efficacy of two catheter-based imaging probes in prepared root canals containing areas of interest. Areas of interest herein are cited as vertical fracture lines, simulated perforations, resorptive-like defects, sites of intact dentin, and void space variance of the lumen. 33 human teeth were selected and underwent root canal analysis using 2 commercially available intravascular catheter-based imaging probes integrated with either OCT or US technology. This study proved that intravascular OCT is a very powerful imaging modality capable of (1) detecting various areas of endodontic interest, (2) yielding superficial imaging data of root canal architecture, and (3) trans-imaging tooth specimens from the canal lumen to the external surface of intact teeth at various cross-sections. Intravascular US probe was not capable of producing useful imaging data per the methodology herein. To date there are no FDA approved OCT probes commercially available for use in endodontics. Hopefully this study furthers our understanding of how useful and multimodal OCT technology truly is.

<p dir="ltr">From transonic to hypersonic regimes, the characterization of high-speed flow dynamics is critical for the development, testing, and improvement of launch and reentry vehicles, boost-glide vehicles, and thermal protection systems. The design of this technology often relies on computational/empirical models for predictions which make quantitative thermodynamic measurements crucial for numerical validation. Laser diagnostic techniques facilitate non-intrusive, <i>in situ</i> measurements of fluid dynamic properties as well as visualization of flows, shocks, and boundary layer interactions. However, many diagnostics rely on seeding the flow with foreign materials to make measurements, such as the application of particle image velocimetry (PIV), Doppler global velocimetry (DGV), and planar laser-induced fluorescence (PLIF). Molecular filtered Rayleigh scattering (FRS) diagnostics are attractive for flow characterization due to the fact that pressure, temperature, density and velocity measurements can be made directly from air or N₂ molecules without the need for seeding materials. The development of the burst-mode laser (BML) has enabled high-energy pulses generated at the rates necessary to resolve phenomena such as instabilities in boundary-layers and shock-wave evolution using Rayleigh scattering methods. The goal of this dissertation is to advance molecular burst-mode FRS for quantitative, high resolution, multi-parameter measurements. For fixed-wavelength FRS measurements, the spectral characteristics of a BML system were investigated and improved by integrating an etalon for spectral-gating. For multi-parameter measurements, two strategies for wavelength-agility, the ability to quickly switch between two or more laser wavelengths, of the BML were explored: frequency-scanning and frequency-shifting. The frequency-scanning FRS (FS-FRS) technique measurement rate was increased to 1 kHz and demonstrated for 1-ms pressure, temperature, and radial velocity measurements in an underexpanded jet flow. Building upon this, an acousto-optic modulator-based method was implemented to generate frequency-shifted pulses. The rapid frequency-shifting increased the effective FRS multi-parameter measurement rate to 25 kHz and planar pressure, temperature, and radial velocity measurements were captured in an overexpanded jet flow. Finally, design tools for the laser configuration of wavelength-agile FRS were developed for the optimization of relative absolute measurement errors.</p>

<p>A previously designed lens system is constructed and characterized for possible application to engine diagnostics and 3D reconstructions of combusting flows. Since optical engines cannot be operated at the same conditions as a production engine, optical access to a production engine, with minimum changes in the engine geometry is necessary for developing a better understanding of the in-cylinder processes. The application of a probe designed to fit in the pressure transducer port of a diesel engine was demonstrated in this work. Measurement of various optical parameters established the ability of the lens system to have a good resolution over the entire stroke length of the cylinder. The temperature analysis of the probe and lens system confirmed its ability to withstand the high-temperature conditions in the engine cylinder head. The lens system design was coupled with imaging fibers to transmit images from the image plane of the probe to a high-speed camera located at a safe distance from the combusting environment. Due to the robust design of the probe and its compatibility with an imaging fiber, the probe was identified to be a good alternative as an inexpensive lens system for tomography in challenging environments. To validate its use, 3D reconstruction of a sewing pin using a range of views was demonstrated. Parameters affecting the reconstructions were identified and optimized to obtain high-quality reconstructions. </p>

This research was inspired by a need to discover more refined technologies for imaging growing joints to facilitate research in childhood arthritis, which is among the most common chronic conditions of childhood. The objective of this project was to develop and test a new technology for imaging growing joints using diffraction enhanced imaging (DEI) combined with computed tomography (CT) using a synchrotron radiation source. DEI is a modality that derives contrast from x-ray refraction, extinction (an extreme form of scatter rejection), and absorption (as in conventional radiography). The ability to add to an image’s contrast from the refraction of x-rays, rather than that solely from absorption, generates more detailed visualization of soft tissue and of interfaces between tissues. Additionally, refraction-based imaging allows reduction of absorbed radiation dose by the sample tissue. For this research, stifle joints from four-week piglet joints were imaged by DEI-CT using the BioMedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source (CLS) synchrotron facility. This new modality for imaging growing joints incorporated a novel feedback control to maintain precise alignment of the analyzer crystal, which is used to re- diffract the beam that passes through the object, throughout the scanning procedure. Results showed that high-resolution DEI-CT provided three-dimensional images of the bone and soft tissue of growing joints at a resolution on the order of microns. Fine detail within and between all joint structures and tissues, including striking detail of cartilage vasculature, a iii characteristic of growing but not mature joints, was demonstrated. This report documents for the first time that DEI combined with CT and using a synchrotron radiation source can generate more detailed images of intact, growing joints than is currently available from conventional imaging modalities. The development of this high resolution imaging system, which provides excellent contrast for both hard and soft tissues, fills an important gap in the suite of imaging modalities available for joint research, particularly during growth.