Brian Bewer

Diffraction Enhanced X-ray Imaging of the Distal Radius: A Novel Approach for Visualization of Trabecular Bone Architecture

In Canada, osteoporotic fractures result in direct health care costs that exceed CAD

A new method to image heme-Fe, total Fe, and aggregated protein levels after intracerebral hemorrhage

1.3 billion annually [1]. Fractures are related to compromised bone strength, a parameter that reflects both density (quantity) and architecture (quality) [2]. The current clinical standard for bone assessment, dual energy x-ray absorptiometry, provides only a 2-dimensional areal measurement of density and no architectural information [3]; therefore, the development of improved methods for visualizing and quantifying of bone architecture remains an important goal with respect to improving detection and treatment of osteoporosis. Advances are currently being sought in the development of new technologies [3], such as high-resolution peripheral quantitative tomography [4], and through texture-based analysis of trabecular structure from radiographs [5]. In this pictorial essay, we explore the use of x-rayebased diffraction enhanced imaging (DEI) by using synchrotron radiation [6] as a novel means of visualizing the internal architecture of the human distal radius, a clinically significant fracture site. Imaging for this study was conducted at the Canadian Light Source (CLS) synchrotron during commissioning of the BioMedical Imaging and Therapy (BMIT) bending magnet beam line [7]. As such, our goal here is 2-fold: (1) establishment of proof-of-principle

Development of a combined K-edge subtraction and fluorescence subtraction imaging system for small animals

An intracerebral hemorrhage (ICH) is a devastating stroke that results in high mortality and significant disability in survivors. Unfortunately, the underlying mechanisms of this injury are not yet fully understood. After the primary (mechanical) trauma, secondary degenerative events contribute to ongoing cell death in the peri-hematoma region. Oxidative stress is thought to be a key reason for this delayed injury, which is likely due to free-Fe-catalyzed free radical reactions. Unfortunately, this is difficult to prove with conventional biochemical assays that fail to differentiate between alterations that occur within the hematoma and peri-hematoma zone. This is a critical limitation, as the hematoma contains tissue severely damaged by the initial hemorrhage and is unsalvageable, whereas the peri-hematoma region is less damaged but at risk from secondary degenerative events. Such events include oxidative stress mediated by free Fe presumed to originate from hemoglobin breakdown. Therefore, minimizing the damage caused by oxidative stress following hemoglobin breakdown and Fe release is a major therapeutic target. However, the extent to which free Fe contributes to the pathogenesis of ICH remains unknown. This investigation used a novel imaging approach that employed resonance Raman spectroscopic mapping of hemoglobin, X-ray fluorescence microscopic mapping of total Fe, and Fourier transform infrared spectroscopic imaging of aggregated protein following ICH in rats. This multimodal spectroscopic approach was used to accurately define the hematoma/peri-hematoma boundary and quantify the Fe concentration and the relative aggregated protein content, as a marker of oxidative stress, within each region. The results revealed total Fe is substantially increased in the hematoma (0.90 μg cm(-2)), and a subtle but significant increase in Fe that is not in the chemical form of hemoglobin is present within the peri-hematoma zone (0.32 μg cm(-2)) within 1 day of ICH, relative to sham animals (0.22 μg cm(-2)). Levels of aggregated protein were significantly increased within both the hematoma (integrated band area 0.10 AU) and peri-hematoma zone (integrated band area 0.10 AU) relative to sham animals (integrated band area 0.056 AU), but no significant difference in aggregated protein content was observed between the hematoma and peri-hematoma zone. This result suggests that the chemical form of Fe and its ability to generate free radicals is likely to be a more critical predictor of tissue damage than the total Fe content of the tissue. Furthermore, this article describes a novel approach to colocalize nonheme Fe and aggregated protein in the peri-hematoma zone following ICH, a significant methodological advancement for the field.

Development of an x-ray prism for analyzer based imaging systems.

A novel combined imaging system for small animals using dilute concentrations of iodine as a contrast agent was developed for wide and pencil photon beam image acquisitions. This combined imaging system used K-edge subtraction (KES) and fluorescence subtraction imaging (FSI) and was tested at the Hard x-ray Microanalysis beamline at the Canadian Light Source. The initial wide beam KES image acquired with a charge-coupled device camera was used to identify regions of interest for further investigation and determine the location and area of the raster scan for pencil beam imaging. The pencil photon beam scanning mode acquired simultaneously KES and FSI measurements with an ionization chamber measuring the KES data and a multielement germanium detector measuring the FSI data. A description of the system is given as well as preliminary results using an iodine test object.

Preliminary Bone Imaging on 05B1-1 Beamline at the Canadian Light Source: Exploration of Diffraction Enhanced Imaging

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 large intensity changes for small angle changes introduced from the x-ray beam traversing the sample. Objects that have very little absorption contrast may have considerable refraction and ultrasmall angle x-ray scattering contrast improving visualization and extending the utility of x-ray imaging. To improve on the current DEI technique an x-ray prism (XRP) was designed and included in the imaging system. The XRP allows the analyzer crystal to be aligned anywhere on the rocking curve without physically 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 submicroradians for direct mechanical movement of the analyzer crystal to tens of milliradians for movement of the XRP angle. However, this improvement in angle positioning comes at the cost of absorption loss in the XRP and depends on the x-ray energy. In addition to using an XRP for crystal alignment it has the potential for scanning quickly through the entire rocking curve. This has the benefit of collecting all the required data for image reconstruction in a single measurement thereby removing some problems with motion artifacts which remain a concern in current DEI/MIR systems especially for living animals.

Bystander Effects During Synchrotron Imaging Procedures

The bending magnet line (05B1-1) of the BioMedical Imaging and Therapy (BMIT) facility of the Canadian Light Source saw initial research application (Figure 1) during commissioning which began in December 2008 and continued intermittently through May 2010. Following an initial run based upon letters of intent (June-Dec. 2010), the bending magnet line is now available for regular user access. The mandate to advance research related to human and animal health, combined with an active bone imaging community at the University of Saskatchewan, has resulted in a strong representation of skeletal imaging during initial experiments at BMIT. To date, specific manifestations of bone imaging have ranged from micro-CT imaging of human cortical bone samples to in vitro diffraction enhanced imaging (DEI) of rat and pig bones and, ultimately, to in vivo DEI of bones within young chickens. In this article we focus on the diffraction enhanced imaging capabilities of BMIT and describe our efforts to apply this technology to human trabecular bone microarchitecture – a potential clinical application in the future.

Bent Laue X‐ray Fluorescence Imaging of Manganese in Biological Tissues—Preliminary Results

Using monochromatic beam and synchrotron phase‐contrast technique at the biomedical beamline of the Italian synchrotron facility Elettra (SYRMEP), we have shown in a small animal model of malignant brain tumor that it is possible to obtain high‐resolution images of very small tumors when they have developed from implanted tumor cells loaded with colloidal gold nanoparticles (GNP). All previous experiments were conducted in post‐mortem samples. We have now designed a cell culture experiment to investigate the effects of synchrotron radiation with an energy and dose profile similar to that expected in our first in vivo imaging studies according to the protocol developed at SYRMEP.Materials and Methods: Culture flasks containing either gold‐loaded or naive C6 glioma cells were exposed to a dose of 0.5 Gy at 24 keV. The irradiated medium was aspirated and replaced with fresh growth medium. Twenty‐four hours later this non‐irradiated medium exposed to irradiated cells was aspirated, then added to non‐irradiate...

Comparison of iodine K-edge subtraction and fluorescence subtraction imaging in an animal system

Manganese (Mn) is not abundant in human brain tissue, but it is recognized as a neurotoxin. The symptoms of manganese intoxication are similar to Parkinson’s disease (PD), but the link between environmental, occupational or dietary Mn exposure and PD in humans is not well established. X‐ray Absorption Spectroscopy (XAS) and in particular X‐ray fluorescence can provide precise information on the distribution, concentration and chemical form of metals. However the scattered radiation and fluorescence from the adjacent abundant element, iron (Fe), may interfere with and limit the ability to detect ultra‐dilute Mn. A bent Laue analyzer based Mn fluorescence detection system has been designed and fabricated to improve elemental specificity in XAS imaging. This bent Laue analyzer of logarithmic spiral shape placed upstream of an energy discriminating detector should improve the energy resolution from hundreds of eV to several eV. The bent Laue detection system was validated by imaging Mn fluorescence from Mn fo...