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

Abstract

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. Bone fractures and clinical assessmentBone fractures are related to compromised strength -a parameter which reflects both the quantity and quality of bone tissue [1]. While "quality" is a difficult term to define, most attempts focus on architectural properties. Bone architecture takes two general formsthe outer compact or cortical bone and the more lattice-like internal trabecular (spongy) bone. The current standard for clinical bone assessment, dual energy X-ray absorptiometry (DXA), provides only a 2D areal measurement of mineral density and no architectural information [2]. Advances in bone imaging, which provide improved architectural information, are currently being sought in the application of established clinical technologies (Quantitative Computed Tomography (QCT); magnetic resonance imaging (MRI)) and the development of new modalities such as High Resolution peripheral Quantitative Computed Tomography (HR-pQCT) [2,3]. Shifting from 2D to 3D methodologies has been a key focus, with the quantitative assessment of 3D trabecular architecture a common goal. While these pursuits are certainly bearing fruit, they also have practical limitations including, in the case of X-ray based approaches (e.g. QCT), increased dose relative to DXA [4][5][6]. The push for higher resolution (e.g. to visualize individual trabeculae) requires increased dose and this, in part, explains why even cutting-edge tools (e.g. HR-pQCT) are limited to around 100 um voxel size. Peripheral scanners, which target the limbs, have an additional limitation in that fracture sites located centrally within the body, such as the hip and vertebrae, cannot be imaged. It is within this larger context that we are exploring 2D projection DEI as a means of improving the assessment of trabecular bone microarchitecture with reduced radiation dose. Figure 1: Dean Chapman (left), Tomasz Wysokinski (middle), and Bill Thomlinson (right) prepare a sample in December 20...