Browsing by Author "Pauchard, Yves"
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- ItemOpen AccessCompensation of metallic implant related artifcats in magnetic resonance imaging(2004) Pauchard, Yves; Mintchev, Martin P.; Smith, Michael Richard
- ItemOpen AccessIn vivo monitoring of longitudinal changes in bone micro-architecture using high-resolution peripheral computed tomography(2012) Pauchard, Yves; Vigmond, Edward J.; Boyd, StevenOsteoporosis is a disease characterized by low bone quality and increased risk of fracture. In order to improve osteoporosis treatment, it is essential to monitor bone quality and its changes over time in healthy, diseased and treated bones. V/ith the recent development of in vivo high-resolution peripheral quantitative computed tomography (HR-pQCT) it became possible to capture bone micro-architecture, an important determinant of bone quality, in humans. The aim of this dissertation was to propose new ways to analyze the resulting time series of three-dimensional (3D) image data to gain novel insight into bone behaviour. In a first step. a novel method for tracking and predicting micro-architectural changes using deformable image registration was validated. Applied to an osteoporotic and healthy pre-clinical model, this study demonstrated successful prediction of 3D architecture based on a time series of images without knowledge of disease state. Prior to extending the monitoring of changes to human bone, the problem of subject motion artifacts in HR-pQCT imaging was addressed. An automatic, fast and objective method was developed to quantify three separate components of subject motion using projection data. \i\Tith this tool, guidelines for image quality management in the presence of subject motion were established. Understanding and managing these artifacts is pivotal for guaranteeing consistent image quality in large multi-centre studies. In addition to motion quantification, a novel method for compensating movement artifacts was developed. The proposed method for motion compensation paves the way for future research into improving image quality, potentially increasing viable data benefiting drug trials and studies of rare diseases with small sample sizes. Lastly, in order to monitor bone micro-architecture changes in humans, an automated registration methodology was devised to align 3D HR-pQCT images and techniques to visualize local architectural changes were developed. It was possible to visualize local changes due to normal bone remodelling, and in response to osteoporosis treatment, aiding interpretation of changes in traditional bone quality parameters. The developed methods form the foundation for tracking bone adaptation over time, ultimately furthering our understanding of bone mechanisms in humans.
- ItemOpen AccessThe utility of multi-stack alignment and 3D longitudinal image registration to assess bone remodeling in rheumatoid arthritis patients from second generation HR-pQCT scans(2020-04-07) Brunet, Scott C; Kuczynski, Michael T; Bhatla, Jennifer L; Lemay, Sophie; Pauchard, Yves; Salat, Peter; Barnabe, Cheryl; Manske, Sarah LAbstract Background Medical imaging plays an important role in determining the progression of joint damage in rheumatoid arthritis (RA). High resolution peripheral quantitative computed tomography (HR-pQCT) is a sensitive tool capable of evaluating bone microarchitecture and erosions, and 3D rigid image registration can be used to visualize and quantify bone remodeling over time. However, patient motion during image acquisition can cause a “stack shift” artifact resulting in loss of information and reducing the number of erosions that can be analyzed using HR-pQCT. The purpose of this study was to use image registration to improve the number of useable HR-pQCT scans and to apply image-based bone remodeling assessment to the metacarpophalangeal (MCP) joints of RA patients. Methods Ten participants with RA completed HR-pQCT scans of the 2nd and 3rd MCP joints at enrolment to the study and at a 6-month follow-up interval. At 6-months, an additional repeat scan was acquired to evaluate reliability. HR-pQCT images were acquired in three individual 1 cm acquisitions (stacks) with a 25% overlap. We completed analysis first using standard evaluation methods, and second with multi-stack registration. We assessed whether additional erosions could be evaluated after multi-stack registration. Bone remodeling analysis was completed using registration and transformation of baseline and follow-up images. We calculated the bone formation and resorption volume fractions with 6-month follow-up, and same-day repositioning as a negative control. Results 13/57 (23%) of erosions could not be analyzed from raw images due to a stack shift artifact. All erosions could be volumetrically assessed after multi-stack registration. We observed that there was a median bone formation fraction of 2.1% and resorption fraction of 3.8% in RA patients over the course of 6 months. In contrast to the same-day rescan negative control, we observed median bone formation and resorption fractions of 0%. Conclusions Multi-stack image registration is a useful tool to improve the number of useable scans when analyzing erosions using HR-pQCT. Further, image registration can be used to longitudinally assess bone remodeling. These methods could be implemented in future studies to provide important pathophysiological information on the progression of bone damage.