Browsing by Author "Salat, Peter"

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    A multicenter review of deep venous thrombosis prophylaxis practice patterns for blunt hepatic trauma
    (BioMed Central, 2009-06) Datta, Indraneel; Ball, Chad G; Rudmik, Lucas R.; Paton-Gay, Damian; Bhayana, Deepak; Salat, Peter; Schieman, Colin; Smith, Dean F.; vanWijngaarden-Stephens, Mary; Kortbeek, John B.
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    The 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 L
    Abstract 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.
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    Using Advanced Medical Imaging to Study Bone and Joint Changes in Rheumatoid Arthritis
    (2019-06-18) Brunet, Scott Cameron; Manske, Sarah Lynn; Barnabé, Cheryl Carmelle Marie; Salat, Peter
    Inflammatory processes in rheumatoid arthritis (RA) lead to the damage of joints which results in functional decline. Medical imaging plays an important role in evaluating the onset and progression of RA. High resolution peripheral quantitative computed tomography (HR-pQCT) permits 3-dimensional visualization of the bony microarchitecture allowing for improved erosion detection, joint space width, and bone microstructure measurements. The purpose of this research was to use HR-pQCT and other advanced imaging techniques to visualize and quantify bone changes in the metacarpophalangeal (MCP) joints in RA patients. First, the reproducibility of a semi-automated erosion segmentation program was assessed using intra-rater and scan-rescan measurements on a cohort of early RA participants. HR-pQCT was used to assess possible erosion healing in participants’ initiating a new biologic therapy. We observed that the majority of participants maintained stable joints space, bone mineral density, and erosion volume over a 9-month follow-up period, but 17% of the joints showed a significant decrease in total erosion volume suggesting potential erosion healing. Finally, the impact of subclinical inflammation on bone damage progression for patients in clinical remission was assessed using a combination of HR-pQCT and Magnetic Resonance Imaging (MRI). All 9 of the participants assessed in this study had evidence of subclinical inflammation on MRI, but there was no progression of joint damage seen on HR-pQCT. One participant had a significant decrease in erosion volume. An image registration algorithm, applied for the first time for MCP joints, was used to successfully localize areas of inflammation as seen on MRI with bone damage seen on HR-pQCT. It is demonstrated that even with a sensitive measure of bone damage, healing and progression can be difficult to visualize and quantify due to the heterogeneity of the disease. However, applying other imaging modalities that can provide information on inflammation, as displayed in this thesis, could allow us to gain further insight on the individual characteristics that lead to bone change. The imaging findings and techniques described in this thesis will provide a novel insight into the progression of bone damage in RA to help evaluate current treatment targets and improve patient outcomes in future research.