Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention | Year: 2010
This study investigates a new parameterization of deformation fields for image registration. Instead of standard displacements, this parameterization describes a deformation field with its transformation Jacobian and curl of end velocity field. It has two important features which make it appealing to image registration: 1) it relaxes the need of an explicit regularization term and the corresponding ad hoc weight in the cost functional; 2) explicit constraints on transformation Jacobian such as topology preserving and incompressibility constraints are straightforward to impose in a unified framework. In addition, this parameterization naturally describes a deformation field in terms of radial and rotational components, making it especially suited for processing cardiac data. We formulate diffeomorphic image registration as a constrained optimization problem which we solve with a step-then-correct strategy. The effectiveness of the algorithm is demonstrated with several examples and a comprehensive evaluation of myocardial delineation over 120 short-axis cardiac cine MRIs acquired from 20 subjects. It shows competitive performance in comparison to two recent segmentation based approaches.
Soliman A.M.,University of Western Ontario |
ACI Materials Journal | Year: 2011
This study pioneers the concept of self-accelerated concrete. The effect of adding partially hydrated cementitious materials (premade or from returned/unused concrete) on the setting and hardening process of reactive powder concrete (RPC) cured at various temperatures was investigated. The partially hydrated cementitious materials (PHCMs) were added at rates of 25, 33, and 50% of the overall batch weight. Similar mixtures incorporating chloridebased accelerating admixtures (CAs) and nonchloride-based accelerating admixtures (NCAs) were also tested for comparison. The results indicate that the added PHCMs alert the hydration kinetics and act as a setting and hardening accelerator. Mixtures incorporating PHCMs showed comparable or higher early-age compressive strengths than those of both the control mixture and mixtures incorporating accelerating admixtures. Microstructure analyses indicate that the addition of PHCMs enhances the nucleation and renews the formation process of calcium silicate hydrates (CSHs) through diminishing the protective layer formed around anhydrated tricalcium silicate (C3S) during the pre-induction period. Therefore, using PHCMs paves the way for self-accelerated concrete without the need for accelerating admixtures, providing a safe and cost-effective method for precast and cast-in-place concrete. Using leftover and unused concrete in this process enhances the sustainability of concrete and minimizes disposal in ready mixed concrete operations. © 2011, American Concrete Institute. All rights reserved.
Azimian H.,Lawson Health Research Institute |
Azimian H.,University of Western Ontario |
Patel R.V.,CSTAR |
Naish M.D.,UWO |
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011
In this paper, robust preoperative planning of RAMICS is formulated. The intent of the proposed planning framework is to improve surgical outcomes by contemplating the intraoperative conditions of the surgical procedure and the geometry of the patient's thoracic anatomy. This includes improvements in target reachability, instrument dexterity for critical surgical tasks, surgical task feasibility and visibility. Given the patient's preoperative computed tomography images of the chest, the planning framework aims to determine the optimal location of the access ports on the ribcage, along with the optimal pose of the robotic arms relative to the patient's anatomy. To minimize susceptibility of the results to intraop-erative geometric uncertainty, the planning is formulated as a Generalized Semi-Infinite Program (GSIP) with a convex lower level problem and a multi-criteria objective function. By solving the GSIP, tolerable geometric uncertainty within the task space is increased by eliminating the likelihood of collisions and joint limit violation in a neighborhood of the surgical target. © 2011 IEEE.
Petrella R.J.,University of Western Ontario |
Lattanzio C.N.,UWO |
Shapiro S.,UWO |
Canadian Family Physician | Year: 2010
OBJECTIVE: To determine the effects of adding stages of change-based counseling to an exercise prescription for older, sedentary adults in family practice. DESIGN: The Step Test Exercise Prescription Stages of change counseling study was a 12-month cluster randomized trial. SETTING: Forty family practices in 4 regions of Canada. PARTICIPANTS: Healthy, community-dwelling men (48%) and women (52%) with a mean (SD) age of 64.9 (7.1) years (range 55 to 85 years). There were a total of 193 participants in the intervention group and 167 in the control group. INTERVENTION: Intervention physicians were trained to deliver a tailored exercise prescription and a transtheoretical behaviour change counseling program. Control physicians were trained to deliver the exercise prescription alone. MAIN OUTCOME MEASURES: Predicted cardiorespiratory fitness, measured by predicted maximal oxygen consumption (pVO2max), and energy expenditure, measured by 7-day physical activity recall. RESULTS: Mean increase in pVO2max was significant for both the intervention (3.02 [95% confidence interval 2.40 to 3.65] mL/kg/min) and control (2.21 [95% confidence interval 1.27 to 3.15] mL/kg/min) groups at 12 months (P < .001); however, there was no difference between groups. Women in the intervention group improved their fitness significantly more than women in the control group did (3.20 vs 1.23 mL/kg/min). The intervention group had a 4-mm Hg reduction in systolic blood pressure, while the control group's mean reduction was 0.4 mm Hg (P < .001). The mean (SD) energy expended significantly increased and was higher in the intervention group than in the control group (69.06 [169.87] kcal/d vs -6.96 [157.06] kcal/d, P < .006). Practice setting characteristics did not significantly affect the primary outcomes. CONCLUSION: The Step Test Exercise Prescription Stages of change exercise and behavioural intervention improved fitness and activity and lowered systolic blood pressure across a range of Canadian practices, but this was not significantly different from the control group, which received only the exercise prescription. Women in the intervention group showed higher levels of fitness than women in the control group did; men in both groups showed similar improvement.
Dixon J.,University of Waterloo |
Luginaah I.N.,UWO |
Mkandawire P.,Carleton University
Journal of Health Care for the Poor and Underserved | Year: 2014
This article addresses the implications of the mandatory delay in coverage for individuals residing in the Upper West Region (UWR) of Ghana who have dropped out of the National Health Insurance Scheme (NHIS) but later attempt to reenroll. Using data collected in 2011 in Ghana's UWR, we use a negative log-log model (n=1,584) to compare those who remain enrolled in the scheme with those who have dropped out. Women with unreliable incomes, who reported being food-insecure and those living with young children were more likely to drop out (OR range: 1.22-1.79, p<.05). Men, in contrast, were 50% more likely to drop out of the NHIS for being unsatisfied with services provided (OR range: 1.25-1.62, p<.01). Contrary to the original mandate of the NHIS, our study reveals clear gender differences in the factors contributing to dropouts, pointing to a bias in the impact of the block-out policy that is penalizing women for being poor. © Meharry Medical College.