Seaman Family Research Center
Seaman Family Research Center
Kosior R.K.,University of Calgary |
Kosior R.K.,Seaman Family Research Center |
Lauzon M.L.,University of Calgary |
Lauzon M.L.,Seaman Family Research Center |
And 4 more authors.
NeuroImage | Year: 2011
Seizure related abnormalities may be detected with T2 relaxometry, which involves quantitative estimation of T2 values. Accounting for the partial-volume effect of cerebrospinal fluid (CSF) is important, especially for voxel-based relaxometry, VBR. With a mono-exponential decay model, this can be accomplished by including a baseline constant. An algebraic calculation, which accommodates this constant, offers improved T2 estimation speed over the commonly used non-linear fitting approach. Our objective was to compare the algebraic approach against three fitting approaches for the detection of seizure related abnormalities. We tested the performance of the four methods in the presence of noise using simulated data as well as real data acquired at 3 T with a Carr-Purcell-Meiboom-Gill sequence from 45 healthy subjects and 24 patients with confirmed right temporal lobe epilepsy. A quantitative analysis was performed on spatially normalized data by measuring T2 in various regions and with a whole brain tissue segmentation analysis. The detection rate of hippocampal T2 changes in patients was assessed by comparing the regional T2 measurements from each patient against the control data with a z-score threshold of 2.33. The algebraic method yielded high sensitivity for detection of hippocampal abnormalities in the epileptic patients in regional assessment and in follow-up single-subject VBR. This can be attributed to the relatively small variance across healthy subjects and improved precision in the presence of CSF and noise in simulation. In conclusion, the algebraic method is better than fitting based on faster calculation speed and better sensitivity for detecting seizure-related T2 changes. © 2011 Elsevier Inc.
Menon B.K.,University of Calgary |
Goyal M.,University of Calgary |
Goyal M.,Seaman Family Research Center
Expert Review of Cardiovascular Therapy | Year: 2011
Stroke is the third leading cause of death and a leading cause of severe long-term disability worldwide. It costs the world's economy billions of dollars each year in physician services, hospital costs, lost wages and decreased productivity. Rapid advances in medical technology have resulted in an explosion of treatment strategies in the management of acute ischemic stroke. Each clinical scenario presents unique challenges related to risks and benefits of therapy. In this article, we review the evolution of endovascular therapy in acute ischemic stroke, discuss the latest advances, challenges and controversies in the field and speculate on the future of this therapy. © 2011 Expert Reviews Ltd.
Doiron A.L.,University of Calgary |
Doiron A.L.,Seaman Family Research Center |
Clark B.,University of Calgary |
Rinker K.D.,University of Calgary
Biotechnology and Bioengineering | Year: 2011
Nanoparticles are increasingly important in medical research for application to areas such as drug delivery and imaging. Understanding the interactions of nanoparticles with cells in physiologically relevant environments is vital for their acceptance, and cell-particle interactions likely vary based on the design of the particle including its size, shape, and surface chemistry. For this reason, the kinetic interactions of fluorescent nanoparticles of sizes 20, 100, 200, and 500nm with human umbilical vein endothelial cells (HUVEC) were determined by (1) measuring nanoparticles per cell at 37 and 4°C (to inhibit endocytosis) and (2) modeling experimental particle uptake data with equations describing particle attachment, detachment, and internalization. Additionally, the influence of cell substrate compliance on nanoparticle attachment and uptake was investigated. Results show that the number of binding sites per cell decreased with increasing nanoparticle size, while the attachment coefficient increased. By comparing HUVEC grown on either a thin coating of collagen or on top of three-dimensional collagen hydrogel, nanoparticle attachment and internalization were shown to be influenced significantly by the substrate on which the cells are cultured. This study concludes that both particle size and cell culture substrate compliance appreciably influence the binding of nanoparticles; important factors in translating in vitro studies of nanoparticle interactions to in vivo studies focused on therapeutic or diagnostic applications. © 2011 Wiley Periodicals, Inc..
Evans A.,Sunnybrook Health science Center |
Demchuk A.,Seaman Family Research Center |
Symons S.P.,Sunnybrook Health science Center |
Dowlatshahi D.,Seaman Family Research Center |
And 3 more authors.
Stroke | Year: 2010
Background And Purpose-: Mural thickening and permeability changes in patients with amyloid angiopathy (CAA) and chronic hypertension are implicated in the pathophysiology of multiple, chronic subclinical microbleeds. The Spot sign, contrast extravasation on CT angiography, predicts hematoma expansion and is presumed to represent acute vessel damage. We hypothesize that the Spot sign is more common in patients without multiple prior chronic microbleeds. Methods-: A retrospective study was conducted of 59 patients presenting within 6 hours of primary intracranial hemorrhage onset undergoing CT angiography and MRI. CT angiography spot sign presence was documented blinded to MRI. Hematoma expansion was defined as >6 mL or 30% enlargement. The Boston criteria were applied to microbleed interpretation dichotomizing subjects into probable and negative CAA. Basal ganglia, thalamic, and brain stem microbleed location were interpreted as chronic hypertensive pattern. Univariate logistic regression and ordinal logistic regression analysis identified significant predictive factors between spot-positive and -negative patients or microbleed pattern. Results-: The incidence of spot positivity was 42%, 22%, and 0% for CAA-negative, chronic hypertensive, and CAA-positive patients, respectively (P=0.01). CAA-negative patients had higher baseline National Institutes of Health Stroke Scale (P=0.039), larger follow-up hematoma volume (P=0.02), and poorer Rankin score (P=0.049) than chronic hypertensive or CAA-positive patients. After age adjustment, spot-positive (P=0.023), age-related white matter change (P=0.041), number of microbleeds (P<0.0001), and modified Rankin score (P=0.027) remained significantly different between groups. Conclusion-: Boston criteria-defined CAA-negative status demonstrates the highest risk of spot positivity compared with patients with probable CAA and chronic hypertension. © 2010 American Heart Association, Inc.
Motkoski J.W.,Seaman Family Research Center |
Sutherland G.R.,University of Calgary
Neuromethods | Year: 2016
Progress in neurosurgery has paralleled technological innovation. Image-guided surgical robotic systems have emerged as a potential hub for integration of the complex sensory, pathologic, and imaging data sets that are available to contemporary neurosurgeons. These systems couple the executive capacity of surgeons with the technical capabilities of machines and have the potential to improve surgical care as neurosurgery progresses towards the cellular level. Surgery is often performed in animal models prior to clinical application, representing a very important safety step in regulatory approval. As the capital investment for surgical robotic systems decreases, robotic systems may be specifically designed for animal application. In this chapter, we review neurosurgical robotic systems used in humans and animals; present the development, preclinical testing, and early clinical use of a unique image guided MR-compatible neurosurgical robot called neuroArm; and review the strengths and limitations of using surgical robotic systems in animal models. © Springer Science+Business Media New York 2016.
Yerly J.,University of Calgary |
Yerly J.,Seaman Family Research Center |
Louis Lauzon M.,University of Calgary |
Louis Lauzon M.,Seaman Family Research Center |
And 4 more authors.
Magnetic Resonance in Medicine | Year: 2010
Passive MRI is a promising approach to visualize catheters in guiding and monitoring endovascular intervention and may offer several clinical advantages over the current x-ray fluoroscopy "gold standard." Endovascular MRI has limitations, however, such as difficulty in visualizing catheters and insufficient temporal resolution. The multicycle projection dephaser method is a background signal suppression technique that improves the conspicuity of passive catheters by generating a sparse (i.e., catheter only) image. One approach to improve the temporal resolution is to undersample the k-space and then apply nonlinear methods, such as compressed sensing, to reconstruct the MR images. This feasibility study investigates the potential synergies between multicycle projection dephaser and compressed sensing reconstruction for realtime passive catheter tracking. The multicycle projection dephaser method efficiently suppressed the background signal, and compressed sensing allowed MR images to be reconstructed with superior catheter conspicuity and spatial resolution when compared to the more conventional zero-filling reconstruction approach. Moreover, compressed sensing allowed the shortening of total acquisition time (by up to 32 times) by vastly undersampling the k-space while simultaneously preserving spatial resolution and catheter conspicuity. © 2010 Wiley-Liss, Inc.
Eesa M.,University of Calgary |
Almekhlafi M.A.,University of Calgary |
Almekhlafi M.A.,King Abdulaziz University |
Mitha A.P.,University of Calgary |
And 3 more authors.
Neuroradiology | Year: 2012
Introduction: Timely recanalization during endovascular procedures for acute ischemic stroke can be challenging in cases with large clot burden, such as those encountered in the terminal internal carotid T- or L-type occlusion. Methods: A novel but simple technique to achieve fast reduction in clot burden in stroke patients with occlusion of the internal carotid artery termination is described where manual suction using a 60-ml syringe applied through an 8-F balloon guide catheter positioned in the cervical carotid vasculature with proximal flow arrest allows subsequent revascularization of the residual middle cerebral artery clot. Results: The use of manual suction through a balloon-tipped guide catheter in internal carotid artery L- or T-type occlusion is illustrated. This resulted in a significant reduction of the clot burden and facilitated further interventions leading to full recanalization. Conclusion: Manual suction using a 60-ml syringe through a ballon guide catheter is a useful and feasible technique that facilitates thrombectomy of large burden cerebral clots. © 2012 Springer-Verlag.
Devetten G.,Seaman Family Research Center |
Devetten G.,University of Calgary |
Coutts S.B.,Seaman Family Research Center |
Hill M.D.,University of Calgary |
And 6 more authors.
Stroke | Year: 2010
BACKGROUND AND PURPOSE-: In children with stroke, poor motor outcome is associated with early Wallerian degeneration of the corticospinal tract that is seen on diffusion-weighted MRI. In this study we test the hypothesis that early diffusion changes also occur in the corticospinal tract (CST) of adults after stroke and that these lesions are associated with poor outcome. METHODS-: In this retrospective study, we assessed images from a serial MRI study of adults with acute middle cerebral/internal carotid artery stroke. MRI-negative TIA patients served as controls. Custom software measured signal along the CST on different sequences, including the apparent diffusion coefficient (ADC). Visual detection of abnormal signal by blinded neuroradiologists was also evaluated. We then determined associations between CST signal changes and 3-month motor outcome (NIHSS score). RESULTS-: Thirty-eight patients (20 stroke/18 control) were included. ADC measures were much more accurate than other MRI sequences for detection of degeneration in the CST. The ADC decreased in a time-dependent fashion in the CST of patients with poor motor outcome but not in those with good outcome. Changes in ADC were maximal at 7 days. Neuroradiologists could visually detect these changes with accuracy comparable to the software method. CONCLUSION-: CST ADC decreases after acute stroke in patients with poor motor outcome and may represent early Wallerian degeneration. Recognition of this imaging marker may improve early outcome prediction and patient selection for rehabilitation and neuroprotection trials. © 2010 American Heart Association, Inc.
Kosior J.C.,University of Calgary |
Kosior J.C.,Seaman Family Research Center |
Frayne R.,University of Calgary |
Frayne R.,Seaman Family Research Center
Journal of Magnetic Resonance Imaging | Year: 2010
Purpose: To investigate the impact of tracer recirculation on estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Materials and Methods: The theoretical model used to derive CBF, CBV, and MTT was examined. CBF and CBV estimates with and without tracer recirculation were compared in computer simulations to examine the effects of tracer recirculation. Results: The equations used to derive CBF, CBV, and MTT assume that the arterial input function and tissue tracer signals define the input and output signals, respectively, of a linear time-invariant system. As a result of the principle of superposition, these perfusion parameters are immune to tracer recirculation, which was confirmed by computer simulation. However, limited acquisition durations can lead to CBV and CBF errors of up to 50%. Conclusion: Tracer recirculation does not impact estimation of CBF, CBV, or MTT. However, previous approaches used to remove recirculation effects may be beneficial when used to compensate for limited acquisition durations in which the passage of the bolus is not adequately captured. © 2010 Wiley-Liss, Inc.
PubMed | Seaman Family Research Center
Type: Journal Article | Journal: NMR in biomedicine | Year: 2016
Quantitative MR imaging is as sensitive in detecting lesions as qualitative imaging, but it is potentially more specific in differentiating disease. T1 mapping in particular might help to assess acute ischemic stroke, multiple sclerosis, epilepsy and Alzheimers disease better. Thus, a rapid and robust clinical technique is vital. In 1990, Ordidge and colleagues developed the multislice T1 -prepared two-dimensional (2D) single-shot echo planar imaging technique. Subsequent studies demonstrated its clinical viability, but none performed an in-depth analysis of the strengths and advantages of this T1 mapping method. Herein, theoretical and experimental evidence shows that the technique accounts for 2D slice profile effects and is unbiased by B0 or B1 inhomogeneity. This is verified explicitly by varying the linear shims, the T1 preparation flip angle and the excitation flip angle. Furthermore, it is shown that the repetition time (and hence scan time) can be reduced without a loss of T1 accuracy. Copyright 2016 John Wiley & Sons, Ltd.