Medical Biophysics Commons^™

Impact Of Incremental Perfusion Loss On Oxygen Transport In A Capillary Network Mathematical Model., Graham M Fraser, Michael D Sharpe, Daniel Goldman, Christopher G Ellis

Medical Biophysics Publications

OBJECTIVES: To quantify how incremental capillary perfusion loss, such as that seen in experimental models of sepsis, affects tissue oxygenation using a computation model of oxygen transport.

METHODS: A computational model was applied to capillary networks with dimensions 84x168x342 (NI) and 70x157x268 (NII) μm, reconstructed in vivo from rat skeletal muscle. Functional capillary density (FCD) loss was applied incrementally up to ~40% and combined with high tissue oxygen consumption to simulate severe sepsis.

RESULTS: A loss of ~40% FCD loss decreased median tissue PO2 to 22.9 and 20.1 mmHg in NI and NII compared to 28.1 and 27.5 mmHg under …

The Dissociative Subtype Of Posttraumatic Stress Disorder: Unique Resting-State Functional Connectivity Of Basolateral And Centromedial Amygdala Complexes., Andrew A Nicholson, Maria Densmore, Paul A Frewen, Jean Théberge, Richard W J Neufeld, Margaret C Mckinnon, Ruth A Lanius

Medical Biophysics Publications

Previous studies point towards differential connectivity patterns among basolateral (BLA) and centromedial (CMA) amygdala regions in patients with posttraumatic stress disorder (PTSD) as compared to controls. Here, we describe the first study to compare directly connectivity patterns of the BLA and CMA complexes between PTSD patients with and without the dissociative subtype (PTSD+DS and PTSD-DS, respectively). Amygdala connectivity to regulatory prefrontal regions and parietal regions involved in consciousness and proprioception were expected to differ between these two groups based on differential limbic regulation and behavioural symptoms. PTSD patients (n=49), with (n=13) and without (n=36) the dissociative subtype, and age-matched healthy …

A Biomechanical Approach For In Vivo Lung Tumor Motion Prediction During External Beam Radiation Therapy, Abbas Samani, Elham Karami, Ting-Yim Lee, Stewart Gaede

Medical Biophysics Publications

No abstract provided.

Collectivization Of Vascular Smooth Muscle Cells Via Tgf-Β-Cadherin-11-Dependent Adhesive Switching., Brittany Balint, Hao Yin, Subrata Chakrabarti, Michael W A Chu, Stephen M Sims, J Geoffrey Pickering

Medical Biophysics Publications

OBJECTIVE: Smooth muscle cells (SMCs) in healthy arteries are arranged as a collective. However, in diseased arteries, SMCs commonly exist as individual cells, unconnected to each other. The purpose of this study was to elucidate the events that enable individualized SMCs to enter into a stable and interacting cell collective.

APPROACH AND RESULTS: Human SMCs stimulated to undergo programmed collectivization were tracked by time-lapse microscopy. We uncovered a switch in the behavior of contacting SMCs from semiautonomous motility to cell-cell adherence. Central to the cell-adherent phenotype was the formation of uniquely elongated adherens junctions, ≤60 μm in length, which appeared …

Evidence Of Ventricular Contamination Of The Optical Signal In Preterm Neonates With Post Hemorrhagic Ventricle Dilation, J Kishimoto, M Diop, S De Ribaupierre, Dsc Lee, K St. Lawrence

Medical Biophysics Publications

No abstract provided.

Resting State And Diffusion Neuroimaging Predictors Of Clinical Improvements Following Constraint-Induced Movement Therapy In Children With Hemiplegic Cerebral Palsy., Kathryn Y Manning, Darcy Fehlings, Ronit Mesterman, Jan Willem Gorter, Lauren Switzer, Craig Campbell, Ravi S Menon

Medical Biophysics Publications

The aim was to identify neuroimaging predictors of clinical improvements following constraint-induced movement therapy. Resting state functional magnetic resonance and diffusion tensor imaging data was acquired in 7 children with hemiplegic cerebral palsy. Clinical and magnetic resonance imaging (MRI) data were acquired at baseline and 1 month later following a 3-week constraint therapy regimen. A more negative baseline laterality index characterizing an atypical unilateral sensorimotor resting state network significantly correlated with an improvement in the Canadian Occupational Performance Measure score (r = -0.81, P = .03). A more unilateral network with decreased activity in the affected hemisphere was associated with …

Investigation Of The Best Model To Characterize Diffuse Correlation Spectroscopy Measurements Acquired Directly On The Brain, K Verdecchia, M Diop, K St. Lawrence

Medical Biophysics Publications

No abstract provided.

Follow-Up Of Patients After Stereotactic Radiation For Lung Cancer: A Primer For The Nonradiation Oncologist., Kitty Huang, David A Palma

Medical Biophysics Publications

BACKGROUND: The use of stereotactic ablative radiotherapy (SABR) as primary treatment for early stage non-small-cell lung cancer, or for ablation of metastases, has increased rapidly in the past decade. With local recurrence rates reported at approximately 10%, and a patient population that is becoming increasingly fit and amenable to salvage treatment, appropriate multidisciplinary follow-up care is critical. Appropriate follow-up will allow for detection and management of radiation-related toxicity, early detection of recurrent disease and differentiation of recurrence from radiation-induced lung injury.

METHODS: This narrative review summarizes issues surrounding follow-up of patients treated with SABR in the context of a multidisciplinary …

Effect Of Taper Design On Trunnionosis In Metal On Polyethylene Total Hip Arthroplasty., Sok Chuen Tan, Matthew G Teeter, Christopher Del Balso, James L Howard, Brent A Lanting

Medical Biophysics Publications

This study examines how taper design affects corrosion and fretting at the head trunnion surface. All hip prostheses retrieved between 1999 and 2013 with 28mm/+0 heads were selected, resulting in 44 cobalt-chrome-on-polyethylene implants, representing six taper designs. Mean implantation time: 8.9±3.7years. The femoral head tapers were scored for fretting and corrosion using the Goldberg scale as both a combined score and by three zones (apex, central and base). There was no difference in age (P=0.34), BMI (P=0.29), or implantation time (P=0.19) between taper groups. The 11/13 taper had the highest combined corrosion and fretting score, but no difference (P=0.22) between …

Effect Of Ascorbate On Plasminogen Activator Inhibitor-1 Expression And Release From Platelets And Endothelial Cells In An In-Vitro Model Of Sepsis., Scott B Swarbreck, Dan Secor, Christopher G Ellis, Michael D Sharpe, John X Wilson, Karel Tyml

Medical Biophysics Publications

The microcirculation during sepsis fails due to capillary plugging involving microthrombosis. We demonstrated that intravenous injection of ascorbate reduces this plugging, but the mechanism of this beneficial effect remains unclear. We hypothesize that ascorbate inhibits the release of the antifibrinolytic plasminogen activator inhibitor-1 (PAI-1) from endothelial cells and platelets during sepsis. Microvascular endothelial cells and platelets were isolated from mice. Cells were cultured and stimulated with lipopolysaccharide (LPS), tumor necrosis factor alpha (TNFα), or thrombin (agents of sepsis), with/without ascorbate for 1-24 h. PAI-1 mRNA was determined by quantitative PCR. PAI-1 protein release into the culture medium was measured by …

Dynamic Perfusion Ct In Brain Tumors., Timothy Pok Chi Yeung, Glenn Bauman, Slav Yartsev, Enrico Fainardi, David Macdonald, Ting-Yim Lee

Medical Biophysics Publications

Dynamic perfusion CT (PCT) is an imaging technique for assessing the vascular supply and hemodynamics of brain tumors by measuring blood flow, blood volume, and permeability-surface area product. These PCT parameters provide information complementary to histopathologic assessments and have been used for grading brain tumors, distinguishing high-grade gliomas from other brain lesions, differentiating true progression from post-treatment effects, and predicting prognosis after treatments. In this review, the basic principles of PCT are described, and applications of PCT of brain tumors are discussed. The advantages and current challenges, along with possible solutions, of PCT are presented.

Right Ventricular Segmentation In Cardiac Mri With Moving Mesh Correspondences., Kumaradevan Punithakumar, Michelle Noga, Ismail Ben Ayed, Pierre Boulanger

Medical Biophysics Publications

This study investigates automatic propagation of the right ventricle (RV) endocardial and epicardial boundaries in 4D (3D+time) magnetic resonance imaging (MRI) sequences. Based on a moving mesh (or grid generation) framework, the proposed algorithm detects the endocardium and epicardium within each cardiac phase via point-to-point correspondences. The proposed method has the following advantages over prior RV segmentation works: (1) it removes the need for a time-consuming, manually built training set; (2) it does not make prior assumptions as to the intensity distributions or shape; (3) it provides a sequence of corresponding points over time, a comprehensive input that can be …

Feasibility Of A Unified Approach To Intensity-Modulated Radiation Therapy And Volume-Modulated Arc Therapy Optimization And Delivery, Jerry J. Battista, Michael Macfarlane, Eugene Wong, Jeff Z. Chen, Douglas A. Hoover

Medical Biophysics Publications

Purpose:

To study the feasibility of unified intensity-modulated arc therapy (UIMAT) which combines intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT)optimization and delivery to produce superior radiation treatment plans, both in terms of dosedistribution and efficiency of beam delivery when compared with either VMAT or IMRT alone.

Methods:

An inverse planning algorithm for UIMAT was prototyped within the pinnacle treatment planningsystem (Philips Healthcare). The IMRT and VMAT deliveries are unified within the same arc, with IMRT being delivered at specific gantry angles within the arc. Optimized gantry angles for the IMRT and VMAT phases are assigned automatically by the inverse …

Rapid Desiccation Hardening Changes The Cuticular Hydrocarbon Profile Of Drosophila Melanogaster., Joseph R Stinziano, Richard J Sové, Howard D Rundle, Brent J Sinclair

Medical Biophysics Publications

The success of insects in terrestrial environments is due in large part to their ability to resist desiccation stress. Since the majority of water is lost across the cuticle, a relatively water-impermeable cuticle is a major component of insect desiccation resistance. Cuticular permeability is affected by the properties and mixing effects of component hydrocarbons, and changes in cuticular hydrocarbons can affect desiccation tolerance. A pre-exposure to a mild desiccation stress increases duration of desiccation survival in adult female Drosophila melanogaster, via a decrease in cuticular permeability. To test whether this acute response to desiccation stress is due to a change …

Pulmonary Abnormalities And Carotid Atherosclerosis In Ex-Smokers Without Airflow Limitation., Damien Pike, Miranda Kirby, Tamas J Lindenmaier, Khadija Sheikh, Casey E Neron, Daniel G Hackam, J David Spence, Aaron Fenster, Nigel A M Paterson, Don D Sin, Harvey O Coxson, David G Mccormack, Grace Parraga

Medical Biophysics Publications

Abstract It is well-established that COPD patients have a burden of vascular disease that cannot be fully-explained by smoking history but the mechanistic links between atherosclerosis and pulmonary disease in COPD patients are not well-understood. Moreover, in ex-smokers without symptoms or other evidence of COPD, subclinical pulmonary and vascular disease, although potentially present, has not been described or evaluated. Hence our aim was to use sensitive three-dimensional (3D) pulmonary and carotid imaging to quantify pulmonary airway/parenchyma abnormalities and atherosclerosis in ex-smokers without airflow limitation or symptoms consistent with COPD. We evaluated 61 subjects without airflow limitation including 34 never- (72 …

Pulmonary Imaging Abnormalities In An Adult Case Of Congenital Lobar Emphysema., Damien Pike, Sindu Mohan, Weijing Ma, James F Lewis, Grace Parraga

Medical Biophysics Publications

Congenital lobar emphysema is mainly diagnosed in infants, although rare cases are reported in adults. A 20-yr-old female with acute dyspnea, chest pain and left upper lobe (LUL) chest x-ray hyperlucency underwent 3He magnetic resonance imaging (MRI) for ventilation and apparent diffusion coefficient (ADC) measurements, as well as CT for emphysema and airway wall measurements. Forced expiratory volume in 1s, residual volume, and airways-resistance were abnormal, but there was normal carbon-monoxide-diffusing-capacity. The LUL relative area of the density histogram

Skeletal Muscle Fibrosis In The Mdx/Utrn+/- Mouse Validates Its Suitability As A Murine Model Of Duchenne Muscular Dystrophy, Lisa M. Hoffman, William T. Hrinivich, Kelly M. Gutpell

Medical Biophysics Publications

Various therapeutic approaches have been studied for the treatment of Duchenne muscular dystrophy (DMD), but none of these approaches have led to significant long-term effects in patients. One reason for this observed inefficacy may be the use of inappropriate animal models for the testing of therapeutic agents. The mdx mouse is the most widely used murine model of DMD, yet it does not model the fibrotic progression observed in patients. Other murine models of DMD are available that lack one or both alleles of utrophin, a functional analog of dystrophin. The aim of this study was to compare fibrosis and …

Feasibility Of Simultaneous Whole-Brain Imaging On An Integrated Pet-Mri System Using An Enhanced 2-Point Dixon Attenuation Correction Method., Udunna C Anazodo, Jonathan D Thiessen, Tracy Ssali, Jonathan Mandel, Matthias Günther, John Butler, William Pavlosky, Frank S Prato, R Terry Thompson, Keith S St Lawrence

Medical Biophysics Publications

PURPOSE: To evaluate a potential approach for improved attenuation correction (AC) of PET in simultaneous PET and MRI brain imaging, a straightforward approach that adds bone information missing on Dixon AC was explored.

METHODS: Bone information derived from individual T1-weighted MRI data using segmentation tools in SPM8, were added to the standard Dixon AC map. Percent relative difference between PET reconstructed with Dixon+bone and with Dixon AC maps were compared across brain regions of 13 oncology patients. The clinical potential of the improved Dixon AC was investigated by comparing relative perfusion (rCBF) measured with arterial spin labeling to relative glucose …

Detective Quantum Efficiency Of Photon-Counting X-Ray Detectors., Jesse Tanguay, Seungman Yun, Ho Kyung Kim, Ian A Cunningham

Medical Biophysics Publications

PURPOSE: Single-photon-counting (SPC) x-ray imaging has the potential to improve image quality and enable novel energy-dependent imaging methods. Similar to conventional detectors, optimizing image SPC quality will require systems that produce the highest possible detective quantum efficiency (DQE). This paper builds on the cascaded-systems analysis (CSA) framework to develop a comprehensive description of the DQE of SPC detectors that implement adaptive binning.

METHODS: The DQE of SPC systems can be described using the CSA approach by propagating the probability density function (PDF) of the number of image-forming quanta through simple quantum processes. New relationships are developed to describe PDF transfer …

Pretreatment Of Human Cerebrovascular Endothelial Cells With Co-Releasing Molecule-3 Interferes With Jnk/Ap-1 Signaling And Suppresses Lps-Induced Proadhesive Phenotype., Fukashi Serizawa, Eric Patterson, Richard F Potter, Douglas D Fraser, Gediminas Cepinskas

Medical Biophysics Publications

OBJECTIVE: Exogenously administered CO interferes with PMN recruitment to the inflamed organs. The mechanisms of CO-dependent modulation of vascular proadhesive phenotype, a key step in PMN recruitment, are unclear.

METHODS: We assessed the effects/mechanisms of CO liberated from a water-soluble CORM-3 on modulation of the proadhesive phenotype in hCMEC/D3 in an in vitro model of endotoxemia. To this end, hCMEC/D3 were stimulated with LPS (1 μg/mL) for six hours. In some experiments hCMEC/D3 were pretreated with CORM-3 (200 μmol/L) before LPS-stimulation. PMN rolling/adhesion to hCMEC/D3 were assessed under conditions of laminar shear stress (0.7 dyn/cm(2) ). In parallel, expression of …

Hippocampal Volume, Early Cognitive Decline And Gait Variability: Which Association?, Olivier Beauchet, Cyrille P Launay, Cédric Annweiler, Gilles Allali

Medical Biophysics Publications

BACKGROUND: In contrast to its prominent function in cognition, the involvement of the hippocampus in gait control is still a matter of debate. The present study aimed to examine the association of the hippocampal volume with mean values and coefficients of variation (CoV) of spatio-temporal gait parameters among cognitively healthy individuals (CHI) and patients with mild cognitive impairment (MCI).

METHODS: A total of 90 individuals (47 CHI with a mean age of 69.7±3.6years and 48.9% women, and 43 MCI individuals with a mean age of 70.2±3.7years and 62.8% women) were included in this cross-sectional study. The hippocampal volume was quantified …

'Vitamin D And Cognition In Older Adults': Updated International Recommendations., C Annweiler, E Dursun, F Féron, D Gezen-Ak, A V Kalueff, T Littlejohns, D J Llewellyn, P Millet, T Scott, K L Tucker, S Yilmazer, O Beauchet

Medical Biophysics Publications

BACKGROUND: Hypovitaminosis D, a condition that is highly prevalent in older adults aged 65 years and above, is associated with brain changes and dementia. Given the rapidly accumulating and complex contribution of the literature in the field of vitamin D and cognition, clear guidance is needed for researchers and clinicians.

METHODS: International experts met at an invitational summit on 'Vitamin D and Cognition in Older Adults'. Based on previous reports and expert opinion, the task force focused on key questions relating to the role of vitamin D in Alzheimer's disease and related disorders. Each question was discussed and voted using …

Validation Of Volumetric And Single-Slice Mri Adipose Analysis Using A Novel Fully Automated Segmentation Method., Bryan T Addeman, Shelby Kutty, Thomas G Perkins, Abraam S Soliman, Curtis N Wiens, Colin M Mccurdy, Melanie D Beaton, Robert A Hegele, Charles Mckenzie

Medical Biophysics Publications

PURPOSE: To validate a fully automated adipose segmentation method with magnetic resonance imaging (MRI) fat fraction abdominal imaging. We hypothesized that this method is suitable for segmentation of subcutaneous adipose tissue (SAT) and intra-abdominal adipose tissue (IAAT) in a wide population range, easy to use, works with a variety of hardware setups, and is highly repeatable.

MATERIALS AND METHODS: Analysis was performed comparing precision and analysis time of manual and automated segmentation of single-slice imaging, and volumetric imaging (78-88 slices). Volumetric and single-slice data were acquired in a variety of cohorts (body mass index [BMI] 15.6-41.76) including healthy adult volunteers, …

Unified Voxel- And Tensor-Based Morphometry (Uvtbm) Using Registration Confidence., Ali R Khan, Lei Wang, Mirza Faisal Beg

Medical Biophysics Publications

Voxel-based morphometry (VBM) and tensor-based morphometry (TBM) both rely on spatial normalization to a template and yet have different requirements for the level of registration accuracy. VBM requires only global alignment of brain structures, with limited degrees of freedom in transformation, whereas TBM performs best when the registration is highly deformable and can achieve higher registration accuracy. In addition, the registration accuracy varies over the whole brain, with higher accuracy typically observed in subcortical areas and lower accuracy seen in cortical areas. Hence, even the determinant of Jacobian of registration maps is spatially varying in their accuracy, and combining these …

The Effects Of Nonvascularized Versus Vascularized Bone Grafting On Calvarial Defect Healing., Stephanie M Power, Damir B Matic, David W Holdsworth

Medical Biophysics Publications

It remains unknown whether bone graft vascularity influences calvarial healing. The purposes of this study were (1) to develop a model to study nonvascularized and vascularized calvarial grafts as well as (2) to compare effects of bone graft vascularity on calvarial healing. Bilateral calvarial defects were created in 26 Wistar rats. The defects were left empty within 1 parietal region. On the contralateral side, the defects were partially closed with native parietal bone (control group, n = 6), nonvascularized (N-V, n = 10), or vascularized bone grafts (VAS, n = 10). The vascularized grafts were supplied by perforating dural arterioles. …

Tracking The Fate Of Stem Cell Implants With Fluorine-19 Mri., Jeffrey M Gaudet, Emeline J Ribot, Yuhua Chen, Kyle M Gilbert, Paula J Foster

Medical Biophysics Publications

BACKGROUND: In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (19F) agent. 19F-MRI offers unambiguous detection and in vivo quantification of labeled cells.

METHODS: We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. 19F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using 19F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty.

RESULTS: Immediately following transplantation, 19F-MRI quantification correlated …

Human Severe Sepsis Cytokine Mixture Increases Β2-Integrin-Dependent Polymorphonuclear Leukocyte Adhesion To Cerebral Microvascular Endothelial Cells In Vitro., Chris Blom, Brittany L Deller, Douglas D Fraser, Eric K Patterson, Claudio M Martin, Bryan Young, Patricia C Liaw, Payam Yazdan-Ashoori, Angelica Ortiz, Brian Webb, Greg Kilmer, David E Carter, Gediminas Cepinskas

Medical Biophysics Publications

INTRODUCTION: Sepsis-associated encephalopathy (SAE) is a state of acute brain dysfunction in response to a systemic infection. We propose that systemic inflammation during sepsis causes increased adhesion of leukocytes to the brain microvasculature, resulting in blood-brain barrier dysfunction. Thus, our objectives were to measure inflammatory analytes in plasma of severe sepsis patients to create an experimental cytokine mixture (CM), and to use this CM to investigate the activation and interactions of polymorphonuclear leukocytes (PMN) and human cerebrovascular endothelial cells (hCMEC/D3) in vitro.

METHODS: The concentrations of 41 inflammatory analytes were quantified in plasma obtained from 20 severe sepsis patients and …

Face And Content Validity Of A Novel, Web-Based Otoscopy Simulator For Medical Education., Brandon Wickens, Jordan Lewis, David P Morris, Murad Husein, Hanif M Ladak, Sumit K Agrawal

Medical Biophysics Publications

BACKGROUND: Despite the fact that otoscopy is a widely used and taught diagnostic tool during medical training, errors in diagnosis are common. Physical otoscopy simulators have high fidelity, but they can be expensive and only a limited number of students can use them at a given time.

OBJECTIVES: 1) To develop a purely web-based otoscopy simulator that can easily be distributed to students over the internet. 2) To assess face and content validity of the simulator by surveying experts in otoscopy.

METHODS: An otoscopy simulator, OtoTrain™, was developed at Western University using web-based programming and Unity 3D. Eleven experts from …

Respective And Combined Effects Of Impairments In Sensorimotor Systems And Cognition On Gait Performance: A Population-Based Cross-Sectional Study., Olivier Beauchet, Cyrille P Launay, Bruno Fantino, Gilles Allali, Cédric Annweiler

Medical Biophysics Publications

BACKGROUND: Respective and combined effects of impairments in sensorimotor systems and cognition on gait performance have not been fully studied. This study aims to describe the respective effects of impairments in muscle strength, distance vision, lower-limb proprioception and cognition on the Timed Up & Go (TUG) scores (i.e., performed TUG [pTUG], imagined TUG [iTUG] and the time difference between these two tests [delta TUG]) in older community-dwellers; and to examine their combined effects on TUG scores.

METHODS: Based on a cross-sectional design, 1792 community-dwellers (70.2±4.8 years; 53.6% female) were recruited. Gait performance was assessed using pTUG, iTUG and delta TUG. …

A Method For 3d Histopathology Reconstruction Supporting Mouse Microvasculature Analysis., Yiwen Xu, J Geoffrey Pickering, Zengxuan Nong, Eli Gibson, John-Michael Arpino, Hao Yin, Aaron D Ward

Medical Biophysics Publications

Structural abnormalities of the microvasculature can impair perfusion and function. Conventional histology provides good spatial resolution with which to evaluate the microvascular structure but affords no 3-dimensional information; this limitation could lead to misinterpretations of the complex microvessel network in health and disease. The objective of this study was to develop and evaluate an accurate, fully automated 3D histology reconstruction method to visualize the arterioles and venules within the mouse hind-limb. Sections of the tibialis anterior muscle from C57BL/J6 mice (both normal and subjected to femoral artery excision) were reconstructed using pairwise rigid and affine registrations of 5 µm-thick, paraffin-embedded …