Medical Biophysics Commons^™

In-Vivo Longitudinal Mri Study: An Assessment Of Melanoma Brain Metastases In A Clinically Relevant Mouse Model., Mariama N Henry, Yuhua Chen, Catherine D Mcfadden, Felicia C Simedrea, Paula J Foster

Medical Biophysics Publications

Brain metastases are an important clinical problem. Few animal models exist for melanoma brain metastases; many of which are not clinically relevant. Longitudinal MRI was implemented to examine the development of tumors in a clinically relevant mouse model of melanoma brain metastases. Fifty thousand human metastatic melanoma (A2058) cells were injected intracardially into nude mice. Three Tesla MRI was performed using a custom-built gradient insert coil and a mouse solenoid head coil. Imaging was performed on consecutive days at four time points. Tumor burden and volumes of metastases were measured from balanced steady-state free precession image data. Metastases with a …

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 …

Three-Dimensional Computed Tomography Measurements Of Pulmonary Artery Volumes: Development And Application, Tamas J. Lindenmaier

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) is a major contributor to hospitalizations and healthcare costs in North America. While the hallmark of COPD is airflow limitation, it is also associated with abnormalities of the cardiovascular system. Enlargement of the pulmonary artery (PA) is a morphological marker of pulmonary hypertension, and was previously shown to predict acute exacerbations using a one-dimensional (1D) diameter measurement of the main PA. We hypothesized that a three-dimensional (3D) quantification of PA size would be more sensitive than 1D methods and encompass morphological changes along the entire central PA. Hence, we developed a 3D measurement of the …

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.

Estimating Hemodynamics In Skeletal Muscle Arteriolar Networks Reconstructed From In Vivo Data, Amani H. Saleem

Electronic Thesis and Dissertation Repository

The objective of this work was to develop a computational model that could accurately predict blood flow in skeletal muscle arteriolar trees in the absence of complete boundary data. We used arteriolar trees in the rat gluteus maximus muscle (GM) that were reconstructed from montages obtained via intravital videomicroscopy, and incorporated a recently published method for approximating unknown boundary conditions into our existing steady-state model of two-phase blood flow. For varying numbers of unknown boundary conditions, we used the new flow model and GM arteriolar geometry to approximately match red blood cell (RBC) flows corresponding to experimental measurements. We showed …

A Proposed Framework For Consensus-Based Lung Tumour Volume Auto-Segmentation In 4d Computed Tomography Imaging., Spencer Martin, Mark Brophy, David Palma, Alexander V Louie, Edward Yu, Brian Yaremko, Belal Ahmad, John L Barron, Steven S Beauchemin, George Rodrigues, Stewart Gaede

Medical Biophysics Publications

This work aims to propose and validate a framework for tumour volume auto-segmentation based on ground-truth estimates derived from multi-physician input contours to expedite 4D-CT based lung tumour volume delineation. 4D-CT datasets of ten non-small cell lung cancer (NSCLC) patients were manually segmented by 6 physicians. Multi-expert ground truth (GT) estimates were constructed using the STAPLE algorithm for the gross tumour volume (GTV) on all respiratory phases. Next, using a deformable model-based method, multi-expert GT on each individual phase of the 4D-CT dataset was propagated to all other phases providing auto-segmented GTVs and motion encompassing internal gross target volumes (IGTVs) …

Registration Of In-Vivo To Ex-Vivo Mri Of Surgically Resected Specimens: A Pipeline For Histology To In-Vivo Registration., Maged Goubran, Sandrine De Ribaupierre, Robert R Hammond, Catherine Currie, Jorge G Burneo, Andrew G Parrent, Terry M Peters, Ali R Khan

Medical Biophysics Publications

BACKGROUND: Advances in MRI have the potential to improve surgical treatment of epilepsy through improved identification and delineation of lesions. However, validation is currently needed to investigate histopathological correlates of these new imaging techniques. The purpose of this work is to develop and evaluate a protocol for deformable image registration of in-vivo to ex-vivo resected brain specimen MRI. This protocol, in conjunction with our previous work on ex-vivo to histology registration, completes a registration pipeline for histology to in-vivo MRI, enabling voxel-based validation of novel and existing MRI techniques with histopathology.

NEW METHOD: A combination of image-based and landmark-based 3D …

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 …

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

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 …