Medical Biophysics Commons^™

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 …

Magnetic Resonance Imaging Biomarkers Of Chronic Obstructive Pulmonary Disease Prior To Radiation Therapy For Non-Small Cell Lung Cancer., Khadija Sheikh, Dante P I Capaldi, Douglas A Hoover, David A Palma, Brian P Yaremko, Grace Parraga

Medical Biophysics Publications

OBJECTIVE: In this prospectively planned interim-analysis, the prevalence of chronic obstructive lung disease (COPD) phenotypes was determined using magnetic resonance imaging (MRI) and X-ray computed tomography (CT) in non-small-cell-lung-cancer (NSCLC) patients.

MATERIALS AND METHODS: Stage-III-NSCLC patients provided written informed consent for pulmonary function tests, imaging and the 6-min-walk-test. Ventilation defect percent (VDP) and CT lung density (relative-of-CT-density-histogram

RESULTS: Seventeen stage-III NSCLC patients were evaluated (68 ± 7 years, 7 M/10 F, mean FEV1 = 77%pred) including seven current and 10 ex-smokers and eight patients with a prior lung disease diagnosis. There was a significant difference for smoking history (p = …

Gadolinium Modifies The Cell Membrane To Inhibit Permeabilization By Nanosecond Electric Pulses, Elena C. Gianulis, Andrei G. Pakhomov

Bioelectrics Publications

Lanthanide ions are the only known blockers of permeabilization by electric pulses of nanosecond duration (nsEP), but the underlying mechanisms are unknown. We employed timed applications of Gd³⁺ before or after nsEP (600-ns, 20 kV/cm) to investigate the mechanism of inhibition, and measured the uptake of the membrane-impermeable YO-PRO-1 (YP) and propidium (Pr) dyes. Gd³⁺ inhibited dye uptake in a concentration-dependent manner. The inhibition of Pr uptake was always about 2-fold stronger. Gd³⁺ was effective when added after nsEP, as well as when it was present during nsEP exposure and removed afterward. Pores formed by nsEP in …

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 …

Functional Lung Avoidance For Individualized Radiotherapy (Flair): Study Protocol For A Randomized, Double-Blind Clinical Trial., Douglas A Hoover, Dante Pi Capaldi, Khadija Sheikh, David A Palma, George B Rodrigues, A Rashid Dar, Edward Yu, Brian Dingle, Mark Landis, Walter Kocha, Michael Sanatani, Mark Vincent, Jawaid Younus, Sara Kuruvilla, Stewart Gaede, Grace Parraga, Brian P Yaremko

Medical Biophysics Publications

BACKGROUND: Although radiotherapy is a key component of curative-intent treatment for locally advanced, unresectable non-small cell lung cancer (NSCLC), it can be associated with substantial pulmonary toxicity in some patients. Current radiotherapy planning techniques aim to minimize the radiation dose to the lungs, without accounting for regional variations in lung function. Many patients, particularly smokers, can have substantial regional differences in pulmonary ventilation patterns, and it has been hypothesized that preferential avoidance of functional lung during radiotherapy may reduce toxicity. Although several investigators have shown that functional lung can be identified using advanced imaging techniques and/or demonstrated the feasibility and …

Free-Breathing Pulmonary (1)H And Hyperpolarized (3)He Mri: Comparison In Copd And Bronchiectasis., Dante P I Capaldi, Khadija Sheikh, Fumin Guo, Sarah Svenningsen, Roya Etemad-Rezai, Harvey O Coxson, Jonathon A Leipsic, David G Mccormack, Grace Parraga

Medical Biophysics Publications

RATIONALE AND OBJECTIVES: In this proof-of-concept demonstration, we aimed to quantitatively and qualitatively compare pulmonary ventilation abnormalities derived from Fourier decomposition of free-breathing (1)H magnetic resonance imaging (FDMRI) to hyperpolarized (3)He MRI in subjects with chronic obstructive pulmonary disease (COPD) and bronchiectasis.

MATERIALS AND METHODS: All subjects provided written informed consent to a protocol approved by a local research ethics board and Health, Canada, and they underwent MRI, computed tomography (CT), spirometry, and plethysmography during a single 2-hour visit. Semiautomated segmentation was used to generate ventilation defect measurements derived from FDMRI and (3)He MRI, and these were compared using analysis …

Anatomical, Functional And Metabolic Imaging Of Radiation-Induced Lung Injury Using Hyperpolarized Mri., Giles Santyr, Matthew Fox, Kundan Thind, Elaine Hegarty, Alexei Ouriadov, Michael Jensen, Timothy J Scholl, Jacob Van Dyk, Eugene Wong

Medical Biophysics Publications

MRI of hyperpolarized (129)Xe gas and (13)C-enriched substrates (e.g. pyruvate) presents an unprecedented opportunity to map anatomical, functional and metabolic changes associated with lung injury. In particular, inhaled hyperpolarized (129)Xe gas is exquisitely sensitive to changes in alveolar microanatomy and function accompanying lung inflammation through decreases in the apparent diffusion coefficient (ADC) of alveolar gas and increases in the transfer time (T(tr)) of xenon exchange from the gas and into the dissolved phase in the lung. Furthermore, metabolic changes associated with hypoxia arising from lung injury may be reflected by increases in lactate-to-pyruvate signal ratio obtained by magnetic resonance spectroscopic …

Vitamin D And White Matter Abnormalities In Older Adults: A Cross-Sectional Neuroimaging Study., C Annweiler, T Annweiler, R Bartha, F R Herrmann, R Camicioli, O Beauchet

Medical Biophysics Publications

BACKGROUND AND PURPOSE: Morphological brain changes related to hypovitaminosis D have been poorly studied. In particular, the age-related decrease in vitamin D concentrations may explain the onset of white matter abnormalities (WMA) in older adults. Our objectives were (i) to investigate whether there was an association between serum 25-hydroxyvitamin D (25OHD) concentration and the grade of WMA in older adults and (ii) to determine whether the location of WMA was associated with 25OHD concentration.

METHODS: One hundred and thirty-three Caucasian older community-dwellers with no clinical hydrocephalus (mean 71.6 ± 5.6 years; 43.6% female) received a blood test and a magnetic …

P-I-N Heterojunctions With Bifeo3 Perovskite Nanoparticles And P- And N-Type Oxides: Photovoltaic Properties., Soumyo Chatterjee, Abhijit Bera, Amlan J Pal

Medical Biophysics Publications

We formed p-i-n heterojunctions based on a thin film of BiFeO3 nanoparticles. The perovskite acting as an intrinsic semiconductor was sandwiched between a p-type and an n-type oxide semiconductor as hole- and electron-collecting layer, respectively, making the heterojunction act as an all-inorganic oxide p-i-n device. We have characterized the perovskite and carrier collecting materials, such as NiO and MoO3 nanoparticles as p-type materials and ZnO nanoparticles as the n-type material, with scanning tunneling spectroscopy; from the spectrum of the density of states, we could locate the band edges to infer the nature of the active semiconductor materials. The energy level …

Euvolemia In Hemodialysis Patients: A Potentially Dangerous Goal?, Shih-Han S Huang, Guido Filler, Robert Lindsay, Chris W Mcintyre

Medical Biophysics Publications

Dialysis patients have high mortality rate and the leading cause of death is cardiovascular disease. Uremic cardiomyopathy differs from that due to conventional atherosclerosis, where cardiovascular changes result in ineffective circulation and lead to tissue ischemia. Modern dialysis has significant limitations with fluid management probably the most challenging. Current evidence suggests that both volume overload and aggressive fluid removal can induce circulatory stress and multi-organ injury. Furthermore, we do not have accurate volume assessment tools. As a result, targeting euvolemia might result in more harm than benefit with conventional hemodialysis therapy. Therefore, it might be time to consider a degree …

Ct Perfusion Imaging As An Early Biomarker Of Differential Response To Stereotactic Radiosurgery In C6 Rat Gliomas, Timothy Pok Chi Yeung, Maher Kurdi, Yong Wang, Baraa Al-Khazraji, Laura Morrison, Lisa Hoffman, Dwayne Jackson, Cathie Crukley, Ting-Yim Lee, Glenn Bauman, Slav Yartsev

Medical Biophysics Publications

BACKGROUND: The therapeutic efficacy of stereotactic radiosurgery for glioblastoma is not well understood, and there needs to be an effective biomarker to identify patients who might benefit from this treatment. This study investigated the efficacy of computed tomography (CT) perfusion imaging as an early imaging biomarker of response to stereotactic radiosurgery in a malignant rat glioma model.

METHODS: Rats with orthotopic C6 glioma tumors received either mock irradiation (controls, N = 8) or stereotactic radiosurgery (N = 25, 12 Gy in one fraction) delivered by Helical Tomotherapy. Twelve irradiated animals were sacrificed four days after stereotactic radiosurgery to assess acute …

Longitudinal Computed Tomography And Magnetic Resonance Imaging Of Copd: Thoracic Imaging Network Of Canada (Tincan) Study Objectives, Miranda Kirby, Damien Pike, David G Mccormack, Stephen Lam, Harvey O Coxson, Grace Parraga

Medical Biophysics Publications

Although the human and societal burden and cost of COPD is staggering, there are few clinical tools that provide earlier diagnoses or a means to regionally monitor disease in a way that might lead to improved therapies and outcomes. In acknowledgement of the current gaps in COPD therapy, the objective of the Thoracic Imaging Network of Canada (TINCan) is to improve COPD patient phenotyping through imaging, to provide methods and imaging-based intermediate endpoints for the development of new treatments, and to evaluate disease progression and patient-based outcomes in COPD patients and those at risk of COPD. Here we summarize and …

Implementation And Validation Of Aortic Remodeling In Hypertensive Rats, Shijia Zhao, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

A computational framework was implemented and validated to better understand the hypertensive artery remodeling in both geometric dimensions and material properties. Integrating the stress-modulated remodeling equations into commercial finite element codes allows a better control and visualization of local mechanical parameters. Both arterial thickening and stiffening effects were captured and visualized. An adaptive material remodeling strategy combined with the element birth and death techniques for the geometrical growth were implemented. The numerically predicted remodeling results in terms of the wall thickness, inner diameter, and the ratio of elastin to collagen content of the artery were compared with and fine-tuned by …

Validating Hemoglobin Saturation And Dissolved Oxygen In Tumors Using The Oxylab Probe And Photoacoustic Imaging, Jenna Burnett, Justin Sick, Ms, Marc Mendonca, Keith Stantz, Phd

The Summer Undergraduate Research Fellowship (SURF) Symposium

The goal of this experiment is to validate the relationship between hemoglobin saturation (SaO₂) and partial pressure of dissolved oxygen (pO₂) in breast tumors in mice using photoacoustic computed tomographic (PCT) imaging and OxyLite probe, respectively. In its simplest form, the relationship is described by the dissociation curve, or Hill’s equation, for hemoglobin, and is modeled as a sigmoidal curve that is a function of two parameters – the Hill coefficient, n, and the net association constant of HbO₂, K (or pO₂ at 50% SaO₂). First, a calibration study to validate …

Pulmonary Ventilation Defects In Older Never-Smokers, Khadija Sheikh, Gregory A Paulin, Sarah Svenningsen, Miranda Kirby, Nigel A M Paterson, David G Mccormack, Grace Parraga

Medical Biophysics Publications

Hyperpolarized (3)He MRI previously revealed spatially persistent ventilation defects in healthy, older compared with healthy, younger never-smokers. To understand better the physiological consequences and potential relevance of (3)He MRI ventilation defects, we evaluated (3)He-MRI ventilation-defect percent (VDP) and the effect of deep inspiration (DI) and salbutamol on VDP in older never-smokers. To identify the potential determinants of ventilation defects in these subjects, we evaluated dyspnea, pulmonary function, and cardiopulmonary exercise test (CPET) measurements, as well as occupational and second-hand smoke exposure. Fifty-two never-smokers (71 ± 6 yr) with no history of chronic respiratory disease were evaluated. During a single visit, …

Development Of A New Independent Monte Carlo Dose Calculation Quality Assurance Audit To Ol For Clinical Trials, Austin M. Faught

Dissertations and Theses (Open Access)

Introduction: Commercially available treatment planning systems (TPS) may use a number of different radiation dose calculation algorithms during the planning process. The Radiological Physics Center (RPC), tasked with ensuring clinically comparable and consistent dose delivery amongst institutions participating in NCI funded multi-institutional clinical trials, has traditionally relied upon measurements to achieve this objective. As a supplement to the tools used by the RPC, an independent dose calculation tool is needed to determine patient dose distributions in three dimensions so as to act as a quality assurance tool for the dose calculations.

Methods: Multiple source models representing the output of Elekta …

Three-Dimensional Carotid Ultrasound Plaque Texture Predicts Vascular Events, Arna Van Engelen, Thapat Wannarong, Grace Parraga, Wiro J Niessen, Aaron Fenster, J David Spence, Marleen De Bruijne

Medical Biophysics Publications

BACKGROUND AND PURPOSE: Carotid ultrasound atherosclerosis measurements, including those of the arterial wall and plaque, provide a way to monitor patients at risk of vascular events. Our objective was to examine carotid ultrasound plaque texture measurements and the change in carotid plaque texture during 1 year in patients at risk of events and to compare these with measurements of plaque volume and other risk factors as predictors of vascular events.

METHODS: We evaluated 298 patients with carotid atherosclerosis using 3-dimensional (3D) ultrasound at baseline and after 1 year and measured carotid plaque volume and 376 measures of plaque texture. Patients …

Hyperpolarized 3he And 129xe Magnetic Resonance Imaging Apparent Diffusion Coefficients: Physiological Relevance In Older Never- And Ex-Smokers, Miranda Kirby, Alexei Ouriadov, Sarah Svenningsen, Amir Owrangi, Andrew Wheatley, Roya Etemad-Rezai, Giles E Santyr, David G Mccormack, Grace Parraga

Medical Biophysics Publications

Noble gas pulmonary magnetic resonance imaging (MRI) is transitioning away from (3)He to (129)Xe gas, but the physiological/clinical relevance of (129)Xe apparent diffusion coefficient (ADC) parenchyma measurements is not well understood. Therefore, our objective was to generate (129)Xe MRI ADC for comparison with (3)He ADC and with well-established measurements of alveolar structure and function in older never-smokers and ex-smokers with chronic obstructive pulmonary disease (COPD). In four never-smokers and 10 COPD ex-smokers, (3)He (b = 1.6 sec/cm(2)) and (129)Xe (b = 12, 20, and 30 sec/cm(2)) ADC, computed tomography (CT) density-threshold measurements, and the diffusing capacity for carbon monoxide (DLCO) …

Volume Of Carotid Artery Ulceration As A Predictor Of Cardiovascular Events, Mariya Kuk, Thapat Wannarong, Vadim Beletsky, Grace Parraga, Aaron Fenster, J David Spence

Medical Biophysics Publications

BACKGROUND AND PURPOSE: Previous studies have shown the presence of ulceration in atherosclerotic plaque either by categorizing the plaque as complex (irregular morphology with ulcers) or smooth or by quantifying the number of ulcers observed in a specific region of interest. The aim of this study was to quantify carotid total ulcer volume by 3-dimensional ultrasound to investigate the relationship of total ulcer volume to vascular events (strokes, transient ischemic attack, myocardial infarction, revascularization, or death because of cardiovascular reasons).

METHODS: In total, 349 at-risk subjects provided written informed consent to carotid 3-dimensional ultrasound and were analyzed for ulcerations. Ulcer …