Medical Biophysics Commons^™

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 …

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 …