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Spinal cord computational model

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https://www.readbyqxmd.com/read/28047696/su-d-brc-05-effects-of-motion-and-variable-rbe-in-a-lung-patient-treated-with-passively-scattered-protons
#1
D Mirkovic, U Titt, P Yepes, R Mohan
PURPOSE: To evaluate effects of motion and variable relative biological effectiveness (RBE) in a lung cancer patient treated with passively scattered proton therapy using dose volume histograms associated with patient dose computed using three different methods. METHODS: A proton treatment plan of a lung cancer patient optimized using clinical treatment planning system (TPS) was used to construct a detailed Monte Carlo (MC) model of the beam delivery system and the patient specific aperture and compensator...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047535/su-f-i-38-patient-organ-specific-dose-assessment-in-coronary-ct-angiograph-using-voxellaized-volume-dose-index-in-monte-carlo-simulation
#2
Mohammadi Gh Fallal, Alam N Riyahi, Gh Graily, R Paydar
PURPOSE: Clinical use of multi detector computed tomography(MDCT) in diagnosis of diseases due to high speed in data acquisition and high spatial resolution is significantly increased. Regarding to the high radiation dose in CT and necessity of patient specific radiation risk assessment, the adoption of new method in the calculation of organ dose is completely required and necessary. In this study by introducing a conversion factor, patient organ dose in thorax region based on CT image data using MC system was calculated...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046412/we-ab-209-12-quasi-constrained-multi-criteria-optimization-for-automated-radiation-therapy-treatment-planning
#3
W T Watkins, J V Siebers
PURPOSE: To introduce quasi-constrained Multi-Criteria Optimization (qcMCO) for unsupervised radiation therapy optimization which generates alternative patient-specific plans emphasizing dosimetric tradeoffs and conformance to clinical constraints for multiple delivery techniques. METHODS: For N Organs At Risk (OARs) and M delivery techniques, qcMCO generates M(N+1) alternative treatment plans per patient. Objective weight variations for OARs and targets are used to generate alternative qcMCO plans...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28034635/patient-specific-bone-mineral-density-distribution-in-the-tibia-of-individuals-with-chronic-spinal-cord-injury-derived-from-multi-slice-peripheral-quantitative-computed-tomography-pqct-a-cross-sectional-study
#4
Sylvie Coupaud, Magnus K Gislason, Mariel Purcell, Keisuke Sasagawa, K Elizabeth Tanner
BACKGROUND: The high risk of fracture associated with chronic spinal cord injury (SCI) is attributed to extensive disuse-related bone loss in previously weight-bearing long bones. Changes in bone mineral density (BMD) after SCI have been documented extensively for the epiphyses of the tibia and femur, fracture-prone sites in this patient group. Less attention has been given to patterns of cortical bone loss in the diaphyses, but variability in BMD distributions throughout the long bones may contribute to some patients' increased susceptibility to shaft fractures in chronic SCI...
December 26, 2016: Bone
https://www.readbyqxmd.com/read/27939751/estimating-axonal-strain-and-failure-following-white-matter-stretch-using-contactin-associated-protein-as-a-fiduciary-marker
#5
Sagar Singh, Assimina A Pelegri, David I Shreiber
Axonal injury occurs during trauma when tissue-scale loads are transferred to individual axons. Computational models are used to understand this transfer and predict the circumstances that cause injury. However, these findings are limited by a lack of validating experimental work examining the mechanics of axons in their in situ state. As a first step towards validation for dynamic stretch, we use contactin-associated protein (Caspr), expressed at the nodes of Ranvier, as a fiduciary marker of quasistatic axonal stretch...
January 25, 2017: Journal of Biomechanics
https://www.readbyqxmd.com/read/27843686/effect-of-spinal-cord-compression-on-local-vascular-blood-flow-and-perfusion-capacity-by-alshareef-m-krishna-v-ferdous-j-aishareef-a-kindy-m-kolachalama-vb-et-al
#6
Nancy E Epstein
BACKGROUND: Different degrees of blood flow/vascular compromise occur with anterior, posterior, or circumferential spinal cord compression/spinal cord injury (SCI). SCI is also divided into primary and secondary injury. Primary SCI refers to the original neurological damage to tissues, whereas secondary injury reflects interruption of normal blood flow leading to further inflammatory response/other local changes which contribute to additional neurological injury. METHODS: The authors developed a quantitative "3-D finite element fluid structure interaction model" of spinal cord blood flow to better document the mechanisms of secondary ischemic damage occurring in the spinal cord anteriorly, posteriorly, or circumferentially...
2016: Surgical Neurology International
https://www.readbyqxmd.com/read/27834648/epidural-stimulation-of-rat-spinal-cord-at-lumbosacral-segment-using-a-surface-electrode-a-computer-simulation-study
#7
Qi Xu, Li Kong, Hui Zhou, Jiping He
Clinical research indicates that the epidural spinal cord stimulation (ESCS) at lumbosacral segment has shown potential for promoting locomotor recovery in patients with incomplete spinal cord injury. However, the underlying neural mechanism needs to be determined by animal experiments. In order to refine experimental protocols, we used a finite element simulation to investigate the activation of nerve fibers in a rat spinal cord model. Our model is composed of a volume conductor model from L1 to S2 spinal segments and the McIntyre-Richard-Grill axon model, which is used to investigate the threshold of selected spinal fibers with different diameters at varied locations and predict the neural responses of any target fibers with bipolar electrode configuration...
November 4, 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/27799905/cerebellar-and-spinal-direct-current-stimulation-in-children-computational-modeling-of-the-induced-electric-field
#8
Serena Fiocchi, Paolo Ravazzani, Alberto Priori, Marta Parazzini
Recent studies have shown that the specific application of transcranial direct current stimulation (tDCS) over the cerebellum can modulate cerebellar activity. In parallel, transcutaneous spinal DC stimulation (tsDCS) was found to be able to modulate conduction along the spinal cord and spinal cord functions. Of particular interest is the possible use of these techniques in pediatric age, since many pathologies and injuries, which affect the cerebellar cortex as well as spinal cord circuits, are diffuse in adults as well as in children...
2016: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/27760818/descending-propriospinal-neurons-mediate-restoration-of-locomotor-function-following-spinal-cord-injury
#9
Katelyn N Benthall, Ryan A Hough, Andrew D McClellan
: Following spinal cord injury (SCI) in the lamprey, there is virtually complete recovery of locomotion within a few weeks, but interestingly, axonal regeneration of reticulospinal (RS) neurons is mostly limited to short distances caudal to the injury site. To explain this situation, we hypothesize that descending propriospinal (PS) neurons relay descending drive from RS neurons to indirectly activate spinal central pattern generators (CPGs). In the present study, the contributions of PS neurons to locomotor recovery were tested in the lamprey following SCI...
January 1, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/27734100/meagre-effects-of-disuse-on-the-human-fibula-are-not-explained-by-bone-size-or-geometry
#10
A Ireland, R F Capozza, G R Cointry, L Nocciolino, J L Ferretti, J Rittweger
: Fibula response to disuse is unknown; we assessed fibula bone in spinal cord injury (SCI) patients and able-bodied counterparts. Group differences were smaller than in the neighbouring tibia which could not be explained by bone geometry. Differential adaptation of the shank bones may indicate previously unknown mechanoadaptive behaviours of bone. INTRODUCTION: The fibula supports only a small and highly variable proportion of shank compressive load (-8 to +19 %), and little is known about other kinds of stresses...
October 12, 2016: Osteoporosis International
https://www.readbyqxmd.com/read/27712091/sustained-high-pressure-in-the-spinal-subarachnoid-space-while-arterial-expansion-is-low-may-be-linked-to-syrinx-development
#11
Elizabeth C Clarke, David F Fletcher, Lynne E Bilston
Syringomyelia (a spinal cord cyst) usually develops as a result of conditions that cause cerebrospinal fluid (CSF) obstruction. The mechanism of syrinx formation and enlargement remains unclear, though previous studies suggest that the fluid enters via the perivascular spaces (PVS) of the penetrating arteries of the spinal cord, and that alterations in the CSF pulse timing and pressure could contribute to enhanced PVS inflow. This study uses an idealised computational model of the PVS to investigate the factors that influence peri-arterial fluid flow...
October 7, 2016: Computer Methods in Biomechanics and Biomedical Engineering
https://www.readbyqxmd.com/read/27676678/evaluation-of-bone-cancer-pain-induced-by-different-doses-of-walker-256-mammary-gland-carcinoma-cells
#12
Changsheng Dong, RuiXin Wu, Jing Wu, Jing Guo, Fangyuan Wang, Yanli Fu, Qing Wang, Ling Xu, Juyong Wang
BACKGROUND: Cancer pain is a complex medical syndrome. Understanding its underlying mechanisms relies on the use of animal models which can mimic the human condition. A crucial component of this model is the quantity of tumor cells; however, the exact relationship between the doses of tumor cells on bone cancer pain is yet unknown. OBJECTIVE: We explored the relationship of different doses of Walker 256 carcinoma cells using a bone cancer pain model in rats, and evaluated its success and stability...
September 2016: Pain Physician
https://www.readbyqxmd.com/read/27664830/g-ratio-weighted-imaging-of-the-human-spinal-cord-in-vivo
#13
T Duval, S Le Vy, N Stikov, J Campbell, A Mezer, T Witzel, B Keil, V Smith, L L Wald, E Klawiter, J Cohen-Adad
The fiber g-ratio is defined as the ratio of the inner to the outer diameter of the myelin sheath. This ratio provides a measure of the myelin thickness that complements axon morphology (diameter and density) for assessment of demyelination in diseases such as multiple sclerosis. Previous work has shown that an aggregate g-ratio map can be computed using a formula that combines axon and myelin density measured with quantitative MRI. In this work, we computed g-ratio weighted maps in the cervical spinal cord of nine healthy subjects...
January 15, 2017: NeuroImage
https://www.readbyqxmd.com/read/27633893/central-control-of-interlimb-coordination-and-speed-dependent-gait-expression-in-quadrupeds
#14
Simon M Danner, Simon D Wilshin, Natalia A Shevtsova, Ilya A Rybak
KEY POINTS: Quadrupeds express different gaits depending on speed of locomotion. Central pattern generators (one per limb) within the spinal cord generate locomotor oscillations and control limb movements. Neural interactions between these generators define interlimb coordination and gait. We present a computational model of spinal circuits representing four rhythm generators with left-right excitatory and inhibitory commissural and fore-hind inhibitory interactions within the cord. Increasing brainstem drive to all rhythm generators and excitatory commissural interneurons induces an increasing frequency of locomotor oscillations accompanied by speed-dependent gait changes from walk to trot and to gallop and bound...
December 1, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27610400/abdomen-and-spinal-cord-segmentation-with-augmented-active-shape-models
#15
Zhoubing Xu, Benjamin N Conrad, Rebeccah B Baucom, Seth A Smith, Benjamin K Poulose, Bennett A Landman
Active shape models (ASMs) have been widely used for extracting human anatomies in medical images given their capability for shape regularization of topology preservation. However, sensitivity to model initialization and local correspondence search often undermines their performances, especially around highly variable contexts in computed-tomography (CT) and magnetic resonance (MR) images. In this study, we propose an augmented ASM (AASM) by integrating the multiatlas label fusion (MALF) and level set (LS) techniques into the traditional ASM framework...
July 2016: Journal of Medical Imaging
https://www.readbyqxmd.com/read/27561702/estimation-of-excitatory-and-inhibitory-synaptic-conductance-variations-in-motoneurons-during-locomotor-like-rhythmic-activity
#16
Ryota Kobayashi, Hiroshi Nishimaru, Hisao Nishijo
The rhythmic activity of motoneurons (MNs) that underlies locomotion in mammals is generated by synaptic inputs from the locomotor network in the spinal cord. Thus, the quantitative estimation of excitatory and inhibitory synaptic conductances is essential to understand the mechanism by which the network generates the functional motor output. Conductance estimation is obtained from the voltage-current relationship measured by voltage-clamp- or current-clamp-recording with knowledge of the leak parameters of the recorded neuron...
October 29, 2016: Neuroscience
https://www.readbyqxmd.com/read/27534535/integrated-analysis-of-omics-data-using-microrna-target-mrna-network-and-ppi-network-reveals-regulation-of-gnai1-function-in-the-spinal-cord-of-ews-ewsr1-ko-mice
#17
Chai-Jin Lee, Hongryul Ahn, Sean Bong Lee, Jong-Yeon Shin, Woong-Yang Park, Jong-Il Kim, Junghee Lee, Hoon Ryu, Sun Kim
BACKGROUND: Multifunctional transcription factor (TF) gene EWS/EWSR1 is involved in various cellular processes such as transcription regulation, noncoding RNA regulation, splicing regulation, genotoxic stress response, and cancer generation. Role of a TF gene can be effectively studied by measuring genome-wide gene expression, i.e., transcriptome, in an animal model of Ews/Ewsr1 knockout (KO). However, when a TF gene has complex multi-functions, conventional approaches such as differentially expressed genes (DEGs) analysis are not successful to characterize the role of the EWS gene...
2016: BMC Medical Genomics
https://www.readbyqxmd.com/read/27509542/spinal-cord-inflammation-molecular-imaging-after-thoracic-aortic-ischemia-reperfusion-injury
#18
Hassan Albadawi, John W Chen, Rahmi Oklu, Yue Wu, Gregory Wojtkiewicz, Benjamin Pulli, John D Milner, Richard P Cambria, Michael T Watkins
Purpose To evaluate whether noninvasive molecular imaging technologies targeting myeloperoxidase (MPO) can reveal early inflammation associated with spinal cord injury after thoracic aortic ischemia-reperfusion (TAR) in mice. Materials and Methods The study was approved by the institutional animal care and use committee. C57BL6 mice that were 8-10 weeks old underwent TAR (n = 55) or sham (n = 26) surgery. Magnetic resonance (MR) imaging (n = 6) or single photon emission computed tomography (SPECT)/computed tomography (CT) (n = 15) studies targeting MPO activity were performed after intravenous injection of MPO sensors (bis-5-hydroxytryptamide-tetraazacyclododecane [HT]-diethyneletriaminepentaacetic acid [DTPA]-gadolinium or indium 111-bis-5-HT-DTPA, respectively)...
January 2017: Radiology
https://www.readbyqxmd.com/read/27465752/cardiometabolic-syndrome-in-people-with-spinal-cord-injury-disease-guideline-derived-and-nonguideline-risk-components-in-a-pooled-sample
#19
Mark S Nash, Rochelle E Tractenberg, Armando J Mendez, Maya David, Inger H Ljungberg, Emily A Tinsley, Patricia A Burns-Drecq, Luisa F Betancourt, Suzanne L Groah
OBJECTIVE: To assess cardiometabolic syndrome (CMS) risk definitions in spinal cord injury/disease (SCI/D). DESIGN: Cross-sectional analysis of a pooled sample. SETTING: Two SCI/D academic medical and rehabilitation centers. PARTICIPANTS: Baseline data from subjects in 7 clinical studies were pooled; not all variables were collected in all studies; therefore, participant numbers varied from 119 to 389. The pooled sample included men (79%) and women (21%) with SCI/D >1 year at spinal cord levels spanning C3-T2 (American Spinal Injury Association Impairment Scale [AIS] grades A-D)...
October 2016: Archives of Physical Medicine and Rehabilitation
https://www.readbyqxmd.com/read/27403420/inverse-kinematics-for-upper-limb-compound-movement-estimation-in-exoskeleton-assisted-rehabilitation
#20
Camilo Cortés, Ana de Los Reyes-Guzmán, Davide Scorza, Álvaro Bertelsen, Eduardo Carrasco, Ángel Gil-Agudo, Oscar Ruiz-Salguero, Julián Flórez
Robot-Assisted Rehabilitation (RAR) is relevant for treating patients affected by nervous system injuries (e.g., stroke and spinal cord injury). The accurate estimation of the joint angles of the patient limbs in RAR is critical to assess the patient improvement. The economical prevalent method to estimate the patient posture in Exoskeleton-based RAR is to approximate the limb joint angles with the ones of the Exoskeleton. This approximation is rough since their kinematic structures differ. Motion capture systems (MOCAPs) can improve the estimations, at the expenses of a considerable overload of the therapy setup...
2016: BioMed Research International
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