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Medical Engineering & Physics

Xudong Ge, Prosper Adangwa, Ja Young Lim, Yordan Kostov, Leah Tolosa, Richard Pierson, Daniel Herr, Govind Rao
Blood gas measurements provide vital clinical information in critical care. The current "gold standard" for blood gas measurements involves obtaining blood samples, which can be painful and can lead to bleeding, thrombus formation, or infection. Mass transfer equilibrium-based transcutaneous blood gas monitors have been used since the 1970s, but they require heating the skin to ≥42 °C to speed up the transcutaneous gas diffusion. Thus, these devices have a potential risk for skin burns. Here we report a new generation of noninvasive device for respiratory status assessment...
April 5, 2018: Medical Engineering & Physics
Nobuhiro Yoda, Keke Zheng, Junning Chen, Zhipeng Liao, Shigeto Koyama, Christopher Peck, Michael Swain, Keiichi Sasaki, Qing Li
Whilst the newly established biomechanical conditions following mandibular reconstruction using fibula free flap can be a critical determinant for achieving favorable bone union, little has been known about their association in a time-dependent fashion. This study evaluated the bone healing/remodeling activity in reconstructed mandible and its influence on jaw biomechanics using CT data, and further quantified their correlation with mechanobiological responses through an in-silico approach. A 66-year-old male patient received mandibular reconstruction was studied...
March 30, 2018: Medical Engineering & Physics
B H van Duren, K Sugand, R Wescott, R Carrington, A Hart
BACKGROUND: Hip fractures contribute to a significant clinical burden globally with over 1.6 million cases per annum and up to 30% mortality rate within the first year. Insertion of a dynamic hip screw (DHS) is a frequently performed procedure to treat extracapsular neck of femur fractures. Poorly performed DHS fixation of extracapsular neck of femur fractures can result in poor mobilisation, chronic pain, and increased cut-out rate requiring revision surgery. A realistic, affordable, and portable fluoroscopic simulation system can improve performance metrics in trainees, including the tip-apex distance (the only clinically validated outcome), and improve outcomes...
March 29, 2018: Medical Engineering & Physics
Justine S Pujos, Mathilde Reyssat, Anne Le Goff
Blood platelets circulate in the blood and adhere to wounded vessels to initiate coagulation and healing. The first step of this process is the capture of flowing platelets by adhesive molecules located at the wounded vessel wall. In this article, we study the transport of fixed blood platelets in a microfluidic channel coated with von Willebrand factor (vWF), a large multimeric protein expressed by endothelial cells in the vicinity of wounds. We measure the number of platelets adsorbed at the channel surface as a function of both time and space...
March 26, 2018: Medical Engineering & Physics
Marija Smoljkić, Peter Verbrugghe, Matilda Larsson, Erik Widman, Heleen Fehervary, Jan D'hooge, Jos Vander Sloten, Nele Famaey
Patient-specific biomechanical modelling can improve preoperative surgical planning. This requires patient-specific geometry as well as patient-specific material properties as input. The latter are, however, still quite challenging to estimate in vivo. This study focuses on the estimation of the mechanical properties of the arterial wall. Firstly, in vivo pressure, diameter and thickness of the arterial wall were acquired for sheep common carotid arteries. Next, the animals were sacrificed and the tissue was stored for mechanical testing...
March 23, 2018: Medical Engineering & Physics
Javad Mortazavi, Farzam Farahmand, Saeed Behzadipour, Ali Yeganeh, Mohammad Aghighi
Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone...
March 22, 2018: Medical Engineering & Physics
Arvind Gautam, Miguel A Callejas, Amit Acharyya, Swati Ghosh Acharyya
This study introduced a shape memory alloy (SMA)-based smart knee spacer for total knee arthroplasty (TKA). Subsequently, a 3D CAD model of a smart tibial component of TKA was designed in Solidworks software, and verified using a finite element analysis in ANSYS Workbench. The two major properties of the SMA (NiTi), the pseudoelasticity (PE) and shape memory effect (SME), were exploited, modelled, and analysed for a TKA application. The effectiveness of the proposed model was verified in ANSYS Workbench through the finite element analysis (FEA) of the maximum deformation and equivalent (von Mises) stress distribution...
March 22, 2018: Medical Engineering & Physics
Alexis Nez, Laetitia Fradet, Pierre Laguillaumie, Tony Monnet, Patrick Lacouture
Gyroscopes are now becoming one of the most sold MEMS sensors, given that the many applications that require their use are booming. In the medical field, gyroscopes can be found in Inertial Measurement Units used for the development of clinical tools that are dedicated to human-movement monitoring. However, MEMS gyroscopes are known to suffer from a drift phenomenon, which is mainly due to temperature variations. This drift dramatically affects measurement capability, especially that of cheap MEMs gyroscopes...
March 22, 2018: Medical Engineering & Physics
Tao Liu, Jian Li, Zengwu Shao, Kaige Ma, Zhicai Zhang, Baichuan Wang, Yannan Zhang
Due to its moldability, biocompatibility, osteoconductivity and resorbability, calcium phosphate cement (CPC) is a highly promising scaffold material for orthopedic applications. However, pH changes and ionic activity during the CPC setting reaction may adversely affect cells seeded directly on CPC. Moreover, a lack of macropores in CPC limits ingrowth of new bone. The objectives of this study were to prepare macroporous CPC scaffolds via porogen leaching, using mannitol crystals as the porogen and to evaluate the in vitro proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) encapsulated in chitosan/β-glycerophosphate (C/GP) hydrogel prior to exposure to the novel CPC scaffold...
March 22, 2018: Medical Engineering & Physics
Paulina Trybek, Michal Nowakowski, Lukasz Machura
Up to 40% of patients treated for rectal cancer suffer from therapy-related symptoms. Innervation injury is one of the suggested pathomechanisms of those symptoms hence the development of a valid, non-invasive tool for the assessment of neural systems is crucial. The aim of this work is to study the fractal properties of the surface electromyography signals obtained from patients suffering from rectal cancer. The anal sphincter activity was investigated for the group of 15 patients who underwent surgical treatment...
March 21, 2018: Medical Engineering & Physics
Ifaz T Haider, John Goldak, Hanspeter Frei
Nonlinear finite element (FE) modeling can be a powerful tool for studying femoral fracture. However, there remains little consensus in the literature regarding the choice of material model and failure criterion. Quasi-brittle models recently have been used with some success, but spurious mesh sensitivity remains a concern. The purpose of this study was to implement and validate a new model using a custom finite element designed to mitigate mesh sensitivity problems. Six specimen-specific FE models of the proximal femur were generated from quantitative tomographic (qCT) scans of cadaveric specimens...
March 15, 2018: Medical Engineering & Physics
A Krull, M M Morlock, N E Bishop
Stem modularity of revision hip implant systems offers the advantage of the restoration of individual patient geometry but introduces additional interfaces, which are subjected to repetitive bending loading and have a propensity for fretting corrosion. The male stem taper is the weakest part of the modular junction due to its reduced cross section compared to the outside diameter of the stem. Taper fractures can be the consequence of overloading in combination with corrosion. The purpose of this study was to assess the influence of implant design factors, patient factors, and surgical factors on the risk of taper failure of the modular junction of revision stems...
February 27, 2018: Medical Engineering & Physics
Francesco Montecchia, Fabio Midulla, Paola Papoff
Measuring work of breathing (WOB) is an intricate task during high-flow nasal cannula (HFNC) therapy because the continuous unidirectional flow toward the patient makes pneumotachography technically difficult to use. We implemented a new method for measuring WOB based on a differential pneumotachography (DP) system, equipped with one pneumotachograph inserted in the HFNC circuit and another connected to a monitoring facemask, combined with a leak correction algorithm (LCA) that corrects flow measurement errors arising from leakage around the monitoring facemask...
February 24, 2018: Medical Engineering & Physics
Ilan Eskinazi, Benjamin J Fregly
Concurrent estimation of muscle activations, joint contact forces, and joint kinematics by means of gradient-based optimization of musculoskeletal models is hindered by computationally expensive and non-smooth joint contact and muscle wrapping algorithms. We present a framework that simultaneously speeds up computation and removes sources of non-smoothness from muscle force optimizations using a combination of parallelization and surrogate modeling, with special emphasis on a novel method for modeling joint contact as a surrogate model of a static analysis...
February 24, 2018: Medical Engineering & Physics
Elisabetta Tedaldi, Chiara Montanari, Kenneth I Aycock, Francesco Sturla, Alberto Redaelli, Keefe B Manning
Inferior vena cava (IVC) filters have been used for over five decades as an alternative to anticoagulation therapy in the treatment of venous thromboembolic disease. However, complications associated with IVC filters remain common. Though many studies have investigated blood flow in the IVC, the effects of respiration-induced IVC collapse have not been evaluated. Our hypothesis is that IVC collapse may have an influence on IVC filter performance. Therefore, we herein investigate the hemodynamics in uncollapsed and collapsed IVC configurations using in vitro flow experiments and computational simulations...
February 24, 2018: Medical Engineering & Physics
Shangyuan Jiang, Rong Z Gan
The incudostapedial joint (ISJ) is a synovial joint connecting the incus and stapes in the middle ear. Mechanical properties of the ISJ directly affect sound transmission from the tympanic membrane to the cochlea. However, how ISJ properties change with frequency has not been investigated. In this paper, we report the dynamic properties of the human ISJ measured in eight samples using a dynamic mechanical analyzer (DMA) for frequencies from 1 to 80 Hz at three temperatures of 5, 25 and 37 °C. The frequency-temperature superposition (FTS) principle was used to extrapolate the results to 8 kHz...
February 22, 2018: Medical Engineering & Physics
Liming Shu, Naohiko Sugita, Masaya Oshima, Mamoru Mitsuishi
Orthopedic oscillating saws (OOSs) are widely used for plane processing in orthopedic surgery such as knee and hip replacement. However, sawing has been associated with bone breakthrough and necrosis problems. In this paper, a novel elliptical vibration assisted OOS was designed to achieve a low cutting force under the condition of deepening cut depth and reducing cutting speed, based on the analysis of brittle fractures of the bone and elliptical vibration assisted cutting kinematics. The elliptical vibration was generated using two parallel stacked piezoelectric actuators assembled with the fixture...
February 20, 2018: Medical Engineering & Physics
Yen Ngoc Nguyen, Munirah Ismail, Foad Kabinejadian, Edgar Lik Wui Tay, Hwa Liang Leo
Intra-ventricular flow dynamics has recently emerged as an important evaluation and diagnosis tool in different cardiovascular conditions. The formation of vortex pattern during the cardiac cycle has been suggested to play important epigenetic and energy-modulation roles in cardiac remodelling, adaptations and mal-adaptations. In this new perspective, flow alterations due to different cardiovascular procedures can affect the long-term outcome of those procedures. Especially, repairs and replacements performed on atrioventricular valves are likely to exert direct impact on intra-ventricular flow pattern...
February 14, 2018: Medical Engineering & Physics
Giovanni Costantini, Daniele Casali, Fabio Paolizzo, Marco Alessandrini, Alessandro Micarelli, Andrea Viziano, Giovanni Saggio
Human maintain their body balance by sensorimotor controls mainly based on information gathered from vision, proprioception and vestibular systems. When there is a lack of information, caused by pathologies, diseases or aging, the subject may fall. In this context, we developed a system to augment information gathering, providing the subject with warning audio-feedback signals related to his/her equilibrium. The system comprises an inertial measurement unit (IMU), a data processing unit, a headphone audio device and a software application...
February 10, 2018: Medical Engineering & Physics
V Man, S Polzer, T C Gasser, T Novotny, J Bursa
Biomechanics-based assessment of Abdominal Aortic Aneurysm (AAA) rupture risk has gained considerable scientific and clinical momentum. However, computation of peak wall stress (PWS) using state-of-the-art finite element models is time demanding. This study investigates which features of the constitutive description of AAA wall are decisive for achieving acceptable stress predictions in it. Influence of five different isotropic constitutive descriptions of AAA wall is tested; models reflect realistic non-linear, artificially stiff non-linear, or artificially stiff pseudo-linear constitutive descriptions of AAA wall...
February 2, 2018: Medical Engineering & Physics
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