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Showing 1401 - 1600 of 1720 Journals sorted alphabetically
Therya     Open Access  
Tissue and Cell     Hybrid Journal   (Followers: 1)
Tissue Engineering and Regenerative Medicine     Hybrid Journal   (Followers: 11)
Tissue Engineering Part A     Hybrid Journal   (Followers: 10)
Tissue Engineering Part B: Reviews     Hybrid Journal   (Followers: 8)
Tissue Engineering Part C: Methods     Hybrid Journal   (Followers: 8)
Toxicology in Vitro     Hybrid Journal   (Followers: 12)
Traffic     Hybrid Journal   (Followers: 6)
Transactions of the Royal Society of South Australia     Hybrid Journal  
Transcription     Full-text available via subscription   (Followers: 2)
Transgenic Research     Hybrid Journal   (Followers: 1)
Translational Psychiatry     Open Access   (Followers: 10)
Transportation Planning and Technology     Hybrid Journal   (Followers: 8)
Tree Genetics & Genomes     Hybrid Journal   (Followers: 3)
Tree-Ring Research     Full-text available via subscription  
Trees     Hybrid Journal   (Followers: 4)
Trends in Bacteriology     Open Access   (Followers: 4)
Trends in Bioinformatics     Open Access   (Followers: 18)
Trends in Biotechnology     Full-text available via subscription   (Followers: 141)
Trends in Cell Biology     Full-text available via subscription   (Followers: 33)
Trends in Evolutionary Biology     Open Access   (Followers: 13)
Trends in Microbiology     Full-text available via subscription   (Followers: 38)
Trends in Molecular Sciences     Open Access   (Followers: 3)
Trends in Parasitology     Full-text available via subscription   (Followers: 12)
Trends in Plant Science     Full-text available via subscription   (Followers: 20)
Trends in Vector Research and Parasitology     Open Access  
Tropical Drylands     Open Access  
Tropical Freshwater Biology     Full-text available via subscription  
Tumor Biology     Open Access   (Followers: 2)
Tumor Microenvironment and Therapy     Open Access  
Tunnelling and Underground Space Technology     Hybrid Journal   (Followers: 9)
Turtle and Tortoise Newsletter     Full-text available via subscription   (Followers: 1)
Ukrainian Journal of Ecology     Open Access   (Followers: 1)
Ultrasound in Medicine & Biology     Full-text available via subscription   (Followers: 8)
Uniciencia     Open Access  
Universal Journal of Biomedical Engineering     Open Access  
Unnes Journal of Biology Education     Open Access   (Followers: 1)
Vakuum in Forschung und Praxis     Hybrid Journal   (Followers: 2)
Vascular Cell     Open Access  
Victorian Naturalist, The     Full-text available via subscription   (Followers: 3)
Virchows Archiv     Hybrid Journal   (Followers: 1)
Virologica Sinica     Hybrid Journal   (Followers: 1)
Virology Journal     Open Access   (Followers: 6)
Virulence     Full-text available via subscription   (Followers: 2)
Virus Evolution     Open Access   (Followers: 2)
Virus Genes     Hybrid Journal   (Followers: 2)
Virus Research     Hybrid Journal   (Followers: 1)
Visnyk of Dnipropetrovsk University. Biology, ecology     Open Access   (Followers: 2)
Visnyk of Dnipropetrovsk University. Biology, medicine     Open Access  
Walailak Journal of Science and Technology     Open Access  
Web Ecology     Open Access   (Followers: 3)
Weed Science     Full-text available via subscription   (Followers: 5)
Weed Technology     Full-text available via subscription   (Followers: 2)
West African Journal of Applied Ecology     Open Access  
Western Undergraduate Research Journal : Health and Natural Sciences     Open Access  
Wetlands     Hybrid Journal   (Followers: 22)
Wildlife Biology     Open Access   (Followers: 15)
Wildlife Research     Hybrid Journal   (Followers: 16)
Wiley Interdisciplinary Reviews - System Biology and Medicine     Hybrid Journal   (Followers: 5)
Wiley Interdisciplinary Reviews : Developmental Biology     Hybrid Journal   (Followers: 2)
Wiley Interdisciplinary Reviews : Membrane Transport and Signaling     Hybrid Journal  
Wiley Interdisciplinary Reviews : RNA     Hybrid Journal   (Followers: 3)
World Crop Pests     Full-text available via subscription   (Followers: 1)
World Mycotoxin Journal     Full-text available via subscription   (Followers: 5)
Xenobiotica     Hybrid Journal   (Followers: 7)
Yeast     Hybrid Journal   (Followers: 8)
Zebrafish     Hybrid Journal  
Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen     Full-text available via subscription   (Followers: 5)
Zeitschrift für Naturforschung C : A Journal of Biosciences     Open Access   (Followers: 2)
Zygote     Hybrid Journal  

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Journal Cover Medical Engineering & Physics
  [SJR: 0.784]   [H-I: 76]   [9 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1350-4533
   Published by Elsevier Homepage  [3177 journals]
  • Multifractal characteristics of external anal sphincter based on sEMG
    • Authors: Paulina Trybek; Michal Nowakowski; Lukasz Machura
      Pages: 9 - 15
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Multifractal detrended fluctuation analysis was implemented to analyze the data, obtained at four different stages: one before treatment and three times after the surgery. The results from the standard detrended fluctuation analysis and empirical mode decomposition methods are presented and compared. The statistically significant differences between the stages of treatment were identified for the selected spectral parameters: width and maximum of the spectrum.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.007
      Issue No: Vol. 55 (2018)
  • Comparison of in vivo vs. ex situ obtained material properties of sheep
           common carotid artery
    • Authors: Marija Smoljkić; Peter Verbrugghe; Matilda Larsson; Erik Widman; Heleen Fehervary; Jan D’hooge; Jos Vander Sloten; Nele Famaey
      Pages: 16 - 24
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Planar biaxial tests were performed to obtain experimental stress-stretch curves. Finally, parameters for the hyperelastic Mooney–Rivlin and Gasser–Ogden–Holzapfel (GOH) material model were estimated based on the in vivo obtained pressure-diameter data as well as on the ex situ experimental stress-stretch curves. Both material models were able to capture the in vivo behaviour of the tissue. However, in the ex situ case only the GOH model provided satisfactory results. When comparing different fitting approaches, in vivo vs. ex situ, each of them showed its own advantages and disadvantages. The in vivo approach estimates the properties of the tissue in its physiological state while the ex situ approach allows to apply different loadings to properly capture the anisotropy of the tissue. Both of them could be further enhanced by improving the estimation of the stress-free state, i.e. by adding residual circumferential stresses in vivo and by accounting for the flattening effect of the tested samples ex vivo. • Competing interests: none declared • Word count: 4716

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.006
      Issue No: Vol. 55 (2018)
  • Experimental and numerical study of platelets rolling on a von Willebrand
           factor-coated surface
    • Authors: Justine S. Pujos; Mathilde Reyssat; Anne Le Goff
      Pages: 25 - 33
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Experimental results are compared with a new transport model. We show that transverse diffusion is an important feature of our model, while the rolling behaviour of the bounded platelets can be neglected.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.005
      Issue No: Vol. 55 (2018)
  • A patient specific finite element simulation of intramedullary nailing to
           predict the displacement of the distal locking hole
    • Authors: Javad Mortazavi; Farzam Farahmand; Saeed Behzadipour; Ali Yeganeh; Mohammad Aghighi
      Pages: 34 - 42
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model predictions and the experimental observations. There was a three-point contact pattern between the nail and medullary canal, only on the proximal fragment of the fractured bone. The nail deflection was much larger in the sagittal plane and increased for the larger diameter nail, as well as for more distally fractured or intact femur. The altered position of the distal hole was predicted by the model with an acceptable error (mean: 0.95; max: 1.5 mm, in different tests) to be used as the compensatory information for fine tuning of proximally mounted targeting systems.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.004
      Issue No: Vol. 55 (2018)
  • Shape-memory-alloy-based smart knee spacer for total knee arthroplasty: 3D
           CAD modelling and a computational study
    • Authors: Arvind Gautam; Miguel A Callejas; Amit Acharyya; Swati Ghosh Acharyya
      Pages: 43 - 51
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. The proposed model was also compared with a polymethylmethacrylate (PMMA)-based spacer for the upper portion of the tibial component for three subjects with body mass index (BMI) of 23.88, 31.09, and 38.39. The proposed SMA -based smart knee spacer contained 96.66978% less deformation with a standard deviation of 0.01738 than that of the corresponding PMMA based counterpart for the same load and flexion angle. Based on the maximum deformation analysis, the PMMA-based spacer had 30 times more permanent deformation than that of the proposed SMA-based spacer for the same load and flexion angle. The SME property of the lower portion of the tibial component for fixation of the spacer at its position was verified by an FEA in ANSYS. Wherein, a strain life-based fatigue analysis was performed and tested for the PE and SME built spacers through the FEA. Therefore, the SMA-based smart knee spacer eliminated the drawbacks of the PMMA-based spacer, including spacer fracture, loosening, dislocation, tilting or translation, and knee subluxation.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.001
      Issue No: Vol. 55 (2018)
  • Augmented reality fluoroscopy simulation of the guide-wire insertion in
           DHS surgery: A proof of concept study
    • Authors: B.H. van Duren; K. Sugand; R. Wescott; R. Carrington; A. Hart
      Pages: 52 - 59
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Method We developed a digital fluoroscopic imaging simulator using orthogonal cameras to track coloured markers attached to the guide-wire which created a virtual overlay on fluoroscopic images of the hip. To test the accuracy with which the augmented reality system could track a guide-wire, a standard workshop femur was used to calibrate the system with a positional marker fixed to indicate the apex; this allowed for comparison between guide-wire tip-apex distance (TAD) calculated by the system to be compared to that physically measured. Tests were undertaken to determine: (1) how well the apex could be targeted; (2) the accuracy of the calculated TAD. (3) The number of iterations through the algorithm giving the optimal accuracy–time relationship. Results The calculated TAD was found to have an average root mean square error of 4.2 mm. The accuracy of the algorithm was shown to increase with the number of iterations up to 20 beyond which the error asymptotically converged to an error of 2 mm. Conclusion This work demonstrates a novel augmented reality simulation of guide-wire insertion in DHS surgery. To our knowledge this has not been previously achieved. In contrast to virtual reality, augmented reality is able to simulate fluoroscopy while allowing the trainee to interact with real instrumentation and performing the procedure on workshop bone models.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.02.007
      Issue No: Vol. 55 (2018)
  • Simple and efficient thermal calibration for MEMS gyroscopes
    • Authors: Alexis Nez; Laetitia Fradet; Pierre Laguillaumie; Tony Monnet; Patrick Lacouture
      Pages: 60 - 67
      Abstract: Publication date: May 2018
      Source:Medical Engineering & Physics, Volume 55
      Author(s): 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. Calibration is therefore a key factor in achieving accurate measurements. However, traditional calibration procedures are often complex and require costly equipment. This paper therefore proposes an easy protocol for performing a thermal gyroscope calibration. In this protocol, accuracy over the angular velocity is evaluated by referring to an optoelectronic measurement, and is compared with the traditional calibration performed by the manufacturer. The RMSE between the reference angular velocity and that obtained with the proposed calibration was of 0.7°/s, which was slightly smaller than the RMSE of 1.1°/s achieved by the manufacturer's calibration. An analysis of uncertainty propagation shows that offset variability is the major source of error over the computed rate of rotation from the tested sensors, since it accounts for 97% of the error. It can be concluded that the proposed simple calibration method leads to a similar degree of accuracy as that achieved by the manufacturer's procedure.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.002
      Issue No: Vol. 55 (2018)
  • Impact of isotropic constitutive descriptions on the predicted peak wall
           stress in abdominal aortic aneurysms
    • Authors: V. Man; S. Polzer; T.C. Gasser; T. Novotny; J. Bursa
      Pages: 49 - 57
      Abstract: Publication date: March 2018
      Source:Medical Engineering & Physics, Volume 53
      Author(s): 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. Influence of the AAA wall model is tested on idealized ( n = 4 ) and patient-specific ( n = 16 ) AAA geometries. Wall stress computations consider a (hypothetical) load-free configuration and include residual stresses homogenizing the stresses across the wall. Wall stress differences amongst the different descriptions were statistically analyzed. When the qualitatively similar non-linear response of the AAA wall with low initial stiffness and subsequent strain stiffening was taken into consideration, wall stress (and PWS) predictions did not change significantly. Keeping this non-linear feature when using an artificially stiff wall can save up to 30% of the computational time, without significant change in PWS. In contrast, a stiff pseudo-linear elastic model may underestimate the PWS and is not reliable for AAA wall stress computations.

      PubDate: 2018-02-26T04:34:46Z
      DOI: 10.1016/j.medengphy.2018.01.002
      Issue No: Vol. 53 (2018)
  • Editorial
    • Authors: Richard A. Black (PhD CSci CEng FIMechE FIPEM)
      First page: 1
      Abstract: Publication date: January 2018
      Source:Medical Engineering & Physics, Volume 51
      Author(s): Richard A. Black (PhD CSci CEng FIMechE FIPEM)

      PubDate: 2018-01-05T20:47:59Z
      DOI: 10.1016/j.medengphy.2017.12.001
      Issue No: Vol. 51 (2018)
  • CT image segmentation methods for bone used in medical additive
    • Authors: Maureen van Eijnatten; Roelof van Dijk; Johannes Dobbe; Geert Streekstra; Juha Koivisto; Jan Wolff
      Pages: 6 - 16
      Abstract: Publication date: January 2018
      Source:Medical Engineering & Physics, Volume 51
      Author(s): Maureen van Eijnatten, Roelof van Dijk, Johannes Dobbe, Geert Streekstra, Juha Koivisto, Jan Wolff
      Aim of the study The accuracy of additive manufactured medical constructs is limited by errors introduced during image segmentation. The aim of this study was to review the existing literature on different image segmentation methods used in medical additive manufacturing. Methods Thirty-two publications that reported on the accuracy of bone segmentation based on computed tomography images were identified using PubMed, ScienceDirect, Scopus, and Google Scholar. The advantages and disadvantages of the different segmentation methods used in these studies were evaluated and reported accuracies were compared. Results The spread between the reported accuracies was large (0.04 mm – 1.9 mm). Global thresholding was the most commonly used segmentation method with accuracies under 0.6 mm. The disadvantage of this method is the extensive manual post-processing required. Advanced thresholding methods could improve the accuracy to under 0.38 mm. However, such methods are currently not included in commercial software packages. Statistical shape model methods resulted in accuracies from 0.25 mm to 1.9 mm but are only suitable for anatomical structures with moderate anatomical variations. Conclusions Thresholding remains the most widely used segmentation method in medical additive manufacturing. To improve the accuracy and reduce the costs of patient-specific additive manufactured constructs, more advanced segmentation methods are required.

      PubDate: 2018-01-05T20:47:59Z
      DOI: 10.1016/j.medengphy.2017.10.008
      Issue No: Vol. 51 (2018)
  • The effects of cutting parameters on cutting forces and heat generation
           when drilling animal bone and biomechanical test materials
    • Authors: Akos Cseke; Robert Heinemann
      Pages: 24 - 30
      Abstract: Publication date: January 2018
      Source:Medical Engineering & Physics, Volume 51
      Author(s): Akos Cseke, Robert Heinemann
      The research presented in this paper investigated the effects of spindle speed and feed rate on the resultant cutting forces (thrust force and torque) and temperatures while drilling SawBones® biomechanical test materials and cadaveric cortical bone (bovine and porcine femur) specimens. It also investigated cortical bone anisotropy on the cutting forces, when drilling in axial and radial directions. The cutting forces are only affected by the feed rate, whereas the cutting temperature in contrast is affected by both spindle speed and feed rate. The temperature distribution indicates friction as the primary heat source, which is caused by the rubbing of the tool margins and the already cut chips over the borehole wall. Cutting forces were considerably higher when drilling animal cortical bone, in comparison to cortical test material. Drilling direction, and therewith anisotropy, appears to have a negligible effect on the cutting forces. The results suggest that this can be attributed to the osteons being cut at an angle rather than in purely axial or radial direction, as a result of a twist drill's point angle.

      PubDate: 2018-01-05T20:47:59Z
      DOI: 10.1016/j.medengphy.2017.10.009
      Issue No: Vol. 51 (2018)
  • Separation of electrocardiographic from electromyographic signals using
           dynamic filtration
    • Authors: Ivaylo Christov; Rositsa Raikova; Silvija Angelova
      Abstract: Publication date: Available online 24 April 2018
      Source:Medical Engineering & Physics
      Author(s): Ivaylo Christov, Rositsa Raikova, Silvija Angelova
      Trunk muscle electromyographic (EMG) signals are often contaminated by the electrical activity of the heart. During low or moderate muscle force, these electrocardiographic (ECG) signals disturb the estimation of muscle activity. Butterworth high-pass filters with cut-off frequency of up to 60 Hz are often used to suppress the ECG signal. Such filters disturb the EMG signal in both frequency and time domain. A new method based on the dynamic application of Savitzky-Golay filter is proposed. EMG signals of three left trunk muscles and pure ECG signal were recorded during different motor tasks. The efficiency of the method was tested and verified both with the experimental EMG signals and with modeled signals obtained by summing the pure ECG signal with EMG signals at different levels of signal-to-noise ratio. The results were compared with those obtained by application of high-pass, 4th order Butterworth filter with cut-off frequency of 30 Hz. The suggested method is separating the EMG signal from the ECG signal without EMG signal distortion across its entire frequency range regardless of amplitudes. Butterworth filter suppresses the signals in the 0–30 Hz range thus preventing the low-frequency analysis of the EMG signal. An additional disadvantage is that it passes high-frequency ECG signal components which is apparent at equal and higher amplitudes of the ECG signal as compared to the EMG signal. The new method was also successfully verified with abnormal ECG signals.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.007
  • Electrohysterographic characterization of the uterine myoelectrical
           response to labor induction drugs
    • Authors: Carlos Benalcazar-Parra; Yiyao Ye-Lin; Javier Garcia-Casado; Rogelio Monfort-Orti; Jose Alberola-Rubio; Alfredo Perales; Gema Prats-Boluda
      Abstract: Publication date: Available online 23 April 2018
      Source:Medical Engineering & Physics
      Author(s): Carlos Benalcazar-Parra, Yiyao Ye-Lin, Javier Garcia-Casado, Rogelio Monfort-Orti, Jose Alberola-Rubio, Alfredo Perales, Gema Prats-Boluda
      Labor induction is a common practice to promote uterine contractions and labor onset. Uterine electrohysterogram (EHG) has proved its suitability for characterizing the uterus electrophysiological condition in women with spontaneous labor. The aim of this study was to characterize and compare uterine myoelectrical activity during the first 4 h in response to labor induction drugs, Misoprostol (G1) and Dinoprostone (G2), by analyzing the differences between women who achieved active phase of labor and those who did not (successful and failed inductions). A set of temporal, spectral and complexity parameters were computed from the EHG-bursts. As for successful inductions, statistical significant and sustained increases with respect to basal period were obtained for EHG amplitude, mean frequency, uterine activity index (UAI) and Teager, after 60′ for the G1 group; duration, amplitude, number of contractions and UAI for the G2 group, after 120′. Moreover, Teager showed statistical significant and sustained differences between successful and failed inductions (1.43 ± 1.45 µV2.Hz2.105 vs. 0.40 ± 0.26 µV2.Hz2.105 after 240′) for the G1 group, but not in the G2 group, probably due to the slower pharmacokinetics of this drug. These results revealed that EHG could be useful for successful induction prediction in the early stages of induction, especially when using Misoprostol.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.002
  • Three-dimensional printing as a technology supporting the treatment of
           lower limb deformity and shortening with the Ilizarov method
    • Authors: Piotr Morasiewicz; Karolina Burzyńska; Wiktor Orzechowski; Szymon Łukasz Dragan; Szymon Feliks Dragan; Jarosław Filipiak
      Abstract: Publication date: Available online 22 April 2018
      Source:Medical Engineering & Physics
      Author(s): Piotr Morasiewicz, Karolina Burzyńska, Wiktor Orzechowski, Szymon Łukasz Dragan, Szymon Feliks Dragan, Jarosław Filipiak
      Background Treatment of multiplanar deformities, especially in younger children, requires construction of a complex Ilizarov fixator, frequently with small dimensions. The aim of this study is to verify clinical application of a3D-printed bone model in treatment with the Ilizarov method. Methods The study involved a 6-year-old child in whom clinical and radiological examination revealed multiplanar deformity of the right leg. Then, 3D models of individual bones were printed by means of additive manufacturing and were used as a scaffold to install the Ilizarov apparatus. To compare the expected and factual axial correction and lengthening, we measured spatial orientation of bone fragments three times. The factual axial correction and lengthening were determined with a photometric technique. Results Ilizarov fixator with a configuration developed using a 3D model of the treated bone was mounted on the patient's leg. Corticotomy was carried out at the proximal metaphysis of the right tibia, along with osteotomy of the right talus. The treatment resulted in a 3.5-cm lengthening of the limb and a 7° correction of valgus angle. The values of actual lengthening and axial correction were 4.1% lower than the expected values of these parameters. Interpretation Orthopedists should consider differences between the expected and actual lengthening and axial correction in planning treatment with the Ilizarov method. Three-dimensional printing is a useful technology that can be used to support treatment with the Ilizarov method.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.009
  • Detection of daily postures and walking modalities using a single
           chest-mounted tri-axial accelerometer
    • Authors: Milad Nazarahari; Hossein Rouhani
      Abstract: Publication date: Available online 22 April 2018
      Source:Medical Engineering & Physics
      Author(s): Milad Nazarahari, Hossein Rouhani
      This study presents a novel method for the detection and classification of a wide range of physical activities, including standing, sitting, lying, level walking, and walking upstairs and downstairs using a single chest-mounted accelerometer. The trunk inclination angle and variation of the gravitational component of the accelerometer recording were used for detection and classification of postural transitions and walking modalities. In addition, biomechanical features of each transition were used to reject false detections. To validate the accuracy of the presented method, two studies were performed, first in the (1) laboratory environment, where a motion capture system was the reference system (ten healthy subjects), and second (2) in the free-living environment where a handheld camera was the reference system (ten healthy subjects). The first study showed that the proposed method obtained higher accuracy, sensitivity, and specificity in detection of postural transitions and walking modalities compared to other methods in the literature when implemented on the same dataset. The second study obtained (1) the sensitivity and specificity of 100% for detection of sit-to-lie, lie-to-sit, and stand-to-sit, and 100% and 97%, respectively, for detection of sit-to-stand, and (2) the accuracy of 99%, 99%, and 95% for detection of slow, normal, and fast level walking, and 97% and 96% for detection of walking upstairs and downstairs. The proposed method enabled detection and classification of postural transitions and walking modalities with high sensitivity and specificity using only one chest-mounted accelerometer. This approach can be used for convenient and reliable assessment of physical activities in long-term.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.008
  • Establishing the relationship between loading parameters and bone
    • Authors: Abhishek Kumar Tiwari; Navin Kumar
      Abstract: Publication date: Available online 21 April 2018
      Source:Medical Engineering & Physics
      Author(s): Abhishek Kumar Tiwari, Navin Kumar
      Cyclic and low-magnitude loading is considered effective in arresting the bone loss as it promotes osteogenesis (i.e. new bone formation) at the sites of elevated normal strain magnitude. In silico models assumed normal strain as the stimulus to predict the sites of new bone formation. These models, however, may fail to fit the amount of newly formed bone. Loading parameters such as strain, frequency, and loading cycle decide the amount of new bone formation. The models did not incorporate this information. In fact, there is no unifying relationship to quantify the amount of new bone formation as a function of loading parameters. Therefore, the present work aims to establish an empirical relationship between loading parameters and a new bone formation parameter i.e. mineral apposition rate (MAR). A neural network model is used to serve the purpose. Loading parameters are supplied as input, whereas, MAR served as output. The model is trained and tested with experimental data. The model establishes an empirical relationship to estimate MAR as a function of loading parameters. The model's predictions of MAR align with in vivo experimental results. The model's response is analyzed which indicates that the bone adaptation characteristics are successfully captured in the relationship. The relationship established may be incorporated further to improve qualitative and quantitative prediction capabilities of computer models. These findings can be extended in future to design and develop effective biomechanical strategies such as prophylactic exercise to cure bone loss.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.004
  • Kinect V2 implementation and testing of the reaching performance scale for
           motor evaluation of patients with neurological impairment
    • Authors: Alessandro Scano; Andrea Chiavenna; Matteo Malosio; Lorenzo Molinari Tosatti; Franco Molteni
      Abstract: Publication date: Available online 20 April 2018
      Source:Medical Engineering & Physics
      Author(s): Alessandro Scano, Andrea Chiavenna, Matteo Malosio, Lorenzo Molinari Tosatti, Franco Molteni
      Automated procedures for neurological patients’ motor evaluation may take advantage of the coupling between clinical scales and motion tracking devices to provide affordable, quantified and reliable assessment to be used in clinics, in surgeries and domestic environment. In this study, 20 post-stroke patients performed frontal reaching movements with their more affected limb, and a physician administered the Reaching Performance Scale (RPS) to assess motor functionality. At the same time, patients’ kinematics were recorded with the Kinect V2 sensor. An automated algorithm was developed to compute the RPS based on Kinect V2 tracking data, and visual and Kinect V2 RPS scores were compared. Results showed very high statistical correlation between the automated procedure and the visual administration (Pearson Correlation Coefficient: R = 0.90, p < 0.001). While the number of patients is limited, the automated RPS seems to be successfully applicable to different levels of impairment, from mild to severe.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.005
  • Formation of microcapsules by ultrasound stimulation for use in
           remote-controlled drug-eluting stents
    • Authors: Wei Yao; Yan Bao; Yu Chen
      Abstract: Publication date: Available online 18 April 2018
      Source:Medical Engineering & Physics
      Author(s): Wei Yao, Yan Bao, Yu Chen
      Coronary Heart Disease (CHD) is the leading cause of death globally. The placement of drug-eluting stents (DESs) in diseased coronary arteries is the most successful minimally-invasive intervention to treat CHD. The key limitations of such interventional therapy are the risk of in-stent restenosis (ISR) and late stent thrombosis. This paper investigates a new drug-release system by formatting nanoparticles as drug carriers, which are later subjected to an external ultrasonic stimulus for controlled drug release remotely for DESs. The drug delivery could delay smooth muscle cell growth whilst enabling effective regeneration of a functional endothelium. Microcapsules were produced by employing a layer-by-layer technique, encapsulated with Rhodamine 6G dye used in place of anti-restenotic drugs. Gold nanoparticles were employed as a shell in the microcapsules. The presence of gold nanoparticles significantly enhanced the efficiency of the ultrasonically induced dye release from the microcapsules and increased the sensitivity of the microcapsules to ultrasonic stimulation compared to those without gold nanoparticles.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.04.001
  • Development and characterization of a point-of care rate-based
           transcutaneous respiratory status monitor
    • Authors: Xudong Ge; Prosper Adangwa; Ja Young Lim; Yordan Kostov; Leah Tolosa; Richard Pierson; Daniel Herr; Govind Rao
      Abstract: Publication date: Available online 5 April 2018
      Source:Medical Engineering & Physics
      Author(s): 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. Instead of waiting for mass transfer equilibrium, the blood gas levels are monitored by measuring the transcutaneous diffusion rate, which is proportional to blood gas concentration. The startup time of this device is almost independent of skin temperature, so the measurement can be made at any body temperature. The test results show that this device can track the blood gas levels quickly even at normal body temperature.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.009
  • Biomechanical analysis of bone remodeling following mandibular
           reconstruction using fibula free flap
    • Authors: Nobuhiro Yoda; Keke Zheng; Junning Chen; Zhipeng Liao; Shigeto Koyama; Christopher Peck; Michael Swain; Keiichi Sasaki; Qing Li
      Abstract: Publication date: Available online 30 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. Post-operative CT scans were taken at 0, 4, 16 and 28 months. Longitudinal change of bone morphologies and mineral densities were measured at three bone union interfaces (two between the fibula and mandibular bones and one between the osteotomized fibulas) to investigate bone healing/remodeling events. Three-dimensional finite element models were created to quantify mechanobiological responses in the bone at these different time points. Bone mineral density increased rapidly along the bone interfaces over the first four months. Cortical bridging formed at the osteotomized interface earlier than the other two interfaces with larger shape discrepancy between fibula and mandibular bones. Bone morphology significantly affected mechanobiological responses in the osteotomized region (R 2 > 0.77). The anatomic position and shape discrepancy at bone union affected the bone healing/remodeling process.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.008
  • Encapsulation of mesenchymal stem cells in chitosan/β-glycerophosphate
           hydrogel for seeding on a novel calcium phosphate cement scaffold
    • Authors: Tao Liu; Jian Li; Zengwu Shao; Kaige Ma; Zhicai Zhang; Baichuan Wang; Yannan Zhang
      Abstract: Publication date: Available online 22 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. MSCs were found to be adhered to the surfaces of CPC macropores via scanning electron microscopy. The viability and osteogenic differentiation of MSCs in C/GP hydrogel with or without exposure to CPC constructs containing mannitol crystals indicated that coating with C/GP hydrogel protected the cells during cement mixing and setting. In conclusion, novel, macroporous CPC scaffolds were prepared, and our data indicate that a hydrogel encapsulation-based strategy can be used to protect cells during scaffold formation. Thus, the MSC-laden CPC scaffolds show promise for the delivery of stem cells to promote bone regeneration.

      PubDate: 2018-04-24T20:08:38Z
      DOI: 10.1016/j.medengphy.2018.03.003
  • Femoral fracture load and fracture pattern is accurately predicted using a
           gradient-enhanced quasi-brittle finite element model
    • Authors: Ifaz T Haider; John Goldak; Hanspeter Frei
      Abstract: Publication date: Available online 16 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. Material properties were assigned a-priori based on average qCT intensities at element locations. Specimens were experimentally tested to failure in a stumbling load configuration, and the results were compared to FE model predictions. There was a strong linear relationship between FE predicted and experimentally measured fracture load (R 2  = 0.79), and error was less than 14% over all cases. In all six specimens, surface damage was observed at sites predicted by the FE model. Comparison of qCT scans before and after experimental failure showed damage to underlying trabecular bone, also consistent with FE predictions. In summary, the model accurately predicted fracture load and pattern, and may be a powerful tool in future studies.

      PubDate: 2018-03-19T18:35:56Z
      DOI: 10.1016/j.medengphy.2018.02.008
  • A flow-leak correction algorithm for pneumotachographic work-of-breathing
           measurement during high-flow nasal cannula oxygen therapy
    • Authors: Francesco Montecchia; Fabio Midulla; Paola Papoff
      Abstract: Publication date: Available online 2 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. To test this system, we used a mechanical lung model that provided data to compare LCA-corrected respiratory flow, volume and time values with effective values obtained with a third pneumotachograph used instead of the LCA to measure mask flow leaks directly. Effective and corrected volume and time data showed high agreement (Bland–Altman plots) even at the highest leak. Studies on two healthy adult volunteers confirmed that corrected respiratory flow combined with esophageal pressure measurements can accurately determine WOB (relative error < 1%). We conclude that during HFNC therapy, a DP system combined with a facemask and an algorithm that corrects errors due to flow leakages allows pneumotachography to measure reliably the respiratory flow and volume data needed for calculating WOB.

      PubDate: 2018-03-08T17:08:50Z
      DOI: 10.1016/j.medengphy.2018.02.004
  • Factors influencing taper failure of modular revision hip stems
    • Authors: A. Krull; M.M. Morlock; N.E. Bishop
      Abstract: Publication date: Available online 2 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. An analytical bending model was used to estimate the strength of the taper connection for pristine, fatigued and corroded conditions. Additionally, a finite element contact model of the taper connection was developed to assess the relative motion and potential for surface damage at the taper interface under physiological loading for varyied assembly and design parameters. Increasing the male taper diameter was shown to be the most effective means for increasing taper strength but would require a concurrent increase in the outer implant diameter to limit a greater risk of total surface damage for a thinner female taper wall. Increasing the assembly force decreases the total surface damage but not local magnitudes, which are probably responsible for crack initiation. It is suggested that in unfavourable loading conditions a monobloc implant system will reduce the risk of failure.

      PubDate: 2018-03-08T17:08:50Z
      DOI: 10.1016/j.medengphy.2018.02.001
  • A computational framework for simultaneous estimation of muscle and joint
           contact forces and body motion using optimization and surrogate modeling
    • Authors: Ilan Eskinazi; Benjamin J. Fregly
      Abstract: Publication date: Available online 2 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. The approach allows one to efficiently introduce elastic joint contact models within static and dynamic optimizations of human motion. We demonstrate the approach by performing two optimizations, one static and one dynamic, using a pelvis-leg musculoskeletal model undergoing a gait cycle. We observed convergence on the order of seconds for a static optimization time frame and on the order of minutes for an entire dynamic optimization. The presented framework may facilitate model-based efforts to predict how planned surgical or rehabilitation interventions will affect post-treatment joint and muscle function.

      PubDate: 2018-03-08T17:08:50Z
      DOI: 10.1016/j.medengphy.2018.02.002
  • An experimental and computational study of the inferior vena cava
           hemodynamics under respiratory-induced collapse of the infrarenal IVC
    • Authors: Elisabetta Tedaldi; Chiara Montanari; Kenneth I. Aycock; Francesco Sturla; Alberto Redaelli; Keefe B. Manning
      Abstract: Publication date: Available online 2 March 2018
      Source:Medical Engineering & Physics
      Author(s): 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. Particle image velocimetry (PIV) is used to measure the hemodynamics in an idealized, compliant model of the human IVC made of silicone rubber. Flow is studied under uncollapsed and collapsed scenarios, with the minor diameter of the IVC reduced by 30% in the collapsed state. Both rest and exercise flow conditions are investigated, corresponding to suprarenal flow rates of 2 lpm and 5.5 lpm, respectively. Finite element analysis simulations are carried out in a computational model of the undeformed, idealized IVC to reproduce the 30% collapse configuration and an additional 50% collapse configuration. Computational fluid dynamics (CFD) simulations are then performed to predict the flow in the uncollapsed and collapsed scenarios, and CFD results are compared to the experimental data. The results show that the collapsed states generate a higher velocity jet at the iliac junction that propagates farther into the lumen of the vena cava in comparison to the jet generated in the uncollapsed state. Moreover, 50% collapse of the IVC causes a shift of the jet away from the IVC wall and towards the center of the vena cava lumen. The area of maximum wall shear stress occurs where the jet impacts the wall and is larger in the collapsed scenarios. Secondary flow is also more complex in the collapsed scenarios. Interestingly, this study demonstrates that a small variation in the flow rate distribution between the right and left iliac veins induces significant variations in the flow characteristics. We speculate that asymmetries in the flow may generate unbalanced forces on the IVC wall and on placed IVC filters that could promote filter tilting and migration, although this requires further investigation. If unbalanced forces are present in vivo, the forces should be considered when determining the optimal placement positions and geometric features for IVC filters. Therefore, these findings motivate further investigation of the in vivo hemodynamics in the infrarenal IVC.

      PubDate: 2018-03-08T17:08:50Z
      DOI: 10.1016/j.medengphy.2018.02.003
  • Dynamic properties of human incudostapedial joint—Experimental
           measurement and finite element modeling
    • Authors: Shangyuan Jiang; Rong Z. Gan
      Abstract: Publication date: Available online 22 February 2018
      Source:Medical Engineering & Physics
      Author(s): 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. The complex modulus of ISJ was measured with a mean storage modulus of 1.14 MPa at 1 Hz that increased to 3.01 MPa at 8 kHz, and a loss modulus that increased from 0.07 to 0.47 MPa. A 3-dimensional finite element (FE) model consisting of the articular cartilage, joint capsule and synovial fluid was then constructed to derive mechanical properties of ISJ components by matching the model results to experimental data. Modeling results showed that mechanical properties of the joint capsule and synovial fluid affected the dynamic behavior of the joint. This study contributes to a better understanding of the structure–function relationship of the ISJ for sound transmission.

      PubDate: 2018-02-26T04:34:46Z
      DOI: 10.1016/j.medengphy.2018.02.006
  • Design and experimental force analysis of a novel elliptical vibration
           assisted orthopedic oscillating saw
    • Authors: Liming Shu; Naohiko Sugita; Masaya Oshima; Mamoru Mitsuishi
      Abstract: Publication date: Available online 20 February 2018
      Source:Medical Engineering & Physics
      Author(s): 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. In order to reduce the large cutting forces due to the large cutting depth, a series of experiments was also conducted to investigate the influence of processing parameters on cutting forces. It was demonstrated that cutting forces are significantly reduced by increasing the vibration frequency and vibration amplitude, and decreasing the sawing speed in the current design. The new design could minimize the cutting forces during sawing and allow surgeons to have better control over the sawing process.

      PubDate: 2018-02-26T04:34:46Z
      DOI: 10.1016/j.medengphy.2018.02.005
  • Post-operative ventricular flow dynamics following atrioventricular valve
           surgical and device therapies: A review
    • Authors: Yen Ngoc Nguyen; Munirah Ismail; Foad Kabinejadian; Edgar Lik Wui Tay; Hwa Liang Leo
      Abstract: Publication date: Available online 14 February 2018
      Source:Medical Engineering & Physics
      Author(s): 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. In this review, current consensus around the roles of vortex dynamics in cardiac function is discussed. An overview of physiological vortex patterns found in healthy left and right ventricles as well as post-operative ventricular flow phenomenon owing to different atrioventricular valvular procedures are reviewed, followed by the summary of different vortex identification schemes used to characterise intraventricular flow. This paper also emphasises on future research directions towards a comprehensive understanding of intra-cardiac flow and its clinical relevance. The knowledge could encourage more effective pre-operative planning and better outcomes for current clinical practices.

      PubDate: 2018-02-16T03:25:27Z
      DOI: 10.1016/j.medengphy.2018.01.007
  • Towards the enhancement of body standing balance recovery by means of a
           wireless audio-biofeedback system
    • Authors: Giovanni Costantini; Daniele Casali; Fabio Paolizzo; Marco Alessandrini; Alessandro Micarelli; Andrea Viziano; Giovanni Saggio
      Abstract: Publication date: Available online 10 February 2018
      Source:Medical Engineering & Physics
      Author(s): 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. The IMU is a low-weight, small-size wireless instrument that, body-back located between the L2 and L5 lumbar vertebrae, measures the subject's trunk kinematics. The application drives the data processing unit to feeding the headphone with electric signals related to the kinematic measures. Consequently, the user is audio-alerted, via headphone, of his/her own equilibrium, hearing a pleasant sound when in a stable equilibrium, or an increasing bothering sound when in an increasing unstable condition. Tests were conducted on a group of six older subjects (59y-61y, SD = 2.09y) and a group of four young subjects (21y-26y, SD = 2.88y) to underline difference in effectiveness of the system, if any, related to the age of the users. For each subject, standing balance tests were performed in normal or altered conditions, such as, open or closed eyes, and on a solid or foam surface. The system was evaluated in terms of usability, reliability, and effectiveness in improving the subject's balance in all conditions. As a result, the system successfully helped the subjects in reducing the body swaying within 10.65%-65.90%, differences depending on subjects’ age and test conditions.

      PubDate: 2018-02-16T03:25:27Z
      DOI: 10.1016/j.medengphy.2018.01.008
  • Numerical validation of a subject-specific parameter identification
           approach of a quadriceps femoris EMG-driven model
    • Authors: Cláudio Bastos Heine; Luciano Luporini Menegaldo
      Abstract: Publication date: Available online 1 February 2018
      Source:Medical Engineering & Physics
      Author(s): Cláudio Bastos Heine, Luciano Luporini Menegaldo
      Muscle models can be used to estimate muscle forces in motor tasks. Muscle model parameters can be estimated by optimizing cost functions based on error between measured and model-estimated joint torques. This paper is a numerical simulation study addressing whether this approach can accurately identify the parameters of the quadriceps femoris. The simulated identification task is a single joint maximum voluntary knee concentric–eccentric extension in an isokinetic dynamometer, keeping the hip fixed at a neutral position. A curve considered as the nominal torque was obtained by simulating the quadriceps femoris model exerting a maximum knee extension torque using a set of known parameter values. Three parameters, with different expected sensitivities of force estimations by Hill-type muscle models, were studied: very sensitive, sensitive and not sensitive, corresponding to slack tendon length, maximum isometric force, and pennation angle, respectively. The initial values of the parameters were randomly changed, simulating an ignorance of nominal values. EMG generation and torque measurement error models were used to obtain realistic simulated data corrupted by noise. Simulated annealing was chosen as the optimization algorithm. Different sequences of parameter identification and cost functions were tested. The best nominal torque curve reconstruction was obtained by optimizing the parameters sequentially, starting from slack tendon length using the Euclidean norm cost function. However, the simultaneous estimation of all parameters resulted in the most accurate values for the parameters, although dispersion was relatively large. In conclusion, in the present simulation study using realistic synthetic torque and EMG data, the optimization approach based on torque error curve was able to closely approximate the parameter values of the model's quadriceps femoris muscle.

      PubDate: 2018-02-05T07:32:29Z
      DOI: 10.1016/j.medengphy.2018.01.006
  • A finite element modeling study of peripheral nerve recruitment by
           percutaneous tibial nerve stimulation in the human lower leg
    • Authors: Christopher W. Elder; Paul B. Yoo
      Abstract: Publication date: Available online 1 February 2018
      Source:Medical Engineering & Physics
      Author(s): Christopher W. Elder, Paul B. Yoo
      Percutaneous tibial nerve stimulation (PTNS) is a clinical therapy for treating overactive bladder (OAB), where an un-insulated stainless steel needle electrode is used to target electrically the tibial nerve (TN) in the lower leg. Recent studies in anesthetized animals not only confirm that bladder-inhibitory reflexes can be evoked by stimulating the TN, but this reflex can also be evoked by stimulating the adjacent saphenous nerve (SAFN). Although cadaver studies indicate that the TN and major SAFN branch(es) overlap at the location of stimulation, the extent to which SAFN branches are co-activated is unknown. In this study, we constructed a finite element model of the human lower leg and applied a numeric axon model (MRG model) to simulate the electrical recruitment of TN and SAFN fibers during PTNS. The model showed that up to 80% of SAFN fibers (located at the level of the needle electrode) can be co-activated when electrical pulses are applied at the TN activation threshold, the standard therapeutic amplitude. Both the location of the inserted electrode and stimulation amplitude were important variables that affected the recruitment of SAFN branches. This study suggests further work is needed to investigate the potential therapeutic effects of SAFN stimulation in OAB patients.

      PubDate: 2018-02-05T07:32:29Z
      DOI: 10.1016/j.medengphy.2018.01.004
  • Constitutive modeling of compressible type-I collagen hydrogels
    • Authors: Brooks A. Lane; Katrina A. Harmon; Richard L. Goodwin; Michael J. Yost; Tarek Shazly; John F. Eberth
      Abstract: Publication date: Available online 1 February 2018
      Source:Medical Engineering & Physics
      Author(s): Brooks A. Lane, Katrina A. Harmon, Richard L. Goodwin, Michael J. Yost, Tarek Shazly, John F. Eberth
      Collagen hydrogels have been used ubiquitously as engineering biomaterials with a biphasic network of fibrillar collagen and aqueous-filled voids that contribute to a complex, compressible, and nonlinear mechanical behavior - not well captured within the infinitesimal strain theory. In this study, type-I collagen, processed from a bovine corium, was fabricated into disks at 2, 3, and 4% (w/w) and exposed to 0, 105, 106, and 107 microjoules of ultraviolet light or enzymatic degradation via matrix metalloproteinase-2. Fully hydrated gels were subjected to unconfined, aqueous, compression testing with experimental data modeled within a continuum mechanics framework by employing the uncommon Blatz–Ko material model for porous elastic materials and a nonlinear form of the Poisson's ratio. From the Generalized form, the Special Blatz–Ko, compressible Neo–Hookean, and incompressible Mooney–Rivlin models were derived and the best-fit material parameters reported for each. The average root-mean-squared (RMS) error for the General (RMS = 0.13 ± 0.07) and Special Blatz–Ko (RMS = 0.13 ± 0.07) were lower than the Neo–Hookean (RMS = 0.23 ± 0.10) and Mooney–Rivlin (RMS = 0.18 ± 0.08) models. We conclude that, with a single fitted-parameter, the Special Blatz–Ko sufficiently captured the salient features of collagen hydrogel compression over most examined formulations and treatments.

      PubDate: 2018-02-05T07:32:29Z
      DOI: 10.1016/j.medengphy.2018.01.003
  • Kinematic measures for upper limb robot-assisted therapy following stroke
           and correlations with clinical outcome measures: A review
    • Authors: Vi Do Tran; Paolo Dario; Stefano Mazzoleni
      Abstract: Publication date: Available online 1 February 2018
      Source:Medical Engineering & Physics
      Author(s): Vi Do Tran, Paolo Dario, Stefano Mazzoleni
      Aim of the study This review classifies the kinematic measures used to evaluate post-stroke motor impairment following upper limb robot-assisted rehabilitation and investigates their correlations with clinical outcome measures. Methods An online literature search was carried out in PubMed, MEDLINE, Scopus and IEEE-Xplore databases. Kinematic parameters mentioned in the studies included were categorized into the International Classification of Functioning, Disability and Health (ICF) domains. The correlations between these parameters and the clinical scales were summarized. Results Forty-nine kinematic parameters were identified from 67 articles involving 1750 patients. The most frequently used parameters were: movement speed, movement accuracy, peak speed, number of speed peaks, and movement distance and duration. According to the ICF domains, 44 kinematic parameters were categorized into Body Functions and Structure, 5 into Activities and no parameters were categorized into Participation and Personal and Environmental Factors. Thirteen articles investigated the correlations between kinematic parameters and clinical outcome measures. Some kinematic measures showed a significant correlation coefficient with clinical scores, but most were weak or moderate. Conclusions The proposed classification of kinematic measures into ICF domains and their correlations with clinical scales could contribute to identifying the most relevant ones for an integrated assessment of upper limb robot-assisted rehabilitation treatments following stroke. Increasing the assessment frequency by means of kinematic parameters could optimize clinical assessment procedures and enhance the effectiveness of rehabilitation treatments.

      PubDate: 2018-02-05T07:32:29Z
      DOI: 10.1016/j.medengphy.2017.12.005
  • Mechanical properties of cancellous bone from the acetabulum in relation
           to acetabular shell fixation and compared with the corresponding femoral
    • Authors: Rianne van Ladesteijn; Holly Leslie; William A Manning; James P Holland; David J Deehan; Thomas Pandorf; Richard M Aspden
      Abstract: Publication date: Available online 1 February 2018
      Source:Medical Engineering & Physics
      Author(s): Rianne van Ladesteijn, Holly Leslie, William A Manning, James P Holland, David J Deehan, Thomas Pandorf, Richard M Aspden
      To gain initial stability for cementless fixation the acetabular components of a total hip replacement are press-fit into the acetabulum. Uneven stiffness of the acetabular bone will result in irregular deformation of the shell which may hinder insertion of the liner or lead to premature loosening. To investigate this, we removed bone cores from the ilium, ischium and pubis within each acetabulum and from selected sites in corresponding femoral heads from four cadavers for mechanical testing in unconfined compression. From a stress-relaxation test over 300 s, the residual stress, its percentage of the initial stress and the stress half-life were calculated. Maximum modulus, yield stress and energy to yield (resilience) were calculated from a load-displacement test. Acetabular bone had a modulus about 10–20%, yield stress about 25% and resilience about 40% of the values for the femoral head. The stress half-life was typically between 2–4 s and the residual stress was about 60% of peak stress in both acetabulum and femur. Pubic bone was mechanically the poorest. These results may explain uneven deformation of press-fit acetabular shells as they are inserted. The measured half-life of stress-relaxation indicates that waiting a few minutes between insertion of the shell and the liner may allow seating of a poorly congruent liner.

      PubDate: 2018-02-05T07:32:29Z
      DOI: 10.1016/j.medengphy.2018.01.005
  • Spring assisted cranioplasty: A patient specific computational model
    • Authors: Alessandro Borghi; Naiara Rodriguez-Florez; Will Rodgers; Gregory James; Richard Hayward; David Dunaway; Owase Jeelani; Silvia Schievano
      Abstract: Publication date: Available online 19 January 2018
      Source:Medical Engineering & Physics
      Author(s): Alessandro Borghi, Naiara Rodriguez-Florez, Will Rodgers, Gregory James, Richard Hayward, David Dunaway, Owase Jeelani, Silvia Schievano
      Implantation of spring-like distractors in the treatment of sagittal craniosynostosis is a novel technique that has proven functionally and aesthetically effective in correcting skull deformities; however, final shape outcomes remain moderately unpredictable due to an incomplete understanding of the skull-distractor interaction. The aim of this study was to create a patient specific computational model of spring assisted cranioplasty (SAC) that can help predict the individual overall final head shape. Pre-operative computed tomography images of a SAC patient were processed to extract a 3D model of the infant skull anatomy and simulate spring implantation. The distractors were modeled based on mechanical experimental data. Viscoelastic bone properties from the literature were tuned using the specific patient procedural information recorded during surgery and from x-ray measurements at follow-up. The model accurately captured spring expansion on-table (within 9% of the measured values), as well as at first and second follow-ups (within 8% of the measured values). Comparison between immediate post-operative 3D head scanning and numerical results for this patient proved that the model could successfully predict the final overall head shape. This preliminary work showed the potential application of computational modeling to study SAC, to support pre-operative planning and guide novel distractor design.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2018.01.001
  • Instantaneous VO2 from a wearable device
    • Authors: Andrew J. Cook; Ben Ng; Gaetano D. Gargiulo; Diane Hindmarsh; Mark Pitney; Torsten Lehmann; Tara Julia Hamilton
      Abstract: Publication date: Available online 17 January 2018
      Source:Medical Engineering & Physics
      Author(s): Andrew J. Cook, Ben Ng, Gaetano D. Gargiulo, Diane Hindmarsh, Mark Pitney, Torsten Lehmann, Tara Julia Hamilton
      We present a method for calculating instantaneous oxygen uptake (VO2) through the use of a non-invasive and non-obtrusive (i.e. without a face mask) wearable device, together with its clinical evaluation against a standard technique based upon expired gas calorimetry. This method can be integrated with existing wearable devices, we implemented it in the “Device for Reliable Energy Expenditure Monitoring” (DREEM). The DREEM comprises a single lead electrocardiogram (ECG) device combined with a tri-axial accelerometer and is worn around the waist. Our clinical evaluation tests the developed method against a gold standard for VO2, expired gas calorimetry, using an ethically approved protocol comprising active exercise and sedentary periods. The study was performed on 42 participants from a wide sample population including healthy people, athletes and an at-risk health group including persons affected by obesity. We developed an algorithm combining heart rate (HR) and the integral of absolute acceleration (IAA), with results showing a correlation of r = 0.93 for instantaneous VO2, and r = 0.97 for 3 min mean VO2, this is a considerably improved estimation of VO2 in comparison to methods utilising HR and IAA independently.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2017.12.008
  • An adaptive, real-time cadence algorithm for unconstrained sensor
    • Authors: B.T. van Oeveren; C.J. de Ruiter; P.J. Beek; S.M. Rispens; J.H. van Dieën
      Abstract: Publication date: Available online 17 January 2018
      Source:Medical Engineering & Physics
      Author(s): B.T. van Oeveren, C.J. de Ruiter, P.J. Beek, S.M. Rispens, J.H. van Dieën
      This paper evaluates a new and adaptive real-time cadence detection algorithm (CDA) for unconstrained sensor placement during walking and running. Conventional correlation procedures, dependent on sensor position and orientation, may alternately detect either steps or strides and consequently suffer from false negatives or positives. To overcome this limitation, the CDA validates correlation peaks as strides using the Sylvester's criterion (SC). This paper compares the CDA with conventional correlation methods. 22 volunteers completed 7 different circuits (approx. 140 m) at three gaits-speeds: walking (1.5 m s− 1), running (3.4 m s− 1), and sprinting (5.2 and 5.7 m s− 1), disturbed by various gait-related activities. The algorithm was simultaneously evaluated for 10 different sensor positions. Reference strides were obtained from a foot sensor using a dedicated offline algorithm. The described algorithm resulted in consistent numbers of true positives (85.6–100.0%) and false positives (0.0–2.9%) and showed to be consistently accurate for cadence feedback across all circuits, subjects and sensors (mean ± SD: 98.9 ± 0.2%), compared to conventional cross-correlation (87.3 ± 13.5%), biased (73.0 ± 16.2) and unbiased (82.2 ± 20.6) autocorrelation procedures. This study shows that the SC significantly improves cadence detection, resulting in robust results for various gaits, subjects and sensor positions.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2017.12.007
  • Design, optimisation and testing of a compact, inexpensive elastic element
           for series elastic actuators
    • Authors: Cornelius Irmscher; Elmar Woschke; Erik May; Christian Daniel
      Abstract: Publication date: Available online 17 January 2018
      Source:Medical Engineering & Physics
      Author(s): Cornelius Irmscher, Elmar Woschke, Erik May, Christian Daniel
      This paper presents the development of a compact torsion spring for use as an elastic element in a lightweight series elastic actuator for an active orthosis. This orthosis is going to be utilised as an assistive device for motorically impaired stroke-patients. In the design a two-step optimisation strategy was implemented to meet all requirements for the torsion spring. The first step was to identify a promising topology for the element. In the second step, the shape was optimised based on a finite element model using two different optimisation methods in order to minimise the von Mises equivalent stresses. Four promising variants of the identified topology were extracted from these calculations, one of which was then chosen as the final design. A prototype was manufactured by a laser cutting process, which is a new procedure in the context of elastic elements for series elastic actuators. The calculation results were validated successfully by measurement of the spring properties of this prototype.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2017.12.004
  • Automatic recognition of gait patterns in human motor disorders using
           machine learning: A review
    • Authors: Joana Figueiredo; Cristina P. Santos; Juan C. Moreno
      Abstract: Publication date: Available online 17 January 2018
      Source:Medical Engineering & Physics
      Author(s): Joana Figueiredo, Cristina P. Santos, Juan C. Moreno
      Background automatic recognition of human movement is an effective strategy to assess abnormal gait patterns. Machine learning approaches are mainly applied due to their ability to work with multidimensional nonlinear features. Purpose to compare several machine learning algorithms employed for gait pattern recognition in motor disorders using discriminant features extracted from gait dynamics. Additionally, this work highlights procedures that improve gait recognition performance. Methods we conducted an electronic literature search on Web of Science, IEEE, and Scopus, using “human recognition”, “gait patterns’’, and “feature selection methods” as relevant keywords. Results analysis of the literature showed that kernel principal component analysis and genetic algorithms are efficient at reducing dimensional features due to their ability to process nonlinear data and converge to global optimum. Comparative analysis of machine learning performance showed that support vector machines (SVMs) exhibited higher accuracy and proper generalization for new instances. Conclusions automatic recognition by combining dimensional data reduction, cross-validation and normalization techniques with SVMs may offer an objective and rapid tool for investigating the subject's clinical status. Future directions comprise the real-time application of these tools to drive powered assistive devices in free-living conditions.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2017.12.006
  • Sin-quadratic model for chest tomosynthesis respiratory signal analysis
           and its application in four dimensional chest tomosynthesis reconstruction
    • Authors: Xi Tao; Hua Zhang; Genggeng Qin; Jianhua Ma; Qianjin Feng; Wufan Chen
      Abstract: Publication date: Available online 12 January 2018
      Source:Medical Engineering & Physics
      Author(s): Xi Tao, Hua Zhang, Genggeng Qin, Jianhua Ma, Qianjin Feng, Wufan Chen
      Chest tomosynthesis (CTS) is a newly developed imaging technique which provides pseudo-3D volume anatomical information of thorax from limited-angle projections and contains much less of superimposed anatomy than the chest X-ray radiography. One of the relatively common problems in CTS is the patient respiratory motion during image acquisition, which negatively impacts the detectability. In this work, we propose a sin-quadratic model to analyze the respiratory motion during CTS scan, which is a real time method where the respiratory signal is generated by extracting the motion of diaphragm from projection radiographs. According to the estimated respiratory signal, the CTS projections were then amplitude-based sorted into four to eight phases, and an iterative reconstruction strategy with total variation regularization was adopted to reconstruct the CTS images at each phase. Simulated digital XCAT phantom data and three sets of patient data were adopted for the experiments to validate the performance of the sin-quadratic model and its application in four dimensional (4D) CTS reconstruction. Results of the XCAT phantom simulation study show that the correlation coefficient between the extracted respiratory signal and the originally designed respiratory signal is 0.9964, which suggests that the proposed model could exactly extract the respiratory signal from CTS projections. The 4D CTS reconstructions of both the phantom data and the patient data show clear reduction of motion-induced blur.

      PubDate: 2018-01-27T06:57:28Z
      DOI: 10.1016/j.medengphy.2017.12.003
  • Acknowledgement to Reviewers 2017
    • Abstract: Publication date: January 2018
      Source:Medical Engineering & Physics, Volume 51

      PubDate: 2018-01-05T20:47:59Z
  • In vitro simulation of fretting-corrosion in hip implant modular
           junctions: The influence of pH
    • Authors: Dmitry Royhman; Megha Patel; Joshua J. Jacobs; Markus A. Wimmer; Nadim J. Hallab; Mathew T. Mathew
      Abstract: Publication date: Available online 29 December 2017
      Source:Medical Engineering & Physics
      Author(s): Dmitry Royhman, Megha Patel, Joshua J. Jacobs, Markus A. Wimmer, Nadim J. Hallab, Mathew T. Mathew
      Background The fretting-corrosion behavior of mixed metal contacts is affected by various mechanical and electrochemical parameters. Crevice conditions at the junction and patient-specific pathologies can affect the pH of the prosthetic environment. The main objective of this study is to understand the effect of pH variation at the stem/head junction of the hip implant under fretting corrosion exposure. We hypothesized that pH will have a significant influence on the fretting-corrosion behavior hip implant modular junctions. Materials and methods A custom-made setup was used to evaluate the fretting corrosion behavior of hip implant modular junctions. A Newborn calf serum solution (30 g/L protein content) was used to simulate the synovial fluid environment. A sinusoidal fretting motion, with a displacement amplitude of +50 µm, was applied to the Ti alloy rod. The effects of pathology driven, periprosthetic pH variation were simulated at four different pH levels (3.0, 4.5, 6.0 and 7.6). Electrochemical and mechanical properties were evaluated before, during, and after the applied fretting motion. Results The impedance of the system was increased in response to the fretting motion. The hysteresis tangential load/displacement behavior was not affected by pH level. The worn surfaces of CoCrMo pins exhibited the presence of tribolayer or organic deposits, in the pH 4.5 group, which may explain the lower drop in potential and mass loss observed in that group. Mechanically dominated wear mechanisms, namely, adhesive wear was shown in the pH 7.6 group, which may account for a higher potential drop and metal content loss. Conclusions This study suggests that the fretting-corrosion mechanisms in hip implant are affected by the pH levels of the surrounding environment and patient-specific factors.
      Graphical abstract image

      PubDate: 2018-01-05T20:47:59Z
      DOI: 10.1016/j.medengphy.2017.10.016
  • In vitro validation of measurement of volume elastic modulus using
    • Authors: Haneen Njoum; Panayiotis A Kyriacou
      Abstract: Publication date: Available online 28 December 2017
      Source:Medical Engineering & Physics
      Author(s): Haneen Njoum, Panayiotis A Kyriacou
      Arterial stiffness (AS) is one of the earliest detectable symptoms of cardiovascular diseases and their progression. Current AS measurement methods provide an indirect and qualitative estimation of AS. The purpose of this study is to explore the utilisation of Photoplethysmography (PPG) as a measure of volumetric strain in providing a direct quantification of the Volume Elastic modulus (Ev ). An in vitro experimental setup was designed using an arterial model to simulate the human circulation in health (Model 2) and disease (Model 1). Flow, pressure, and PPG signals were recorded continuously under varied conditions of flow dynamics. The obtained Ev values were validated with the gold standard mechanical testing techniques. Values obtained from both methods had no significant difference for both models with a percent error of 0.26% and 1.9% for Model 1 and Model 2, respectively. This study shows that PPG and pressure signals can provide a direct measure of AS in an in vitro setup. With emerging noninvasive pressure measurement methods, this research paves the way for the direct quantification of AS in vivo.

      PubDate: 2018-01-05T20:47:59Z
      DOI: 10.1016/j.medengphy.2017.11.011
  • Concurrent prediction of ground reaction forces and moments and
           tibiofemoral contact forces during walking using musculoskeletal modelling
    • Authors: Yinghu Peng; Zhifeng Zhang; Yongchang Gao; Zhenxian Chen; Hua Xin; Qida Zhang; Xunjian Fan; Zhongmin Jin
      Abstract: Publication date: Available online 19 December 2017
      Source:Medical Engineering & Physics
      Author(s): Yinghu Peng, Zhifeng Zhang, Yongchang Gao, Zhenxian Chen, Hua Xin, Qida Zhang, Xunjian Fan, Zhongmin Jin
      Ground reaction forces and moments (GRFs and GRMs) measured from force plates in a gait laboratory are usually used as the input conditions to predict the knee joint forces and moments via musculoskeletal (MSK) multibody dynamics (MBD) model. However, the measurements of the GRFs and GRMs data rely on force plates and sometimes are limited by the difficulty in some patient's gait patterns (e.g. treadmill gait). In addition, the force plate calibration error may influence the prediction accuracy of the MSK model. In this study, a prediction method of the GRFs and GRMs based on elastic contact element was integrated into a subject-specific MSK MBD modelling framework of total knee arthroplasty (TKA), and the GRFs and GRMs and knee contact forces (KCFs) during walking were predicted simultaneously with reasonable accuracy. The ground reaction forces and moments were predicted with an average root mean square errors (RMSEs) of 0.021 body weight (BW), 0.014 BW and 0.089 BW in the antero–posterior, medio–lateral and vertical directions and 0.005 BW•body height (BH), 0.011 BW•BH, 0.004 BW•BH in the sagittal, frontal and transverse planes, respectively. Meanwhile, the medial, lateral and total tibiofemoral (TF) contact forces were predicted by the developed MSK model with RMSEs of 0.025–0.032 BW, 0.018–0.022 BW, and 0.089–0.132 BW, respectively. The accuracy of the predicted medial TF contact force was improved by 12% using the present method. The proposed method can extend the application of the MSK model of TKA and is valuable for understanding the in vivo knee biomechanics and tribological conditions without the force plate data.

      PubDate: 2017-12-23T19:11:50Z
      DOI: 10.1016/j.medengphy.2017.11.008
  • A surface-based approach to determine key spatial parameters of the
           acetabulum in a standardized pelvic coordinate system
    • Authors: Xiaojun Chen; Pengfei Jia; Yiping Wang; Henghui Zhang; Liao Wang; Alejandro F. Frangi; Zeike A. Taylor
      Abstract: Publication date: Available online 18 December 2017
      Source:Medical Engineering & Physics
      Author(s): Xiaojun Chen, Pengfei Jia, Yiping Wang, Henghui Zhang, Liao Wang, Alejandro F. Frangi, Zeike A. Taylor
      Accurately determining the spatial relationship between the pelvis and acetabulum is challenging due to their inherently complex three-dimensional (3D) anatomy. A standardized 3D pelvic coordinate system (PCS) and the precise assessment of acetabular orientation would enable the relationship to be determined. We present a surface-based method to establish a reliable PCS and develop software for semi-automatic measurement of acetabular spatial parameters. Vertices on the acetabular rim were manually extracted as an eigenpoint set after 3D models were imported into the software. A reliable PCS consisting of the anterior pelvic plane, midsagittal pelvic plane, and transverse pelvic plane was then computed by iteration on mesh data. A spatial circle was fitted as a succinct description of the acetabular rim. Finally, a series of mutual spatial parameters between the pelvis and acetabulum were determined semi-automatically, including the center of rotation, radius, and acetabular orientation. Pelvic models were reconstructed based on high-resolution computed tomography images. Inter- and intra-rater correlations for measurements of mutual spatial parameters were almost perfect, showing our method affords very reproducible measurements. The approach will thus be useful for analyzing anatomic data and has potential applications for preoperative planning in individuals receiving total hip arthroplasty.

      PubDate: 2017-12-23T19:11:50Z
      DOI: 10.1016/j.medengphy.2017.11.009
  • Full-field strain distribution in multi-vertebra spine segments: An in
           vitro application of digital image correlation
    • Authors: Marco Palanca; Miguel Marco; Maria Luisa Ruspi; Luca Cristofolini
      Abstract: Publication date: Available online 8 December 2017
      Source:Medical Engineering & Physics
      Author(s): Marco Palanca, Miguel Marco, Maria Luisa Ruspi, Luca Cristofolini
      The biomechanics of the spine is experimentally assessed in terms of range of motion and overall stiffness. Quantification of the surface strain distribution is currently limited either to the vertebrae or the discs, whereas a full-field approach to measure the strain distribution in a multi-vertebra segment is currently missing. The aim of this work was to explore the feasibility of using Digital Image Correlation (DIC) to measure the strain distribution simultaneously on the vertebral bodies and the intervertebral discs of spine segments in different loading configurations. Three porcine spine segments were tested. A white-on-black speckle pattern was prepared which covered the hard and soft tissues. Two different loading configurations (flexion and lateral bending) were reproduced, while two sides of the spine were analyzed with DIC. Measurements were successfully performed on the entire region of interest of all specimens, in both configurations. The DIC analysis highlighted the strain gradients present on the spine segments including tension and compression associated with bending, the direction of principal strains in the different regions, as well as bulging of the discs under compression. Strains of tens of thousands microstrain were measured in the discs, and below 2000 microstrain in the bone. This work showed the feasibility of applying DIC on spine segments including hard and soft tissues. It also highlights the need for a full-field investigation, because of the strain inhomogeneity in the vertebrae and discs.
      Graphical abstract image

      PubDate: 2017-12-11T06:42:52Z
      DOI: 10.1016/j.medengphy.2017.11.003
  • Validation of single-plane fluoroscopy and 2D/3D shape-matching for
           quantifying shoulder complex kinematics
    • Authors: Rebekah L. Lawrence; Arin M. Ellingson; Paula M. Ludewig
      Abstract: Publication date: Available online 8 December 2017
      Source:Medical Engineering & Physics
      Author(s): Rebekah L. Lawrence, Arin M. Ellingson, Paula M. Ludewig
      Fluoroscopy and 2D/3D shape-matching has emerged as the standard for non-invasively quantifying kinematics. However, its accuracy has not been well established for the shoulder complex when using single-plane fluoroscopy. The purpose of this study was to determine the accuracy of single-plane fluoroscopy and 2D/3D shape-matching for quantifying full shoulder complex kinematics. Tantalum markers were implanted into the clavicle, humerus, and scapula of four cadaveric shoulders. Biplane radiographs were obtained with the shoulder in five humerothoracic elevation positions (arm at the side, 30°, 60°, 90°, maximum). Images from both systems were used to perform marker tracking, while only those images acquired with the primary fluoroscopy system were used to perform 2D/3D shape-matching. Kinematics errors due to shape-matching were calculated as the difference between marker tracking and 2D/3D shape-matching and expressed as root mean square (RMS) error, bias, and precision. Overall RMS errors for the glenohumeral joint ranged from 0.7 to 3.3° and 1.2 to 4.2 mm, while errors for the acromioclavicular joint ranged from 1.7 to 3.4°. Errors associated with shape-matching individual bones ranged from 1.2 to 3.2° for the humerus, 0.5 to 1.6° for the scapula, and 0.4 to 3.7° for the clavicle. The results of the study demonstrate that single-plane fluoroscopy and 2D/3D shape-matching can accurately quantify full shoulder complex kinematics in static positions.

      PubDate: 2017-12-11T06:42:52Z
      DOI: 10.1016/j.medengphy.2017.11.005
  • Functional testing on engineered cartilage to identify the role played by
    • Authors: Ling Wang; Hao Shen; Jichang Nie; Dichen Li; Hongbin Fan; Zhongmin Jin; Chaozong Liu
      Abstract: Publication date: Available online 24 November 2017
      Source:Medical Engineering & Physics
      Author(s): Ling Wang, Hao Shen, Jichang Nie, Dichen Li, Hongbin Fan, Zhongmin Jin, Chaozong Liu
      Compressive loading is crucial for tissue regeneration in cartilage; however, the role played by shearing induced from translational or rotational motion of the knee joint has yet to be identified. This study aims at investigating the effects of in vivo like dynamic load–compression integrated with shearing on tissue regeneration, particularly to identify the role played by shearing induced from rotational motion. Tissue samples fabricated from a calcium alginate hydrogel embedded with chondrocytes were subjected to a dynamic tissue culture. Three culturing regimes were included: a static culture control (CON), compression combined with shearing induced from translational motion (CS), and compression combined with shearing induced from both translational and rotational motion (CSR). The results indicate that the CS group has a significantly larger chondrocyte proliferation rate (p < .01), and that the CSR group has no advantages over the CS group. However, the CSR group was found to have a marked influence on the matrix synthesis compared to that of the CS group (p < .01). It can be concluded that shearing from individual joint motions offers a different contribution to the chondrocyte proliferation, matrix synthesis, and phenotype maintenance, and better insight into these individual roles will be necessary for determining the efficacy of in vivo/vitro cartilageous tissue functionalization.

      PubDate: 2017-12-11T06:42:52Z
      DOI: 10.1016/j.medengphy.2017.10.011
  • Measurement of physical activity in the pre- and early post-operative
           period after total knee arthroplasty for Osteoarthritis using a Fitbit
           Flex device
    • Authors: Joshua Twiggs; Lucy Salmon; Elizabeth Kolos; Emily Bogue; Brad Miles; Justin Roe
      Abstract: Publication date: Available online 6 November 2017
      Source:Medical Engineering & Physics
      Author(s): Joshua Twiggs, Lucy Salmon, Elizabeth Kolos, Emily Bogue, Brad Miles, Justin Roe
      Total knee arthroplasty (TKA) is a standard treatment for patients with end stage knee Osteoarthritis (OA) to reduce pain and restore function. The aim of this study was to assess pre- and early post-operative physical activity (PA) with Fitbit Flex devices for patients with OA undergoing TKA and determine any benchmarks for expected post-operative activity. Significant correlations of pre-operative step count, post-operative step count, Body Mass Index (BMI) and Short Form 12 Physical Component Summaries (SF-12 PCS) were found. Mean step counts varied by 3,203 steps per day between obese and healthy weight patients, and 3,786 steps per day between those with higher and lower SF-12 PCS scores, suggesting the need for benchmarks for recovery that vary by patient pre-operative factors. A backwards stepwise regression model developed to provide patient specific step count predictions at 6 weeks had an R 2 of 0.754, providing a robust patient specific benchmark for post-operative recovery, while population means from BMI and SF-12 subgroups provide a clinically practical alternative.

      PubDate: 2017-11-10T21:04:18Z
      DOI: 10.1016/j.medengphy.2017.10.007
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