Regensburg Center of Biomedical Engineering - RCBE
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Aims
Drug-eluting stents (DES) represent a major advance in interventional cardiology. Along with the success shown, current DES also present limitations related to the presence of polymer-coating, fixed drug, and dose used. With the ISAR (Individualized Drug-Eluting Stent System to Abrogate Restenosis) project, a DES system has been developed that permits individualized choice of the drug and dose to use for the given patient. The objective of this prospective dose finding study was to assess the feasibility, safety, and efficacy of a polymer-free on-site stent coating with increasing rapamycin doses.
Methods and results
In this dose finding study, 602 patients were sequentially enrolled in four groups: microporous bare metal stent (BMS), DES stents coated with a 0.5, 1.0, and 2.0% rapamycin solution. The angiographic in-segment restenosis rate at follow-up angiography was the primary study endpoint. In-segment restenosis was significantly reduced from 25.9% with BMS to 18.9, 17.2, and 14.7% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.024). Similarly, the need for target lesion revascularization at 1 year follow-up was reduced from 21.5% with BMS to 16.4, 12.6, and 8.8% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.006).
Conclusion
The placement of polymer-free stents coated on-site with rapamycin is feasible and safe. Furthermore, a dose-dependent efficacy in restenosis prevention is achievable with this new DES concept.
Objective
The risk of in-stent restenosis can be considerably reduced by stents eluting cytostatic compounds. We created a novel drug-eluting stent system that includes several new features in the rapidly evolving field of stent-based drug delivery.
Methods and Results
The aim of the present study was the preclinical evaluation of a stent-coating system permitting individual, on-site coating of stents with a unique microporous surface allowing for individualizable, dose-adjustable, and multiple coatings with identical or various compounds, designated ISAR (individualizable drug-eluting stent system to abrogate restenosis). Stents were coated with 0.75% rapamycin solution, and high-performance liquid chromatography (HPLC)-based determination of drug release profile indicated drug release for >21 days. Rapamycin-eluting microporous (REMP) stents implanted in porcine coronary arteries were safe. To determine the efficacy of REMP stents, this novel drug-eluting stent platform was compared with the standard sirolimus-eluting stent. At 30 days, in-stent neointima formation in porcine coronary arteries was similar in both groups, yielding a significant decrease of neointimal area and injury-dependent neointimal thickness compared with bare-metal stents.
Conclusion
The ISAR drug-eluting stent platform as a novel concept for stent coating allows for a safe, effective, on-site stent coating process, thus justifying further clinical evaluation to decrease in-stent restenosis in humans.
In-stent neointima formation can be successfully attenuated by drug-eluting stents. We introduce a novel conceptual approach for stent-coating that allows for dose-adjustable, on-site stent coating process if desired with multiple compounds. Microporous stents coated with rapamycin proved safe and effective for the limitation of neointima formation in a porcine coronary stent model.
Fragestellung
Es soll in dieser Computersimulationsstudie untersucht werden, wie der Osteosyntheseverbund Platte mit Schrauben im Verbund mit einer im mittleren Drittel gebrochenen Clavicula durch das Bewegungsausmaß
in vivo belastet ist. Was sind die grundlegenden Kräfte die auf Clavicula und Implantat wirken und welchen Einfl uss hat die Bruchform.
Methodik
Die Muskel- und Gelenkkräfte sowie die Belastung des Implantatverbundes wurden mit einer muskuloskelletalen
Simulationssoftware (AnyBody Technology, V.4) berechnet. Hierfür wurden mit einem komplexen Model des menschlichen Körpers folgende Bewegungen analysiert: eine Flexion von 160° und Abduktion 160° mit
einem Gewicht von 2 kg in der Hand. Aus CT-Patientendaten wurden zwei dreidimensionale Modelle des Clavicula-Implantat Verbundes gebildet, die sich in der Frakturform unterscheiden (Querfraktur und vertikale
Fraktur). In beiden Modellen wurde eine Claviculaosteosynthese in superiorer Position mit einer 6 Loch LCP mit 2 Schrauben pro Hauptfragment verwendet. Die Materialeigenschaften wurden aus der Dichte des Materials sowie aus Literaturdaten verwendet. Die Muskel- und Gelenkkräfte aus der muskuloskelletalen Berechnung wurden auf das Finite Elemente Modell übertragen und die Spannungen und Dehnungen des Implantat-Knochenverbundes
wurden berechnet.
Ergebnisse
Es zeigte sich, dass die simulierte in vivo Belastung stark abhängig vom Flexionswinkel ist. Das Implantat ist in der superioren Lage auf Biegung belastet, welche maximale Werte im Überschulterniveau erreicht. Die Bruchform mit anatomischer Reposition und Kontakt der Hauptfragmente zueinander führt zu einer deutlichen Entlastung des Osteosyntheseverbundes im Vergleich zu einer Bruchform mit vertikaler Fraktur.
Schlussfolgerung
Aus den Analysen ist eine Positionierung der Plattenosteosynthese für die im mittleren Drittel frakturierte Clavicula in anterior-superiorer Lage wünschenswert. Die anatomische Reposition entlastet den Osteosyntheseverbund und sollte möglichst erreicht werden. Die Nachbehandlung sollte ein Bewegungsausmaß für den Arm für 4 Wochen für einfache Bruchformen auf 70° Flexion und Abduktion limitieren und für komplexe Bruchformen diese Limitierung ausgedehnt werden.
INTRODUCTION
Several clinical studies demonstrated long-term adjacent-level effects after implantation of spinal fusion devices[1]. These effects have been reported as adjacent joint degeneration and the development of new symptoms correlating with adjacent segment degeneration[2] and the trend has therefore gone to motion preservation devices; however, these effects have not been understood very well and have not been investigated thoroughly[3].
The aim of this study is to investigate the effect of varying the stiffness of spinal fusion devices on the adjacent vertebral levels. Disc forces, moments and facet joint forces were analyzed.
METHODS
The AnyBody Modeling System was used to compute the in-vivo muscle and joint reaction forces of a musculoskeletal model. The full body model used in this study consists of 188 muscle fascicles in the lumbar spine and more than 1000 individual muscle branches in total. The model has been proposed by de Zee et al.[3], validated by Rasmussen et al.[4] and by Galibarov et al.[5]. The new model[5] determines the individual motions between vertebrae based on the equilibrium between forces acting on the vertebrae from muscles and joints and the passive stiffness in disks and ligaments, figure 1a. An adult of 1.75 m and 75 kg with a spinal implant in L4L5 was modeled. This model was subjected to a flexion-extension motion using different elastic moduli to analyze and compare to a non-implanted scenario. The analyzed variables were vertebral motion, the disc reaction forces and moments, as well as facet joint forces in the treated and the adjacent levels: L2L3, L3L4, L4L5 and L5-Sacrum.
RESULTS
When introducing a spinal fusion device in the L4L5 joint the reaction forces and moments decreased in this joint with stiffer devices leading to lower joint loads. However, in the adjacent joints, L3L4 and L5Sacrum, an increase was observed when implanting stiffer devices. Similar trends could be found for the L2L3 joint. The loads in the facet joints showed the same trends. While introducing a spinal fusion device reduced the facet joint forces in the treated joint, the loads in the adjacent facet joints were increased according to the stiffness of the implanted device, figure 1b.
DISCUSSION
While the treated disc joint showed reduced motion and loads, the adjacent levels demonstrated a significant increase. In particular, the increased facet joint forces in the adjacent levels can lead to adjacent level facet pain or accelerated facet joint degeneration. Introducing a device resulted in preventing facet contact and therefore facet joint loads, even using the device with the lowest stiffness.
CONCLUSION
The presented model shows that clinical complications such as facet joint degeneration in adjacent levels after implantation of spinal fusion device are consistent with the change in the mechanical-stimulus distribution in the system.
On modelling spine curvature dependent on muscular and external forces in multibody dynamics system
(2011)
This paper presents a computational approach for investigating effect of muscular and external forces on curvature of the lumbar spine. Multibody dynamics system is used to compute the lumbar spine curvature using a force-dependent kinematics facility, e.g. this method allows releasing some degrees of freedom in order to be computed based on the current load configuration.
Subject-specific Musculoskeletal Simulation of Hip Dislocation Risk in Activities of Daily Living
(2011)
Innovationsmanagement
(2011)
High quality semi-finished products with reproducible properties of basaltic fibres are hardly available on the market. In order to examine the properties of basalt fibre reinforced plastics high quality specimens are necessary. The fibre volume content and the porosity of the produced specimen are used as the typical criteria to evaluate the achieved quality of the produced material. The effect of the geometrical properties of the different semi-finished products on the fibre volume contents is relatively small whereas the porosity content is considerably affected.
Einführung in die Mechanik
(2013)
Influence of minimally invasive total hip replacement on hip reaction forces and their orientations
(2014)
Minimally invasive surgery (MIS) is becoming increasingly popular. Supporters claim that the main advantages of MIS total hip replacement (THR) are less pain and a faster rehabilitation and recovery. Critics claim that safety and efficacy of MIS are yet to be determined. We focused on a biomechanical comparison between surgical standard and MIS approaches for THR during the early recovery of patients. A validated, parameterized musculoskeletal model was set to perform a squat of a 50th percentile healthy European male. A bilateral motion was chosen to investigate effects on the contralateral side. Surgical approaches were simulated by excluding the incised muscles from the computations. Resulting hip reaction forces and their symmetry and orientation were analyzed. MIS THR seemed less influential on the symmetry index of hip reaction forces between the operated and nonoperated leg when compared to the standard lateral approach. Hip reaction forces at peak loads of the standard transgluteal approach were 24% higher on the contralateral side when compared to MIS approaches. Our results suggest that MIS THR contributes to a greater symmetry of hip reaction forces in absolute value as well as force-orientation following THR.
In the last few years, increasingly kicks to the head were observed as a criminal offense. This study examined the
influence of age, shoe type and kicking direction on the severity of head trauma.
Male test persons were divided into two groups “Old” and “Young”. Both groups were equipped with light
sneakers and combat boots. A standard laboratory crash dummy was used to simulate the victim’s body. First, the
dummy’s head, free floating above the ground, was kicked vertically. Second, the dummy’s head was kicked
horizontally. Established injury criteria were used to quantify the injury risk.
No influence concerning the type of foot wear and no difference between the groups “Old” and “Young” could be
found. For all analyses, kicking vertically generally lead to a higher risk for the subject compared to kicking
horizontally.
In this study, only the integral effect of the kicks could be analyzed. A detailed injury pattern cannot directly be
derived from the data. Nevertheless, the presented data show the massive potential of injuries associated with head
kicks.
High loads can appear in the individual joints of the human foot while the driver uses the pedals, in particular, during breaking. Measuring these internal forces is very difficult or almost impossible; therefore, advanced models are necessary to perform musculoskeletal simulations. The objective of this investigation was to see what loads are acting in the individual foot joints from the phalanges to calcaneus and talus during different brake scenarios. The Glasgow-Maastricht AnyBody Foot Model with 26 separate segments, connected by joints, ligaments and muscles was used inside the AnyBody Modeling System to compute individual mid foot joint loads. The amount, the direction of the force and additionally also the load insertion point was varied for several simulations. Figure 1: Seated musculoskeletal body model with applied brake force and forces for the lateral, intermediate and medial cuneiform-navicular joint for two different brake forces. The simulation showed that for the different brake scenarios, different muscles will be activated in the human and therefore different loads are apply in the fore-and mid-foot, respectively. The torso of the subject was assumed to be fixed in the seat. Further studies are ongoing to simulate the seat as an elastic element that allows different H-point locations according to the different loadings in the foot from the brake pedal using a new inverse dynamics analysis method called force-dependent kinematics.
Das Management in der Medizinprodukteindustrie steht vor vielfältigen Herausforderungen. So sinken einerseits die Produktpreise, anderseits wird auch für die kommenden Jahre in vielen Segmenten ein Mengenwachstum erwartet. Dies stellt die internen Prozesse, vom Customer Service bis hin zur Forschung & Entwicklung, auf den Prüfstand. Die Entscheidungsträger auf Kundenseite verändern sich, weg vom Produktanwender hin zu professionellen Einkaufsgemeinschaften mit immer größerer Verhandlungsmacht. Der hohe Internationalisierungsgrad der Unternehmen führt zu einer steigenden Komplexität bei der Implementierung von Marketing-, Vertriebs- und Produktentwicklungsstrategien auf Länderebene. Darüber hinaus werden zunehmend neue Geschäftsmodelle mit hohem Dienstleistungsanteil entwickelt, die mit der traditionellen Lieferantenrolle wenig zu tun haben und von Managern eine neue Fähigkeiten für die Umsetzung erfordern. Die Autoren des Sammelbands greifen die genannten Herausforderungen auf und bieten mit ihren Beiträgen Lösungsansätze, die sowohl für Manager im Medizinprodukteunternehmen als auch für Wissenschaftler und Studierende relevant sind.
Serial 2D section images with high resolution, resulting from innovative imaging methods become even more valuable, if they are fused with in vivo volumes. Achieving this goal, the 3D context of the sections would be restored, the deformations would be corrected and the artefacts would be eliminated. However, the registration in this field faces big challenges and is not solved in general. On the other hand, several approaches have been introduced dealing at least with some of these difficulties. Here, a brief overview of the topic is given and some of the solutions are presented. It does not constitute the claim to be a complete review, but could be a starting point for those who are interested in this field.
Background and aims:
Rapid pre-hospital identification of stroke symptoms result in therapy directed admission to dedicated stroke units. Widespread application of stroke scales reveal high sensitivity but low specificity, especially in non-academic first aid personal. In our previous work we show that prehospital stroke diagnostics based on neurolo-gical examination and transcranial color-coded Duplex so-nography (TCCS) is feasible and results in high sensitivity and specificity for middle cerebral artery / distal internal carotid artery occlusion. The aim of our ongoing study is to design and evaluate a dedicated stroke educational program for paramedics including transcranial ultrasound. This is a prerequisite for a telemedical decision support system in the absence of stroke experienced emergency doctors.
Methods:
We currently educate 6 paramedics in advanced stroke neurology and also transcranial ultrasound examina-tion during a course of 2 months. The web-based curricu-lum was designed in two parts. The first was theoretical and the second will be the real-life training under neurological supervision. For final assessment of the theoretical know-ledge a control group will be implemented without specific stroke expertise. The stroke-educated paramedics will have to assist stroke investigation, perform pre-hospital TCCS and enter the date in a mobile telestroke pad. The data set will be send to an in-hospital stroke physician. We will as-sess the mean time to reach the diagnostic assessment, its sensitivity and specificity and the patient outcome after 30 days.
Results:
Our study is ongoing
Conclusion:
The study just reach the 2 part and we will be glad to present our data on the meeting EAN 2015.
Disclosure:
Nothing to disclose
The Impact of the ObamaCare Excise Tax on Innovation and Entrepreneurship – Early Empirical Findings
(2015)
This study addresses aspects of governmental influence on innovation by analyzing the impact of the ObamaCare excise tax on the medical device industry. We initially give an overview of common approaches to measuring innovativeness and entrepreneurship, empirically assess whether existing metrics are suitable for investigating the innovation performance of the U.S. medical device industry, and define a new measure (firm innovation activity) for entrepreneurship. Then we perform a quantitative analysis to explore the impact of the tax. We analyze more than 60,000 product clearances from 1996 to 2013, using the FDA database. We find a significant relationship between product counts and revenues for one segment. Contrary to the present criticism of the excise tax, we find hardly any noteworthy response in either firm innovation activity or number of products launched in the year after the tax was introduced. The 2013 reduction of new product submissions is well within the limits of typical annual fluctuations observed in previous years. This provides a first indication that the excise tax act did not have a strong impact on innovative activities through the present.
We report the kinematic and early clinical results of a patient- and observer-blinded randomised controlled trial in which CT scans were used to compare potential impingement-free range of movement (ROM) and acetabular component cover between patients treated with either the navigated 'femur-first' total hip arthroplasty (THA) method (n = 66; male/female 29/37, mean age 62.5 years; 50 to 74) or conventional THA (n = 69; male/female 35/34, mean age 62.9 years; 50 to 75). The Hip Osteoarthritis Outcome Score, the Harris hip score, the Euro-Qol-5D and the Mancuso THA patient expectations score were assessed at six weeks, six months and one year after surgery. A total of 48 of the patients (84%) in the navigated 'femur-first' group and 43 (65%) in the conventional group reached all the desirable potential ROM boundaries without prosthetic impingement for activities of daily living (ADL) in flexion, extension, abduction, adduction and rotation (p = 0.016). Acetabular component cover and surface contact with the host bone were > 87% in both groups. There was a significant difference between the navigated and the conventional groups' Harris hip scores six weeks after surgery (p = 0.010). There were no significant differences with respect to any clinical outcome at six months and one year of follow-up. The navigated 'femur-first' technique improves the potential ROM for ADL without prosthetic impingement, although there was no observed clinical difference between the two treatment groups.
Different target areas within the concept of combined cup and stem anteversion have been published for total hip arthroplasty (THA). We asked whether component positioning according to eight standard combined anteversion rules is associated with (1) more physiological gait patterns, (2) higher improvement of gait variables and (3) better clinical outcome after THA.In a prospective clinical study, 60 patients received cementless THA through an anterolateral MIS approach in a lateral decubitus position. Six weeks postoperatively, implant position was analysed using 3D-CT by an independent external institute. Preoperatively, six and 12 months postoperatively range of motion, normalized walking speed and hip flexion symmetry index were measured using 3D motion-capture gait analysis. Patient-related outcome measures (HHS, HOOS, EQ-5D) were obtained by an observer blinded to 3D-CT results. Eight combined anteversion definitions and Lewinnek's "safe zone" were evaluated regarding their impact on gait patterns and clinical outcome.Combined cup and stem anteversion according to standard combined anteversion definitions as well as cup placement within Lewinnek's "safe zone" did not influence range of motion, normalized walking speed and/or hip flexion symmetry index six and 12 months after THA. Similarly, increase of gait parameters within the first year after THA was comparable between all eight combined anteversion rules. Clinical outcome measures like HHS, HOOS and EQ-5D did not show any benefit for either of the combined anteversion definitions.Standard combined cup and stem anteversion rules do not improve postoperative outcome as measured by gait analysis and clinical scores within one year after THA.
Effect of the fractured calcaneus's peripheral fragment displacement on the triceps surae function
(2015)
The musculoskeletal load scenario of computer-assisted Femur-First THR up to one year after surgery
(2015)
Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential.
These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised.
Thoracolumbar spine model with articulated rigcage for the prediction of dynamic spinal loading
(2015)
Navigated Femur First Total Hip Arthroplasty leads to improved Biomechanical Outcome after surgery
(2015)
Purpose:
Patients with primary open-angle glaucoma (POAG) show a stiffer peripapillary sclera, reactive astrocytes and a remodeled lamina cribrosa (LC). The changes are thought to be mediated by TGFβ2 and its downstream mediator CTGF. Recently we developed a murine glaucoma model by overexpressing CTGF in the anterior eye (βb1CTGF). In this study we investigated the glial lamina region of βb1CTGF mice, and the changes of astrocytes in response to CTGF and TGFβ2 as well as increasing substratum stiffness.
Methods:
Tangential sections of the glial LC of 2-month-old βb1CTGF mice and their wild-type littermates (WT) were stained with phalloidin and antibodies against GFAP, CTGF and fibronectin (FN). Murine optic nerve (ON) astrocytes from CD1 mice were isolated, cultured and characterized by GFAP staining. The astrocytes were treated with TGFβ2 (1ng/ml) and CTGF (50ng/ml and 100ng/ml). In addition, the cells were seeded on PDMS substrata with different stiffness (10, 30 and 60 kPa). Treated cells were analyzed by Western blotting, real-time RT-PCR and immunohistochemistry. Wound healing assays were performed to analyze migration rate following growth factor treatment.
Results:
βb1CTGF mice showed a massive increase in CTGF and GFAP in the glial LC when compared with WT mice. Moreover, an increase in FN staining and phalloidin-labeled actin was observed in the peripapillary sclera. Murine ON astrocytes reacted on increased substrate stiffness by increasing the synthesis of GFAP, vimentin and CTGF. Treatment of the cells with TGFβ2 and CTGF led to an enhanced migration rate. In addition, treatment resulted in an increased expression and synthesis of ECM proteins, including FN, tropoelastin, collagen type I and III. The in vitro findings correlated with those seen in the glaucoma mouse model.
Conclusions:
We conclude that changes in the ECM of LC and peripapillary sclera alter their biomechanical properties and thereby induce reactive changes in resident astrocytes. The reactive changes induced by higher stiffness of their surrounding ECM give rise to a self-amplifying process that includes increased TGFβ2/CTGF signaling and leads to synthesis of ECM and cytoskeletal proteins, a process that in turn augments the stiffness at the optic nerve head (ONH). Such a scenario may finally result in a vicious circle as the causative mechanism for ONH deformation in POAG.
We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of “femur first/combined anteversion,” which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient’s gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome.
Structural MRI brain analysis and segmentation is a crucial part in the daily routine in neurosurgery for intervention planning. Exemplarily, the free software FSL-FAST (FMRIB’s Segmentation Library – FMRIB’s Automated Segmentation Tool) in version 4 is used for segmentation of brain tissue types. To speed up the segmentation procedure by parallel execution, we transferred FSL-FAST to a General Purpose Graphics Processing Unit (GPGPU) using Open Computing Language (OpenCL) [1]. The necessary steps for parallelization resulted in substantially different and less useful results. Therefore, the underlying methods were revised and adapted yielding computational overhead. Nevertheless, we achieved a speed-up factor of 3.59 from CPU to GPGPU execution, as well providing similar useful or even better results.
Die Lehre der medizinischen Bildverarbeitung vermittelt Kenntnisse mit einem breiten Methodenspektrum. Neben den Grundlagen der Verfahren soll ein Gefühl für eine geeignete Ausführungsreihenfolge und ihrer Wirkung auf medizinische Bilddaten entwickelt werden. Die Komplexität der Methoden erfordert vertiefte Programmierkenntnisse, sodass bereits einfache Operationen mit großem Programmieraufwand verbunden sind. Die Software GraphMIC stellt Bildverarbeitungsoperationen in Form interaktiver Knoten zur Verfügung und erlaubt das Arrangieren, Parametrisieren und Ausführen komplexer Verarbeitungssequenzen in einem Graphen. Durch den Fokus auf das Design einer Pipeline, weg von sprach- und frameworkspezifischen Implementierungsdetails, lassen sich grundlegende Prinzipien der Bildverarbeitung anschaulich erlernen. In diesem Beitrag stellen wir die visuelle Programmierung mit GraphMIC der nativen Implementierung äquivalenter Funktionen gegenüber. Die in C++ entwickelte Applikation basiert auf Qt, ITK, OpenCV, VTK und MITK.
Despite multimodal treatment, the prognosis of high-grade gliomas is grim. As tumor growth is critically dependent on new blood vessel formation, antiangiogenic treatment approaches offer an innovative treatment strategy. Bevacizumab, a humanized monoclonal antibody, has been in the spotlight of antiangiogenic approaches for several years. Currently, MRI including contrast-enhanced T1-weighted and T2/fluid-attenuated inversion recovery (FLAIR) images is routinely used to evaluate antiangiogenic treatment response (Response Assessment in Neuro-Oncology criteria). However, by restoring the blood–brain barrier, bevacizumab may reduce T1 contrast enhancement and T2/FLAIR hyperintensity, thereby obscuring the imaging-based detection of progression. The aim of this review is to highlight the recent role of imaging biomarkers from MR and PET imaging on measurement of disease progression and treatment effectiveness in antiangiogenic therapies. Based on the reviewed studies, multimodal imaging combining standard MRI with new physiological MRI techniques and metabolic PET imaging, in particular amino acid tracers, may have the ability to detect antiangiogenic drug susceptibility or resistance prior to morphological changes. As advances occur in the development of therapies that target specific biochemical or molecular pathways and alter tumor physiology in potentially predictable ways, the validation of physiological and metabolic imaging biomarkers will become increasingly important in the near future.
GraphMIC is a cross-platform image processing application utilizing the libraries ITK and OpenCV. The abstract structure of image processing pipelines is visually represented by user interface components based on modern QtQuick technology and allows users to focus on arrangement and parameterization of operations rather than implementing the equivalent functionality natively in C++. The application's central goal is to improve and simplify the typical workflow by providing various high level features and functions like multi threading, image sequence processing and advanced error handling. A built-in python interpreter allows the creation of custom nodes, where user defined algorithms can be integrated to extend basic functionality. An embedded 2d/3d visual-izer gives feedback of the resulting image of an operation or the whole pipeline. User inputs like seed points, contours or regions are forwarded to the processing pipeline as parameters to offer semi-automatic image computing. We report the main concept of the application and introduce several features and their implementation. Finally, the current state of development as well as future perspectives of GraphMIC are discussed
A prospective randomized controlled trial is presented that is used to compare gait performance between the computer assisted Femur First (CAS FF) operation method and conventional THR (CON). 60 patients underwent a 3D gait analysis of the lower extremity at pre-operative, 6 months post-operative and twelve months post-operative. Detailed verification experiments were facilitated to ensure the quality of data as well as to avoid over-interpreting of the data. The results confirm a similar data-quality as reported in the literature. Walking speed, range of motion and symmetry thereof improved over the follow-up period, without significant differences between the groups. While all parameters do significantly increase over the follow-up period for both groups, there were no significant differences between them at any given time-point. Patients undergoing CAS FF showed a trend to improved hip flexion angle indicating a possible long-term benefit.
We aimed to investigate the relationship between postoperative leg length/offset (LL/OS) reconstruction and gait performance after total hip arthroplasty (THA). In the course of a prospective randomized controlled trial, 60 patients with unilateral hip arthrosis received cementless THA through a minimally-invasive anterolateral surgical approach. One year post-operatively, LL and global OS restoration were analyzed and compared to the contralateral hip on AP pelvic radiographs. The combined postoperative limb length/OS reconstruction of the operated hip was categorized as restored (within 5 mm) or non-restored (more than 5 mm reduction or more than 5 mm increment). The acetabular component inclination, anteversion and femoral component anteversion were evaluated using CT scans of the pelvis and the femur. 3D gait analysis of the lower extremity and patient related outcome measures (HHS, HOOS, EQ-5D) were obtained pre-operatively, six months and twelve months post-operatively by an observer blinded to radiographic results. Component position of cup and stem was comparable between the restored and non-restored group. Combined LL and OS restoration within 5 mm resulted in higher Froude number (p < 0.001), normalized walking speed (p < 0.001) and hip range-of-motion (ROM) (p = 0.004) during gait twelve months postoperatively, whereas gait symmetry was comparable regardless of LL and OS reconstruction at both examinations. Clinical scores did not show any relevant association between the accuracy of LL or OS reconstruction and gait six/twelve months after THA. In summary, postoperative LL/OS discrepancies larger than 5 mm relate to unphysiological gait kinematics within the first year after THA. DRKS00000739, German Clinical Trials Register.
Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading
(2016)
Musculoskeletal modeling offers an invaluable insight into the spine biomechanics. A better understanding of thoracic spine kinetics is essential for understanding disease processes and developing new prevention and treatment methods. Current models of the thoracic region are not designed for segmental load estimation, or do not include the complex construct of the ribcage, despite its potentially important role in load transmission. In this paper, we describe a numerical musculoskeletal model of the thoracolumbar spine with articulated ribcage, modeled as a system of individual vertebral segments, elastic elements and thoracic muscles, based on a previously established lumbar spine model and data from the literature. The inverse dynamics simulations of the model allow the prediction of spinal loading as well as costal joints kinetics and kinematics. The intradiscal pressure predicted by the model correlated well (R2=0.89) with reported intradiscal pressure measurements, providing a first validation of the model. The inclusion of the ribcage did not affect segmental force predictions when the thoracic spine did not perform motion. During thoracic motion tasks, the ribcage had an important influence on the predicted compressive forces and muscle activation patterns. The compressive forces were reduced by up to 32%, or distributed more evenly between thoracic vertebrae, when compared to the predictions of the model without ribcage, for mild thoracic flexion and hyperextension tasks, respectively. The presented musculoskeletal model provides a tool for investigating thoracic spine loading and load sharing between vertebral column and ribcage during dynamic activities. Further validation for specific applications is still necessary.
One of the main goals in reconstructing rotator cuff tears is the restoration of glenohumeral joint stability, which is subsequently of utmost importance in order to prevent degenerative damage such as superior labral anterior posterior (SLAP) lesion, arthrosis, and malfunction. The goal of the current study was to facilitate musculoskeletal models in order to estimate glenohumeral instability introduced by muscle weakness due to cuff lesions. Inverse dynamics simulations were used to compute joint reaction forces for several static abduction tasks with different muscle weakness. Results were compared with the existing literature in order to ensure the model validity. Further arm positions taken from activities of daily living, requiring the rotator cuff muscles were modeled and their contribution to joint kinetics computed. Weakness of the superior rotator cuff muscles (supraspinatus; infraspinatus) leads to a deviation of the joint reaction force to the cranial dorsal rim of the glenoid. Massive rotator cuff defects showed higher potential for glenohumeral instability in contrast to single muscle ruptures. The teres minor muscle seems to substitute lost joint torque during several simulated muscle tears to maintain joint stability. Joint instability increases with cuff tear size. Weakness of the upper part of the rotator cuff leads to a joint reaction force closer to the upper glenoid rim. This indicates the comorbidity of cuff tears with SLAP lesions. The teres minor is crucial for maintaining joint stability in case of massive cuff defects and should be uprated in clinical decision-making.
Background
There is a wide range of mechanical properties of spinal ligaments documented in literature. Due to the fact that ligaments contribute in stabilizing the spine by limiting excessive intersegmental motion, those properties are of particular interest for the implementation in musculoskeletal models. The aim of this study was to investigate the effect of varying ligament stiffness on the kinematic behaviour of the lumbar spine.
Methods
A musculoskeletal model with a detailed lumbar spine was modified according to fluoroscopic recordings and corresponding data files of three different subjects. For flexion, inverse dynamics analysis with a variation of the ligament stiffness matrix were conducted. The influence of several degrees of ligament stiffness on the lumbar spine model were investigated by tracking ligament forces, disc forces and resulting moments generated by the ligaments. Additionally, the kinematics of the motion segments were evaluated.
Results
An increase of ligament stiffness resulted in an increase of ligament and disc forces, whereas the relative change of disc force increased at a higher rate at the L4/L5 level (19 %) than at the L3/L4 (10 %) level in a fully flexed posture. The same behaviour applied to measured moments with 67 % and 45 %. As a consequence, the motion deflected to the lower levels of the lumbar spine and the lower discs had to resist an increase in loading.
Conclusions
Higher values of ligament stiffness over all lumbar levels could lead to a shift of the loading and the motion between segments to the lower lumbar levels. This could lead to an increased risk for the lower lumbar parts.
Medical confidentiality is very important because it builds the fundament of trust between doctors and patients. In modern health services data protection is essential. But there are also other important security objectives, such as integrity and authenticity of medical data and health services, as their breach can potentially lead to life threatening conditions. State of the art security mechanisms are necessary to protect medical data and services and prevent attacks known as “hacking”. They should include in particular cryptography, as you can usually rely on mathematics, more than in software security and access control mechanisms. As patients normally cannot assess the security of a service, security audits or certifications of health services should be provided to generate trust and confidence.
Biomechanik des Alterns
(2016)
Die Implantation eines Cochlea Implantates benötigt einen chirurgischen Zugang im Felsenbein und durch die Paukenhöhle des Patienten. Der Chirurg hat eine eingeschränkte Sicht im Operationsgebiet, die weiterhin viele Risikostrukturen enthält. Um eine Cochlea Implantation sicher und fehlerfrei durchzuführen, ist eine umfangreiche theoretische und praktische (teilweise berufsbegleitende) Fortbildung sowie langjährige Erfahrung notwendig. Unter Nutzung von realen klinischen CT/MRT Daten von Innen- und Mittelohr und der interaktiven Segmentierung der darin abgebildeten Strukturen (Nerven, Cochlea, Gehörknöchelchen,...) wird im HaptiVisT Projekt ein haptisch-visuelles Trainingssystem für die Implantation von Innen- und Mittelohr-Implantaten realisiert, das als sog. „Serious Game“ mit immersiver Didaktik gestaltet wird. Die Evaluierung des Demonstrators hinsichtlich Zweckmäßigkeit erfolgt prozessbegleitend und ergebnisorientiert, um mögliche technische oder didaktische Fehler vor Fertigstellung des Systems aufzudecken. Drei zeitlich versetzte Evaluationen fokussieren dabei chirurgisch-fachliche, didaktische sowie haptisch-ergonomische Akzeptanzkriterien.
Introduction – Diagnosis of abnormal cilia function is based on ultrastructural analysis of axoneme defects, especialy the features of inner and outer dynein arms which are the motors of ciliar motility. Sub-optimal biopsy material, methodical, and intrinsic electron microscopy factors pose difficulty in ciliary defects evaluation. We present a computer-assisted approach based on state-of-the-art image analysis and object recognition methods yielding a time-saving and efficient diagnosis of cilia dysfunction. Method – The presented approach is based on a pipeline of basal image processing methods like smoothing, thresholding and ellipse fitting. However, integration of application specific knowledge results in robust segmentations even in cases of image artifacts. The method is build hierarchically starting with the detection of cilia within the image, followed by the detection of nine doublets within each analyzable cilium, and ending with the detection of dynein arms of each doublet. The process is concluded by a rough classification of the dynein arms as basis for a computer-assisted diagnosis. Additionally, the interaction possibilities are designed in a way, that the results are still reproducible given the completion report. Results – A qualitative evaluation showed reasonable detection results for cilia, doublets and dynein arms. However, since a ground truth is missing, the variation of the computer-assisted diagnosis should be within the subjective bias of human diagnosticians. The results of a first quantitative evaluation with five human experts and six images with 12 analyzable cilia showed, that with default parameterization 91.6% of the cilia and 98% of the doublets were found. The computer-assisted approach rated 66% of those inner and outer dynein arms correct, where all human experts agree. However, especially the quality of the dynein arm classification may be improved in future work.
Common Schanz screw systems can be used to stabilize pelvic ring fractures. In order to accommodate for different patient’s requirements, implants can be placed in cranio-caudal direction into the os ilium (T1), or into the supraacetabular bone canal, and thus, in dorso-ventral direction (T2). Whereas both techniques are currently used, no data of the biomechanical behavior is available up to this date. The aim of this study is to analyze, whether T2 shows biomechanical advantages with respect to tissue and implant stresses due to the enlarged bone-implant interface. Forces acting on the pelvis were analyzed using motion capture data of a gait cycle obtained by the utilization of a musculoskeletal simulation program. A three dimensional finite element (FE) model of the pelvis with grayscale-based material properties was generated. The muscle and joint reaction forces at toe-off were applied to the FE model and instable pelvis fractures were implemented. The osteosynthesis systems were positioned within the model in order to enable the comparison between the two different surgical techniques. Stresses and displacements were analyzed for bone tissue, fracture zone and implant.
T2 lead to approx. 30% larger displacements in the fracture zone. Von-Mises stresses were larger for T2 in the implant (80 MPa vs. 227 MPa), whereas T1 leads to larger stresses in the bone tissue (200 MPa vs. 140 MPa).
Both implantation techniques showed a good biomechanical behavior. Differences could be found with respect to tissue strains and deformations in the fracture zone. If bone quality or fracture healing are of concern, T2 or T1 should be used, respectively. However, both techniques seem to be applicable for cases with no special requirements. Further analyses aim to investigate the behavior under cyclic loading.
Work places and conditions strains the human body, both psychologically and biomechanically. In order to analyse working conditions and in the following to improve them, detailed knowledge about the effect of the different stressors on the body is needed. This manuscript discusses methods on how to evaluate biomechanical and mental loading and its effect on the musculoskeletal system. A possible workflow for the analysis is presented.
The gold standard for the analysis of human kinematics and kinetics is a camera-based motion capture system in combination with force measurement platforms. Alternatively, inertial measurement units can be utilized to obtain human kinematics, while ground reaction forces are computed from full body dynamics. This setup represents a system independent from the spatial confinement of a gait laboratory. The aim of this study is the comparison of the two methods by the investigation of lower limb kinematics and the resulting joint reaction forces within the ankle-, knee- and hip joints. For this purpose, human motion during gait was captured simultaneously by both measurement techniques. 13 trials from 8 different test subjects were evaluated in total. IMU data was processed with a quaternion based Kalman Filter. The data sets were implemented into a musculoskeletal simulation program in order to drive a virtual human body model. Each sensor was aligned to the gravitational and magnetic field vectors of the earth. The angles of flexions, extensions and rotations were analyzed to determine kinematic differences. Joint reaction forces defined kinetic dissimilarities. The overall kinematic differences of both models yielded root mean square errors of 7.62°, 6.02°, 4.95°, 2.79°, 2.38° and 3.56° for ankle flexion, subtalar eversion, knee flexion, hip external rotation, hip abduction and hip flexion, respectively. The proximo-distal differences in force peaks between the models yielded overall for the ankle, 57.33 %Bodyweight(BW) ± 46.86 %BW (16.66 %(Maximum peak to peak) ± 13.62 %) for the knee 37.09 %BW ± 29.33 %BW (17.65 % ± 15.44 %) and 32.03 %BW ± 24.33 %BW (15.6 % ± 12.54 %) for the hip. The overall outcome of this work investigated an approach independent of the common setup of the gait laboratory, thus enabling a cheaper and more flexible technology as an alternative. However, kinematic and thus kinetic differences remain rather large. Future work aims to improve the contact criterion for the calculation of the ground reaction forces and the implementation of a full-body calibration algorithm for the IMU system in order to counteract magnetic field disturbances.
Simulation of Fluid-Structure Interaction between injection medium and balloon catheter using ICFD
(2017)
Arteriosclerosis is a major health issue worldwide. While it is commonly treated by the implantation of an balloon-expandable stent, micro injuries may occur during stent deployment, and induce in-stent restenosis, whose consequence can be fatal. Studying this undesirable phenomenon is usually limited as experimental data is hard to obtain on ethical ground. Numerical simulation are performed to better understand this problem. To construct a more realistic simulation of a balloon-expandable stent, a partitioned strongly-coupled FSI simulation of the balloon deployment was set up using the ICFD solver of LS-DYNA, - a quite innovative approach. The complex balloon configuration as well as the interaction of the injection medium and the balloon structure was considered. The balloon structure consisting of shell elements was obtained from preliminary balloon folding and pleating simulations. The balloon consists of a flexible thin walled polyamide. The injection fluid is implemented using volume elements. Balloon deployment was initiated by a pressure boundary condition inducing a volume flow into the balloon. The initial feasibility analysis showed promising result including a continuous balloon deployment and a reasonable development of the fluid pressure and velocity field. However, applying this FSI approach to a more complex balloon structure led to a non convergent solution. The non-convergence could be mainly reduced to mechanical factors including the low wall thickness of the balloon (< 0.05 mm) and the flexibility of the polyamide. Further, the ICFD solver shows less accuracy concerning the FSI conditions when dealing with thin flexible structures as well as enclosed volumes. A shell thickness of 0.06 mm is believed to result in a convergent solution.
Computer-assisted analysis of endoscopic images can be helpful to the automatic diagnosis and classification of neoplastic lesions. Barrett's esophagus (BE) is a common type of reflux that is not straight forward to be detected by endoscopic surveillance, thus being way susceptible to erroneous diagnosis, which can cause cancer when not treated properly. In this work, we introduce the Optimum-Path Forest (OPF) classifier to the task of automatic identification of Barrett'sesophagus, with promising results and outperforming the well known Support Vector Machines (SVM) in the aforementioned context. We consider describing endoscopic images by means of feature extractors based on key point information, such as the Speeded up Robust Features (SURF) and Scale-Invariant Feature Transform (SIFT), for further designing a bag-of-visual-wordsthat is used to feed both OPF and SVM classifiers. The best results were obtained by means of the OPF classifier for both feature extractors, with values lying on 0.732 (SURF) - 0.735(SIFT) for sensitivity, 0.782 (SURF) - 0.806 (SIFT) for specificity, and 0.738 (SURF) - 0.732 (SIFT) for the accuracy.
The Impact of Semi-Automated Segmentation and 3D Analysis on Testing New Osteosynthesis Material
(2017)
A new protocol for testing osteosynthesis material postoperatively combining semi-automated segmentation and 3D analysis of surface meshes is proposed. By various steps of transformation and measuring, objective data can be collected. In this study the specifications of a locking plate used for mediocarpal arthrodesis of the wrist were examined. The results show, that union of the lunate, triquetrum, hamate and capitate was achieved and that the plate is comparable to coexisting arthrodesis systems. Additionally, it was shown, that the complications detected correlate to the clinical outcome. In synopsis, this protocol is considered beneficial and should be taken into account in further studies.
The development of adenocarcinoma in Barrett’s esophagus is difficult to detect by endoscopic surveillance of patients with signs of dysplasia. Computer assisted diagnosis of endoscopic images (CAD) could therefore be most helpful in the demarcation and classification of neoplastic lesions. In this study we tested the feasibility of a CAD method based on Speeded up Robust Feature Detection (SURF). A given database containing 100 images from 39 patients served as benchmark for feature based classification models. Half of the images had previously been diagnosed by five clinical experts as being ”cancerous”, the other half as ”non-cancerous”. Cancerous image regions had been visibly delineated (masked) by the clinicians. SURF features acquired from full images as well as from masked areas were utilized for the supervised training and testing of an SVM classifier. The predictive accuracy of the developed CAD system is illustrated by sensitivity and specificity values. The results based on full image matching where 0.78 (sensitivity) and 0.82 (specificity) were achieved, while the masked region approach generated results of 0.90 and 0.95, respectively.
We propose an automatic approach for early detection of adenocarcinoma in the esophagus. High-definition endoscopic images (50 cancer, 50 Barrett) are partitioned into a dataset containing approximately equal amounts of patches showing cancerous and non-cancerous regions. A deep convolutional neural network is adapted to the data using a transfer learning approach. The final classification of an image is determined by at least one patch, for which the probability being a cancer patch exceeds a given threshold. The model was evaluated with leave one patient out cross-validation. With sensitivity and specificity of 0.94 and 0.88, respectively, our findings improve recently published results on the same image data base considerably. Furthermore, the visualization of the class probabilities of each individual patch indicates, that our approach might be extensible to the segmentation domain.
Epigenetic modifiers of the histone deacetylase (HDAC) family contribute to autoimmunity, cancer, HIV infection, inflammation, and neurodegeneration. Hence, histone deacetylase inhibitors (HDACi), which alter protein acetylation, gene expression patterns, and cell fate decisions, represent promising new drugs for the therapy of these diseases. Whereas pan-HDACi inhibit all 11 Zn2+-dependent histone deacetylases (HDACs) and cause a broad spectrum of side effects, specific inhibitors of histone deacetylase 6 (HDAC6i) are supposed to have less side effects. We present the synthesis and biological evaluation of Marbostats, novel HDAC6i that contain the hydroxamic acid moiety linked to tetrahydro-β-carboline derivatives. Our lead compound Marbostat-100 is a more potent and more selective HDAC6i than previously established well-characterized compounds in vitro as well as in cells. Moreover, Marbostat-100 is well tolerated by mice and effective against collagen type II induced arthritis. Thus, Marbostat-100 represents a most selective known HDAC6i and the possibility for clinical evaluation of a HDAC isoform-specific drug.
Introduction
Aim of this study is to validate some constitutive models by assessing their capabilities in describing and predicting uniaxial and biaxial behavior of porcine aortic tissue.
Methods
14 samples from porcine aortas were used to perform 2 uniaxial and 5 biaxial tensile tests. Transversal strains were furthermore stored for uniaxial data. The experimental data were fitted by four constitutive models: Holzapfel-Gasser-Ogden model (HGO), model based on generalized structure tensor (GST), Four-Fiber-Family model (FFF) and Microfiber model. Fitting was performed to uniaxial and biaxial data sets separately and descriptive capabilities of the models were compared. Their predictive capabilities were assessed in two ways. Firstly each model was fitted to biaxial data and its accuracy (in term of R2 and NRMSE) in prediction of both uniaxial responses was evaluated. Then this procedure was performed conversely: each model was fitted to both uniaxial tests and its accuracy in prediction of 5 biaxial responses was observed.
Results
Descriptive capabilities of all models were excellent. In predicting uniaxial response from biaxial data, microfiber model was the most accurate while the other models showed also reasonable accuracy. Microfiber and FFF models were capable to reasonably predict biaxial responses from uniaxial data while HGO and GST models failed completely in this task.
Conclusions
HGO and GST models are not capable to predict biaxial arterial wall behavior while FFF model is the most robust of the investigated constitutive models. Knowledge of transversal strains in uniaxial tests improves robustness of constitutive models.
Background
Iliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest.
Methods
Finite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed.
Results
Critical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest.
Conclusion
A harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture.
BACKGROUND:
Validation and verification of multibody musculoskeletal models sEMG is a difficult process because of the reliability of sEMG data and the complex relationship of muscle force and sEMG.
OBJECTIVE:
This work aims at comparing experimentally recorded and simulated muscle activities considering a numerical model for crosstalk. METHODS:
For providing an experimentally derived reference data set, subjects were performing elevations of the arm, where the activities of the contemplated muscle groups were measured by sEMG sensors. Computed muscle activities were further processed and transformed into an artificial electromyographical signal, which includes a numerical crosstalk model. In order to determine whether the crosstalk model provides a better agreement with the measured muscle activities, the Pearson correlation coefficient has been computed as a qualitative way of assessing the curve progression of the data sets.
RESULTS:
The results show an improvement in the correlation coefficient between the experimental data and the simulated muscle activities when taking crosstalk into account.
CONCLUSIONS:
Although the correlation coefficient increased when the crosstalk model was utilized, it is questionable if the discretization of both, the crosstalk and the musculoskeletal model, is accurate enough.