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A meshfree computational methodology for surgical simulation
$214
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
technical principle has been verified by different test applications including an interactive human torso, an interactive mandible joint and an interactive brain. Together with the touch-sensitive anatomical object a new one degree-offreedom (DOF) haptic device can be used to simulate any puncture procedure (e.g. ventricular shunt insertion, needle biopsy, etc.). The design of the haptic device is based on a push-pull cable concept. The rendered forces produced by a linear motor connected at one end of the cable are transferred to the user via a sliding mechanism at the end-effector located at the other end of the cable. The touch simulator is more flexible than passive phantoms without electronics. The touch simulator and the 1 DOF haptic injection device provides improved user friendliness and fidelity compared to other purely graphically oriented simulation environments. 7821 Fr, 11:45-12:00 (P51) OR simulation in minimally invasive surgery D. Wilhelm, H. Feul~ner. Chirurgische Klinik und Poliklinik, Klinikum rechts der Isar der TUM, Munich, Germany The challenges in minimally invasive surgery are different from those in conventional open procedures. Pronounced learning curves in advanced laparoscopic techniques cause an urgent need for OR simulation in virtual reality. Within the last 15 years, various OR simulation devices were developed comprehending both the training in basic motor skills as well as a detailed training in specific surgical procedures. First experience with training assistance in VR clearly indicates an improvement of the surgical skills. The learning curve becomes significantly steeper. The focus of further development is to create even more complex scenarios. As soon as a higher degree of immersion is achieved the VR training systems will also be suitable for bench marking of surgical skills. 4067 Fr, 12:00-12:15 (P51) A meshfree computational m e t h o d o l o g y for surgical simulation S. De, '~-J. Lim. Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, USA With its many advantages of reduced postoperative pain, shorter hospital stays, quicker recoveries, less scarring and better cosmetic results, minimally invasive surgical (MIS) procedures demand a very high skill level of the surgeon. Current training paradigms using cadavers and animals are inadequate and efforts are under way to develop computer-based surgical simulators, much like flight simulators, which are in use in the aviation industry. Such multimodal simulators provide the surgeons with visual and haptic (touch) cues much like the tool handles used in actual surgery. The generation of multimodal virtual environments for surgical training is complicated by the necessity to develop heterogeneous scenarios involving the interaction of surgical tools with soft biological tissues in real time with complex outcomes such as surgical incision, cauterization, bleeding and smoke generation. While several techniques ranging from rapid but nonphysical geometrybased procedures to complex but tardy finite element (FE) techiniques have been proposed, none is uniquely suited to solve the virtual surgery problem. In this paper we present a promising new technique, the point-associated finite field (PAFF) approach, for real time surgery simulation. PAFF is a specialized version of a meshfree discretization scheme known as the method of finite spheres [1] in which partial differential equations may be solved on geometrically complex domains discretized using a scattered distribution of points. Unlike traditional mesh-based FE techniques, large tissue deformations, including surgical cutting, are particularly straightforward to handle using PAFF since interpolation functions are compactly supported on spherical subdomains which may intersect and overlap and are not constrained to abut each other as in the FEM. We will present several specializations of this scheme having various operational complexities. The accuracy and efficiency of this technique will be compared with solutions using traditional finite element methods and simulation results will be reported on segmented models obtained from the Visible Human Project. References [1] De S., and Bathe K.J. The Method of Finite Spheres. Computational Mechanics 2000; 25: p. 329-345.
Oral Presentations
Track 9
Tissue Engineering 9.1. Bone Tissue Engineering and Cell Mechanobiology 9.1.1. Bone Tissue Engineering and Cell Mechanobiology 6604 Mo, 11:00-11:30 (P8) Magnetic nanoparticle-based tagging of mechanosensors for bone tissue engineering A.J. El Haj, H. Sura, H. Yiu, S. Hughes, J. Magnay, J. Dobson, S.H. Cartmell. Institute of Science and Technology in Medicine, Keele University Medical School, Stoke on Trent, UK Mechanosensors in membranes are key regulators in the differentiation, proliferation and activity of bone cells. Activation and regulation of these mechanosensors has been proposed as a means by which engineering of tissues may be enhanced. Generating functional bone and connective tissue in vitro relies on culture environments which condition the tissue prior to implantation. Multiple protocols for the use of bioreactors which exert forces such as fluid flow and compression have been proposed. In this presentation, we describe a different approach where we target specific mechanosensors directly on human bone cell membranes within 3D constructs. By controlling the mechanical environment of the cells within the construct, we are no longer reliant on using strong materials which are capable of withstanding significant loading for bone tissue engineering. Hence, we aim to increase the turnover relationship between matrix and more rapidly degrading scaffolds in response to mechanical stimulation. Using a magnetic force bioreactor developed in our lab, we describe our investigations into the internalization of magnetic nanoparticles which can bind to receptor sites on the internal membrane. By applying time-varying magnetic fields, we can generate forces on these receptors which result in downstream changes in gene expression and enhanced matrix production. A comparison of data generated from the type of receptor tagged such as integrins, ion channels and growth factor receptor sites will be described. In addition, this technique can be applied to human mesenchymal stem cells (Poetics, Ltd) in monolayer culture. We describe our recent data on the upregulation of differentiation markers such as osterix, cbfal after 1 week of cyclical loading in culture. 4867 Mo, 11:30-11:45 (P8) Effect o f mechanical strain on o s t e o g e n i c progenitor cells in a collagen matrix A. Thiel 1, L. Kreja 1, B. Friemert 2, G. Bergenthal 2, L. Claes 1, A. Ignatius 1. 1Institute of Orthopaedic Research and Biomechanics, University of UIm, Germany, 2Military Hospital, Department of Surgery, UIm, Germany Introduction: Mechanical loading might be useful in improving the functionality of in vitro generated bone. The study aim was to investigate the effect of mechanical strain on human mesenchymal progenitor cells (MPC) in type I collagen gels, by evaluating the expression of several osteogenic marker and matrix turnover genes. Methods: MPC isolated from bone marrow of 7 donors were seeded in type I collagen gels (ArsArthro AG, Esslingen, Germany). During the first 7 days, the cell-seeded scaffolds were cultured either in basal medium or medium containing supplements for osteogenic differentiation. Over the next 7 days, scaffolds underwent daily mechanical stimulation (cyclic strain, 30 min, frequency 1 Hz, amplitude 1%). The expression of core binding factor 1 (cbfal), alkaline phosphatase (AP), osteopontin (OP), osteocalcin (OC), and matrix metalloproteinases (MMP 1, 2, 3, 13) was investigated by real-time PCR and normalized to GAPDH. A Wilcoxon signed-rank test was used to compare stimulated and unstimulated samples (p ~<0.05). Results: The mechanical stimulation led to a 1.6-fold upregulation of cbfal in both media. AP expression was increased only in differentiation medium (2.5-fold, p ~<0.05). OP expression was reduced by 55% (p ~<0.05) in basal medium. OC expression was not influenced. MMP 1 expression was mechanically induced in differentiation medium (7-fold, p~< 0.05). There was a nonsignificant increase in basal medium (2-fold, p >0.05). MMP2 expression was slightly reduced in basal medium but not influenced in more differentiated cells. MMP13 expression was significantly reduced in basal medium (50%, p ~<0.05) and differentiation medium (80%, p ~<0.05). MMP3 expression was not influenced. Discussion: The mechanically induced expression changes of cbfal, AP, OP and MMP1, MMP13 suggested that mechanical strain may be involved in regulation of both osteogenic differentiation and matrix turnover. The response
Journal o f Biomechanics 2006, Vol. 39 (Suppl 1)
technical principle has been verified by different test applications including an interactive human torso, an interactive mandible joint and an interactive brain. Together with the touch-sensitive anatomical object a new one degree-offreedom (DOF) haptic device can be used to simulate any puncture procedure (e.g. ventricular shunt insertion, needle biopsy, etc.). The design of the haptic device is based on a push-pull cable concept. The rendered forces produced by a linear motor connected at one end of the cable are transferred to the user via a sliding mechanism at the end-effector located at the other end of the cable. The touch simulator is more flexible than passive phantoms without electronics. The touch simulator and the 1 DOF haptic injection device provides improved user friendliness and fidelity compared to other purely graphically oriented simulation environments. 7821 Fr, 11:45-12:00 (P51) OR simulation in minimally invasive surgery D. Wilhelm, H. Feul~ner. Chirurgische Klinik und Poliklinik, Klinikum rechts der Isar der TUM, Munich, Germany The challenges in minimally invasive surgery are different from those in conventional open procedures. Pronounced learning curves in advanced laparoscopic techniques cause an urgent need for OR simulation in virtual reality. Within the last 15 years, various OR simulation devices were developed comprehending both the training in basic motor skills as well as a detailed training in specific surgical procedures. First experience with training assistance in VR clearly indicates an improvement of the surgical skills. The learning curve becomes significantly steeper. The focus of further development is to create even more complex scenarios. As soon as a higher degree of immersion is achieved the VR training systems will also be suitable for bench marking of surgical skills. 4067 Fr, 12:00-12:15 (P51) A meshfree computational m e t h o d o l o g y for surgical simulation S. De, '~-J. Lim. Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, USA With its many advantages of reduced postoperative pain, shorter hospital stays, quicker recoveries, less scarring and better cosmetic results, minimally invasive surgical (MIS) procedures demand a very high skill level of the surgeon. Current training paradigms using cadavers and animals are inadequate and efforts are under way to develop computer-based surgical simulators, much like flight simulators, which are in use in the aviation industry. Such multimodal simulators provide the surgeons with visual and haptic (touch) cues much like the tool handles used in actual surgery. The generation of multimodal virtual environments for surgical training is complicated by the necessity to develop heterogeneous scenarios involving the interaction of surgical tools with soft biological tissues in real time with complex outcomes such as surgical incision, cauterization, bleeding and smoke generation. While several techniques ranging from rapid but nonphysical geometrybased procedures to complex but tardy finite element (FE) techiniques have been proposed, none is uniquely suited to solve the virtual surgery problem. In this paper we present a promising new technique, the point-associated finite field (PAFF) approach, for real time surgery simulation. PAFF is a specialized version of a meshfree discretization scheme known as the method of finite spheres [1] in which partial differential equations may be solved on geometrically complex domains discretized using a scattered distribution of points. Unlike traditional mesh-based FE techniques, large tissue deformations, including surgical cutting, are particularly straightforward to handle using PAFF since interpolation functions are compactly supported on spherical subdomains which may intersect and overlap and are not constrained to abut each other as in the FEM. We will present several specializations of this scheme having various operational complexities. The accuracy and efficiency of this technique will be compared with solutions using traditional finite element methods and simulation results will be reported on segmented models obtained from the Visible Human Project. References [1] De S., and Bathe K.J. The Method of Finite Spheres. Computational Mechanics 2000; 25: p. 329-345.
Oral Presentations
Track 9
Tissue Engineering 9.1. Bone Tissue Engineering and Cell Mechanobiology 9.1.1. Bone Tissue Engineering and Cell Mechanobiology 6604 Mo, 11:00-11:30 (P8) Magnetic nanoparticle-based tagging of mechanosensors for bone tissue engineering A.J. El Haj, H. Sura, H. Yiu, S. Hughes, J. Magnay, J. Dobson, S.H. Cartmell. Institute of Science and Technology in Medicine, Keele University Medical School, Stoke on Trent, UK Mechanosensors in membranes are key regulators in the differentiation, proliferation and activity of bone cells. Activation and regulation of these mechanosensors has been proposed as a means by which engineering of tissues may be enhanced. Generating functional bone and connective tissue in vitro relies on culture environments which condition the tissue prior to implantation. Multiple protocols for the use of bioreactors which exert forces such as fluid flow and compression have been proposed. In this presentation, we describe a different approach where we target specific mechanosensors directly on human bone cell membranes within 3D constructs. By controlling the mechanical environment of the cells within the construct, we are no longer reliant on using strong materials which are capable of withstanding significant loading for bone tissue engineering. Hence, we aim to increase the turnover relationship between matrix and more rapidly degrading scaffolds in response to mechanical stimulation. Using a magnetic force bioreactor developed in our lab, we describe our investigations into the internalization of magnetic nanoparticles which can bind to receptor sites on the internal membrane. By applying time-varying magnetic fields, we can generate forces on these receptors which result in downstream changes in gene expression and enhanced matrix production. A comparison of data generated from the type of receptor tagged such as integrins, ion channels and growth factor receptor sites will be described. In addition, this technique can be applied to human mesenchymal stem cells (Poetics, Ltd) in monolayer culture. We describe our recent data on the upregulation of differentiation markers such as osterix, cbfal after 1 week of cyclical loading in culture. 4867 Mo, 11:30-11:45 (P8) Effect o f mechanical strain on o s t e o g e n i c progenitor cells in a collagen matrix A. Thiel 1, L. Kreja 1, B. Friemert 2, G. Bergenthal 2, L. Claes 1, A. Ignatius 1. 1Institute of Orthopaedic Research and Biomechanics, University of UIm, Germany, 2Military Hospital, Department of Surgery, UIm, Germany Introduction: Mechanical loading might be useful in improving the functionality of in vitro generated bone. The study aim was to investigate the effect of mechanical strain on human mesenchymal progenitor cells (MPC) in type I collagen gels, by evaluating the expression of several osteogenic marker and matrix turnover genes. Methods: MPC isolated from bone marrow of 7 donors were seeded in type I collagen gels (ArsArthro AG, Esslingen, Germany). During the first 7 days, the cell-seeded scaffolds were cultured either in basal medium or medium containing supplements for osteogenic differentiation. Over the next 7 days, scaffolds underwent daily mechanical stimulation (cyclic strain, 30 min, frequency 1 Hz, amplitude 1%). The expression of core binding factor 1 (cbfal), alkaline phosphatase (AP), osteopontin (OP), osteocalcin (OC), and matrix metalloproteinases (MMP 1, 2, 3, 13) was investigated by real-time PCR and normalized to GAPDH. A Wilcoxon signed-rank test was used to compare stimulated and unstimulated samples (p ~<0.05). Results: The mechanical stimulation led to a 1.6-fold upregulation of cbfal in both media. AP expression was increased only in differentiation medium (2.5-fold, p ~<0.05). OP expression was reduced by 55% (p ~<0.05) in basal medium. OC expression was not influenced. MMP 1 expression was mechanically induced in differentiation medium (7-fold, p~< 0.05). There was a nonsignificant increase in basal medium (2-fold, p >0.05). MMP2 expression was slightly reduced in basal medium but not influenced in more differentiated cells. MMP13 expression was significantly reduced in basal medium (50%, p ~<0.05) and differentiation medium (80%, p ~<0.05). MMP3 expression was not influenced. Discussion: The mechanically induced expression changes of cbfal, AP, OP and MMP1, MMP13 suggested that mechanical strain may be involved in regulation of both osteogenic differentiation and matrix turnover. The response