TY - CHAP A1 - Deuflhard, Peter A1 - Dössel, Olaf A1 - Louis, Alfred A1 - Zachow, Stefan T1 - Mehr Mathematik wagen in der Medizin T2 - acatech diskutiert, Produktionsfaktor Mathematik - Wie Mathematik Technik und Wirtschaft bewegt Y1 - 2008 U6 - https://doi.org/10.1007/978-3-540-89435-3 SP - 435 EP - 459 PB - Springer ER - TY - JOUR A1 - Zachow, Stefan A1 - Deuflhard, Peter T1 - Computergestützte Planung in der kraniofazialen Chirurgie JF - Face 01/08, Int. Mag. of Orofacial Esthetics Y1 - 2008 SP - 43 EP - 49 PB - Oemus Journale Leipzig ER - TY - CHAP A1 - Zilske, Michael A1 - Lamecker, Hans A1 - Zachow, Stefan T1 - Adaptive Remeshing of Non-Manifold Surfaces T2 - Eurographics 2008 Annex to the Conf. Proc. Y1 - 2008 SP - 207 EP - 211 ER - TY - CHAP A1 - Seim, Heiko A1 - Lamecker, Hans A1 - Zachow, Stefan T1 - Segmentation of Bony Structures with Ligament Attachment Sites T2 - Bildverarbeitung für die Medizin 2008 Y1 - 2008 U6 - https://doi.org/10.1007/978-3-540-78640-5_42 SP - 207 EP - 211 PB - Springer ER - TY - JOUR A1 - Zachow, Stefan A1 - Steinmann, Alexander A1 - Hildebrandt, Thomas A1 - Heppt, Werner T1 - Understanding nasal airflow via CFD simulation and visualization JF - Proc. Computer Aided Surgery around the Head Y1 - 2007 SP - 173 EP - 176 ER - TY - JOUR A1 - Lamecker, Hans A1 - Kamer, Lukas A1 - Wittmers, Antonia A1 - Zachow, Stefan A1 - Kaup, Thomas A1 - Schramm, Alexander A1 - Noser, Hansrudi A1 - Hammer, Beat T1 - A method for the three-dimensional statistical shape analysis of the bony orbit JF - Proc. Computer Aided Surgery around the Head Y1 - 2007 SP - 94 EP - 97 ER - TY - JOUR A1 - Zachow, Stefan A1 - Muigg, Philipp A1 - Hildebrandt, Thomas A1 - Doleisch, Helmut A1 - Hege, Hans-Christian T1 - Visual Exploration of Nasal Airflow JF - IEEE Transactions on Visualization and Computer Graphics Y1 - 2009 U6 - https://doi.org/10.1109/TVCG.2009.198 VL - 15 IS - 8 SP - 1407 EP - 1414 ER - TY - JOUR A1 - Kainmüller, Dagmar A1 - Lamecker, Hans A1 - Seim, Heiko A1 - Zachow, Stefan T1 - Multi-object segmentation of head bones JF - MIDAS Journal Y1 - 2009 ER - TY - CHAP A1 - Seim, Heiko A1 - Kainmüller, Dagmar A1 - Lamecker, Hans A1 - Zachow, Stefan T1 - A System for Unsupervised Extraction of Orthopaedic Parameters from CT Data T2 - GI Workshop Softwareassistenten - Computerunterstützung für die medizinische Diagnose und Therapieplanung Y1 - 2009 SP - 1328 EP - 1337 CY - Lübeck, Germany ER - TY - JOUR A1 - Heppt, Werner A1 - Hildebrandt, Thomas A1 - Steinmann, Alexander A1 - Zachow, Stefan T1 - Aesthetic and Function in Rhinoplasty JF - Springer Journal Y1 - 2007 VL - 264 (Suppl 1), RL 126 SP - 307 ER - TY - CHAP A1 - Zachow, Stefan A1 - Zilske, Michael A1 - Hege, Hans-Christian T1 - 3D Reconstruction of Individual Anatomy from Medical Image Data: Segmentation and Geometry Processing T2 - 25. ANSYS Conference & CADFEM Users’ Meeting Y1 - 2007 CY - Dresden ER - TY - JOUR A1 - Gessat, Michael A1 - Zachow, Stefan A1 - Burgert, Oliver A1 - Lemke, Heinz T1 - Geometric Meshes in Medical Applications - Steps towards a specification of Geometric Models in DICOM JF - Int. J. of Computer Assisted Radiology and Surgery (CARS) Y1 - 2007 U6 - https://doi.org/10.1007/s11548-007-0112-6 SP - 440 EP - 442 ER - TY - JOUR A1 - Hildebrandt, Thomas A1 - Zachow, Stefan A1 - Steinmann, Alexander A1 - Heppt, Werner T1 - Innovation in der Funktionell-Ästhetischen Nasenchirurgie: Rhino-CFD JF - Face, Int. Mag. of Orofacial Esthetics Y1 - 2007 SP - 20 EP - 23 PB - Oemus Journale Leipzig ER - TY - GEN A1 - Kamer, Lukas A1 - Noser, Hansrudi A1 - Lamecker, Hans A1 - Zachow, Stefan A1 - Wittmers, Antonia A1 - Kaup, Thomas A1 - Schramm, Alexander A1 - Hammer, Beat T1 - Three-dimensional statistical shape analysis - A useful tool for developing a new type of orbital implant? Y1 - 2006 SP - 20 EP - 21 PB - AO Development Institute, New Products Brochure 2/06 ER - TY - CHAP A1 - Zachow, Stefan A1 - Hege, Hans-Christian A1 - Deuflhard, Peter T1 - Computergestützte Operationsplanung in der Gesichtschirurgie T2 - Proc. VDE Kongress 2004 - Innovationen für Menschen, Band 2, Fachtagungsberichte DGBMT - GMM - GMA Y1 - 2004 SP - 53 EP - 58 ER - TY - CHAP A1 - Zachow, Stefan A1 - Hierl, Thomas A1 - Erdmann, Bodo T1 - A quantitative evaluation of 3D soft tissue prediction in maxillofacial surgery planning T2 - Proc. 3. Jahrestagung der Deutschen Gesellschaft für Computer- und Roboter-assistierte Chirurgie e.V. Y1 - 2004 CY - München ER - TY - JOUR A1 - Hierl, Thomas A1 - Zachow, Stefan A1 - Wollny, Gert A1 - Berti, Guntram A1 - Schmidt, Jens-Georg A1 - Fingberg, Jochen T1 - Computer-based simulation in distraction osteogenesis JF - Proc. of 3rd Int. Oxford Distraction Symposium of the Craniofacial Skeleton Y1 - 2004 SP - 33 EP - 34 ER - TY - JOUR A1 - Hierl, Thomas A1 - Zachow, Stefan A1 - Wollny, Gert A1 - Berti, Guntram A1 - Schmidt, Jens-Georg A1 - Fingberg, Jochen T1 - Concepts of computer-based simulation in orthognathic surgery JF - Journal of Cranio-Maxillofacial Surgery 32 Suppl. 1 Y1 - 2004 SP - 81 EP - 82 ER - TY - JOUR A1 - Haberl, Hannes A1 - Hell, Bertold A1 - Zöckler, Maja A1 - Zachow, Stefan A1 - Lamecker, Hans A1 - Sarrafzadeh, Asita A1 - Riecke, B. A1 - Langsch, Wolfgang A1 - Deuflhard, Peter A1 - Bier, Jürgen A1 - Brock, Mario T1 - Technical aspects and results of surgery for craniosynostosis JF - Zentralblatt für Neurochirurgie Y1 - 2004 VL - 65 IS - 2 SP - 65 EP - 74 ER - TY - JOUR A1 - Nkenke, Emeka A1 - Zachow, Stefan A1 - Benz, Michaela A1 - Maier, Tobias A1 - Veit, Klaus A1 - Kramer, Manuel A1 - Benz, St. A1 - Häusler, Gerd A1 - Neukam, Friedrich A1 - Lell, Michael T1 - Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery JF - Journal of Dento-Maxillofacial Radiology Y1 - 2004 U6 - https://doi.org/10.1259/dmfr/27071199 VL - 33 SP - 226 EP - 232 ER - TY - CHAP A1 - Zachow, Stefan A1 - Hierl, Thomas A1 - Erdmann, Bodo T1 - On the Predictability of tissue changes after osteotomy planning in maxillofacial surgery T2 - Computer Assisted Radiology and Surgery (CARS) Y1 - 2004 U6 - https://doi.org/10.1016/j.ics.2004.03.043 SP - 648 EP - 653 CY - Chicago, USA ER - TY - CHAP A1 - Zachow, Stefan A1 - Hierl, Thomas A1 - Erdmann, Bodo T1 - Über die Genauigkeit einer 3D Weichgewebeprädiktion in der MKG-Cirurgie T2 - Workshop ’Bildverarbeitung für die Medizin’ (BVM) Y1 - 2004 SP - 75 EP - 79 CY - Berlin, Germany ER - TY - CHAP A1 - Lamecker, Hans A1 - Zöckler, Maja A1 - Haberl, Hannes A1 - Zachow, Stefan A1 - Hege, Hans-Christian T1 - Statistical shape modeling for craniosynostosis planning T2 - 2nd International Conference Advanced Digital Technology in Head and Neck Reconstruction 2005, Abstract Volume Y1 - 2005 SP - 64 CY - Banff, Alberta ER - TY - JOUR A1 - Westermark, Anders A1 - Zachow, Stefan A1 - Eppley, Barry T1 - 3D osteotomy planning in maxillofacial surgery, including 3D soft tissue prediction JF - Journal of Craniofacial Surgery Y1 - 2005 VL - 16(1) SP - 100 EP - 104 ER - TY - JOUR A1 - Zachow, Stefan A1 - Hege, Hans-Christian A1 - Deuflhard, Peter T1 - Maxillofacial surgery planning with 3D soft tissue prediction - modeling, planning, simulation JF - 2. Int. Conf. on Advanced Digital Technology in Head and Neck Reconstruction, Abstract 33 Y1 - 2005 SP - 64 CY - Banff, Alberta, CA ER - TY - JOUR A1 - Lamecker, Hans A1 - Zachow, Stefan A1 - Haberl, Hannes A1 - Stiller, Michael T1 - Medical applications for statistical shape models JF - Computer Aided Surgery around the Head, Fortschritt-Berichte VDI - Biotechnik/Medizintechnik Y1 - 2005 VL - 17 (258) SP - 61 ER - TY - CHAP A1 - Zachow, Stefan A1 - Lamecker, Hans A1 - Elsholtz, Barbara A1 - Stiller, Michael T1 - Reconstruction of mandibular dysplasia using a statistical 3D shape model T2 - Proc. Computer Assisted Radiology and Surgery (CARS) Y1 - 2005 U6 - https://doi.org/10.1016/j.ics.2005.03.339 SP - 1238 EP - 1243 CY - Berlin, Germany ER - TY - CHAP A1 - Nkenke, Emeka A1 - Häusler, Gerd A1 - Neukam, Friedrich A1 - Zachow, Stefan T1 - Streak artifact correction of CT data by optical 3D imaging in the simulation of orthognathic surgery T2 - Computer Assisted Radiology and Surgery (CARS) Y1 - 2005 U6 - https://doi.org/doi:10.1016/j.ics.2005.03.278 CY - Berlin Germany ER - TY - CHAP A1 - Nkenke, Emeka A1 - Zachow, Stefan A1 - Häusler, Gerd T1 - Fusion von optischen 3D- und CT-Daten des Gebisses zur Metallartefaktkorrektur vor computerassistierter Planung MKG-chirurgischer Eingriffe T2 - Symposium der Arbeitsgemeinschaf für Kieferchirurgie Y1 - 2005 CY - Bad Homburg v.d.H ER - TY - GEN A1 - Wilson, David A1 - Bücher, Pia A1 - Grewe, Carl Martin A1 - Anglin, Carolyn A1 - Zachow, Stefan A1 - Michael, Dunbar T1 - Validation of Three Dimensional Models of the Distal Femur Created from Surgical Navigation Point Cloud Data T2 - 15th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery (CAOS) Y1 - 2015 ER - TY - CHAP A1 - Ehlke, Moritz A1 - Heyland, Mark A1 - Märdian, Sven A1 - Duda, Georg A1 - Zachow, Stefan T1 - 3D Assessment of Osteosynthesis based on 2D Radiographs T2 - Proceedings of the Jahrestagung der Deutschen Gesellschaft für Computer- und Roboterassistierte Chirurgie (CURAC) N2 - We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patient-specific surface of the distal femur based on postoperative 2D radiographs. In a first step, the implant geometry is used as a calibration object to relate the implant and the individual X-ray images spatially in a virtual X-ray setup. Second, the patient- specific femoral shape and pose are reconstructed by fitting a deformable statistical shape and intensity model (SSIM) to the X-rays. The relative positioning between femur and implant is then assessed in terms of the displacement between the reconstructed 3D shape of the femur and the plate. We believe that the approach presented in this paper constitutes a meaningful tool to elucidate the effect of implant positioning on fracture healing and, ultimately, to derive load recommendations after surgery. KW - 3d-reconstruction from 2d X-rays KW - osteosynthesis follow-up KW - statistical shape and intensity models Y1 - 2015 SP - 317 EP - 321 ER - TY - GEN A1 - Ehlke, Moritz A1 - Heyland, Mark A1 - Märdian, Sven A1 - Duda, Georg A1 - Zachow, Stefan T1 - 3D Assessment of Osteosynthesis based on 2D Radiographs N2 - We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patient-specific surface of the distal femur based on postoperative 2D radiographs. In a first step, the implant geometry is used as a calibration object to relate the implant and the individual X-ray images spatially in a virtual X-ray setup. Second, the patient-specific femoral shape and pose are reconstructed by fitting a deformable statistical shape and intensity model (SSIM) to the X-rays. The relative positioning between femur and implant is then assessed in terms of the displacement between the reconstructed 3D shape of the femur and the plate. We believe that the approach presented in this paper constitutes a meaningful tool to elucidate the effect of implant positioning on fracture healing and, ultimately, to derive load recommendations after surgery. T3 - ZIB-Report - 15-47 KW - 3d-reconstruction from 2d X-rays KW - statistical shape and intensity models KW - osteosynthesis follow-up Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-56217 SN - 1438-0064 ER - TY - CHAP A1 - Krämer, Martin A1 - Herrmann, Karl-Heinz A1 - Boeth, Heide A1 - Tycowicz, Christoph von A1 - König, Christian A1 - Zachow, Stefan A1 - Ehrig, Rainald A1 - Hege, Hans-Christian A1 - Duda, Georg A1 - Reichenbach, Jürgen T1 - Measuring 3D knee dynamics using center out radial ultra-short echo time trajectories with a low cost experimental setup T2 - ISMRM (International Society for Magnetic Resonance in Medicine), 23rd Annual Meeting 2015, Toronto, Canada Y1 - 2015 ER - TY - CHAP A1 - Ehlke, Moritz A1 - Heyland, Mark A1 - Märdian, Sven A1 - Duda, Georg A1 - Zachow, Stefan T1 - Assessing the relative positioning of an osteosynthesis plate to the patient-specific femoral shape from plain 2D radiographs T2 - Proceedings of the 15th Annual Meeting of CAOS-International (CAOS) N2 - We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patient­specific surface of the distal femur based on 2D X­ray images. Our goal is to study from clinical data, how the plate­to­bone distance affects bone healing. The patient­specific 3D shape of the femur is, however, seldom recorded for cases of femoral osteosynthesis since this typically requires Computed Tomography (CT), which comes at high cost and radiation dose. Our method instead utilizes two postoperative X­ray images to derive the femoral shape and thus can be applied on radiographs that are taken in clinical routine for follow­up. First, the implant geometry is used as a calibration object to relate the implant and the individual X­ray images spatially in a virtual X­ray setup. In a second step, the patient­specific femoral shape and pose are reconstructed in the virtual setup by fitting a deformable statistical shape and intensity model (SSIM) to the images. The relative positioning between femur and implant is then assessed in terms of displacement between the reconstructed 3D shape of the femur and the plate. A preliminary evaluation based on 4 cadaver datasets shows that the method derives the plate­to­bone distance with a mean absolute error of less than 1mm and a maximum error of 4.7 mm compared to ground truth from CT. We believe that the approach presented in this paper constitutes a meaningful tool to elucidate the effect of implant positioning on fracture healing. KW - 3d-­reconstruction from 2d X­rays KW - statistical shape and intensity models KW - fracture fixation of the distal femur KW - pose estimation Y1 - 2015 ER - TY - GEN A1 - Ehlke, Moritz A1 - Heyland, Mark A1 - Märdian, Sven A1 - Duda, Georg A1 - Zachow, Stefan T1 - Assessing the Relative Positioning of an Osteosynthesis Plate to the Patient-Specific Femoral Shape from Plain 2D Radiographs N2 - We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patient­specific surface of the distal femur based on 2D X­ray images. Our goal is to study from clinical data, how the plate­to­bone distance affects bone healing. The patient­specific 3D shape of the femur is, however, seldom recorded for cases of femoral osteosynthesis since this typically requires Computed Tomography (CT), which comes at high cost and radiation dose. Our method instead utilizes two postoperative X­ray images to derive the femoral shape and thus can be applied on radiographs that are taken in clinical routine for follow­up. First, the implant geometry is used as a calibration object to relate the implant and the individual X­ray images spatially in a virtual X­ray setup. In a second step, the patient­specific femoral shape and pose are reconstructed in the virtual setup by fitting a deformable statistical shape and intensity model (SSIM) to the images. The relative positioning between femur and implant is then assessed in terms of displacement between the reconstructed 3D shape of the femur and the plate. A preliminary evaluation based on 4 cadaver datasets shows that the method derives the plate­to­bone distance with a mean absolute error of less than 1mm and a maximum error of 4.7 mm compared to ground truth from CT. We believe that the approach presented in this paper constitutes a meaningful tool to elucidate the effect of implant positioning on fracture healing. T3 - ZIB-Report - 15-21 KW - 3d-­reconstruction from 2d X­rays KW - statistical shape and intensity models KW - fracture fixation of the distal femur KW - pose estimation Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-54268 SN - 1438-0064 ER - TY - JOUR A1 - Campoli, Gianni A1 - Baka, Nora A1 - Kaptein, Bart A1 - Valstar, Edward A1 - Zachow, Stefan A1 - Weinans, Harrie A1 - Zadpoor, Amir Abbas T1 - Relationship between the shape and density distribution of the femur and its natural frequencies of vibration JF - Journal of Biomechanics N2 - It has been recently suggested that mechanical loads applied at frequencies close to the natural frequencies of bone could enhance bone apposition due to the resonance phenomenon. Other applications of bone modal analysis are also suggested. For the above-mentioned applications, it is important to understand how patient-specific bone shape and density distribution influence the natural frequencies of bones. We used finite element models to study the effects of bone shape and density distribution on the natural frequencies of the femur in free boundary conditions. A statistical shape and appearance model that describes shape and density distribution independently was created, based on a training set of 27 femora. The natural frequencies were then calculated for different shape modes varied around the mean shape while keeping the mean density distribution, for different appearance modes around the mean density distribution while keeping the mean bone shape, and for the 27 training femora. Single shape or appearance modes could cause up to 15% variations in the natural frequencies with certain modes having the greatest impact. For the actual femora, shape and density distribution changed the natural frequencies by up to 38%. First appearance mode that describes the general cortical bone thickness and trabecular bone density had one of the strongest impacts. The first appearance mode could therefore provide a sensitive measure of general bone health and disease progression. Since shape and density could cause large variations in the calculated natural frequencies, patient-specific FE models are needed for accurate estimation of bone natural frequencies. Y1 - 2014 U6 - https://doi.org/10.1016/j.jbiomech.2014.08.008 VL - 47 SP - 3334 EP - 3343 PB - Elsevier ER - TY - JOUR A1 - Hochfeld, Mascha A1 - Lamecker, Hans A1 - Thomale, Ulrich W. A1 - Schulz, Matthias A1 - Zachow, Stefan A1 - Haberl, Hannes T1 - Frame-based cranial reconstruction JF - Journal of Neurosurgery: Pediatrics N2 - The authors report on the first experiences with the prototype of a surgical tool for cranial remodeling. The device enables the surgeon to transfer statistical information, represented in a model, into the disfigured bone. The model is derived from a currently evolving databank of normal head shapes. Ultimately, the databank will provide a set of standard models covering the statistical range of normal head shapes, thus providing the required template for any standard remodeling procedure as well as customized models for intended overcorrection. To date, this technique has been used in the surgical treatment of 14 infants (age range 6-12 months) with craniosynostosis. In all 14 cases, the designated esthetic result, embodied by the selected model, has been achieved, without morbidity or mortality. Frame-based reconstruction provides the required tools to precisely realize the surgical reproduction of the model shape. It enables the establishment of a self-referring system, feeding back postoperative growth patterns, recorded by 3D follow-up, into the model design. Y1 - 2014 U6 - https://doi.org/10.3171/2013.11.PEDS1369 VL - 13 IS - 3 SP - 319 EP - 323 ER - TY - JOUR A1 - Lemanis, Robert A1 - Zachow, Stefan A1 - Fusseis, Florian A1 - Hoffmann, René T1 - A new approach using high-resolution computed tomography to test the buoyant properties of chambered cephalopod shells JF - Paleobiology N2 - The chambered shell of modern cephalopods functions as a buoyancy apparatus, allowing the animal to enter the water column without expending a large amount of energy to overcome its own weight. Indeed, the chambered shell is largely considered a key adaptation that allowed the earliest cephalopods to leave the ocean floor and enter the water column. It has been argued by some, however, that the iconic chambered shell of Paleozoic and Mesozoic ammonoids did not provide a sufficiently buoyant force to compensate for the weight of the entire animal, thus restricting ammonoids to a largely benthic lifestyle reminiscent of some octopods. Here we develop a technique using high-resolution computed tomography to quantify the buoyant properties of chambered shells without reducing the shell to ideal spirals or eliminating inherent biological variability by using mathematical models that characterize past work in this area. This technique has been tested on Nautilus pompilius and is now extended to the extant deep-sea squid Spirula spirula and the Jurassic ammonite Cadoceras sp. hatchling. Cadoceras is found to have possessed near-neutral to positive buoyancy if hatched when the shell possessed between three and five chambers. However, we show that the animal could also overcome degrees of negative buoyancy through swimming, similar to the paralarvae of modern squids. These calculations challenge past inferences of benthic life habits based solely on calculations of negative buoyancy. The calculated buoyancy of Cadoceras supports the possibility of planktonic dispersal of ammonite hatchlings. This information is essential to understanding ammonoid ecology as well as biotic interactions and has implications for the interpretation of geochemical data gained from the isotopic analysis of the shell. Y1 - 2015 U6 - https://doi.org/10.1017/pab.2014.17 VL - 41 IS - 2 SP - 313 EP - 329 PB - Cambridge University Press CY - Cambridge ER - TY - CHAP A1 - Ehlke, Moritz A1 - Frenzel, Thomas A1 - Ramm, Heiko A1 - Shandiz, Mohsen Akbari A1 - Anglin, Carolyn A1 - Zachow, Stefan T1 - Towards Robust Measurement Of Pelvic Parameters From AP Radiographs Using Articulated 3D Models T2 - Computer Assisted Radiology and Surgery (CARS) N2 - Patient-specific parameters such as the orientation of the acetabulum or pelvic tilt are useful for custom planning for total hip arthroplasty (THA) and for evaluating the outcome of surgical interventions. The gold standard in obtaining pelvic parameters is from three-dimensional (3D) computed tomography (CT) imaging. However, this adds time and cost, exposes the patient to a substantial radiation dose, and does not allow for imaging under load (e.g. while the patient is standing). If pelvic parameters could be reliably derived from the standard anteroposterior (AP) radiograph, preoperative planning would be more widespread, and research analyses could be applied to retrospective data, after a postoperative issue is discovered. The goal of this work is to enable robust measurement of two surgical parameters of interest: the tilt of the anterior pelvic plane (APP) and the orientation of the natural acetabulum. We present a computer-aided reconstruction method to determine the APP and natural acetabular orientation from a single, preoperative X-ray. It can easily be extended to obtain other important preoperative and postoperative parameters solely based on a single AP radiograph. KW - Articulated Models, Statistical Shape And Intensity Models, 2D/3D Anatomy Reconstruction, Pelvic Parameters Measurement, Total Hip Arthroplasty Y1 - 2015 ER - TY - GEN A1 - Ehlke, Moritz A1 - Frenzel, Thomas A1 - Ramm, Heiko A1 - Shandiz, Mohsen Akbari A1 - Anglin, Carolyn A1 - Zachow, Stefan T1 - Towards Robust Measurement of Pelvic Parameters from AP Radiographs using Articulated 3D Models N2 - Patient-specific parameters such as the orientation of the acetabulum or pelvic tilt are useful for custom planning for total hip arthroplasty (THA) and for evaluating the outcome of surgical interventions. The gold standard in obtaining pelvic parameters is from three-dimensional (3D) computed tomography (CT) imaging. However, this adds time and cost, exposes the patient to a substantial radiation dose, and does not allow for imaging under load (e.g. while the patient is standing). If pelvic parameters could be reliably derived from the standard anteroposterior (AP) radiograph, preoperative planning would be more widespread, and research analyses could be applied to retrospective data, after a postoperative issue is discovered. The goal of this work is to enable robust measurement of two surgical parameters of interest: the tilt of the anterior pelvic plane (APP) and the orientation of the natural acetabulum. We present a computer-aided reconstruction method to determine the APP and natural acetabular orientation from a single, preoperative X-ray. It can easily be extended to obtain other important preoperative and postoperative parameters solely based on a single AP radiograph. T3 - ZIB-Report - 15-11 KW - Articulated Models, Statistical Shape And Intensity Models, 2D/3D Anatomy Reconstruction, Pelvic Parameters Measurement, Total Hip Arthroplasty Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-53707 SN - 1438-0064 ER - TY - GEN A1 - Wilson, David A1 - Bücher, Pia A1 - Grewe, Carl Martin A1 - Mocanu, Valentin A1 - Anglin, Carolyn A1 - Zachow, Stefan A1 - Dunbar, Michael T1 - Validation of Three Dimensional Models of the Distal Femur Created from Surgical Navigation Data T2 - Orthopedic Research Society Annual Meeting Y1 - 2015 CY - Las Vegas, Nevada ER - TY - JOUR A1 - Lube, Juliane A1 - Flack, Natasha A1 - Cotofana, Sebastian A1 - Özkurtul, Orkun A1 - Woodley, Stephanie A1 - Zachow, Stefan A1 - Hammer, Niels T1 - Pelvic and lower extremity physiological cross-sectional areas: An MRI study of the living young and comparison to published research literature JF - Surgical and Radiologic Anatomy N2 - Purpose: Morphological data pertaining to the pelvis and lower extremity muscles are increasingly being used in biomechanical modeling to compare healthy and pathological conditions. Very few data sets exist that encompass all of the muscles of the lower limb, allowing for comparisons between regions. The aims of this study were to (a) provide physiological cross-sectional area (PCSA) data for the pelvic, thigh, and leg muscles in young, healthy participants, using magnetic resonance imaging (MRI), and (b) to compare these data with summarized PCSAs obtained from the literature. Materials and Methods: Six young and healthy volunteers participated and were scanned using 3 T MRI. PCSAs were calculated from volumetric segmentations obtained bilaterally of 28 muscles/muscle groups of the pelvis, thigh, and leg. These data were compared to published, summarized PCSA data derived from cadaveric, computed tomography, MRI and ultrasound studies. Results: The PCSA of the pelvis, thigh, and leg muscles tended to be 20–130% larger in males than in females, except for the gemelli which were 34% smaller in males, and semitendinosus and triceps surae which did not differ (<20% different). The dominant and the non-dominant sides showed similar and minutely different PCSA with less than 18% difference between sides. Comparison to other studies revealed wide ranges within, and large differences between, the cadaveric and imaging PCSA data. Comparison of the PCSA of this study and published literature revealed major differences in the iliopsoas, gluteus minimus, tensor fasciae latae, gemelli, obturator internus, biceps femoris, quadriceps femoris, and the deep leg flexor muscles. Conclusions: These volume-derived PCSAs of the pelvic and lower limb muscles alongside the data synthesised from the literature may serve as a basis for comparative and biomechanical studies of the living and healthy young, and enable calculation of muscle forces. Comparison of the literature revealed large variations in PCSA from each of the different investigative modalities, hampering omparability between studies. Sample size, age, post-mortem changes of muscle tone, chemical fixation of cadaveric tissues, and the underlying physics of the imaging techniques may potentially influence PCSA calculations. Y1 - 2017 U6 - https://doi.org/10.1007/s00276-016-1807-6 VL - 39 IS - 8 SP - 849 EP - 857 ER - TY - CHAP A1 - Mukhopadhyay, Anirban A1 - Morillo, Oscar A1 - Zachow, Stefan A1 - Lamecker, Hans T1 - Robust and Accurate Appearance Models Based on Joint Dictionary Learning Data from the Osteoarthritis Initiative T2 - Lecture Notes in Computer Science, Patch-Based Techniques in Medical Imaging. Patch-MI 2016 N2 - Deformable model-based approaches to 3D image segmentation have been shown to be highly successful. Such methodology requires an appearance model that drives the deformation of a geometric model to the image data. Appearance models are usually either created heuristically or through supervised learning. Heuristic methods have been shown to work effectively in many applications but are hard to transfer from one application (imaging modality/anatomical structure) to another. On the contrary, supervised learning approaches can learn patterns from a collection of annotated training data. In this work, we show that the supervised joint dictionary learning technique is capable of overcoming the traditional drawbacks of the heuristic approaches. Our evaluation based on two different applications (liver/CT and knee/MR) reveals that our approach generates appearance models, which can be used effectively and efficiently in a deformable model-based segmentation framework. Y1 - 2016 U6 - https://doi.org/10.1007/978-3-319-47118-1_4 VL - 9993 SP - 25 EP - 33 ER - TY - JOUR A1 - Sahu, Manish A1 - Mukhopadhyay, Anirban A1 - Szengel, Angelika A1 - Zachow, Stefan T1 - Addressing multi-label imbalance problem of Surgical Tool Detection using CNN JF - International Journal of Computer Assisted Radiology and Surgery N2 - Purpose: A fully automated surgical tool detection framework is proposed for endoscopic video streams. State-of-the-art surgical tool detection methods rely on supervised one-vs-all or multi-class classification techniques, completely ignoring the co-occurrence relationship of the tools and the associated class imbalance. Methods: In this paper, we formulate tool detection as a multi-label classification task where tool co-occurrences are treated as separate classes. In addition, imbalance on tool co-occurrences is analyzed and stratification techniques are employed to address the imbalance during Convolutional Neural Network (CNN) training. Moreover, temporal smoothing is introduced as an online post-processing step to enhance run time prediction. Results: Quantitative analysis is performed on the M2CAI16 tool detection dataset to highlight the importance of stratification, temporal smoothing and the overall framework for tool detection. Conclusion: The analysis on tool imbalance, backed by the empirical results indicates the need and superiority of the proposed framework over state-of-the-art techniques. Y1 - 2017 UR - https://link.springer.com/article/10.1007/s11548-017-1565-x U6 - https://doi.org/10.1007/s11548-017-1565-x N1 - Selected for final oral presentation VL - 12 IS - 6 SP - 1013 EP - 1020 PB - Springer ER - TY - JOUR A1 - Wilson, David A1 - Anglin, Carolyn A1 - Ambellan, Felix A1 - Grewe, Carl Martin A1 - Tack, Alexander A1 - Lamecker, Hans A1 - Dunbar, Michael A1 - Zachow, Stefan T1 - Validation of three-dimensional models of the distal femur created from surgical navigation point cloud data for intraoperative and postoperative analysis of total knee arthroplasty JF - International Journal of Computer Assisted Radiology and Surgery N2 - Purpose: Despite the success of total knee arthroplasty there continues to be a significant proportion of patients who are dissatisfied. One explanation may be a shape mismatch between pre and post-operative distal femurs. The purpose of this study was to investigate a method to match a statistical shape model (SSM) to intra-operatively acquired point cloud data from a surgical navigation system, and to validate it against the pre-operative magnetic resonance imaging (MRI) data from the same patients. Methods: A total of 10 patients who underwent navigated total knee arthroplasty also had an MRI scan less than 2 months pre-operatively. The standard surgical protocol was followed which included partial digitization of the distal femur. Two different methods were employed to fit the SSM to the digitized point cloud data, based on (1) Iterative Closest Points (ICP) and (2) Gaussian Mixture Models (GMM). The available MRI data were manually segmented and the reconstructed three-dimensional surfaces used as ground truth against which the statistical shape model fit was compared. Results: For both approaches, the difference between the statistical shape model-generated femur and the surface generated from MRI segmentation averaged less than 1.7 mm, with maximum errors occurring in less clinically important areas. Conclusion: The results demonstrated good correspondence with the distal femoral morphology even in cases of sparse data sets. Application of this technique will allow for measurement of mismatch between pre and post-operative femurs retrospectively on any case done using the surgical navigation system and could be integrated into the surgical navigation unit to provide real-time feedback. Y1 - 2017 UR - https://link.springer.com/content/pdf/10.1007%2Fs11548-017-1630-5.pdf U6 - https://doi.org/10.1007/s11548-017-1630-5 VL - 12 IS - 12 SP - 2097 EP - 2105 PB - Springer ER - TY - JOUR A1 - Hoffmann, René A1 - Lemanis, Robert A1 - Falkenberg, Janina A1 - Schneider, Steffen A1 - Wesendonk, Hendrik A1 - Zachow, Stefan T1 - Integrating 2D and 3D shell morphology to disentangle the palaeobiology of ammonoids: A virtual approach JF - Palaeontology N2 - We demonstrate, based on data derived from computed tomography, that integrating 2D and 3D morphological data of ammonoid shells represent an important new approach to disentangle the palaeobiology of ammonoids. Characterization of ammonite morphology has long been constrained to 2D data and only a few studies collect ontogenetic data in 180° steps. We combine this traditional approach with 3D data collected from high-resolution nano-computed tomography. For this approach, ontogenetic morphological data of the hollow shell of a juvenile ammonite Kosmoceras (Jurassic, Callovian) is collected. 2D data is collected in 10° steps and show significant changes in shell morphology. Preserved hollow spines show multiple mineralized membranes never reported before, representing temporal changes of the ammonoid mantle tissue. 3D data show that chamber volumes do not always increase exponentially, as was generally assumed, but may represent a proxy for life events, e.g. stress phases. Furthermore, chamber volume cannot be simply derived from septal spacing in forms comparable to Kosmoceras. Vogel numbers, a 3D parameter for chamber shape, of Kosmoceras are similar to other ammonoids (Arnsbergites, Amauroceras) and modern cephalopods (Nautilus, Spirula). Two methods to virtually document the suture line ontogeny, used to document phylogenetic relationships of larger taxonomic entities, were applied for the first time and seem a promising alternative to hand drawings. The curvature of the chamber surfaces increases during ontogeny due to increasing strength of ornamentation and septal complexity. As increasing curvature may allow for faster handling of cameral liquid, it could compensate for decreasing SA/V ratios through ontogeny. Y1 - 2017 UR - http://dx.doi.org/10.1111/pala.12328 U6 - https://doi.org/10.1111/pala.12328 VL - 61 IS - 1 SP - 89 EP - 104 ER - TY - CHAP A1 - Baum, Daniel A1 - Mahlow, Kristin A1 - Lamecker, Hans A1 - Zachow, Stefan A1 - Müller, Johannes A1 - Hege, Hans-Christian T1 - The Potential of Surface-based Geometric Morphometrics for Evolutionary Studies: An Example using Dwarf Snakes (Eirenis) T2 - Abstract in DigitalSpecimen 2014 N2 - Geometric morphometrics plays an important role in evolutionary studies. The state-of-the-art in this field are landmark-based methods. Since the landmarks usually need to be placed manually, only a limited number of landmarks are generally used to represent the shape of an anatomical structure. As a result, shape characteristics that cannot be properly represented by small sets of landmarks are disregarded. In this study, we present a method that is free of this limitation. The method takes into account the whole shape of an anatomical structure, which is represented as a surface, hence the term ‘surface-based morphometrics’. Correspondence between two surfaces is established by defining a partitioning of the surfaces into homologous surface patches. The first step for the generation of a surface partitioning is to place landmarks on the surface. Subsequently, the landmarks are connected by curves lying on the surface. The curves, called ‘surface paths’, might either follow specific anatomical features or they can be geodesics, that is, shortest paths on the surface. One important requirement, however, is that the resulting surface path networks are topologically equivalent across all surfaces. Once the surface path networks have been defined, the surfaces are decomposed into patches according to the path networks. This approach has several advantages. One of them is that we can discretize the surface by as many points as desired. Thus, even fine shape details can be resolved if this is of interest for the study. Since a point discretization is used, another advantage is that well-established analysis methods for landmark-based morphometrics can be utilized. Finally, the shapes can be easily morphed into one another, thereby greatly supporting the understanding of shape changes across all considered specimens. To show the potential of the described method for evolutionary studies of biological specimens, we applied the method to the para-basisphenoid complex of the snake genus Eirenis. By using this anatomical structure as example, we present all the steps that are necessary for surface-based morphometrics, including the segmentation of the para-basisphenoid complex from micro-CT data sets. We also show some first results using statistical analysis as well as classification methods based on the presented technique. Y1 - 2014 ER - TY - JOUR A1 - Brüning, Jan A1 - Goubergrits, Leonid A1 - Heppt, Werner A1 - Zachow, Stefan A1 - Hildebrandt, Thomas T1 - Numerical Analysis of Nasal Breathing - A Pilot Study JF - Facial Plastic Surgery N2 - Background: Currently, there is no fully sufficient way to differentiate between symptomatic and normal nasal breathing. Using the nose’s total resistance is disputed as a valid means to objectify nasal airflow, and the need for a more comprehensive diagnostic method is increasing. This work’s aim was to test a novel approach considering intranasal wall shear stress as well as static pressure maps obtained by computational fluid dynamics (CFD). Methods: X-ray computed tomography (CT) scan data of six symptom-free subjects and seven symptomatic patients were used. Patient-specific geometries of the nasal cavity were segmented from these data sets. Inspiratory and expiratory steady airflow simulations were performed using CFD. Calculated static pressures and wall shear stresses (WSS) were mapped onto a common template of the nasal septum, allowing for comparison of these parameters between the two patient groups. Results: Significant differences in wall shear stress distributions during the inspiratory phase could be identified between the two groups, whereas no differences were found for the expiratory phase. It is assumed that one essential feature of normal nasal breathing probably consists in distinctively different intranasal flow fields for inspiration and expiration. This is in accordance with previous investigations. Conclusion: The proposed method seems to be a promising tool for developing a new kind of patient-specific assessment of nasal breathing. However, more studies and a greater case number of data with an expanded focus, would be ideal. Y1 - 2017 U6 - https://doi.org/doi:10.1055/s-0037-1603789 VL - 33 IS - 4 SP - 388 EP - 395 ER - TY - GEN A1 - Weiser, Martin A1 - Erdmann, Bodo A1 - Schenkl, Sebastian A1 - Muggenthaler, Holger A1 - Hubig, Michael A1 - Mall, Gita A1 - Zachow, Stefan T1 - Uncertainty in Temperature-Based Determination of Time of Death N2 - Temperature-based estimation of time of death (ToD) can be per- formed either with the help of simple phenomenological models of corpse cooling or with detailed mechanistic (thermodynamic) heat transfer mod- els. The latter are much more complex, but allow a higher accuracy of ToD estimation as in principle all relevant cooling mechanisms can be taken into account. The potentially higher accuracy depends on the accuracy of tissue and environmental parameters as well as on the geometric resolution. We in- vestigate the impact of parameter variations and geometry representation on the estimated ToD based on a highly detailed 3D corpse model, that has been segmented and geometrically reconstructed from a computed to- mography (CT) data set, differentiating various organs and tissue types. From that we identify the most crucial parameters to measure or estimate, and obtain a local uncertainty quantifcation for the ToD. T3 - ZIB-Report - 17-18 KW - forensic medicine KW - determination of time of death KW - heat transfer equation KW - sensitivity i.r.t. thermal parameters KW - sensitivity i.r.t. geometric resolution Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-63818 SN - 1438-0064 ER - TY - JOUR A1 - von Tycowicz, Christoph A1 - Ambellan, Felix A1 - Mukhopadhyay, Anirban A1 - Zachow, Stefan T1 - An Efficient Riemannian Statistical Shape Model using Differential Coordinates JF - Medical Image Analysis N2 - We propose a novel Riemannian framework for statistical analysis of shapes that is able to account for the nonlinearity in shape variation. By adopting a physical perspective, we introduce a differential representation that puts the local geometric variability into focus. We model these differential coordinates as elements of a Lie group thereby endowing our shape space with a non-Euclidean structure. A key advantage of our framework is that statistics in a manifold shape space becomes numerically tractable improving performance by several orders of magnitude over state-of-the-art. We show that our Riemannian model is well suited for the identification of intra-population variability as well as inter-population differences. In particular, we demonstrate the superiority of the proposed model in experiments on specificity and generalization ability. We further derive a statistical shape descriptor that outperforms the standard Euclidean approach in terms of shape-based classification of morphological disorders. Y1 - 2018 U6 - https://doi.org/10.1016/j.media.2017.09.004 VL - 43 IS - 1 SP - 1 EP - 9 ER -