Technology and Health Care - Volume 14, issue 6

Authors: Sandilos, P. | Antypas, C. | Paraskevopoulou, C. | Kouvaris, J. | Vlachos, L.

Article Type: Research Article

Abstract: Port films are used in radiotherapy for visual evaluation of the radiation fields and subsequent quantitative analysis. Common port films suffer from poor image quality compared to the simulator-diagnostic films and is desirable to determine the appropriate exposure required for the best image contrast. The aim of this work is to generate technique charts for the Kodak EC-L film screen system for use in a 6MV x-ray beam. Three homogeneous water phantoms were used to simulate head-neck, thorax and abdomen dimensions of adult human, correspondingly. The film screen system was calibrated in a 6MV x-ray beam and under various irradiation …conditions. The film screen system behavior was studied as a function of phantom thickness, field size and air gap between the phantom and the film screen system. In each case the optimum film exposure which produces the maximum image contrast was determined. The generated technique charts for the EC-L film screen system and for a 6 MV x-ray beam are used in our radiotherapy department for daily quality assurance of the radiotherapy procedure. Show more

Keywords: Technique charts, portal localization, contrast-enhanced film-screen systems

DOI: 10.3233/THC-2006-14601

Citation: Technology and Health Care, vol. 14, no. 6, pp. 467-472, 2006

Authors: Citak, M. | Kendoff, D. | Wanich, T. | Pearle, A. | Singhai, R. | Krettek, C. | Hüfner, T.

Article Type: Research Article

Abstract: Computer-assisted treatments have become increasingly common. Consequently, there is an increased desire for navigation methods with simplified workflow. Anatomic-based pair-point registration is often mentioned as a source of error. Alternatively, the use of preoperatively implanted markers for registration remains complex. The self-acting registration of Iso-C-3D at the moment of data acquisition can reduce essential errors. The aim of this study was to evaluate the effect of reference placement on accuracy, and to determine the maximum acceptable distance between the reference and a given isocentre. This study demonstrates the interdependence of the reference distance on the region of interest (ROI). The …mean error of registration amounts to 0.04 mm (0.04–0.05 mm) up to a distance of 200 mm and beyond 0.25 mm (0.24–0.26) for distances beyond 200 mm. The accuracy was significantly lower (p<0.0001) with a distance more than 200 mm. For optimal accuracy when utilizing navigation for pelvic and long bone surgery, the reference base should not been placed at a distance more than 200 mm from the isocentre of interest. Show more

Keywords: Iso-C 3D navigation, precision, registration, computer assisted orthopaedic surgery, reference base

DOI: 10.3233/THC-2006-14602

Citation: Technology and Health Care, vol. 14, no. 6, pp. 473-478, 2006

Authors: Ketata, Hajer | Krichen, Abdelkader | Kharrat, Mohamed | Dammak, Maher

Article Type: Research Article

Abstract: An experimental apparatus has been developed to study the mechanical response of Total Knee Replacement (TKR) prosthesis under compression loading test (Tibial HDPE component and femoral Vitallium component). Analysis of experimental results indicates that the load-displacement curve depends on the initial contact location. The position of this curve varies between two curves of lower and higher stiffness. Experimental compression loading curve for femoral part resting on flat HDPE is located between the extreme curves. This result allows us to model load-displacement curve of TKR prosthesis under compression loading using femoral component resting on flat polyethylene surface. For simple contact geometry …of spherical cap on flat HDPE specimen, Hertz elastic theory can be used to describe the load displacement curve for loads under 635 N. This value corresponds to the load which induces plastic flow of polyethylene. In the case of femoral component on flat HDPE specimen, Hertz elastic theory can be considered for loads under 800 N. Finite element 2D is also used to model the compression load displacement curve for femoral component resting on flat HDPE specimen. The finite element results are similar to the Hertz elastic theory analysis for compression loading under 1200 N. Damage of tibial component can be related to the critical load which induces plastic flow of polyethylene. This load depends on the contact geometry and can be estimated with the Hertz elastic theory. Show more

Keywords: Total Knee Replacement (TKR), UHMWPE (Ultra High Molecular Weigh Polyethylene), HDPE (High Density Polyethylene), compression, contact, Hertz, FE (Finite Element)

DOI: 10.3233/THC-2006-14603

Citation: Technology and Health Care, vol. 14, no. 6, pp. 479-487, 2006

Authors: Al-Waili, Noori S. | Butler, Glenn J. | Petrillo, Richard L. | Carrey, Zev | Hamilton, R.W. Bill

Article Type: Research Article

Abstract: This review addresses the many ways that hyperbaric oxygen (HBO2 ) has been found to mitigate immune reactions, many of which are involved in rejection of allograft transplants, and thus offers a rationale for its possible use as an adjunct to help preserve and protect transplanted tissues. Rejection may involve both immunological reactions of the lymphoid system, or lymphoid-independent damage from trauma or other factors, including reperfusion injury. Lymphoid-induced damage involves cellular elements such as CD4 and macrophage cell types, as well as both proinflammatory and inhibitory cytokines. Cytokines such as TNFs and interleukins activate T-cells and macrophages, resulting in …endothelial damage and its consequences. The immunosuppressive effects of HBO2 include suppression of autoimmune symptoms, decreased production of IL-1 and CD4 cells, and increased percentage and absolute number of CD8 cells. HBO2 normalizes cell-bound immunity and decreases the serum concentration of immune complexes. Studies have shown MHC class I expression to be altered when cultures were exposed to HBO2 , so as to become undetectable by monoclonal antibodies or cytotoxic T lymphocytes. HBO2 has been used in support of replanted rabbit ear grafts, spinal cord tissue transplants, dislocated young permanent teeth in children, replanting of fingers, free fibula reconstruction of segmental mandibular resections, autogenous free bone grafts, transplantations of the cornea, and liver transplants. In addition to its specific effects on the immune system, HBO2 improves tissue oxygenation, reduces free radical damage during reperfusion, maintains marginally ischemic tissue, and accelerates wound healing. These properties make HBO2 a promising intervention to be tested in transplantation recipients. Show more

Keywords: Hyperbaric oxygen, transplant, graft, immunosuppression, lymphocytes

DOI: 10.3233/THC-2006-14604

Citation: Technology and Health Care, vol. 14, no. 6, pp. 489-498, 2006

Authors: Birken, Thomas | Schubert, Jochen | Miekisch, Wolfram | Nöldge-Schomburg, Gabriele

Article Type: Research Article

Abstract: Statement of problem: Different implant geometries present different biomechanical behaviors and in this context, one arising question is how cuneiform implant geometry compares to clinical successful cylindrical threaded implant geometry. Purpose: The purpose of this work was to study stress distribution around cuneiform and cylindrical threaded implant geometries using three-dimensional finite element stress analysis taking the latter as a reference. Material and methods: A model was generated from a computerized tomography of a human edentulous mandible with implants placed in the left first premolar region. The model was supported by the mastication muscles and by temporomandibular …joint. A vertical load of 100N was applied at the top of each implant in the direction of their long axes. The mandibular boundary conditions were modeled considering the actual muscle supporting system. Taking muscle forces intensities and directions, balance moment equations were employed to assess the system equilibrium. Cortical and medullary bones were assumed to be homogeneous, isotropic and linearly elastic. Results: The analysis provided results for maximum (S1) and minimum (S2) principal stress and Von Mises (SEQV) stress field. For both geometries, the results showed concentration on one side of the neck, smooth stress distribution along the body and no considerable concentration at the apical area. Conclusion: Results showed similar stress distribution pattern for cuneiform and cylindrical threaded geometries. The stresses profiles along the implants length reproduced their morphology. In both occurred stress concentration at one side of the neck and no body or apical stress concentration. Show more

Keywords: Breath analysis, alveolar gas sampling, capnometry

DOI: 10.3233/THC-2006-14605

Citation: Technology and Health Care, vol. 14, no. 6, pp. 499-506, 2006

Authors: Fette, A. | Yonekawa, K. | Kothbauer, K.F.

Article Type: Research Article

Abstract: Our descriptive technical report on 7 children describes the microsurgical laser scalpel as an useful tool for removal of firm and soft lesions from a variety of delicate tissues. It combines precise atraumatic tissue dissection with immediate hemostasis while having no adverse side effects on adjacent and neighbouring tissues even through a limited surgical access.

Keywords: Microsurgical laser scalpel, delicate tissue operation, children

DOI: 10.3233/THC-2006-14606

Citation: Technology and Health Care, vol. 14, no. 6, pp. 507-513, 2006

Authors: Citak, M. | Haasper, C. | Kendoff, D. | Geerling, J. | Ortega, G. | Krettek, C. | Kfuri, M. | Hüfner, T.

Article Type: Research Article

Abstract: In recent years, many new tools and techniques have been developed in computer assisted orthopaedic surgery primarily with an industry led effort in software innovation and development. Only a few research and clinical projects have focused on intraoperative difficulties. A common operative challenge in computer assisted orthopaedic surgery is the positioning of the reference base. Rigid fixation of a dynamic reference base is essential in navigated surgery of the extremities. The aim of this study was to develop a minimal-invasive screw which could be placed effectively and efficiently with rotational stability during computer assisted orthopaedic surgery. …The minimal-invasive screw was initially evaluated in an artificial bone experiment. After successful results with the artificial bone experiment, it underwent testing in seven human cadaver thighs with ISO-C3D navigated drilling. Finally the screw was transferred into a clinical application during five foot surgeries. In 10 ISO-C3D navigated drillings, the lesions were targeted 100% of the drillings. A screw dislocation was not observed. In comparison to conventional one or two pin fixation systems, the newly designed small screw did not have any observed side effects such as artifacts. In addition, the screw generated less heterodyning than a conventional fixation system. The small screw design is an advantage in theatre. We believe the minimally-invasive screw allows the surgeon to use a tool that helps avoid common pitfalls from conventional fixation systems, and it may improve efficiency. Show more

Keywords: Reference fixation, pitfall, navigation, CAOS, orthopedic, trauma

DOI: 10.3233/THC-2006-14607

Citation: Technology and Health Care, vol. 14, no. 6, pp. 515-519, 2006

Authors: Fankhauser II, Franz

Article Type: Research Article

Abstract: Objective: To calibrate new dynamic light scattering (DLS) devices in defined solutions and post mortem porcine and human eyes. To examine all segments of the eye and to become familiar with the usage of the technique in living subjects. Methods, design: Three new DLS devices for the usage in patients were developed. Mono-disperse solutions, poly-disperse solutions, gels, post mortem porcine and human eyes as well as healthy volunteers were studied. The detected signals were inverted into autocorrelation functions. Results: We constructed three DLS devices appropriate for in vitro as well as in vivo examinations. In mono …disperse solution precise disintegration rates could be calculated. In poly-disperse solutions, in gel and in the vitreous the results did not correlate with movements of individual particles but we could calculate characteristics of the complete scattering system. In vivo measurements demonstrated that DLS can be used in all human eye segments. Discussion: DLS is a unique technique. With DLS the molecular composition of eye segments can be studied in living subjects. This can be used to understand the molecular basis of severe eye diseases. The presented data demonstrate that DLS delivers reproducible data from all eye segments. Conclusions: It is possible to study the molecular structures of eye segments in living subjects. The developed devices were proved successfully in vitro as well as in vivo. Limitations are the low specificity of DLS and its sensitivity to background noise. Now clinical studies are necessary to demonstrate potential diagnostic benefits of DLS in specific eye diseases. Show more

DOI: 10.3233/THC-2006-14608

Citation: Technology and Health Care, vol. 14, no. 6, pp. 521-535, 2006

Authors: Mahmood, Ali | Silbergleit, Allen

Article Type: Research Article

Abstract: Obesity continues to plague much of the western world. With the novel approach of laparoscopic sleeve gastrectomy (LSG), there are exciting results being reported in weight loss. One key problem in this patient population is hernia occurrences, particularly at the largest site where the specimen was retrieved. Using an interdisciplinary research design, a new technological breakthrough was proposed. A morcellator was introduced through the existing 15 millimeter (mm) incision to retrieve the resected portion of the stomach. This technology utilized widely by the obstetricians and gynecologists has been proven to retrieve specimens through smaller incisions fostering less pain, greater mobility, …earlier discharge from hospitals – ultimately greater patient care. When applied to general bariatric surgery this technology is human centered, is exceedingly affordable, practical yet very forward looking. The morcellator's role in bariatric surgery is drawn from interdisciplinary communication regarding human technology, however the use of this innovative device has the potential to revolutionize the removal of resected specimens. The application of the morcellator in this regards has never been utilized to our knowledge. Show more

Keywords: Morcellator, advances in human surgical technology, interdisciplinary research, laparoscopic sleeve gastrectomy, practical bariatric surgery

DOI: 10.3233/THC-2006-14609

Citation: Technology and Health Care, vol. 14, no. 6, pp. 537-539, 2006

Authors: Fierlbeck, J. | Hammer, J. | Englert, C. | Reuben, R.L.

Article Type: Research Article

Abstract: Articular cartilage integration has been described in in-vitro models, which compare mechanical to biochemical behaviour and histological analysis, respectively. The emphasis of these findings is mainly on the biochemical and histological analysis, rather than on the mechanical performance. The complex in vitro loading conditions and high deviations in the mechanical results due to the biological variance, make interpretations difficult. The aim of this study is to analyse and define the mechanical stress and strain distribution in a single lap configuration by means of an optical strain measurement system. Supportive finite element computation is performed to indicate the heterogeneous …stress strain distribution in the integration area. The optical failure analysis of the experiment reveals crack propagation through the integration area comparable to plane shear in fracture mode two. Using the optical strain measurement set up a direct estimation of the shear modulus is achievable by analysing the relative displacement within the bonded joint before the onset of delamination in the adhesive layer. This result lead to a better interpretation of the mechanical behaviour of articular cartilage integration in vitro. Show more

DOI: 10.3233/THC-2006-14610

Citation: Technology and Health Care, vol. 14, no. 6, pp. 541-547, 2006

Authors: Dendorfer, S. | Maier, H.J. | Hammer, J.

Article Type: Research Article

Abstract: Repetitive cyclic loading from daily activities is reported to induce fatigue damage and microcracking in bone structures. In terms of osteoporotic structures or in cases of serious damage of skeleton segments and the replacement by metallic implants the degree of damage due to cyclic loading will be even more pronounced. It is generally assumed that fatigue induced cracking and crack propagation essentially act as driving forces for complex physiological phenomena such as remodelling processes of bones and the adaptation to applied loads. In cases where the crack propagation rate exceeds the remodelling velocity, sudden and unexpected fracture of the bone …is observed. Especially for implant reinforced structures the deviation in stiffness to the bone material can induce high peak stresses and accelerate crack propagation. Whereas, for cortical bone the mechanical behaviour under cyclic loading is sufficiently described, only rough data are available for trabaecular structures. In this study the deformation behaviour of bovine vertebra trabecular bone specimens is investigated under cyclic compressive loading. A powerlaw relationship was found between the applied load ratio and cycles to failure. A linear decrease of maximum, integral strains at failure with increasing applied load ratio was observed. Optical deformation measurement of the surface strains revealed that low strains (0–1 increasing applied load ratio whereby the higher strains behave directly opposite. This indicates that different failure mechanisms are acting at low cycle and high cycle fatigue, respectively. Show more

DOI: 10.3233/THC-2006-14611

Citation: Technology and Health Care, vol. 14, no. 6, pp. 549-556, 2006