Biomedical subjects
Publications and source records attributed to V Urban.
In rare cases the usage of the internal thoracic vessels as recipient vessels in reconstructive surgery of the head and neck region with free tissue transfer is a challenging but valid alternative if local recipient vessels are unusable.
The deformed structure of silica-filled elastomers under uniaxial strain has been investigated using a combination of both small angle x-ray scattering and small angle neutron scattering methods. Using an extraction procedure and taking into account the two-phase nature of these polymer-based composites, the single chain scattering behavior as well as filler properties could be obtained uniquely on identical samples. For the first time the deformation of the rubbery matrix on the length scale of the network chain in a filled rubber could be determined and therewith the importance of matrix overstrain for the mechanical properties was estimated. Additionally, the determination of filler deformation and filler destruction presents microscopic details of the mechanisms of filler networking and the stress-softening Mullins effect.
In this paper, the ordering in concentrated charge stabilized colloidal dispersions is considered. Despite the impressive Bragg reflections obtained for shear ordered dispersions by light (LS), small-angle neutron (SANS), and small-angle X-ray scattering (SAXS), a number of open questions remain. Sheared dispersions are usually ordered in layers. For such systems, two questions arise: (1) What is the structure in a layer? (2) What is the stacking structure perpendicular to the layers? The second question requires a method to determine the structure perpendicular to the layers. Although originally interested only in structural aspects, we were forced to consider different methods. Two methods are treated both applicable to neutron and X-ray scattering from concentrated dispersions. One has been used by physicists and chemists for many years to determine the structure of crystals by sample rotation. In colloid science, we have used it previously in neutron and X-ray scattering. A second method is treated here which can be applied in small-angle scattering from a Couette cell. It gives the scattering intensity in a certain direction without sample rotation. Although very useful with the Couette cell, it cannot be found in any of the well-known references on colloid science. A theoretical explanation and experimental examples obtained by synchrotron X-ray scattering from a Couette cell are given in the paper.
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We investigate the microscopic mechanisms responsible for microdomain alignment in block copolymer solutions exposed to an electric field. Using time-resolved synchrotron small-angle x-ray scattering, we reveal two distinct processes, i.e., grain boundary migration and rotation of entire grains, as the two dominant microscopic mechanisms. The former dominates in weakly segregating systems, while the latter is predominant in strongly segregated systems. The kinetics of the processes are followed as a function of polymer concentration and temperature and are correlated to the solution viscosity.
Small-angle x-ray scattering (SAXS) patterns are recorded from thin breast tissue samples containing healthy and cancerous regions. The SAXS patterns are compared with histo-pathological observations. The information available from SAXS is reviewed, and a model for scattering from collagen is presented. Scattering patterns of collagen at regions far from the tumours are essentially different from those at tumours. The axial period of collagen fibrils is 65.0 +/- 0.1 nm in healthy regions, and 0.3 nm larger in cancer-invaded regions. The average intensity of scattering from cancerous regions is an order of magnitude higher than the intensity from healthy regions. This is interpreted to arise from an increase of the specific surface area of the scatterers, which is due to a disruption of the molecular and supra-molecular structures in cancerous regions and invasion of new types of cells. The differences of the SAXS patterns are large and distinctive enough to suggest that these phenomena may be utilized in mammography.
BACKGROUND: The aim of this retrospective study is to evaluate the difference in postoperative intraocular pressure (IOP) control, number of antiglaucoma medications and visual acuity (VA) between combined phacoemulsification and trabeculectomy (Glaucoma triple) surgery and two-stage procedures with trabeculectomy first and cataract extraction later. PATIENTS AND METHODS: Two groups of glaucoma patients were assessed: In group 150 consecutive patients undergoing combined phacoemulsification and trabeculectomy were enrolled. In group two, 51 consecutive patients were included, that had undergone trabeculectomy first and cataract surgery later. The mean interval between the two procedures was 3.2 years, 35/51 patients (71%) underwent conventional extracapsular cataract extraction, the other 16 patients (29%) had phacoemusification via clear cornea incision. RESULTS: One year postoperative both groups revealed a significant IOP reduction. IOP-reduction was significantly better in the two-stage group one year after trabeculectomy (12.8 +/- 4.0 mm Hg) and one year after cataract extraction (14.0 +/- 2.8 mm Hg) as compared to the combined surgery group (15.3 +/- 4.0 mm Hg). Kaplan-Meier survival analysis revealed a 90% success-rate 12 months after trabeculectomy only as compared to 65% success-rate in the combined surgery group. The number of antiglaucoma medications was significantly reduced in both groups. One year after cataract surgery no difference in VA could be seen between the two groups. CONCLUSIONS: If medically uncontrolled glaucoma with advanced optic nerve head changes in patients with coexisting glaucoma and cataracts is the main indication for surgery, a two-stage procedure (i.e. trabeculectomy first, cataract extraction later) yields better long-term IOP control. If glaucoma is medically controlled with a simple regimen, conjunctiva-sparing cataract surgery may be the treatment of choice. In all other cases of coexisting glaucoma and cataract combined phacoemulsification and trabeculectomy (Glaucoma triple) is preferrable, either performed through a single incision or as two separate procedures in the same session (i.e. trabeculectomy from above, phacoemulsifiaction via clear cornea from temporal).
This paper describes a test prototype for precision robot-assisted surgery using a hexapod operating robot and a movable operating cockpit for tactile feedback. The objective of the work described is twofold: 1, to evaluate the use of hexapod robots for precisely manipulating endoscopes and surgical instruments in submillimeter surgery; 2, to test a new user interface concept based on tactile feedback. Based on the principle of a flight simulator, the aim is to give the surgeon motion cues in addition to the endoscope image, to assist his spatial orientation. The paper gives a detailed description of the system components and the potential applications.
This paper describes experiments with a voice-controlled robot system to be used in endoscopic neurosurgery. The robot was a modified version of the robot described in previous publications of the group at Fraunhofer IPA and HSK. To control the robot a voice-controlled user interface was developed. The experiments were conducted on cadavers for three standard approaches in neuroendoscopy. The goal was to gain experience with a voice-controlled user interface and also with the set-up and use of the robotic system under clinical conditions. The results indicate that modifications to the robot and user interface are necessary. However the overall feasibility of the application was demonstrated.
The better understanding of the systems of the human body and their specific functions has led to minimally invasive and microsurgical procedures being carried out on an ever smaller scale. New therapies will require precision of 10 microm or better, which will only be achievable with robotic teleoperators. Experience with existing robot-assisted surgery systems shows that the human-machine interface is a critical component for acceptance of this technology, but no universally satisfactory interface has yet been found. Therefore, this article investigates a new concept based on kinesthetic motion feedback and presents details of the implementation of a first prototype.
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This paper describes a test prototype for precision robot-assisted surgery using a hexapod operating robot and a movable operating cockpit. The objective of the work described is twofold: 1) To evaluate the use of hexapod robots for precisely manipulating endoscopes and surgical instruments in sub-millimeter surgery. 2) To test a new user interface concept based on motion feedback. This paper gives an overview of the system components and the user interface concept, and reports results from initial tests. Finally, the paper investigates potential applications and areas for further development.
In January 1991, an image transfer unit was developed and installed in the neurosurgical department of the University in Mainz. The system provides an image transfer of patient data via fibreoptic cable networks (VBN), ISDN, and public telephone line. In the following 4 years, 432 consultations were recorded. Nine departments were linked within this system. They provided an emergency out-patient department for primary treatment and radiology. The lack of a neurosurgical department in these clinics was made up for by the image transfer system. In these rural medical departments, teleconsultation improves the care of daily routine neurosurgical cases, as well as in emergency cases. There is also a decrease of costs due to teleconsultation. The image transfer via simple public telephone line was sufficient.
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Intra-operative SEP monitoring was performed in nine patients with cervical syringomyelia undergoing myelotomy and syringo-endoscopy. Several cortical and subcortical SEP components were evaluated. Pathological latency shifts of brain stem P14 were seen in two patients; other SEP components did not worsen nor recover intra-operatively. The clinical and pathophysiological significance of the data is briefly discussed.
The management of septated, chambered syringomyelia has until now been problematic because the usual operative methods cannot secure drainage of all chambers of the cavity. The development of a flexible neuroendoscope affords the possibility to perforate the septa under visual control which subdivide the cavity. We present our experiences with 11 cases of septated syringomyelia, which have been operated upon using a flexible neuroendoscope.
In 500 mamma needle biopsies that were cytologically examined we found a precision of 87.4%, with 2.6% false negative, and 6.2% false positive results. In 19 cases a cytological diagnosis was not possible resulting in a sensitivity of 0.94 and a specificity of 0.86. False positive findings were due to misinterpretations of the cytological pictures, as were also false negative findings. In the latter cases sampling mistakes could also be the reason. Cytological diagnostic should only be made using triple diagnostic technique since the methods are complementary to each other in respect to their diagnostic security. Practical experience in the puncturing technique as well as an experienced cytologist are prerequisites using this method successfully as a diagnostic tool.