Article
Refine
Year of publication
- 2003 (74) (remove)
Institute
- Fachbereich Medizintechnik und Technomathematik (32)
- INB - Institut für Nano- und Biotechnologien (24)
- IfB - Institut für Bioengineering (13)
- Fachbereich Chemie und Biotechnologie (7)
- Fachbereich Luft- und Raumfahrttechnik (7)
- Fachbereich Elektrotechnik und Informationstechnik (6)
- Fachbereich Energietechnik (6)
- Fachbereich Wirtschaftswissenschaften (6)
- Fachbereich Maschinenbau und Mechatronik (5)
- Fachbereich Bauingenieurwesen (2)
Language
- English (74) (remove)
Document Type
- Article (74) (remove)
Keywords
- Analysis (1)
- Cement infiltration (1)
- Einspielen (1)
- Einspielen <Werkstoff> (1)
- Experiment (1)
- MST (1)
- Mikrosystemtechnik (1)
- Osteoporose (1)
- Osteoporosis (1)
- Permeability (1)
- Permeabilität (1)
- Ratchetting (1)
- VM (1)
- Vertebroplastie (1)
- Vertebroplasty (1)
- Virtuelle Maschine (1)
- Viscous flow (1)
- Viskose Strömung (1)
- Viskosität (1)
- Zug-Druck Belastung (1)
- ratchetting (1)
- shakedown (1)
- tension–torsion loading (1)
- virtual clean room (1)
Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm4/N.s) reduced to approximately 63% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.
Within the Crystal Clear Collaboration four centres are developing 2nd generation high performance small animal PET scanners for different kinds of animals and medical applications. The first prototypes are PMT-based systems including depth of interaction (DOI) detection by using a phoswich layer of LSO and LuYAP. The aim of these simulation studies is to optimize sensitivity and spatial resolution of given designs, which vary in FOVs caused by different detector configurations (ring/octagon) and sizes. For this purpose the simulation tool GEANT3 (CERN) was used. The simulations have shown that all PMT designs with one-to-one coupling of crystals have a very nonlinear axial sensitivity profile. By shifting every other PMT 1/4 of a PMT length in axial direction the sampling of the FOVs became more homogeneous. At an energy threshold of 350keV the regression coefficient increases from 0.818 for the non-shifted to 0.993 for the shifted design. Simulations of a point source centred in the FOV (threshold: 350keV) resulted in sensitivities of 4.2% for a 4×20PMT (LSO/LuYAP a 10mm) and 3.8% for a 4×16PMT (LSO/LuYAP a 8mm) ring design. The 3D-MLEM reconstruction of a point source shows the enormous improvement of resolution using a crystal double layer with DOI (3.1mm at 40mm from CFOV) instead of a 20mm single layer (11.9mm).
Within the Crystal Clear Collaboration (CCC), four centers are developing second generation high performance small animal positron emission tomography (PET) scanners for different kinds of animals and medical applications. The first prototypes are photomultiplier tube (PMT)-based systems including depth of interaction (DOI) detection by using a phoswich layer of lutetium oxyorthosilicate (LSO) and lutetium yttrium aluminum perovskite (LuYAP). The aim of these simulation studies is to optimize sensitivity and spatial resolution of given designs, which vary in fields of view (FOVs) caused by different detector configurations (ring/octagon) and sizes. For this purpose the simulation tool GEANT3 (CERN, Geneva, Switzerland) was used.