Biomedical subjects

G S Beaupre

Publications and source records attributed to G S Beaupre.

6 recordsLinked to original sources

PubMed1998

A new frame-based registration algorithm.

This paper presents a new algorithm for frame registration. Our algorithm requires only that the frame be comprised of straight rods, as opposed to the N structures or an accurate frame model required by existing algorithms. The algorithm utilizes the full 3D information in the frame as well as a least squares weighting scheme to achieve highly accurate registration. We use simulated CT data to assess the accuracy of our algorithm. We compare the performance of the proposed algorithm to two commonly used algorithms. Simulation results show that the proposed algorithm is comparable to the best existing techniques with knowledge of the exact mathematical frame model. For CT data corrupted with an unknown in-plane rotation or translation, the proposed technique is also comparable to the best existing techniques. However, in situations where there is a discrepancy of more than 2 mm (0.7% of the frame dimension) between the frame and the mathematical model, the proposed technique is significantly better (p < or = 0.05) than the existing techniques. The proposed algorithm can be applied to any existing frame without modification. It provides better registration accuracy and is robust against model mis-match. It allows greater flexibility on the frame structure. Lastly, it reduces the frame construction cost as adherence to a concise model is not required.

Algorithms↗

PubMed1996

Letter to the editor.

Explore the source record for details and available documents.

Adaptation, Physiological↗

PubMed1996

Refracture risk after plate removal in the forearm.

In this study we report the results of a retrospective examination of 401 patients who had 459 plates removed from the forearm after successful union. Data were assembled from seven studies that have appeared in the literature. The authors of these seven studies were contacted and asked to complete a detailed questionnaire concerning refracture and the specific type of plating hardware used. The plating systems used varied according to plate design [dynamic compression plate (DCP), semi-tubular, one-third tubular], plate material stainless steel (SS), titanium/titanium alloy (Ti), and screw size (3.5 mm, 4.5 mm). A total of 37 refractures occurred in 29 patients. There were no refractures after the removal of 76 stainless steel, one-third tubular plates; 10 refractures after the removal of 177 stainless steel, small fragment DCP; six refractures after the removal of 91 stainless steel, semitubular plates; and 20 refractures after the removal of 96 stainless steel, narrow, large-fragment DCP. The corresponding refracture rates are: 0.0, 5.6, 6.6, and 21%, respectively. There were insufficient numbers of titanium or titanium alloy plates to calculate refracture rates for plates made from these materials. The refracture risk associated with the narrow, large-fragment DCP system was significantly greater than with either the small-fragment DCP system (p < 0.005) or the one-third tubular system (p < 0.001). There was also a trend for greater risk (p = 0.057) associated with the large-fragment DCP system in comparison with the semitubular system.

Bone Plates↗

PubMed1985

Finite element analysis of a three-dimensional open-celled model for trabecular bone.

Based on a regular array of cubic unit cells, each containing a body-centered spherical void, we created an idealized three-dimensional model for both subchondral trabecular bone and a class of porous foams. By considering only face-to-face stacking of unit cells, the inherent symmetry was such that, except at the surface, the displacements and stresses within any one unit cell were representative of the entire porous structure. Using prescribed displacements the model was loaded in both uniaxial compressive strain and uniaxial shear strain. Based on the response to these loads, we found the tensor of elastic constants for an equivalent homogeneous elastic solid with cubic symmetry. We then compared the predicted modulus with our experimental values for bovine trabecular bone and literature values for an open-celled latex rubber foam.

Bone and Bones↗

PubMed1983

Multiaxial strength characteristics of trabecular bone.

Bovine trabecular bone specimens were tested in multiaxial stress, including pure shear, in a special test device. Shear strength was proportional to apparent density to the exponent 1.65, in approximate agreement with theoretical and experimental studies on the shear strengths of porous foams. The mean shear strength was 6.60 +/- 1.66 MPa, after normalizing for apparent density. This compares well with normalized shear strengths from Saha and Gorman's (1981) study on human femora. A scanning electron microscope study indicated random trabecular architecture and a complex fracture mechanism at the level of the individual trabecular struts. Hoffmann's (1967) 3-D isotropic failure criterion was applied to the multiaxial test data, along with data from uniaxial compression tests, indicating a compressive strength approximately three times the tensile strength.

Animals↗

PubMed1983

Monitoring fracture site properties with external fixation.

An in-vitro system has been devised to monitor the properties of an idealized fracture site immobilized with a Hoffman-Vidal external fixator. A dial gage was used to measure the relative pin displacements under controlled axial loading. The displacement measurements were then used in conjunction with a finite element model to predict the modulus of an idealized fracture site. Five fracture sites made of neoprene disks of different mechanical properties were monitored in order to simulate the increasing modulus of a healing fracture. Good agreement was observed between directly measured mechanical properties of the neoprene and those inferred from the combined finite element and pin displacement tests.

Aluminum↗