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Biomedical subjects

F K Chang

Publications and source records attributed to F K Chang.

11 recordsLinked to original sources
PubMed1999

Operating theater blood transaction system. A "virtual" blood transfusion service that brings the blood bank to the operating table.

We describe an operating theater blood transaction system (OTBTS) that is a novel computer software system incorporating electronic crossmatch and the concept of a "self-service" blood banking system in the operating theater. Through this system, the surgeons and the anesthetists can issue blood units for intraoperative transfusion for the patients with a negative antibody screen without the need for a porter service or pneumatic tube system. Since implementation of the OTBTS, the time for obtaining compatible blood for intraoperative transfusion has been reduced from 20 to 30 minutes to around 1 minute. Furthermore, the crossmatch-transfusion ratio was reduced to 1.05. The 23% of patients who required extra blood units (i.e., more than originally anticipated) during surgery further benefited from the system. The blood stock reserved for patients undergoing surgery was reduced by 20%. Therefore, the OTBTS is a system that can greatly enhance the efficiency and safety of intraoperative transfusion and can also save workforce resources.

Blood Banks↗
PubMed1998

Composite hip prosthesis design. II. Simulation.

An investigation was performed to study the mechanical performance of fiber-reinforced composite hip prostheses. In Part I of the study, a three-dimensional finite element code was developed for analyzing a composite hip prosthesis in a femur. The material properties of the composite were treated as anisotropic and inhomogeneous while the properties of the femoral bone were treated as anisotropic and homogeneous. All the materials were assumed to behave linear-elastically. Thermoplastic graphite/PEEK material was selected for the study. No slippage was assumed at the interface between the implant and the surrounding femoral bone. In Part II, numerical simulations were performed using the code to study the performance of a composite prosthesis in the femur. The stress/strain distributions, micromotions, and strain energy density of the surrounding femoral bone were evaluated and found to be related to initial fixation and long-term stability of the prosthesis in the femur. Numerous fiber orientations were studied, and the results of the calculations were compared with those generated from a prosthesis made of cobalt chrome and Ti-6Al-4V titanium alloys. Based on the analysis, it was shown that compared to conventional metallic implants more favorable stresses and deformations could be generated in the femur using composite implants. In addition, by changing fiber orientations according to femoral loads, a composite implant could be designed specifically for the left or the right femur.

Computer Simulation↗
PubMed1998

Composite hip prosthesis design. I. Analysis.

An investigation was performed to study the mechanical performance of fiber-reinforced composite hip prostheses in a femur. The main objective of the study was to evaluate the effect of fiber orientation of a composite femoral implant on the response of the surrounding femoral bone. A three-dimensional finite element analysis was developed for analyzing a composite implant in the femur. A three-dimensional composite element was proposed to take into account ply drop-off due to a change of cross-section of the composite implant. The element could accommodate multidirectional layers and tapered composites. The material properties of the composite were treated as anisotropic and inhomogeneous while the properties of femoral bone were treated as anisotropic and homogenous. All the materials were assumed to behave linear-elastically. The thermoplastic graphite/PEEK material system was selected for the study. In this presentation, as the first part of the study, the development of the finite element analysis will be described. Numerical calculations were generated and compared with existing data and numerical results available from studies related to metal hip prostheses in the literature. Experiments on the composite hip implants were also conducted for further verification of the analysis and the computer simulations. In Part II, using the finite element code, an extensive study was performed to evaluate the stress/strain distributions, micromotions, and strain-energy density of the surrounding femoral bone, which have been related to initial fixation and long-term stability of the prosthesis in a femoral bone. Numerous fiber orientations were studied, and results of the calculations were compared with those generated by the prosthesis made of cobalt alloy and titanium alloy.

Hip Prosthesis↗
PubMed1990

Stiffness and strength tailoring of a hip prosthesis made of advanced composite materials.

This work is concerned with the design of hip prostheses using advanced fiber reinforced composite materials. The major focus of the study is to evaluate how the stiffness and strength of composite hip prostheses can be affected by variations in ply orientation and stacking sequence for a selected manufacturing method. This investigation involved both analytical and experimental work. An analytical model was developed which consists of a stress analysis and a failure analysis. A finite element program was developed during the course of the investigation for analyzing stresses, strains, and deformations of composite stems with a simplified configuration. Failure and mode of failure were predicted by appropriately selected failure criteria. Experiments were also performed on T300/976 graphite/epoxy composites to verify the analysis and the computer calculations. Both testing and analysis accounted for the various combinations of in-plane and out-of-plane (torsion) loading that can act on the prosthetic hip. Simplified composite stems with a 120 layer thickness were fabricated and tested. An excellent agreement was found between the measured strain data and the numerical calculations. Using the program, parametric studies were performed. It was found that an optimal design of hip stems can be achieved by using advanced fiber-reinforced composite materials, but great care must be taken when selecting the appropriate ply orientation and stacking sequence for a chosen fabrication method.

Biocompatible Materials↗
PubMed1987

Demonstration of persistent left superior vena cava by first pass radionuclide angiography.

A case of the left superior vena cava draining to the coronary sinus without associated intracardiac shunt was initially demonstrated by first pass radionuclide angiography. The patient had atypical chest pain for 8 years, and had sick sinus syndrome with a long cardiac pause. Cardiac catheterization confirmed this diagnosis, and a transvenous pacemaker was successfully implanted through the left superior vena cava.

Aged↗
PubMed1987

Demonstration of intracardiac tumor and its associated hemodynamic derangement by radionuclide angiography.

A case of malignant lymphoma primarily involving the heart is reported for the first time in which the tumor per se and its accompanying hemodynamic abnormalities were demonstrated by radionuclide angiography (RNA). The patient had severe and progressive failure of the right side of the heart of obscure origin. The tumor was pathologically proven to have involvement of the pericardium, right atrium, and right ventricle, causing significant tricuspid and pulmonic obstruction.

Heart Failure↗