Gallery of medical devices

Numerical modelling and experimental investigation of drug release from layered silicone matrix systems

Medical devices and polymeric matrix systems that release drugs or other bioactive compounds are of interest for a variety of applications. The release of the drug can be dependent on a number of factors such as the solubility, diffusivity, dissolution rate and distribution of the solid drug in the matrix. Achieving the goal of an optimal release profile can be challenging when relying solely on traditional experimental work. Accurate modelling complementing experimentation is therefore desirable. Numerical modelling is increasingly becoming an integral part of research and development due to the significant advances in computer simulation technology. This work focuses on numerical modelling and investigation of multi-layered silicone matrix systems. A numerical model that can be used to model multi-layered systems was constructed and validated by comparison with experimental data. The model could account for the limited dissolution rate and effect of the drug distribution on the release profiles. Parametric study showed how different factors affect the characteristics of drug release. Multi-layered medical silicone matrices were prepared in special moulds, where the quantity of drug in each layer could be varied, and release was investigated with Franz-diffusion cell setup. Data for long-term release was fitted to the model and the full depletion of the system predicted. The numerical model constructed for this study, whose input parameters are the diffusion, effective dissolution rate and dimensional solubility coefficients, does not require any type of steady-state approximation. These results indicate that numerical model can be used as a design tool for development of controlled release systems such as drug-loaded medical devices.

Rings and things on upper extremity radiographs of emergency patients

Rings, intravenous lines, and other objects on the injured upper extremities of trauma patients are frequently overlooked by radiology and emergency department (ED) personnel. This can impair proper radiologic evaluation of the injured extremity as well as negatively affect the quality of the patient's treatment. A 1-week sample of radiographs of injured upper extremities from the ED of University Medical Center (UMC), Tucson, Arizona, showed that 20% of the studies (19 of 95) contained at least one object on the injured upper extremity, but only one radiology report (1.1%) mentioned such an object. A review of 2489 upper extremity ED radiology reports from January to June 2002 showed only 47 reports (1.9%) that mentioned the presence of an overlying object. It is important to educate radiology department and ED personnel to remove upper extremity jewelry and place necessary medical devices on noninjured extremities.