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Biomedical subjects

R Witte

Publications and source records attributed to R Witte.

11 recordsLinked to original sources
PubMed2006

A comparison between glass/polyimide and titanium/polyimide microjoint performances in cerebrospinal fluid.

Assessment of neural biocompatibility requires that materials be tested with exposure in neural fluids. Laser bonded microjoint samples made from Ti coated glass substrate and polyimide film (GPI) and titanium foil and polyimide film (TIPI) were evaluated for mechanical performance before and after exposure in artificial cerebrospinal fluid (CSF) for two, four, and 12 weeks at 37 degrees C. These samples represent a critical feature, i.e., the microjoint-a major weakness in the bioencapsulation system. Both material systems showed initial degradation up to 4 weeks which then stabilized afterwards and retained similar strength until 12 weeks. The TIPI system appears to exhibit better overall performance with less degradation compared to its as-received strength. The CSF exposed TIPI samples predominantly failed at the interface, while GPI samples had mixed glass and polyimide substrate and interface failure. The amount of glass failure decreases and interface failure increases with increase in CSF exposure time. The failure mechanism of the as-received (not exposed to CSF) GPI samples under tension was predominantly flexure type failure of the glass substrate.

Biocompatible Materials↗
PubMed2005

Laser bonded microjoints between titanium and polyimide for applications in medical implants.

Bioencapsulation of medical implant devices, and neural implant devices in particular, requires development of reliable hermetic joints between packaging materials that are often dissimilar. Titanium-polyimide is one of the biocompatible material systems, which are of interest to our research groups at Wayne State University and Fraunhofer USA. We have found processing conditions for successful joining of titanium with polyimide using near-infrared diode lasers or fiber lasers along transmission bonding lines with widths ranging from 200 to 300 microm. Laser powers of 2.2 and 3.8 W were used to create these joints. Laser-joined samples were tested in a microtester under tensile loading to determine joint strengths. In addition, finite element analysis (FEA) was conducted to understand the stress distribution within the bond area under tensile loading. The FEA model provides a full-field stress distribution in and around the joint that cause eventual failure. Results from the investigation provide an initial approach to characterize laser-fabricated microjoints between dissimilar materials that can be potentially used in optimization of bio-encapsulation design.

Equipment Failure Analysis↗
PubMed1996

Double-blind, randomized study of primary hormonal treatment of stage D2 prostate carcinoma: flutamide versus diethylstilbestrol.

PURPOSE: Patients with stage D2 prostate carcinoma are often treated initially with hormones to decrease endogenous testosterone. Therapy with diethylstilbestrol (DES), leuprolide, or bilateral orchiectomy has been reported to be equivalent. DES is the cheapest preparation, but has the potential for serious cardiovascular or thromboembolic complications. Flutamide is a novel antiandrogen with fewer side effects. PATIENTS AND METHODS: The Eastern Cooperative Oncology Group (ECOG) conducted a double-blind, randomized study to compare the efficacy of flutamide (250 mg three times daily) to DES (1 mg three times daily) as the primary hormonal therapy for patients with stage D2 prostate cancer. Patients were stratified by performance status, disease sites, and history of cardiovascular disease at randomization. RESULTS: Forty-eight patients received DES and 44 flutamide. Patient characteristics were evenly distributed between the two treatments. The overall response rate was similar (DES, 62%; flutamide, 50%). Grade III or worse cardiovascular or thromboembolic toxicity developed in 33.3% of patients on DES and in 17.6% on flutamide (P = .051). Other toxicities were similar between the two treatment arms. However, DES produced significantly longer time to treatment failure (26.4 v 9.7 months, P = .016) and longer survival than flutamide (43.2 v 28.5 months, P = .040). CONCLUSION: As the primary hormonal therapy for stage D2 prostate cancer, DES caused more serious cardiovascular or thromboembolic complications than flutamide. Despite this, flutamide was not as active an initial agent as DES. However, the effectiveness of flutamide in conjunction with other agents compared with DES remains undetermined, and the optimal initial hormone therapy of stage D2 prostate cancer requires further studies.

Administration, Oral↗
PubMed1993

Patchwork access. Primary care in EDs on the rise.

It's been long known that EDs in the nation's largest cities routinely provide non-emergent primary care. But a new study by the AHA and several allied hospital associations has found that a very high proportion of ED visits in each of the four communities studied could have been handled outside the ED.

American Hospital Association↗
PubMed1991

Long-term survival of patients treated with combination chemotherapy for metastatic breast cancer.

Long-term survival of patients with metastatic breast cancer treated on two prospective stratified randomised trials has been analysed. Patients on study B122 received either cyclophosphamide, methotrexate and 5-fluorouracil (CMF) or cyclophosphamide, doxorubicin and 5-fluorouracil (CAF). On study B141 patients received CAF or mitolactol (dibromodulcitol), doxorubicin and vincristine alternating after every three cycles with three cycles of CMF (DAV/CMF). Long-term follow-up of 172 patients showed no significant survival difference (in multivariate regression models) for treatment with either CMF vs. CAF or CAF vs. DAV/CMF. The difference in median survival times between CMF and CAF showed a trend in favour of CAF. Advances in the management of metastatic breast cancer in postmenopausal women obtained by doxorubicin regimens have had a small but measurable impact on survival, but known patient discriminants were not overridden by the treatment regimens investigated in these studies.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Integrated Academic Information Management Systems (IAIMS). Part II. Planning and implementing integrated information services. IAIMS infrastructure: technological base.

The IAIMS concept calls for the logical integration of information derived from databases in the functional areas of administration, clinical care, education, libraries, and research. To accomplish this task a technological base must be established. It is suggested that such an infrastructure will consist of a systems component, the linked databases component, and a management component. An IAIMS should rapidly evolve into an information utility and, within a decade, provide a knowledge management system.

Academic Medical Centers↗