Biomedical subjects

M H Neumann

Publications and source records attributed to M H Neumann.

3 recordsLinked to original sources

PubMed2000

Bootstrapping neural networks.

Knowledge about the distribution of a statistical estimator is important for various purposes, such as the construction of confidence intervals for model parameters or the determination of critical values of tests. A widely used method to estimate this distribution is the so-called boot-strap, which is based on an imitation of the probabilistic structure of the data-generating process on the basis of the information provided by a given set of random observations. In this article we investigate this classical method in the context of artificial neural networks used for estimating a mapping from input to output space. We establish consistency results for bootstrap estimates of the distribution of parameter estimates.

Artifacts↗

PubMed1999

A systematic review of treatment modalities for primary basal cell carcinomas.

OBJECTIVE: To systematically review the literature for studies reporting on recurrence rates of basal cell carcinomas (BCCs) after different therapies. DESIGN: We reviewed all studies published in English, French, German, Dutch, Spanish, or Italian between 1970 and 1997 that prospectively examined recurrence rates for at least 50 patients with primary BCCs observed for at least 5 years after treatment with Mohs micrographic surgery, surgical excision, curettage and electrodesiccation, cryosurgery, radiotherapy, immunotherapy with interferon or fluorouracil, or photodynamic therapy. SETTING: Department of Dermatology, University Hospital Maastricht, Maastricht, the reference center for dermatologic oncology and Mohs micrographic surgery in the Netherlands. MAIN OUTCOME MEASURES: The recurrence rates after different therapies for BCCs, resulting in the development of guidelines for the treatment of these disorders. RESULTS: Of 298 studies found in several electronic databases, only 18 met the requirements and could be used for analysis. Tumors treated with Mohs micrographic surgery show the lowest recurrence rates after 5 years, followed in order by those treated with surgical excision, cryosurgery, and curettage and electrodesiccation. CONCLUSIONS: Recurrence rates for different therapies could not be compared because of a lack of uniformity in the method of reporting, so evidence-based guidelines could not be developed. We surmise that Mohs micrographic surgery should be used mainly for larger, morphea-type BCCs located in danger zones. For smaller BCCs of the nodular and superficial types, surgical excision remains the first treatment of choice. Other treatment modalities can be used in patients in whom surgery is contraindicated. Immunotherapy and photodynamic therapy are still investigative.

Basal Cell Carcinoma↗

PubMed1998

The effect of addition of calcipotriol ointment (50 micrograms/g) to acitretin therapy in psoriasis.

Our purpose was to find out whether the addition of calcipotriol ointment (50 micrograms/g) to systemic treatment with acitretin produces additional therapeutic effects and thereby an acitretin-sparing effect, and further to investigate the safety and tolerability of this combination. A multicentre, randomized, double-blind placebo-controlled study was designed. Patients were randomized to receive calcipotriol or placebo. All patients were treated with a starting dose of 20 mg acitretin per day and doses were adjusted at 2-weekly intervals with increments of 10 mg per day up to a maximum of 70 mg per day. The dose requirement for acitretin, clinical signs and adverse events were recorded. Seventy-six patients were randomized to treatment with calcipotriol 50 micrograms/g ointment twice daily and 59 patients to treatment with the vehicle only twice daily. Clearance or marked improvement was achieved by 67% of the patients in the calcipotriol group and by 41% of the patients in the placebo group (P = 0.006). Calcipotriol treatment proved to have a statistically significant additional effect to acitretin on the Psoriasis Area and Severity Index, redness, thickness and scaliness as compared with placebo. Clearance or marked improvement was achieved with a statistically significantly lower cumulative dose of acitretin by the patients in the calcipotriol group as compared with the placebo group. The number of patients reporting adverse events was pronounced and largely related to acitretin. No significant differences were observed between the two treatment groups with respect to adverse events. Laboratory assessments were essentially normal. The addition of calcipotriol ointment to acitretin treatment contributes to the efficacy, reduces the cumulative dose of acitretin to reach marked improvement or clearance, and is well-tolerated and safe.

Acitretin↗