Dynamics of pigmentation induction by repeated ultraviolet exposures: dose, dose interval and ultraviolet spectrum dependence.

Background: The dynamics of ultraviolet (UV)-induced melanogenesis have been well characterized for single UV exposures. However, our knowledge of the effects of repeated UV exposures on the development of new pigmentation is limited.

Objectives: To characterize the dynamics and dose dependence of pigmentation induction by repeated UV exposures using two different UV sources.

Longitudinal data analysis in medical device clinical studies.

Several statistical approaches are discussed for analysis of longitudinal clinical data from a two independent groups, randomized, prospective, multicenter study of patients with benign prostate hyperplasia (BPH) who are treated with either a new transurethral microwave thermotherapy device (TUMT, n = 147) or sham control (n = 73) at baseline and at 1, 3, and 6 months follow up. The primary clinical endpoint, based on the American Urological Association (AUA) symptom score from 7 questions (each scored 0-5) with 35 as the worst total score, is illustrated in this paper. The primary effectiveness null hypothesis is no treatment effect at any follow-up time against the alternative hypothesis of a favorable treatment effect at one or more follow-up times.

Improved statistical characterization of prosthetic heart valve hydrodynamics using a performance index and regression analysis.

Background And Aims Of The Study: The ISO 5840 Standard (Cardiovascular implants - Cardiac valves) currently requires a minimum of three test samples per size for hydrodynamic testing. Typically, the only statistical analysis performed is a descriptive analysis, with the mean (+/- SE) given for each size and cardiac output (CO). The study aim was to develop better statistical methods, incorporating regression analysis of a performance index, equal to the effective orifice area divided by the tissue annulus area.

Study design in the evaluation of breast cancer imaging technologies.

Rationale And Objectives: Bringing a new imaging technology to market is a complex process. Beyond conceptualization and proof of concept, obtaining U.S.