Refinement and reduction in animal experimentation: options for new imaging techniques.

Attempts to substitute animal experiments with in vitro or in silico methods were of limited success when complex (regulatory) processes, e.g. of the cardiovascular, metabolic or neuronal system, were to be analysed. Consequently, strategies to reduce the number of and the burden placed on experimental animals in these fields of research are required. One option consists in the application of non-invasive imaging techniques like (functional) magnetic resonance imaging ((f)MRI), positron emission tomography (PET), and optical imaging (OI). All these methods allow for the observation of functional changes within the body of e.g. genetically modified animals without pain, suffering or (premature) termination. The use of these methods has now reached new dimensions of resolution and precision. With this article we would like to demonstrate a few options of these techniques. We hope that our enthusiasm becomes contagious, thus motivating more scientists to make use of the still expensive equipment which has become available in "small animal imaging" centres. On the basis of four examples--three from our group--we would like to highlight some merits of the new technologies.