[en] A technical discussion of beam handling for PIXE in vacuo is presented, directed towards achievement of low detection limits for trace elements in biomedical specimens. A quantitative comparison is given of elemental backgrounds from commonly used specimen backings, e.g. Kapton, Mylar, Kimfol and very thin polystyrene films. The new problems presented by operation in a helium atmosphere are reviewed, with emphasis on gamma ray background arising from nueclear reactions in the proton exit window. Backgrounds and detection limits are discussed for analyis of biomedical specimens both in vacuo and in helium. A brief review is given of some current applications of PIXE in the medical area. (orig.)