THE CENTRAL X-RAY BEAM IN STEREOTAXIS

A common misconception is that there exists only one possible "central x-ray beam" arising from the x-ray tube and that it is the one that somehow is oriented to the axis of the x-ray tube on its collimator. However, the following axiom in radiology is emphasized: emanating from a point source of radiation (the x-ray tube anode) is an infinite number of x-ray beams, any one of which may be selected as "the central x-ray beam." In stereotaxis the particular beam selected will be that one which traverses a pathway from the x-ray tube anode through 2 defined points on the stereotaxic frame.

This pathway can be selected prior to the stereotaxic procedure by sighting through these 2 points and adjusting the x-ray tube and/or stereotaxic frame until these points visually superimpose on the x-ray tube anode or its aluminum filter. Regardless of the gross position of the stereotaxic frame with respect to the x-ray tube, within limits, the 2 defined points will have their roentgenographic images superimposed on the x-ray film.

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