A simple colour subtraction method for angiographic examinations: the photographic method.

The methods used to produce coloured X-ray photographs which have been published up to now can be divided into four different groups according to the meaning of the colour information. A simple and rapid method of photographic colour subtraction is described here. It is a modification of the methods which, with the use of two basic colours and the combination colour, brings out a clear distinction between the differences and the common structures in one coloured X-ray picture.