MEDICAL IMAGING APPARATUS AND METHOD FOR FURNISHING DIFFERENCE IMAGES

The method and apparatus furnish difference images from a video signal which contains a sequence of images that are obtained from a patient under examination. First a first of the images contained in the video signal is recorded in a first storage device. Thereby a so-called primary mask is formed. Then, a subsequent second of the images contained in the video signal is recorded in a second storage device. Subsequently, a third of these images is recorded in a third storage device. From here on, images contained in the video signal following the third image are recorded alternatingly in the second and the third storage device. At a certain point of time, a signal for starting data acquisition is provided. Simultaneously or thereafter, a so-called secondary mask is selected. The secondary mask is an image completely recorded in the second or third storage device shortly prior to the generation of the data acquisition signal. This secondary mask is subtracted from those images contained in the video signal which appear after the data acquisition signal has been generated. Thereby the afore-mentioned difference images are formed for display.