Patent ID: 7233689

Claim:
An image processing method for generating a sequence of digital subtraction angiography images from a digitized mask comprising pixel values and a sequence of digitized opacified images comprising pixel values, said method comprising the steps of: applying a logarithmic function to the values of the pixels of the digitized mask and to the values of the pixels of the sequence of digitized opacified images in order to obtain logarithmic pixel values; subtracting the logarithmic value of each pixel of a digitized opacified image from the logarithmic value of the corresponding pixel in the digitized mask; said method being characterized in that it comprises, before the step of applying a logarithmic function, a processing step able to decrease certain pixel values of the digitized mask and of the digitized opacified images wherein said processing step comprises the substeps of: selecting, in the sequence of digitized opacified images, the lowest pixel value; subtracting, from all the values of the pixels in the sequence of digitized opacified images and the digitized mask, a certain fraction of the selected lowest pixel value, wherein said certain fraction is less than 1 where the applying a logarithmic function to the values of the pixels is applied approximately just before the subtraction step to the individual pixels of the images.