The Working Process Of DSA

The subtraction process of DSA is carried out in four sequences: filming a normal film, preparing a mask image, filming an angiography film, and registering the mask film and the angiography subtraction to form a subtraction image. The preparation of the mask film is the key to subtraction. The mask film is the image without contrast agent, which is exactly the same as the image of the ordinary plain film, but the density is just the opposite. Broadly speaking, a mask is like a reference image subtracted from other images, and any frame of image in the subtraction process can be used as a mask image. The image obtained after the injection of the contrast agent is called the radiographic image, and any frame of the image during the subtraction imaging process can also be used as the radiographic image. The determination of the mask image and the angiographic image is determined by the observed vascular phase, such as the arterial phase, capillary phase, venous phase, etc.