Digital Subtraction Angiography (DSA) is a procedure known from the prior art for visualizing or representing structures in regions of the body of a person by diagnostic imaging methods, e.g., x-rays. Such structures to be visualized may be blood vessels in the body region. In digital subtraction angiography, a number of images following on from one another in time may be created by an angiography apparatus, e.g., an x-ray device. During this sequence of recordings, a contrast medium is injected into the vessel, through which the vessel is made visible and is mapped in the recorded images. Before the injection of the contrast medium, a so-called empty image may be recorded in such cases, which shows structures of the body region, such as bones, differing from the blood vessels. This empty image is a so-called mask image, by which the interfering structures differing from the blood vessels may be edited out in the images recorded with the contrast medium in the blood vessels, the so-called filler images. To do this, the mask image may be subtracted from the filler images. The subtraction images resulting therefrom may only still show the blood vessels filled with the contrast medium. Based on a timing curve of the contrast medium in the blood vessels, which may be determined based on the sequence of subtraction images created from the filler images and the mask image, information may be obtained about a state of the blood vessel and blocked or constricted vessels, cerebral aneurysms, or arteriovenous malformation (AVM) may be detected.
In order to compensate for a movement of the patient, through which a shift of the structures shown in the images is caused, U.S. Patent Publication No. 2012/0201439 A1 describes a method for movement compensation for images, which have been created by digital subtraction angiography. To do this, a shift vector between a recorded image of the sequence and a reference image is determined and the recorded image is corrected based on the shift vector. U.S. Patent Publication No. 2014/0270437 A1 discloses a DSA method in which no empty image or mask image is needed. Instead, only the filler images are used to create the subtraction images.
A DSA sequence may be carried out with a radiation dose of 1.2 μGray/frame at seven and a half frames per second (fps) with a duration of around ten seconds. This produces an overall radiation dose of 90 μGray. Since this radiation used for imaging may be damaging for persons, (e.g., for patients, technicians, and medical staff working on or with the angiography apparatus), it is desirable to keep the radiation dose as small as possible to reduce the radiation load for the persons in this way. To do this, low-dosage DSA methods are known from the prior art. It is problematic here that the quality of the recorded images is also reduced by the reduced radiation dose, in that the recorded images exhibit a high image noise, for example. The noisy images make it more difficult to obtain information about the state of the blood vessels.