X-Ray angiography is a medical imaging technique for diagnosing disorders related to blood vessels. In this technique, a two-dimensional X-Ray image is taken of the region of interest. In general, the X-Ray contrast between the blood vessels and surrounding tissue and bone structures is weak. To enhance the X-Ray contrast, a dye is injected into the blood stream. Since the opacity of the dye is higher than that of the surrounding structures, the contrast in the dye-enhanced image is increased. The resulting contrast, however, is still often too low for detailed diagnostics.
Further contrast enhancement is provided by digital subtraction angiography (DSA). In this technique, a digital background image of the region of interest prior to injection of dye is captured and stored in an image processing system. The dye is then injected, and digital dye-enhanced images are captured and stored as the dye flows through the blood vessels. The images of the blood vessels are enhanced by subtracting the digital background image from the digital dye-enhanced images. The resulting differential images (called subtracted images) are high-contrast images of the blood vessels.
In an ideal test environment, the digital background image prior to injection of dye is identical to the image of the surrounding structures after introduction of dye. In an actual test environment, however, the patient moves during the time in which the images are acquired. Consequently, the digital background image is not identical to the digital image of the surrounding structures after the introduction of dye. The resulting contrast is then lower than in the ideal case. Prior to digital image subtraction, the dye-enhanced images need to be corrected for patient motion.
In common embodiments of DSA processing, motion correction is performed by the user at the time the images are being reviewed for diagnostics. This procedure extends diagnostic time, and interrupts diagnostic review. What is needed is a method for correcting the images prior to diagnostic review.