Evaluation by digital subtraction angiography

Digital subtraction angiography (DSA) is a form of digital radiography. In digital radiography, the X-ray signal is electronically detected, digitized, and proceeded before being displayed and stored. The technique allows detection of very low levels of iodinated contrast media such as those that occur in the arterial system following an intravenous injection of contrast. The X-ray imaging system used is a standard-image intensified fluoroscopy system with a wide dynamic-range TV camera. The video signal from the image intensifier is logarithmically enhanced and digitized on an image processor (computer). This signal, which is stored in one of two memories, serves as a mask. The mask is subtracted from digital images obtained after the injection of contrast media, and the subtraction images are stored on digital or analog disks or on magnetic tapes. Postprocedure reprocessing allows selection of different masks for subtraction, which is useful when patient motion has occurred. Hard copies can be obtained