Recursive Filtering Techniques Applied to Digital Subtraction Angiography

The most successful application of digital radiography to date has been digital subtraction angiography (DSA). Its main clinical use has been in the evaluation of head, neck, and abdominal arteries. Mask-mode image subtraction has been the most widespread DSA technique.(1–5) For non-cardiac studies, this technique uses X-ray exposures made approximately once per second for a total of 15 to 20 exposures spanning the duration of the arrival and washout of the contrast material bolus. Typically, exposure times are in the range of 20 to 200 msec, depending on anatomy. Of the resultant images, two are subtracted from each other to form the final difference image, one taken from among those containing little or no contrast, and another taken at or near peak opacification. Because the two images are acquired at different times, the process is called temporal subtraction.