Research on the gray-level correction in digital subtraction angiography

When using direct subtraction in digital subtraction angiography, the shadow of another tissue which laps over the blood vessel cannot be eliminated completely. A method to solve this problem from theoretical and experimental aspects is presented. First, the imaging system is modeled based on "equivalent single energy" of X-ray's absorbing characteristic in human tissue, and then the X-ray images are calibrated before digital subtraction angiography. After such processing, the subtracting result can remove the shadow greatly. Experimental results proved the validity of this method.