Digital Angiography Using a Matched Filter

Both digital subtraction and recursive filtering schemes have been employed successfully for intravenous and intraarterial arteriography. Either processing method results in an image(s), S, which is a linear combination of discrete images Ij acquired during the flow of iodinated contrast material, i.e., S = Sum of k(j)l(j) from j = 0 to N where k(j) are the weighting coefficients for the N+1 samples. It is shown that for a given set of images {l(j)} there exists a set of weighting coefficients {k(j)} which maximizes the iodine signal to noise ratio and simultaneously removes stationary background anatomy. The k(j) are related to the contrast dilution curve measured over an artery of interest, k(j) = s[j]-Mean(s), where {s[j]} is the set of measured image variations due to the flow of contrast material, and Mean(s), is the mean value of the s[j]. This choice of k(j) defines a matched filter. Compared to subtraction angiography, matched filtering is 4-6 times more dose efficient.