In digital subtraction angiography, two images are acquired, the first before injection of the contrast agent and the other post-injection.
(a) Write an expression for the X-ray intensity, I(t) in the first scan in terms of I(0), u(tissue), x(tissue), u(blood), and x(vessel), where x(tissue) and x(vessel) are the dimensions of the respective organs in the direction of X-ray propagation.
(b) Write a corresponding expression for the X-ray intensity I(2) for the second scan, replacing u(blood) with u(contrast).
(c) Is the image signal intensity from static tissue removed by subtracting the two imagesÉ
(d) Show that the signal from the static tissue is removed by computing the quantity log(I2)-Log(I1)