Problem 2 (20 points) (X-ray) In digital subtraction angiography (DSA), two X-ray images are acquired for the same region. The first is done before the injection of a contrast agent, and the second is after. Assume the imaged region is as shown, and given the attenuation coefficients for X-ray energy of 100 KeV are 0.18 cm for soft tissue, 0.178 cm for blood, and 1.0 cm'l for blood with a small dose of Iodine contrast agent. 2.1 Calculate the detected X-ray intensity Ial as a function of Io before the injection of the contrast agent; 2.2 Calculate the detected X-ray intensity Iaz as a function of Io after the injection of the contrast agent; 2.3 Calculate the quantity DSA-In(Ia2)-In(Id); (In is natural logarithm) 2.4 Will the DSA value change if the type of the soft tissue is changed? Why? In !!!! soft tissue blood vessel soft tissue 10 cm 0.5 cm 2.0 cm