CT, Iodine Subtraction

Dual-energy CT can be used to generate iodine subtraction imaging, which is of tremendous utility in differentiating blood from iodinated contrast.



Post-angiographic CT head of this patient showed diffuse high attenuation in the subarachnoid and intraventricular spaces, with uncertainty regarding contrast or blood (A, C). A repeat CT head in several hours would likely demonstrate the fading of the contrast. However, dual-energy CT head with iodine subtraction (B, D) provides an instant answer.