Mixing of Angiographic Contrast With Blood During Injections in the Cerebral Circulation

In the past, various techniques such as indicator dilution, transit time, parametric imaging, or first-pass distribution have been used to estimate blood flow rates during angiographic contrast injections. We have previously employed the method of modeling contrast concentration curves to assess changes in flow exchange between parent cerebral vessels and cerebral aneurysms due to endovascular treatment by flow divertors [1]. There has been concern, however, that contrast injected under such situations may remain as a separate slug or stream flowing with blood or that contrast may settle from blood in the direction of gravity due to its higher density [2,3]. According to this argument, therefore, the analysis of the transport of angiographic contrast visualized under X-ray cannot be used to represent the transport of blood.