Intravascular contrast medium is essential for enhancement of vessels and parenchyma. In this way the relation between vessels and tumours can be detected. Factors that influence the time required for a contrast bolus are the cardiac output of a patient, body weight, hydration status and the condition of the vessels. When a main vessel is occluded because of thrombosis, embolia or trauma a collateral circulation will form. The blood is supplied to the organs via sidebranches. This has an effect on the contrast arrival and in case of a fixed scan delay time this will result in mis-timing. Bolus triggering is a very reliable method to determine the scan delay. SureStart® is standard on the Toshiba Aquilion 16 systems. A Region of Interest is placed in a vessel where the enhancement is not only measured, but also monitored real time. When the right level of enhancement is reached, the helical scan will start. In this special case SureStart® ensured that the right scan delay was used despite of the collateral circulation.