Schematic time-intensity curve given by the bolus tracking system.

<p>From the injection of contrast into the peripheral vein (point a), until the contrast media reaches the pulmonary artery (b), the curve is flat. After the inflection point (b), there is a brisk rise in intensity measured by the system, and the intensity reaches a predefined threshold to start the sequence of data acquisition (40UH, point (c)). The intensity slope is calculated by subtracting the intensity measured at the inflection point (b) to the highest intensity measured (e) divided by the time between those two points. The point (d) is the intensity reached at 10 seconds. ROI: region of interest; HU: Hounsfield units; s: seconds.