Figure 2:Sequential time-points from CTP acquisition show contrast traversing the capillary bed at a fixed level. The time post contrast injection is noted at the top of each image. During cine acquisition, two images are performed every second. The image numbers are referred to as “ranks” in the post-processing software program, indicated in the left lower corner of the image highlighted in red. In this example, there are 89 ranks (images) for a 45 sec scan acquisition. Note that the contrast arrives in the imaged slice at approximately 15 seconds, and peaks at 20 seconds. The contrast starts to wash-out after 25 seconds. These patterns of contrast wash-in and wash-out, for a given voxel of tissue, are graphically represented in the time-density curves (TDC), as described in Fig. 3.