This video clip shows how to estimate peak enhancement time by using the test injection technique.

W Choi et al. Individually Optimized Contrast-Enhanced 4D-CT for Radiotherapy Simulation in Pancreatic Ductal Adenocarcinoma http://onlinelibrary.wiley.com/doi/10.1118/1.4963213/full

https://youtu.be/Vo1IBDz3DBs