(a) An experimental model to examine the sustainability of contrast agents in a slow flow environment. Normal saline (①) is infused into the bag (②) filled with foam contrast or conventional contrast, and the outflow was collected every 2 minutes. (b) Results of the sustainability of contrast effect. CT numbers of collected outflow from conventional contrast (dotted line) and foam contrast (solid line) were plotted over time. Note the rapid decrease in CT number of conventional contrast and sluggish curve of foam contrast agent.