This paper explores the use of Computer Aided Engineering (CAE) to model angiography dye flow in the detection of cerebral aneurysms. To obtain a discernable image, the concentration of the dye, Conray-60 ? , needed to be above 0.2 in the desired region. The design goal was to optimize the appropriate dye injection catheter diameter while maintaining dye flow rate constant to provide the longest time window to take an angiogram of the carotid artery. A geometric model of the system, consisting of a tubular 5 mm diameter artery of 0.3 m in length with the catheter outlet at the beginning of the tube, was produced using the graphical program GAMBITTM. After specifying initial and boundary conditions of the model, including velocities and concentrations, the CAE program FIDAPTM was used to compute the resulting fluid velocity and concentration change of the imaging dye, Conray-60? . Analysis was performed using a 2 mm diameter catheter and a 3 mm diameter catheter. The time window was obtained by finding the amount of time when the entire length of the region 5 cm from the inlet to the end of the tube maintained the desired concentration. For the 2 mm catheter, the time window was determined to be 1.5 seconds. The 3 mm catheter provided a time of 1.3 seconds. This analysis concludes that a smaller catheter provides a larger time window for the purpose of taking an angiogram when the flow rate cannot be changed.