When applying the doppler signal to the flaccid penis, we can get a measure of blood flow.
Ten or so minutes after injecting the penis with a vasodilator, you can see the increase in flow velocity. The tall peaks represent systolic flow, or when blood is entering the penis. The shorter regions represent diastolic flow, which is a measure of venous function.
After 30 minutes, the man has a rigid erection, and there is no venous flow. The arterial flow has peaked. This man has normal vascular function in his penis and his ED is unlikely to be the result of a vascular problem.
Use of color flow duplex ultrasound can be a useful evaluation tool for certain men with ED.
