Figure 49

Figure 49 Color duplex Doppler ultrasonography (CDDU). (a) The probe is placed on the penis, which has been lubricated with ultrasound
jelly. Both dorsal arteries and the paired cavernous arteries can usually be visualized; (b) normal CDDU trace after injection of 20 mg of
prostaglandin E1 when full erection has been achieved. Systolic velocity is normal and the flow is reversed during diastole; (c) schematic
representation of the time course of changes in peak systolic and end-diastolic velocities during development of a pharmacologically
induced erection. Once full rigidity is achieved, end-diastolic velocity is very low and the flow may be reversed at this point