Figure 7.

Diagrammatic representation of multiphasic Doppler waveforms encountered during normal erection in the cavernosal arteries. Phase 1—initial low flow arterial waveform. Phase 2—elevation of systolic and diastolic velocities approximately 5 min following injection. Phase 3—reduction in end-diastolic velocity as sinusoidal distension causes increased intracavernosal pressure and reduction in venous outflow. Phase 4—reversal in diastolic waveform as intracavernosal pressure exceeds diastolic pressure. Phase 5—intracavernosal pressure exceeds systolic pressure at maximal tumescence, causing reduction in the systolic velocity and narrowing of the systolic peak.