change in volume with erection =
= (volume of the penis after erection) - (volume of the flaccid penis)
The change in volume with an erection is due primarily to engorgement of the corpora cavernosum. Most of the other components (skin, urethra) are relatively constant.
Each corpus cavernosum is roughly a cylinder.
erectile volume for left or right corpus cavernosum in mL =
= (length in cm) * π * (((diameter in cm) / 2)^2)
total erectile volume of the left and right corpus cavernosum in mL =
= (erectile volume in mL on left side) + (erectile volume in mL on right side)
change in erectile volume with an intervention in mL =
= (erectile volume in mL after intervention) - (erectile volume in mL before intervention)
People who respond to an intervention tend to have a greater increased in the diameters for both corpora.
Ultrasound can also monitor peak blood flow velocity in the cavernous arteries. A peak blood flow velocity > 25 cm per second was considered a good response to prostaglandin PGE1 injections.
