1. A method for determining pubic arch interference relative to the prostate gland of a patient, comprising the steps of: acquiring an initial ultrasound image of the pubic arch; acquiring an ultrasound image of a transverse cross-sectional outline of the prostate; outlining the approximate true shape of the pubic arch from the initial ultrasound image thereof; and merging the outline of the pubic arch with the transverse cross-sectional image of the prostate to determine pubic arch interference.