Which of the following is not a prerequisite for transvaginal sonography (TVS)?

Ans-BREF: Danforth s Obstetrics and Gynaecology 10th edition page 541-542Transabdominal sonography (TAS)Transvaginal sonography (TVS)TAS uses lower frequency sound waves (3.5 to 5.0 MHz) to allow for the deeper penetration required to visualize intra-abdominal structures.TVUS uses higher frequency sound waves (5 to 8 MHz), which allow higher image resolution but with less tissue penetration.Image clarity is comparatively lower.TAS is most useful in fully assessing large masses that extend out of the pelvis.Image clarity with TVUS usually is superior when evaluating ovarian abnormalities as compared with TAS.Helpful to distinguish between ovarian and uterine masses.In addition, TVUS with Doppler sonography affords assessment of the flow of blood within vessels adjacent to and within the uterus and ovaries.Where TVS cannot be performed, such as in pediatric or adolescent patients. Best performed with a fully distended urinary bladder, enabling a better acoustic window without interfaces to reflect echoes to visualize the uterus and adnexa.Best performed in patients placed in the lithotomy position with an empty bladder.Consent required.Consent required.