Introduction

Ultrasound (US) is an essential part of infertility evaluation of the female, and is indispensable for obtaining optimal results from intrauterine insemination (IUI) and ovulation induction (OI). Use of US for evaluation and management of infertility is of recent origin. The first report of follicle changes throughout a complete menstrual cycle appeared in 1979. Sonohysterography (SHG), instillation of sonolucent fluid into the uterus in order to improve visualization of the fallopian tubes and soft tissue abnormalities of the uterine cavity, followed in 1984. Recent developments include the use of three-dimensional US to delineate uterine structural abnormalities, and the adoption of color Doppler blood-flow analysis of uterine and ovarian blood vessels.

Transabdominal ultrasound (AUS) is the preferred method for evaluation of pelvic masses larger than 5 cm, and for evaluation of the pregnant uterus after the first trimester. Transabdominal US requires a distended bladder, which is uncomfortable for the patient, particularly when pressure is applied on the lower abdomen during scanning. Accurate delineation of pelvic structures is not possible in all women due to beam scatter by excessive subcutaneous fat and overlying gas-filled bowel loops, or when the ovaries and uterus are located deep in the pelvis. Transabdominal US utilizes frequencies between 2.5 and 3.5 MHz. As frequency is increased, imaging depth decreases and ambiguity occurs because of attenuation. For soft tissue, attenuation in decibels (dB) is approximately 0.5 dB per cm for each MHz of frequency.