Chapter 38: Contrast-Enhanced Gynecologic Sonography

KEY TERMS

INTRODUCTION

This chapter serves as a guide to the use of contrast-enhanced ultrasound (CEUS) in gynecology. It covers applications of CEUS in the diagnosis of various gynecological conditions, ranging from benign uterine anomalies to ovarian malignancies.

As with any other organ system, perfusion studies and study of blood-flow patterns help to characterize gynecological lesions. Conventional techniques (B-mode ultrasound and Doppler ultrasound) have limitations in depicting perfusion at the microvascular level (typically <2 mm diameter), in deep vessels (>10 cm from the skin), and in regions with tissue motion. These limitations are due to the weak reflection of ultrasound waves by blood relative to surrounding tissue.^1,2 This limits their use in gynecology, especially in characterization of ovarian and endometrial malignancies. However, these limitations have been largely overcome by the introduction of CEUS. CEUS utilizes microbubbles, the small size (1-10 microns) of which enables them to mix up with red blood cells. The high intrinsic compressibility of microbubbles with resultant high echogenicity makes CEUS an extremely suitable technique to study blood flow at the microvascular level.³

CEUS is a well-established technique in the characterization of liver masses. The World Federation for Ultrasound in Medicine and Biology (WFUMB) has published guidelines for the use of contrast in liver applications,⁴ and guidelines for the use of contrast in nonliver applications have been published by the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB).⁵ However, these guidelines do not include gynecological applications. CEUS has potential in evaluating various gynecological disorders. It can be helpful in distinguishing between fibroids and adenomyomas,^6-8 characterizing endometrial pathologies,^9-13 characterizing adnexal masses,^14-21 confirming adnexal torsion,²² distinguishing between retained products of conception and arteriovenous malformations, testing tubal patency,^23-26 and diagnosing vaginal fistulas.²⁷ These applications along with distinguishing features of corresponding pathologies are tabulated in Appendix 38-1.

ULTRASOUND CONTRAST AGENTS (UCA)/MICROBUBBLES

Adoption of ultrasound contrast agents (UCAs) in clinical practice was pioneered by Gramiak and Shah in 1968 for use in echocardiography. Since then, UCA have evolved from “unprotected unstable room air bubbles” to a “complex stable system of core-shell structures” with a coating of biodegradable material such as albumin, phospholipids, and polymers containing low diffusivity gases like nitrogen and perfluorocarbons^2...