Contrast-enhanced endoscopic ultrasonography

Abstract

Contrast agents are increasingly being used to characterize the vasculature in an organ of interest, to better delineate benign from malignant pathology and to aid in staging and directing therapeutic procedures. We review the mechanisms of action of first, second and third generation contrast agents and their use in various endoscopic procedures in the gastrointestinal tract. Various applications of contrast-enhanced endoscopic ultrasonography include differentiating benign from malignant mediastinal lymphadenopathy, assessment of depth of invasion of esophageal, gastric and gall bladder cancers and visualization of the portal venous system and esophageal varices. In addition, contrast agents can be used to differentiate pancreatic lesions. The use of color Doppler further increases the ability to diagnose and differentiate various pancreatic malignancies. The sensitivity of power Doppler sonography to depict tumor neovascularization can be increased by contrast agents. Contrast-enhanced harmonic imaging is a useful aid in identifying the tumor vasculature and studying pancreatic microperfusion. In the future, these techniques could potentially be used to quantify tumor perfusion, to assess and monitor the efficacy of antiangiogenic agents, to assist targeted drug delivery and allow molecular imaging.

Keywords: Contrast media; Doppler ultrasonography; Endoscopic ultrasonography; Gastrointestinal neoplasms; Pancreatic cancer.

Figure 1

Contrast enhanced endoscopic ultrasonography exam of lung adenocarcinoma. A: Non-enhanced power Doppler image of a lung adenocarcinoma visualized in the aorto-pulmonary window from the mid-esophagus, with discrete Doppler signals in the periphery of the mass and embedding of a large branch of the left pulmonary artery; B: Same tumor visualized after contrast-enhancement with SonoVue, with a better depiction of the vascular peripheral signals and the possibility of quantification of the vascular index. The relationship to the aorta and pulmonary artery is clearly depicted.

Figure 2

Contrast enhanced endoscopic ultrasonography of pancreatic cancer. A: Pancreatic head adenocarcinoma visualized in bidirectional non-enhanced power Doppler mode; B: Contrast-enhancement with SonoVue indicates a hypovascular mass with increased collateral circulation.

Figure 3

Contrast-enhanced (SonoVue) harmonic endoscopic ultrasound imaging showing a small (12 mm) hypovascular adenocarcinoma in the head of the pancreas. The tumor tissue did not enhance in the early arterial phase, nor in the late venous phase, as compared to the surrounding pancreatic parenchyma.