Contrast enhanced endoscopic ultrasound: More than just a fancy Doppler

Table 1 Second generation contrast agents currently available

Contrast agent	Shell components	Gas	Mechanical index
Definity®	Phospholipid	Perfluoropropane	Low
Imagent®	Phospholipid	Perfluorohexane	Low
SonoVue®	Phospholipid	Sulfur hexafluoride	Low
Sonavist®	Polymer	Sulfur hexafluoride	Low
Sonazoid®	Lipid	Perfluorocarbon	Low
Optison®	Albumin	Perfluoropropane	Low
Sonogen®	Surfactant	Perfluoropentane	Low
Levovist®	Galactose/Palmitic acid	Air	High
Albunex®	Albumin	Air	High

Table 2 Effect of mechanical index on second generation microbubbles

Mechanical index	Effect on microbubble oscillation	Relationship between emitted sound waves and detected signal
Low (< 0.1)	Symmetrical	Linear
Moderate (0.1-0.6)	Asymmetrical	Non-linear
High (> 0.6)	Destruction	N/A

N/A: No detected signal as oscillation at the high frequency causes the microbubbles to burst.

Table 3 Accuracy of contrast enhanced endoscopic ultrasound versus other imaging modalities

	Sensitivity (%)	Specificity (%)	Accuracy (%)
Pancreatic neoplasm
CEUS[31-35,60]	~ 91	~ 93	~ 92
EUS +/- FNA[8,47,60-70]	85-98	67-91	91-95
CT[61,63,64,71-73]	77-86	64-93	66
MRI[61,64,73-75]	85-99	60-95	79-81
Lymphadenopathy
CEUS[54,60,76]	60	91	82-92
EUS +/- FNA[52,77-83]	68	86	75-99
CT[52,78,81-83]	33	75	51-74

CEUS: Contrast enhanced endoscopic ultrasound; EUS: Endoscopic ultrasound; FNA: Fine needle aspiration; CT: Computed tomography; MRI: Magnetic resonance imaging.