Liver Mass Evaluation with Ultrasound: The Impact of Microbubble Contrast Agents and Pulse Inversion Imaging

ABSTRACT

Liver mass evaluation includes two essential elements-lesion detection and lesion characterization. Both of these are greatly improved on sonography with the addition of contrast agents and the use of specialized imaging techniques, particularly pulse inversion imaging. Ultrasound contrast agents are comprised of tiny microbubbles of gas that interact with the ultrasound beam producing an enhancement of the Doppler signal from blood. Pulse inversion imaging allows preferential detection of the signal from the microbubble agents with suppresion of the signal from background tissue. Two imaging techniques include a low mechanical index (MI) nondestructive method to show lesional vascularity and a high MI destructive mode that produces disruption of the bubbles in a single frame. The latter allows for quantitative assessment of the relative enhancement of a lesion as compared with the adjacent liver parenchyma, which is a reflection of the relative vascular volumes. Vascular imaging has shown characteristic and reproducible features of common liver masses, including hemangioma, focal nodular hyperplasia, hepatocellular carcinoma, and liver metastases. Delayed postvascular enhancement of the normal liver, a phenomenon that is unique to certain classes of microbubble contrast agents, allows detection of more and smaller malignant lesions than on baseline.

KEYWORD

Contrast agents - liver - neoplasm - pulse inversion imaging - ultrasound

REFERENCES

• 1 Becher H, Burns P N. Handbook of contrast echocardiography. Berlin: Springer; 2000
• 2 Burns P N, Wilson S R, Muradali D. Microbubble destruction is the origin of harmonic signals from FS069.  Radiology . 1996;  201 158
• 3 Burns P N, Powers J E, Fritzsch T. Harmonic imaging: a new imaging and Doppler method for contrast enhanced ultrasound.  Radiology (Abst). 1992;  185(P) 142
• 4 Burns P N, Powers J E, Hope Simpson D. Harmonic imaging: principles and preliminary results.  Angiology . 1996;  47 63-73
• 5 Hope Simpson D, Chin C T, Burns P N. Pulse inversion Doppler: a new method for detecting nonlinear echoes from microbubble contrast agents.  IEEE Transactions UFFC . 1999;  46 372-382
• 6 Burns P N, Hope Simpson D, Averkiou M. Nonlinear imaging.  Ultrasound Med Biol . 2000;  26 19-22
• 7 Burns P N, Wilson S R, Hope Simpson D. Pulse inversion imaging of liver blood flow: an improved method for characterization of focal masses with microbubble contrast.  Invest Radiol . 2000;  35 58-71
• 8 Wilson S R, Burns P N, Muradali D. Harmonic hepatic ultrasound with microbubble contrast agent: initial experience showing improved characterization of hemangioma, hepatocellular carcinoma, and metastasis.  Radiology . 2000;  215 153-161
• 9 Kim T K, Choi B I, Han J K. Hepatic tumors: contrast agent-enhancement patterns with pulse-inversion harmonic US.  Radiology . 2000;  216 411-417
• 10 Tiemann K, Lohmeier S, Kuntz S. Real-time contrast echo assessment of myocardial perfusion at low emission power: first experimental and clinical results using power pulse inversion imaging.  Echocardiography . 1999;  16 799-809
• 11 Ophir J, Parker K J. Contrast agents in diagnostic ultrasound [published erratum appears in Ultrasound Med Biol 1990; 16(2):209].  Ultrasound Med Biol . 1989;  15 319-333
• 12 Bertolotto M, dalla Parma L, Quaia E, Locatelli M. Characterization of unifocal liver lesions with pulse inversion harmonic imaging after Levovist injection: preliminary results.  Eur Radiol . 2000;  10 1369-1376
• 13 Dill-Macky M J, Burns P N, Khalili K, Wilson S R. Focal liver masses: interpreting patterns of enhancement with Levovist and pulse inversion imaging.  Radiology (in press).
• 14 Uggowitzer M, Kugler C, Groll R. Sonographic evaluation of focal nodular hyperplasia (FNH) of the liver with a transpulmonary contrast agent (Levovist).  Br J Radiol . 1998;  71 1026-1032
• 15 Blomley M JK, Albrecht T, Cosgrove D O. Improved imaging of liver metastases with stimulated acoustic emission in the late phase of enhancement with the US contrast agent SH U 508A: early experience.  Radiology . 1999;  210 409-416
• 16 Blomley M J, Albrecht T, Wilson S R. Improved detection of metastic liver lesions using pulse inversion harmonic imaging with Levovist: a multicenter study.  Radiology . 1999;  213(P) 491