Role of contrast enhanced ultrasound in hepatic imaging

Abstract

Grey scale ultrasound (US) is the first line imaging modality used for the evaluation of liver by the radiologists and clinicians worldwide. It is a simple, inexpensive, safe and an easily available technique. US has the ability to delineate the hepatic parenchyma and differentiate the cystic from solid hepatic lesions. However, it has limited accuracy in the detection and characterization of focal liver lesions (FLL). CEUS is a major breakthrough in ultrasound imaging which evolved with the aim of overcoming these limitations of US. With the use of ultrasound contrast agents(UCAs), CEUS has the ability to detect the intranodular hemodynamics and thereby provide information of the enhancement pattern of the lesion resulting in reliable characterization of the FLL. This capability brings it at par with the cross sectional contrast enhanced imaging techniques of computed tomography and magnetic resonance imaging. UCAs are safe, non-nephrotoxic and thus can be used to evaluate patients with renal failure as well. The technique of CEUS is simple, requires few minutes to perform, portable, lacks ionising radiation and above all is a cost-effective modality. These advantages have made CEUS an established modality for hepatic imaging. Besides detection and characterization of FLL, it also plays a vital role in the management and repeated follow up of treated patients of FLL. Newer clinical applications of CEUS with promising results are also being unravelled .This review highlights the multifaceted role of CEUS in hepatic imaging and its upcoming clinical applications.

Ultrasound and contrast-enhanced ultrasound (CEUS) in infective liver lesions

“…In cases of multiple lesions, the largest lesion should be investigated [14]. Also, it may be necessary to re-inject a fresh dose of UCA to study more than a single lesion [15]. It is advisable to rupture any remnant UCA in the tissue using a high-MI pulse before re-injection in such cases [9].…”

Usefulness of contrast enhanced ultrasound in monitoring therapeutic response after hepatocellular carcinoma treatment

“…On the contrary, when the therapy has failed zones of wellperfused residual tumour remain in the target lesion and focal contrast enhancement is detected in these areas. The residual unablated tumour appears like an irregular, eccentric or nodular peripheral enhancement [14][15][16][17] .…”

“…In large tumours, incomplete ablations might look as zones with contrast up-taking, which usually are localised nearby the periphery of the lesions. In these cases, an accurate comparison between the pre-and post-ablation images is necessary to achieve a correct evaluation of treatment efficacy [17] .…”

Optimisation of ultrasound liver perfusion through a digital reference object and analysis tool

“…It has significantly evolved over time, incorporating the use of contrast agents to improve tissue and lesion contrast as well as allowing dynamic perfusion studies. US contrast media have opened a new panorama for quantitative imaging, significantly expanding US clinical applications in several organs such as liver, breast, and heart diseases, among many others [1][2][3][4].…”