Contrast-enhanced ultrasonography in interventional oncology

Abstract

Contrast-enhanced ultrasound (CEUS) has evolved from the use of agitated saline to second generation bioengineered microbubbles designed to withstand insonation with limited destruction. While only one of these newer agents is approved by the Food and Drug Administration for use outside echocardiography, interventional radiologists are increasingly finding off-label uses for ultrasound contrast agents. Notably, these agents have an extremely benign safety profile with no hepatic or renal toxicities and no radiation exposure. Alongside diagnostic applications, CEUS has begun to develop its own niche within the realm of interventional oncology. Certainly, the characterization of focal solid organ lesions (such as hepatic and renal lesions) by CEUS has been an important development. However, interventional oncologists are finding that the dynamic and real-time information afforded by CEUS can improve biopsy guidance, ablation therapy, and provide early evidence of tumor viability after locoregional therapy. Even more novel uses of CEUS include lymph node mapping and sentinel lymph node localization. Critical areas of research still exist. The purpose of this article is to provide a narrative review of the emerging roles of CEUS in interventional oncology.

Keywords: Contrast-enhanced ultrasound; Interventional oncology; Interventional radiology.

Fig. 1.

Contrast-enhanced ultrasound of an indeterminate liver lesion (arrow) showing peripheral discontinuous globular enhancement (from the left of the image and extending towards the center of the lesion) with progressive central filling and persistent hyper-enhancement, consistent with hemangioma. (A) 16 s after bolus injection. (B) 39 s after bolus injection. (C) 167 s after bolus injection.

Fig. 2.

Indeterminate renal lesion better characterized by contrast-enhanced ultrasound. (A) Non-contrast CT demonstrating a 7.4 × 4.2 × 8.6 cm exophytic left renal mass (arrow). (B) Gray-scale ultrasound demonstrating a 7.1 × 7.0 × 6.2 complex hypoechoic cystic lesion with septations. (C) Contrast-enhanced ultrasound demonstrating a 7.1 × 7.0 × 6.2 complex cystic lesion with no internal enhancement consistent with a benign or indolent lesion.

Fig. 3.

Contrast-enhanced biopsy guidance. (A) Contrast-enhanced CT scan showing an enlarging 8 × 4 × 5 cm left flank mass (arrow) in the setting of known stable metastatic melanoma. (B) Gray-scale ultrasound demonstrating a 8 × 4 × 5 cm complex hypoechoic lesion. (C) Contrast-enhanced ultrasound of the same lesion showing clear areas of perfusion (star) and lack of perfusion. The biopsy needle is depicted (arrow), passing through an area of perfused lesion (star). Areas of poor enhancement (triangle) represent hypo-perfused or necrotic regions of the lesion that may be less likely to provide a definitive diagnosis.

Fig. 4.

Treatment effect monitoring by contrast-enhanced ultrasound after cryoablation of high-risk renal lesion. (A) 3.4-cm right renal lesion (arrow) with soft tissue enhancement concerning for renal cell carcinoma. (B) Gray-scale ultrasound of treated kidney. (C) Contrast-enhanced ultrasound of the same window showing treatment ablation cavity without nodular enhancement. Minimal peripheral enhancement suggestive of post-procedure scar. No viable tumor is present.

Fig. 5.

Treatment effect monitoring by contrast-enhanced ultrasound after trans-arterial chemoembolization (TACE) of hepatocellular carcinoma. (A) Post-contrast T1-weighted fat suppressed MRI demonstrating a 2.8 × 2.6 × 2.5 cm segment VI LI-RADS 5 lesion (arrow) with arterial phase enhancement (and washout on delayed imaging) before TACE treatment. (B) Gray-scale ultrasound with difficulty delineating the lesion bed post-treatment. (C) Contrast-enhanced ultrasound of the same ultrasound window demonstrating the lesion with partial treatment response and some residual enhancement (arrow) concerning for viable tumor.