Performance of Contrast-Enhanced Ultrasound in Thyroid Nodules: Review of Current State and Future Perspectives

Abstract

Ultrasound has been established as a baseline imaging technique for thyroid nodules. The main advantage of adding CEUS is the ability to assess the sequence and intensity of vascular perfusion and hemodynamics in the thyroid nodule, thus providing real-time characterization of nodule features, considered a valuable new approach in the determination of benign vs. malignant nodules. Original studies, reviews and six meta-analyses were included in this article. A total of 624 studies were retrieved, and 107 were included in the study. As recognized for thyroid nodule malignancy risk stratification by US, for acceptable accuracy in malignancy a combination of several CEUS parameters should be applied: hypo-enhancement, heterogeneous, peripheral irregular enhancement in combination with internal enhancement patterns, and slow wash-in and wash-out curve lower than in normal thyroid tissue. In contrast, homogeneous, intense enhancement with smooth rim enhancement and "fast-in and slow-out" are indicative of the benignity of the thyroid nodule. Even though overlapping features require standardization, with further research, CEUS may achieve reliable performance in detecting or excluding thyroid cancer. It can also play an operative role in guiding ablation procedures of benign and malignant thyroid nodules and metastatic lymph nodes, and providing accurate follow-up imaging to assess treatment efficacy.

Keywords: contrast-enhanced ultrasound (CEUS); follicular thyroid cancer; papillary thyroid cancer; thyroid cancer; thyroid nodules.

Figure 1

Right lobe hypoechoic lesion with halo sign, TIRADS 3, Bethesda 2, Follicular hyperplasia (a)—B mode hypo-echogenicity of the structure; (b) color Doppler shows hypervascularity in peripheral part of the lesion; (c) contrast enhancement is predominantly peripheral with smooth ring enhancement, with areas of rapid and intense vascularization in periphery and slow in the center (d) and suggestive slow wash-out (e) in comparison to the adjacent parenchyma.

Figure 2

Right lobe heterogeneous lesion, TIRADS 4, Bethesda 5, Papillary cancer (a)—B mode hypo-echogenicity of the structure with cystic components; (b) Color Doppler shows hypervascularity in one part of the lesion, (c) contrast enhancement is heterogeneous with areas of low vascularization suggestive of malignancy and (d) confirming quantitative difference within the malignant tumor parts (yellow—necrotic areas, blue—intense enhancement and slow wash-out curve).

Figure 3

Right lobe heterogeneous lesion, TIRADS 3, Bethesda 2, Follicular adenoma, (a) B mode mildly heterogeneous structure with cystic components; (b) Color Doppler shows hypervascularity in periphery of the lesion, (c) contrast enhancement is predominantly hyper-vascular and homogeneous with minor parts of lower vascularization prior to the ablation treatment; (d) 6 months after radiofrequency ablation volume reduction by 52% has been reached, and avascular necrotic areas (black areas) are well delineated within nodule for further treatment planning.