Volume reduction of benign thyroid nodules 3 months after a single treatment with high-intensity focused ultrasound (HIFU)

Abstract

Background: High-intensity focused ultrasound (HIFU) is a promising, non-invasive technique in treating benign thyroid nodules (TNs). The aim of this study was to evaluate the efficacy of HIFU to induce clinically meaningful shrinkage in benign predominantly solid TNs and to identify variables that influence or predict the magnitude of TN volume reduction.

Methods: For each of ten subjects, HIFU treatment was conducted on a single nodule. Nodular volume was measured sonographically at baseline and at 3 months post-procedure. Nodular function and early treatment assessment was done scintigraphically.

Results: Median nodular volume reduction was 0.7 ml absolute and 48.8% relative to pre-interventional size (p < 0.05). Absolute shrinkage was negatively correlated with the average treatment depth (τ = -0.61, p < 0.05). Absolute nodular volume was positively correlated with the scintigraphic nodular uptake reduction (τ = 0.66, p < 0.05).

Conclusions: HIFU treatment of benign predominantly solid TNs appears to be safe and effective for inducing nodular shrinkage. Despite potential for improvement, a single treatment session with HIFU is already a viable alternative to more standard methods. The feasibility of multiple HIFU treatments requires further investigation. Due to the small sample size, the findings of this analysis need conformation by larger studies.

Keywords: Ablation techniques; High-intensity focused ultrasound ablation; Thyroid nodule; Volume reduction.

Figure 1

Visual feedback during initial test pulse. During initial test pulses, beam intensity was set to be just below the point where the generation of a so-called hyperechoic mark (HEM) indicates temperatures above 80°C–90°C. This mark is visible in B-mode US due to the hyperechogenic character of microbubbles. These consist of steam. Shown is an exemplary nodule before (A) and directly after (B) such a test pulse. Clearly visible is the HEM, which vanishes within seconds afterwards.

Figure 2

Short-term change of nodule appearance due to HIFU treatment. An exemplary nodule in B-mode US before (A) and directly after the completion of HIFU treatment (B). An estimation of ablation magnitude is not possible due to reactive edema formation.

Figure 3

Volume reduction. Median nodular volume reduction within 3 months after HIFU treatment was 0.7 ml. The asterisk indicates a significant change with p < 0.05.

Figure 4

Volume measurement. Sonographical volume measurement of an exemplary thyroidal nodule before (A) and 3 months after (B) HIFU treatment.