Roles of contrast-enhanced ultrasonography in identifying volume change of benign thyroid nodule and optical time of secondary radiofrequency ablation

Abstract

Background: Ultrasonography-guided radiofrequency ablation (RFA) was was proved to be an effective and safe treatment with few complications for benign thyroid nodule. In cases of incompletely treated nodule margin, secondary RFAs are necessary. The present study was designed to analyze the dynamic change of nodular volume of benign thyroid tumors accessed using contrast-enhanced ultrasonography (CEUS) after RFA, and hopefully to offer evidence for time decision of secondary RFA. Methods: A total of 105 patients who received ultrasonography-guided RFA in the Department of Ultrasound, Chinese PLA General Hospital between April 2014 and August 2018 for benign thyroid nodule were enrolled in this retrospective study. Vt increase (regrowth) and vital volume (Vv) of thyroid nodule were followed up at 0, 1, 3, 6, 12, 24 and 36 months after RFA. Results: A total of 105 nodules of 105 patients were enrolled in the present study, with a mean age of 46.70 ± 13.05 years, and 87 of them (82.9%) were female. The median follow up time was 25.1 months (12 months to 36 months). During the follow up, regrowth occurred in 43 cases, 95.35% of nodular regrowth occurred in 12 months after RFA, and the rate showed substantial consistency with that on the 36th month postoperatively (Kappa = 0.656). Conclusions: CEUS was an effective and safe tool to monitor volume change of benign thyroid nodules after RFA. The majority cases of regrowth occurred in 12 months after RFA, thus, the 12th month after RFA might be the optimal time for volume assessment to make the decision of secondary RFAs.

Learning curve for radiofrequency ablation of benign thyroid nodules

“…This means that volume reduction is quite rapidly mastered, but that more complete ablation with the moving shot technique takes more time to acquire. This indicator of AR, first described by Sim et al [15,16], is all the more important that it has been shown and confirmed to be a risk marker for regrowth [17][18][19]. Therefore, the strategy of minimally invasive treatment should attempt to complete ablation of the entire nodule.…”

“…However, comparison with the literature shows similarities. Regarding immediate and delayed appreciation of ablated tissue volume, use of CEUS might increase the detection of incomplete treatment [17][18][19]. However, it has been shown a considerable similarity in terms of findings of power Doppler US and CEUS imaging for thyroid nodule [30], probably even better when microvascular imaging is used.…”

“…However, because it can be technically difficult to completely ablate all the nodule margin from a single-session, it was hypothesized this could represent a supplementary difficulty in the RFA learning curve of benign thyroid nodules. Thus, the criterion called ablation ratio (AR) proposed by Sim et al [15,16] and later studied by other authors with contrast-enhancement ultrasound (CEUS) [17][18][19] could also be used to study the learning curve. The AR is the ratio of the ablated volume to the total remaining volume.…”

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

“…A typical protocol for thyroid nodules CEUS examination includes low mechanical index (MI < 0.10) and the focus zone should be placed at the lower portion of the FOV [29] preferably including the entire nodule and surrounding thyroid tissue in the longitudinal plane. When the conventional B-mode image is properly adjusted and the CEUS mode activated, a microbubble contrast agent is injected as an intravenous bolus, generally with a dose of around 1.0-2.0 mL, followed by 5-10 mL of saline; however, specific amounts of CA and saline vary between operators and institutions [30][31][32][33]. A CEUS timer is started simultaneously with the injection of the contrast agent, and cine-clips of the scanning are stored digitally as raw data for 2-3 min before being processed, but the length of examination differs between sources and institutions, with most authors choosing a time period of at least 2 min [34,35].…”

RFA and benign thyroid nodules: Review of the current literature

“…A recent study showed that CEUS was very effective in monitoring volume change of benign thyroid nodules after RFA. It picked up 95.35% of regrowth at 12 month post RFA 96 . Currently, European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) recommends that US elastography can be used as part of nodule characterization 97 .…”