The iceberg technique: an innovative approach for radiofrequency ablation of diving thyroid nodules

Abstract

Diving thyroid nodules are a limitation of radiofrequency ablation because the mediastinal component cannot be adequately identified by ultrasound (US). We aim to describe a new technique, the iceberg technique, to overcome this issue and explain our three-year experience of using this novel method. The iceberg technique consists of a two-stage treatment. First, the ablation of the cervical portion of the nodules (easily visualized during the initial US exam) using trans-isthmic access is performed using the moving-shot technique. After three to six months, there is a volumetric reduction of the treated portion, leading to retraction of the thyroid parenchyma. This brings the mediastinal component to the cervical region, thereby enabling a perfect visualization by US. Then, the second stage of treatment is carried out with complete nodule ablation, and the region that was treated first is looked at a second time. From April 2018 to April 2021, nine patients with nine benign nodules were submitted for the iceberg technique. No complications occurred during the entire follow-up period. The patients displayed normal hormonal levels after the procedures, and there was a significant volume reduction of the nodules until three months post-ablation. The iceberg technique is an effective and safe option for the radiofrequency treatment of diving goiters.

Keywords: Ablation; goiter; interventional; nodule; thyroid.

Figure 1

(a) Danger triangle zone: a space between thyroid parenchyma, trachea, and laryngeous recurrent nerve. This area must be protected from heat. Hydrodissection is an excellent option to protect these structures. (b) Pre-procedural hydrodissection with a 5% glucose solution. We got a protection layer of 0.7 cm (white arrow), allowing a larger area ablative zone with greater protection.

Figure 2

(a) Initial thyroid ultrasound assessment showing a diving thyroid nodule with its mediastinal component, the brachiocephalic trunk, and the left common carotid artery. (b) First stage ablation of the nodule’s cervical portion. The white arrow shows the radiofrequency probe.

Figure 3

(a) Second thyroid color Doppler ultrasound assessment showing retraction of the mediastinal nodule’s component (now well visualized) to the cervical region. Color Doppler US demonstrates the clear difference between the previously ablated zone (with no color flow and heterogeneous and hypoechogenic) and the residual portion (with color flow and isoechogenic). (b) Follow-up images demonstrate a 90% volume reduction after two ablative sessions.