Novel and Advanced Ultrasound Techniques for Thyroid Thermal Ablation

Abstract

Thyroid radiofrequency ablation and microwave ablation are widely adopted minimally invasive treatments for diverse thyroid conditions worldwide. Fundamental skills such as the trans-isthmic approach and the moving shot technique are crucial for performing thyroid ablation, and advanced techniques, including hydrodissection and vascular ablation, improve safety and efficacy and reduce complications. Given the learning curve associated with ultrasound-guided therapeutic procedures, operators need training and experience. While training models exist, limited attention has been given to ultrasound maneuvers in ablation needle manipulation. This article introduces two essential maneuvers, the zigzag moving technique and the alienate maneuver, while also reviewing the latest ultrasound techniques in thyroid ablation, contributing valuable insights into this evolving field.

Keywords: Ablation techniques; Microwaves; Radiofrequency ablation; Thyroid nodule.

Fig. 1.

(A) Pre-radiofrequency ablation (RFA) ultrasound of thyroid nodule. (B) Post-RFA ultrasound of the same thyroid nodule (arrows). CCA, common carotid artery; T, trachea.

Fig. 2.

Illustrations of the procedure for the zigzag moving technique from a front view. (A) After ablating the lower unit, the needle tip is withdrawn to the periphery of the nodule. (B) The needle is then maneuvered within the nodule in a zigzag or sawtooth-like pattern towards the upper ablation unit (the path of the needle tip is indicated by the white line). (C) This movement is continued until the desired ultrasound plane is accurately reached. Subsequently, the electrode is advanced to the deepest part of the target area to begin ablation of the upper unit (the white line depicts the complete trajectory of the needle).

Fig. 3.

Perithyroidal lidocaine injection and antero-lateral hydrodissection with a retained needle for continuous hydrodissection. CCA, common carotid artery; T, trachea.

Fig. 4.

(A) Ultrasonography of a high-risk thyroid nodule (N) adjacent to the trachea (T) and danger triangle. A perithyroidal lidocaine injection was performed (arrows). (B) Hydrodissection by the danger triangle approach with a continuous injection of 5% dextrose solution (arrows). A sufficient safety margins between the N and peri-tracheal region was secured. CCA, common carotid artery.

Fig. 5.

Image illustrating the actual performance of continuous hydrodissection and radiofrequency ablation. A 21G needle was connected to a dextrose solution syringe by the danger triangle approach through the isthmus (arrow). US, ultrasound; D5W, 5% dextrose water.

Fig. 6.

Hydrodissection by the posterior approach with a continuous injection. With a large enough amount of hydrodissection solution, both the lateral compartment and posterior compartment were covered. CCA, common carotid artery; N, nodule; T, trachea.

Fig. 7.

The alienate maneuver. After advancing the electrode to the deepest portion of the nodule (N), upward pressure (arrow) can be applied towards the antero-lateral part of the neck. With the help of antero-lateral and danger triangle hydrodissection (HD), the N was isolated from critical structures. CCA, common carotid artery; T, trachea.

Fig. 8.

Feeding vessel entering a hyper-vascular nodule (N). The feeding artery can be distinguished and located by color and spectral Doppler showing an arterial waveform. CCA, common carotid artery; T, trachea.

Fig. 9.

Ultrasound of a hyper-vascular nodule (N) after marginal vein ablation. Hyperechoic air bubbles (arrows) fill the veins and can be observed at the superficial part of the ablated N. CCA, common carotid artery; T, trachea.