Before laser ablation a careful administration of local anesthesia, xylocaine, on the skin, prethyroid muscles, and thyroid capsule should be performed along the planned track of fiber insertion. Usually, from one to two 21G spinal needles are inserted under US guidance into the nodule. A 300 μm optical fiber is then positioned through the needle sheath into the target zone, and the tip is placed in direct contact with the tissue for a length of about 5 mm [25, 26]. A careful US evaluation should be performed to confirm the appropriate positioning of the fiber optic(s) and the presence of a 10 mm safety distance from the vital structures of the neck. Then, laser firing is initiated with an output power from 3 to 5 W, and the energy delivery is usually carried out for 5–10 min, with a total energy delivery from 1800 to 3000 J. Laser illumination is terminated when a cloud of hyperechoic spots, due to the production of gas bubbles, stops enlarging and becomes steady in size. In large volume nodules, a second treatment may be carried out during the same session, after a 1.0–1.5 cm withdrawal of the needle(s) along the longitudinal axis of the lesion (“pullback technique”) [27] (Fig. 13.2).

Laser ablation is successful for decreasing the size of large symptomatic thyroid lesions and for preventing further growth of nonfunctioning nodules. A good-quality evidence, due to randomized trials [29, 30] and multicenter retrospective studies [28], demonstrates that a single LA session is consistently followed by about 50% reduction of the size of the ablated nodule. Volume decrease is progressive during the first 12 months after treatment and in most cases persists for several years. These results are quite similar among different centers and are associated with a significant improvement of local symptoms [28].

Radiofrequency ablation may be performed with local anesthesia or conscious sedation. After the initial trials are carried out in subjects under conscious sedation with large devices, such as multi-tined electrodes with expanding hooks (14-gauge diameter) [36, 37], thinner (18 or 19G) and shorter, internally cooled electrode needles have been developed and are presently used for thyroid lesions [38]. These tools are more practical and less traumatic and permit a repetitive insertion of the tip of the needle within the target area, according to the so-called “moving shot” technique [38]. The electrode is first placed, through a cervical trans-isthmic approach, in the distal part of the nodule, and after the ablation of the initial zone, it is systematically inserted into the central and more proximal areas of the thyroid lesion (Fig. 13.3).

The “moving shot” RF technique [39, 40] generates multiple confluent areas of thermal necrosis that are followed by a relevant shrinkage of the ablated lesion. Several RF trials report a mean size reduction that 6 months after treatment is about 60–80% and may reach 90% of the baseline volume in complex lesions with a fluid component [40]. Volume reduction is persistent over time, and further treatments may be, anyway, performed in case of nodule regrowth [40]. RF ablation is moderately painful, can be carried out in the outpatient clinic, and does not require major analgesics nor antibiotics. Side effects are rather infrequent (about 3.0% in large retrospective studies) and are usually transient [41]. Rare but serious complications, such as extra-thyroid bleeding, vocal cord palsy, nodule rupture and infection, and skin injury, have been described. Thus, RF ablation requires special and specific expertise with a good knowledge of cervical anatomy that should be obtained with a dedicated training period [41].

The treatment is performed with a real-time US-guided HIFU system that consists of an energy generator, an articulated arm with a treatment head, a cooling system for skin preservation, and a touch screen interface for planning and follow-up of the procedure. The treatment head includes both the imaging transducer and the HIFU transducer that convey energy to the target area. A laser-based movement detector shuts off the power in case of patient movement or swallowing.

In few small series of patients, the treated nodules showed at the 6-month follow-up a volume reduction of nearly 50% [47, 48]. The procedure was reported as fairly well tolerated, and most patients did not need analgesic drugs after treatment. At the session conclusion, mild skin redness and subcutaneous edema spontaneously disappearing within a few hours or days may be observed. Blistering or severe edema of the cervical tissues is occasionally reported, while serious adverse events, such as dysphonia, tracheal or esophageal damage, or Horner’s syndrome, are rare [47].