Image of the RFA generator used in thyroid nodule ablations.
The patient is placed in the supine position with mild neck extension, after which
a grounding pad is firmly attached to each thigh.
The “transisthmic approach method” and the “moving
shot technique” have recently been introduced [17, 22]. With
the transisthmic approach, the electrode is inserted from the
isthmus to the lateral aspect of a targeted nodule (Figures 1
and 2). The entire length of the electrode can be visualized via
a transverse US view and with minimal heat exposure to the
danger triangle which includes the recurrent laryngeal nerve
and/or the esophagus. Secure positioning of the electrode
through sufficient thyroid parenchyma also prevents leakage
of ablated hot fluid outside the thyroid gland and change in
the electrode position during swallowing or talking.
The moving shot technique was proposed by Baek et al.
[17, 22] (Figures 1 and 2), as opposed to the fixed electrode
technique which has been used to treat liver tumors. The
fixed electrode technique is dangerous to surrounding critical
structures because thyroid nodules are elliptical in shape.
With the moving shot technique, multiple small conceptual
ablation units are ablated unit-by-unit by moving the
electrode. The electrode tip is initially positioned in the
deepest and most remote portion of the nodule, after which
it is moved backward to the superficial and nearest portion
of the nodule so as to prevent visual disturbance caused by
The RF power is 30–120 W depending on the size of
the active tip and the internal characteristics of the nodules.
Ablation is started with 30–50 W of RF power and is then
increased in 10 W increments, if a transient echogenic zone
does not form at the electrode tip within 5–10 seconds,
to a maximum of 80–120 W. The RF power is reduced
or turned off for several seconds if a patient experiences
severe pain, and the ablation is finished when all conceptual
ablation units have become transient echogenic zones.
International Journal of Endocrinology 3
A danger triangle could remain undertreated because of its
close approximation to a recurrent laryngeal nerve or to the