Radiofrequency ablation of benign thyroid nodules: depicting early sign of regrowth by calculating vital volume

Figures & data

Table 1. Patients’ demographic data and information of nodules.

Variables	Characteristics
Gender (male:female)	5:49
Age (years)	44.1 ± 13.2 (20–78)
Nodule diameter, largest (cm)	3.8 ± 1.1 (1.9–7.7)
Volume (mL)	14.0 ± 12.7 (3.1–56.6)
Volume <10 mL	29
Volume 10–20 mL	13
Volume >20 mL	12
Solidity
Predominantly solid	38
Mixed solid and cystic	11
Predominantly cystic	5

Ranges are in parentheses.

Figure 1. (A) Transverse image from a 29-year-old woman who received RFA for a benign thyroid nodule 4 months previously. The index nodule volume was 21.1 mL. At the centre of the nodule, the ablated area was seen as a hypoechoic area (Va, arrows). At the margin of the nodule, the incompletely treated viable portion showed an isoechoic area (Vv). The volumes at 4 months were Vt = 7.4 mL, Va = 2.1 mL and Vv = 5.3 mL. (B) Transverse image at the 7-month follow-up. The Vt decreased to 5.3 mL whereas the Vv increased to 5.2 mL. (C) Transverse image at the 21-month follow-up. The Va decreased and nearly disappeared. The Vt increased to 12.4 mL through an increase in the Vv (12.3 mL). (D) Colour Doppler US image showing increased vascularity in the viable area of the nodule.

Figure 2. Changes in the Vt, Va and Vv. The Vt and Va showed a declining slope during follow-up, whilst the Vv showed relatively still.

Figure 3. Comparison of the amount of Vv increase and Vt increase. The peak timing of Vv increase was 1 year after RFA. Regrowth started to occur after 1 year and occurred most frequently at 2–4 years after RFA. The mean timing of regrowth was 39.9 ± 17.5 months after RFA.

Table 2. Nodule volume changes according to the follow-up period.

Variables	Index	1 year	3 years	5 years	7 years
No. nodules	54	52	37	16	5
Vt (mL)	14.0	3.7	4.2	3.7	0.3
Va (mL)		1.8	1.0	1.2	0.1
Vv (mL)		1.9	3.2	2.6	0.2
VRR (%)		73.6	69.6	73.5	97.9
No. Vv increase		16	10	4	1
No. regrowth		2	7	4	0
Disappearance		7	2	1	0

No.: Numbers; Vt: total volume; Va: ablated volume; Vv: vital volume; VRR: volume reduction ratio.

Table 3. Complications and side effects.

Complications	Number of complications (%)	Time of detection (days)	Time to recovery (days)
Major complications	1 (1.8)	1	90
Voice change	1 (1.8)	1	90
Minor complications	1 (1.8)	1	<7
Haematoma	1 (1.8)	1	<7
Side effects	2 (3.6)	1	1–2
Pain	2 (3.6)	1	1–2

Numbers in parentheses are the percentage of complications in the total patients.