Sonographic measurement of thyroid nodule changes after microwave ablation: relationship between multiple parameters

Figures & data

Figure 1. Schematic diagram of index R. Index R was defended as the surface area of the unit volume (R = S_surface/V). Between the baseline and first follow-up, volume and surface area reduction was observed after effective treatment. The increasing ratio reflected that volume decrease much faster than the surface area. The value of R reflected volume reduction of the lesion. Between the next follow-up the volume had no changes (V2 = V3), while the shape of lesion was different. With the same volume, oblate ellipsoid earned larger surface area. Index R could reflect shape changes. The surface area in per unit volume improved. D_max of V2, V3 was shorter than V1 after MWA, whereas D_max in next follow-up was much longer than in first ones. V0: Unit volume (constant); V1: baseline volume; D_max: white dotted line; V2, V3: volume after MWA, V2 is equal to V3.

Table 1. Baseline characteristics of different groups.

		Diameter			Volume
	Overall (238)	D ≤ 3.40cm (125)	D > 3.40cm (111)	p	V ≤ 10.47 ml (120)	V > 10.47 ml (116)	p
Sex^2 (M)	67	36	31	0.94	23	44	0.13
Age^1 (years)	50.9 ± 12.2	50.4 ± 11.1	51.4 ± 13.3	0.41	49.5 ± 11.5	52.3 ± 12.7	0.08
Multiple^2	167	83	84	0.08	78	89	0.17
T3^1 (nmol/L)	1.86 ± 0.44	1.72 ± 0.37	1.99 ± 0.47	0.06	1.74 ± 0.41	1.96 ± 0.44	0.13
T4^1 (pmol/L)	16.87 ± 2.80	17.24 ± 2.73	16.51 ± 2.90	0.45	16.24 ± 3.00	17.40 ± 2.58	0.23
TSH^1 (mU/L)	1.75 ± 0.94	1.57 ± 0.77	1.92 ± 1.06	0.27	2.04 ± 0.89	1.50 ± 0.92	0.09

The baseline characteristics of the groups are with no significant difference.

¹ Student t-test.

² Fisher’s exact test.

Table 2. Changes of parameters before MWA and at each follow-up.

Mixed nodules	Baseline	1 M	3 M	6 M	12 M
No.	236	178	103	86	89
Dmax (cm)	3.67 ± 1.40	2.42 ± 0.83*	1.85 ± 0.70*	1.64 ± 0.87*	1.38 ± 0.75*
V (ml)	17.40 ± 22.52	4.47 ± 4.98*	2.10 ± 2.58*	1.90 ± 3.57*	1.31 ± 2.71*
VRR	–	0.61 ± 0.29*	0.81 ± 0.16*	0.86 ± 0.19*	0.90 ± 0.15*
R	2.55 ± 1.08	3.75 ± 1.32*	4.93 ± 2.42*	6.59 ± 3.88*	8.10 ± 5.01*

All parameters express significant difference compared with the baseline.

Data are presented as mean ± SD.

p vs. baseline,

* p < 0.01.

Figure 2. Multiple comparisons in the whole group before ablation and after each follow-up. After MWA, no statistically significant differences were observed in parameters like D_max, V and VRR between the three-month and six-month follow-up periods. Similarly, between the 6-month and 12-month follow-up, the above parameters didn’t show any statistically significant differences. ns: No significance. Those which were not showed had statistical significance difference (p < 0.05). The blue dashed line contains parameters D_max, V and VRR. The blue solid line shows the comparison.

Figure 3. ROC curve of D_max, V, VRR and index R at three-month follow-up. All parameters expressed effective treatment after MWA within three-month whether comparing with the baseline or the former follow-up. And the similar performance in treatment evaluation was obtained by ROC curve of these parameters.

Figure 4. Multiple comparisons in the diameter group before ablation and after each follow-up. Between the 6-month and 12-month follow-up, whatever the initial diameter was, there were no statistically significant differences values of D_max, V and VRR. And so did D_max between the 3-month and 6-month follow-up. When the initial diameter >3.4 cm, the values of V and VRR showed no statistically significant differences in comparing with the next follow-up term, from 3-month to 12-month periods. ns: No significance. Those which were not showed had statistical significance difference (p < 0.05). The blue dashed line contains parameters D_max, V and VRR. The red solid line contains parameters V and VRR. The yellow dashed line represents D_max. The blue solid line shows the comparison.

Figure 5. Receiver operating curve curve of V, VRR and index R at six-month follow-up in nodules baseline diameter ≤3.40 cm. V, VRR and index R reflected treatment effectiveness after MWA within six-month whether comparing with the baseline or the former follow-up. And the similar performance in treatment evaluation was obtained by ROC curve of these parameters.

Figure 6. Multiple comparisons in the volume group before ablation and after each follow-up. After the three-month periods, whatever initial volume was, D_max, V and VRR showed no statistically significant differences compared with the former or the next follow-up. ns: No significance. Those which were not showed had statistical significance difference (p < 0.05). The blue dashed line contains parameters D_max, V and VRR. The blue solid line shows the comparison.

Figure 7. A 43-year-old man had a complex nodule in the left lobe. The changes of the nodules before and after MWA were presented in the following pictures. (a) Ultrasound examination revealed the D_max, V and index R of the nodule were 3.7 cm, 10.20 ml and 2.36 before MWA. (b) One-month after the ablation, D_max, V, VRR and index R of the nodule were 2.5 cm, 3.56 ml, 65.10% and 3.24, respectively. (c) Three-month after the ablation, D_max, V, VRR and index R of the nodule were 1.3 cm, 0.44 ml, 95.69% and 6.54, respectively. (d) Six-month after the ablation, D_max, V, VRR and index R of the nodule were 1.0 cm, 0.16 ml, 98.43% and 9.33, respectively. (e) At final 15-month follow-up of this patient, D_max, V, VRR and index R of the nodule were 1.0 cm, 0.11 ml, 98.92% and 11.00, respectively. It shows more changes of shape rather than volume.

Table 3. Thyroid function before treatment and after one month of follow-up (p > 0.05).

	T3^1 (nmol/L)		T4^1 (pmol/L)		TSH^1 (mU/L)
Group	Initial	One-month	Initial	One-month	Initial	One-month
Total	1.86 ± 0.44	2.01 ± 0.57	16.87 ± 2.80	17.34 ± 3.21	1.75 ± 0.94	1.68 ± 0.57
D ≤ 3.40 cm	1.72 ± 0.37	1.87 ± 0.36	17.24 ± 2.73	18.14 ± 2.87	1.57 ± 0.77	1.55 ± 0.46
D > 3.40 cm	1.99 ± 0.47	2.27 ± 0.61	16.51 ± 2.90	16.78 ± 3.43	1.92 ± 1.06	1.87 ± 0.97
V ≤ 10.47 ml	1.74 ± 0.41	1.80 ± 0.53	16.24 ± 3.00	16.99 ± 2.95	2.04 ± 0.89	1.83 ± 1.02
V > 10.47ml	1.96 ± 0.44	2.11 ± 0.64	17.40 ± 2.58	17.61 ± 3.55	1.50 ± 0.92	1.53 ± 0.43

Thyroid function before ablation and after one month follow-up is with no significant difference.

¹ Student t-test.