Quantitative differentiation of malignant and benign thyroid nodules with multi-parameter diffusion-weighted imaging

Table 1 Interreader reproducibility of measurement of diffusion parameters of thyroid nodules

Diffusion parameter	ICC	95%CI
Mono-exponential
ADC(0 and 1000)	0.944	(0.852, 0.979)
ADC(0 to 1000)	0.938	(0.898, 0.962)
ADC(0 and 2000)	0.904	(0.844, 0.941)
ADC(0 to 2000)	0.942	(0.905, 0.962)
Biexponential
D	0.949	(0.921, 0.967)
D*	0.935	(0.900, 0.958)
f	0.897	(0.844, 0.933)
stretched exponential
DDC	0.994	(0.990, 0.996)
α	0.973	(0.958, 0.983)
Kurtosis DWI
Dapp	0.787	(0.685, 0.859)
Kapp	0.855	(0.782, 0.905)

ADC: Apparent diffusion coefficient; DWI: Diffusion-weighted imaging; D: Slow diffusion coefficient; D*: Fast diffusion coefficient; f: Fraction of fast diffusion; DDC: Distributed diffusion coefficient; ICC: Intraclass correlation; α: Anomalous exponent term; Dapp: Mean diffusivity; Kapp: Mean kurtosis.

Table 2 Comparison of diffusion parameters between benign and malignant thyroid nodules

Diffusion parameter	Benign nodules	Malignant nodules	P value
Mono-exponential
ADC(0 and 1000)	1.85 ± 0.24	1.29 ± 0.27	< 0.01
ADC(0 to 1000)	1.79 ± 0.021	1.19 ± 0.23	< 0.01
ADC(0 and 2000)	1.35 ± 0.15	0.95 ± 0.15	< 0.01
ADC(0 to 2000)	1.41 ± 0.15	0.95 ± 0.15	< 0.01
Biexponential
D	1.34 ± 0.41	0.89 ± 0.26	< 0.01
D*	22.08 ± 18.53	26.09 ± 20.87	> 0.05
f	0.38 ± 0.19	0.30 ± 0.14	< 0.01
Stretched exponential
DDC	2.15 ± 0.62	1.45 ± 0.51	< 0.01
α	0.78 ± 0.19	0.67 ± 0.19	< 0.01
Kurtosis DWI
Dapp	2.88 ± 0.73	2.11 ± 0.67	< 0.01
Kapp	0.57 ± 0.12	0.85 ± 0.19	< 0.01

ADC: Apparent diffusion coefficient; D: Slow diffusion coefficient; D*: Fast diffusion coefficient; f: Fraction of fast diffusion; DDC: Distributed diffusion coefficient; α: Anomalous exponent term; DWI: Diffusion-weighted imaging; Dapp: Mean diffusivity; Kapp, mean kurtosis. The ADC, D, D*, DDC, and Dapp are given in units of ×10^-3 mm²/s. P values from statistical comparison between benign and malignant nodules were obtained by using the Mann–Whitney U test.

Table 3 Diagnostic performance of diffusion parameters for differentiating malignant thyroid nodules from benign thyroid nodules

Diffusion parameter	AUC	Cut-off value	Sensitivity, %	Specificity, %	Youden index	P value
Mono-exponential
ADC(0 and 1000)	0.879	1.6	64.5	100.0	0.645	Ref.
ADC(0 and 2000)	0.874	1.1	79.0	88.2	0.672	0.94
ADC(0 to 1000)	0.882	1.5	72.6	100.0	0.726	0.94
ADC(0 to 2000)	0.878	1.1	77.4	88.2	0.656	0.99
Biexponential
D	0.861	1.1	71.0	94.1	0.651	0.76
D*	0.643	22.2	88.2	56.5	0.447	< 0.01
f	0.709	0.37	46.8	100.0	0.468	< 0.05
Stretched exponential
DDC	0.841	2.0	59.7	100.0	0.597	0.53
α	0.748	0.73	62.9	88.2	0.511	< 0.05
Kurtosis DWI
Dapp	0.815	2.6	61.3	88.2	0.495	0.33
Kapp	0.889	0.65	100.0	74.2	0.742	0.84

AUC: Area under the receiver operating characteristic curve; ADC: Apparent diffusion coefficient; DWI: Diffusion-weighted imaging; D: Slow diffusion coefficient; D*: Fast diffusion coefficient; f: Fraction of fast diffusion; DDC: Distributed diffusion coefficient; α: Anomalous exponent term; Dapp: Mean diffusivity; Kapp: Mean kurtosis. The cut-off values for the ADC, D, D*, DDC, and Dapp are given in units of ×10^-3 mm²/s. P values from statistical comparisons between the AUC values of the ADC_{(0 and 1000)} (Ref) and other diffusion parameters were obtained by using the method of Z test.