Apparent diffusion coefficient-based histogram analysis differentiates histological subtypes of periampullary adenocarcinoma

Table 1 Characteristics of patients enrolled in the two histological groups

	IPAC	PPAC	P value
Total (n)	17	23
Age, yr (mean ± SD)	58.1±8.4	57.8±7.8	0.929
Male/female, n	12/5	14/9	0.524
CA19-9 positive (n)	9	15	0.433
Size, mm (mean ± SD)	15.5±5.1	17.4±5.7	0.273
Tumor differentiation	4/10/3	2/13/8	0.288
Well/moderate/poor (n)
Nodal involvement (n)	4	5	0.893
Perineural invasion (n)	1	9	0.016
Vessel involvement (n)	2	3	0.904

CA19-9 > 34 U/mL was defined as positive. IPAC: Intestinal-type periampullary adenocarcinoma; PPAC: Pancreatobiliary-type periampullary adenocarcinoma; SD: Standard deviation; n: Number; CA19-9: Carbohydrate antigen 19-9.

Table 2 Interobserver agreement for volumetric histogram parameters

	b = 800 s/mm2		b = 1000 s/mm2
ADC parameter	ICC	95%CI	ICC	95%CI
Mean	0.992	0.984-0.996	0.994	0.989-0.997
Entropy	0.959	0.922-0.978	0.952	0.910-0.975
Skewness	0.742	0.153-0.864	0.781	0.585-0.884
Kurtosis	0.399	-0.136-0.682	0.486	0.029-0.728
5th	0.954	0.912-0.976	0.978	0.959-0.989
10th	0.974	0.950-0.986	0.975	0.952-0.987
25th	0.988	0.976-0.993	0.991	0.983-0.995
50th	0.989	0.978-0.994	0.996	0.992-0.998
75th	0.984	0.969-0.991	0.992	0.985-0.996
90th	0.973	0.948-0.986	0.981	0.965-0.990
95th	0.975	0.950-0.987	0.977	0.966-0.988
ADCmin	0.981	0.965-0.990	0.984	0.970-0.992
ADCmax	0.951	0.908-0.974	0.948	0.901-0.972

ICC: Interclass correlation coefficient; CI: Confidence interval; ADC: Apparent diffusion coefficient.

Table 3 Results of apparent diffusion coefficient histogram analysis between intestinal-type and pancreatobiliary-type periampullary adenocarcinoma

	b = 800 s/mm2			b = 1000 s/mm2
	IPAC	PPAC	P	IPAC	PPAC	P
Mean	1.38±0.33	1.24±0.24	0.146	1.33±0.25	1.11±0.25	0.009
5th	1.01 ± 0.23	0.93 ± 0.25	0.312	0.99 ± 0.22	0.85 ± 0.27	0.094
10th	1.07 ± 0.24	0.99 ± 0.24	0.259	1.06 ± 0.23	0.89 ± 0.26	0.040
25th	1.22 ± 0.31	1.09 ± 0.24	0.146	1.16 ± 0.24	0.99 ± 0.25	0.030
50th	1.37 ± 0.33	1.23 ± 0.24	0.123	1.31 ± 0.25	1.09 ± 0.25	0.011
75th	1.51 ± 0.37	1.36 ± 0.25	0.159	1.47 ± 0.28	1.21 ± 0.25	0.004
90th	1.66 ± 0.40	1.49 ± 0.28	0.136	1.61 ± 0.32	1.32 ± 0.26	0.004
95th	1.76 ± 0.42	1.56 ± 0.30	0.136	1.68 ± 0.33	1.40 ± 0.28	0.010
ADCmin	0.87±0.32	0.82±0.30	0.583	0.89±0.24	0.79±0.27	0.227
ADCmax	1.93±0.51	1.73±0.37	0.178	1.84±0.32	1.54±0.36	0.008
Entropy	3.56±0.55	3.55±0.56	0.926	3.46±0.56	3.40±0.60	0.748

Apparent diffusion coefficient values are expressed as ×10^-3 mm²/s. IPAC: Intestinal-type periampullary adenocarcinoma; PPAC: Pancreatobiliary-type periampullary adenocarcinoma; ADC: Apparent diffusion coefficient.

Table 4 Diagnostic performance of the volumetric histogram parameters at b₁₀₀₀

ADC parameter	AUC (95%CI)	Cut-off (10-3 mm2/s)	Sensitivity (%)	Specificity (%)
Mean	0.762(0.601-0.882)	1.40	91	52
5th	0.703 (0.538-0.837)	1.09	78	58
10th	0.723 (0.558-0.825)	0.90	57	82
25th	0.742 (0.579-0.867)	1.34	83	59
50th	0.781 (0.623 0.896)	1.50	91	59
75th	0.774 (0.613-0.892)	1.44	78	69
90th	0.750 (0.581-0.877)	1.52	82	67
ADCmax	0.747(0.585-0.871)	1.63	70	82

ADC: Apparent diffusion coefficient; AUC: Area under the curve; CI: Confidence interval.